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 COPYRIGHT DEPOSIT 
 
MENTAL FATIGUE 
 
Works in German 
 
 BY 
 
 MAX OFFNER 
 
 Professor in K. Ludwig's Gymnasium, 
 Mlinchen 
 
 Author of "Die Geistige Ermudung' 
 
 Die Psychologie Charles Bonnets. A 
 study in the history of psychology. Leip- 
 zig, J. A. Abel, 1893. 
 
 Willensfreiheit, Zurechnung und Verant- 
 wortung. Discussion of important concepts 
 common to psychology, ethics, and criminal 
 law. Leipzig, J. A. Abel, 1904. 
 
 Das Gedachtnis. The results of experi- 
 mental psychology, and their application to 
 problems of instruction and education. 
 Berlin, Reuther & Reichard,(New Edition). 
 
 "The 'Value of Forgetting' is the subject 
 which brings to a conclusion a book which 
 should prove most useful. The usefulness, 
 moreover, will be greatly increased by the 
 bibliography and index which are ap- 
 pended." From Mind, January, 1910. 
 
EiUtratumal Jtegrijoln^g iMnnngrapljfl 
 
 MENTAL FATIGUE 
 
 A Comprehensive Exposition of the Nature of Mental 
 
 Fatigue, of the Methods of Its Measurement and 
 
 of Their Results, with Special Reference to 
 
 the Problems of Instruction 
 
 DR. MAX OFFNER 
 
 Professor at the Kgl. Ludwigs- Gymnasium at Munich 
 
 Author of "Die Psychologie Charles Bonnets" "Willensfreiheit, Zurechnung 
 
 und Verant-wortung" and "Das Gedachtnis" 
 
 Translated from the German 
 
 GUY MONTROSE WHIPPLE 
 
 Assistant Professor of Educational Psychology 
 
 Cornell University 
 
 Author of "A Manual of Mental and Physical Tests." "A Guide to High-school 
 
 Observation" "Questions in Psychology." "Questions in School Hygiene" etc. 
 
 BALTIMORE 
 
 WARWICK & YORK, Inc. 
 
 1911 
 

 Copyright by 
 WARWICK & YORK, Inc. 
 
 1911 
 
 <v; 
 
 CI.A205843 
 
AUTHOR'S PREFACE 
 
 I am glad to avail myself of the opportunity pre- 
 sented by this translation of my monograph on men- 
 tal fatigue to make a few alterations and extensions 
 of the original text and to preface it with a few words 
 of introduction. 
 
 From the circumstance that the monograph has met 
 with a favorable reception outside of Germany, I in- 
 fer with satisfaction that, both in subject-matter and 
 form of presentation, it is meeting adequately the 
 needs of teachers and students whom I wish to sup- 
 ply with a critical, reliable, and intelligible guide 
 through the extensive field of investigation of fatigue. 
 
 Of the great mass of material that is available — 
 material that is difficult to gather up into a system- 
 atic and consistent treatment — I have mentioned, 
 without intending to disparage the works that I have 
 omitted, only those contributions that, in my opinion, 
 are best fitted to introduce us to the more intricate 
 study of fatigue investigation and its history. Nat- 
 urally, I have given preference to German investi- 
 gators, because it was the German teacher primarily 
 that I sought to acquaint with the literature most 
 accessible to him. The American teacher will be able, 
 without much trouble, to choose satisfactory supple- 
 mentary reading out of the numerous journals in his 
 
Vi MENTAL FATIGUE 
 
 own language devoted to psychology, pedagogy, and 
 school hygiene. 
 
 The terminology that I have employed will prob- 
 ably occasion no serious difficulties. If it does, fur- 
 ther information about it and a more detailed justifi- 
 cation of it may be found in my book on memory. 
 
 It will afford me particular gratification if my little 
 book shall avail to contribute in some measure toward 
 the furthering of that intellectual interchange that 
 has for so long prevailed, to the mutual advantage 
 of both, between America and Germany. 
 
 Dk. M. Offnek. 
 
 Munich, Germany. 
 
TRANSLATOR'S PREFACE 
 
 This translation of OfTner's Mental Fatigue has 
 been undertaken because the monograph collates, sys- 
 tematizes, and appraises a mass of scattered and to 
 most readers inaccessible material that bears upon a 
 schoolroom problem of unquestioned importance. 
 
 The author, in his introductory words, points out 
 that the references are primarily adapted for Ger- 
 man readers. To increase the usefulness of the book 
 for American readers, I have, accordingly, at his sug- 
 gestion, added to the bibliography a partial list of the 
 books and articles available in English (Appendix 
 I), and I have, in several places in the course of the 
 text, inserted footnotes that are especially intended 
 to assist those who desire it to gain further informa- 
 tion concerning the several methods of testing fa- 
 tigue, or to undertake for themselves experimental 
 investigation in the schoolroom or the laboratory. 
 For it is one of the merits of this book that its author 
 makes no pretense at finality, but, on the contrary, 
 is concerned to make evident the many gaps in our 
 knowledge. And one of the objects of the translation 
 is, accordingly, to stimulate others to contribute to 
 this scientifically interesting and practically impor- 
 tant aspect of experimental pedagogy. 
 
 No attempt has been made to render into English 
 
Vlll MENTAL FATIGUE 
 
 the terms descriptive of the German school system, 
 but the reader will find in Appendix II an explanation 
 of the German terms that have been retained. 
 
 In the preparation of this translation, I am spe- 
 cially indebted for assistance freely accorded by my 
 colleagues, Prof. E. B. Titchener and Dr. L. R. 
 Geissler. 
 
 Guy Montkose Whipple. 
 
 Cornell University, March, 1911. 
 
TABLE OF CONTENTS. 
 
 Introductory 5 
 
 The Nature and Forms of Fatigue 7 
 
 The Symptoms of Fatigue 8 
 
 Symptoms of Fatigue by Bodily Work 8 
 
 Symptoms of Fatigue by Mental Work ....... 13 
 
 The Measurement of Fatigue 18 
 
 Unreliability for the Measurement of Fatigue of the Sub- 
 jective Symptoms 18 
 
 The Objective Procedure and the Two Chief Groups of 
 
 Measurement Methods 20 
 
 The Physiological Methods 23 
 
 The Dynamometer 23 
 
 The Ergograph 24 
 
 Measurement of Fatigue by the Respiration and by the 
 
 Pulse 28 
 
 Beating Time 28 
 
 Measurement of Fatigue by Means of the Range of Accom- 
 modation of the Eye 30 
 
 The Psychological Methods 31 
 
 Methods of Test-Work 31 
 
 Esthesiometry 31 
 
 Measurement of Fatigue by Means of Other Liminal 
 
 Values 38 
 
 The Kinematometer Method 39 
 
 Method of Time Estimates 41 
 
 The Algesiometer Method ... 41 
 
 Measurement of Fatigue by the Measurement of the Dura- 
 tion of Mental Processes 43 
 
 Methods of Test-Problems in the Narrower Sense ... 44 
 (Dictation, 46; Computation, 46; Memory, 48; Com- 
 pletion, 49 ; Cancellation, 52 ; Copying, 53 ; Combined 
 Methods, 53.) 
 
 Method of Continuous Work 56 
 
 Results 62 
 
 Various Factors in Addition to Fatigue That Determine 
 
 Efficiency 62 
 
 Practice 62 
 
 Habituation 64 
 
 Swing or Fitness for Work 66 
 
 Spurt 68 
 
 Independent Fluctuations of Psychophysical Energy . . 72 
 
 The Laws of Fatigue 74 
 
 The Phases of Fatigue 74 
 
2 CONTENTS 
 
 Types of Fatigue or Types of Work 75 
 
 Age 77 
 
 Puberty 78 
 
 Length of Lesson-Periods 79 
 
 Number of Lessons per Day and per Week 83 
 
 Days of the W T eek 84 
 
 Pauses in School Work 85 
 
 ( Short Pauses, 85 ; The Noon Intermission, 86 ; Sleep, 
 88 ; Vacations, 91 ; Disadvantages of Pauses, 93. ) 
 
 Change of Work : Special and General Fatigue .... 94 
 
 Social Activities 100 
 
 Gymnastics 101 
 
 Fatigue-coefficient of the Studies 104 
 
 Afternoon Instruction 106 
 
 School Program 108 
 
 Fatigue-coefficient of the Teacher 110 
 
 Fatigue-coefficient of the Methods of Teaching and Learn- 
 ing 110 
 
 Individual and Class Instruction 112 
 
 Fatigability of the Teacher 113 
 
 Conclusion 116 
 
 Is it Permissible that Pupils Be Fatigued? 116 
 
 Training in Mental Hygiene 118 
 
 More Intensive Physical Development 119 
 
 Bibliography 122 
 
 Appendix I. Additional References for American Readers . 128 
 
 Appendix II. The Terminology of the German School System 130 
 
 Index of Names 132 
 
MENTAL FATIGUE 
 
 INTRODUCTORY 
 
 In no field of work has experimental psychology 
 come into closer contact with the practical problems 
 of instruction than in the investigation of fatigue. 
 Complaints against the overburdening of school 
 children have been current for a long time. Because 
 the earlier discussions of the problem, which were 
 based upon general observations without the assist- 
 ance of exact methods, were inadequate to settle the 
 pros and cons of the dispute, experimental observa- 
 tion has been applied to its solution. The first con- 
 tribution of this sort appears to have been a research 
 published by the Russian psychiatrist, J. Sikorski, 
 in 1879. There have followed, from year to year, 
 further studies, so that in the last 30 years an exten- 
 sive literature of mental fatigue has accumulated. 
 The very extent of this literature, and the difficulty 
 of getting hold of it, and the fact that thus far the in- 
 vestigations have not been brought to a perfectly 
 satisfactory conclusion, may account for the circum- 
 stance that schoolmen have not, as a rule, shown as 
 much interest in them as they warrant, in spite of 
 their rather modest results. Indeed, it is not unlikely 
 that the results would today be in better shape, that 
 we should have, by now, made better progress in our 
 solution of this complex problem if the schoolmen 
 
 5 
 
6 MENTAL FATIGUE 
 
 themselves, who have at their disposal the richest 
 material for observation, had participated more than 
 they have done in the solution of the problem. For 
 hardly a single one of the investigations that have 
 been undertaken by teachers has failed to make a 
 contribution of more or less value. And so, to 
 awaken the interest, and to bring about in any degree 
 the co-operation in the study of fatigue of those in 
 intimate contact with the activities of the school, 
 cannot fail to be worth while not only for the school, 
 but also for science. 
 
THE NATURE AND FORMS OF FATIGUE 
 
 What do we mean, speaking generally, by fatigue? 
 
 If we make no attempt at explanation and inter- 
 pretation, but confine ourselves simply to the phe- 
 nomena concerned, we designate by fatigue a condi- 
 tion of our organism that is developed by long-con- 
 tinued work, and that, in addition to other symptoms, 
 is characterized in particular by a reduction in ca- 
 pacity for, and pleasure in, work. It is true, these 
 symptoms may, for the time being, be counteracted, 
 even cancelled, by antagonistic factors, so that the 
 fact that the condition of the organism has been 
 altered may be inferred only from other circum- 
 stances. According to the side of our psychophysi- 
 cal organism whose efficiency for work has been re- 
 duced — either by mental or by physical work — we 
 speak of two forms of fatigue — of bodily fatigue as 
 fatigue for bodily work, and of mental fatigue as 
 fatigue for mental work. 
 
 And according to the nature of the work by which 
 we fatigue our organism — either for mental or for 
 physical work — we distinguish between a fatigue by 
 bodily work and a fatigue by mental work. 
 
 We shall at first consider the fatigue of both sides 
 of our nature, divided according to the nature of 
 its cause, of the work which induces it. 
 
 Later we shall limit our consideration to the 
 fatigue of the mental side of our organism (in which 
 we are most interested), regardless of what kind of 
 work has caused this mental fatigue. 
 
THE SYMPTOMS OF FATIGUE 
 
 Symptoms of fatigue induced by bodily ivork. The 
 most important symptoms of fatigue by bodily work 
 are well known. If we indulge in physical activity 
 continuously and for a long time, if we walk or prac- 
 tice gymnastics or attempt mountain-climbing or 
 perform other muscular work, after a certain time 
 there becomes evident a considerable quickening and 
 deepening of respiration and an acceleration of the 
 pulse rate (Mosso, 107, 110; Verworn, 499*), save in 
 the case of intense effort, where the opposite condi- 
 tions are more likely to appear (Binet and Henri, 
 150), and at the same time there appears a rise in 
 temperature sufficient to cause perspiration — at first 
 in the members exercised, and then over the entire 
 body, and finally a reduction of the capacity for work. 
 We work more slowly, and hence accomplish less in 
 a given unit of time than at the beginning ; our gait, 
 for instance, becomes slower and shorter, and also 
 less certain, as mountain-climbers, in particular, find 
 to their cost, and the lessened physical capacity 
 affects not only the members that are directly exer- 
 cised — here the legs — but other members also, as in 
 walking the arms lose something of their muscular 
 
 ♦The Arabic numbers in parentheses here and elsewhere in the 
 text refer, unless otherwise indicated, to pages in the references 
 assembled in the bibliography at the end. 
 
 8 
 
THE SYMPTOMS OF FATIGUE \) 
 
 energy (Mosso, 119). At the same time the feeling 
 of freshness with which we started disappears. 
 Gradually we come to feel dull and uncomfortable 
 (the feeling of weariness). Furthermore, there is 
 developed a disinclination for fatiguing, and ulti- 
 mately for any kind of work, and a desire to end it ; 
 we long for rest. Every movement, every step, 
 exacts greater effort, a greater expenditure of will- 
 power. At the same time our mental processes be- 
 come slower and less varied. Our conversation, 
 accordingly, grows languid, trivial, and tends toward 
 empty word-play ; in the end we cease to talk alto- 
 gether. We are also less sensitive to the stimuli of 
 the outer world. Thus the beauty of the panorama 
 makes little impression upon the tourist who is 
 fatigued by the climb of the mountain ; not until he 
 has recuperated and regained something of his 
 strength does it afford him satisfaction. In many in- 
 stances excessive physical fatigue brings it about that 
 objects that strike the senses make but little impres- 
 sion, so that the most beautiful scenery is quickly for- 
 gotten by people whose memory is ordinarily per- 
 fectly good. Even serious mental disturbances have 
 been observed as a consequence of bodily exhaustion 
 (Cf. Fere, 446 ff. ; Mosso, 200). Physical work, then, 
 unfits us for mental work as well. These and similar 
 phenomena are psychic symptoms of physical fatigue, 
 and show us that bodily activity results in mental, as 
 well as in bodily fatigue. In the last resort, pain 
 sets in, especially in those members whose activity 
 is enforced, and it may come to pass ultimately that 
 they refuse to function further, despite every exer- 
 tion of will. 
 
10 MENTAL FATIGUE 
 
 The physiological processes concerned in the 
 muscle at work, in so far as they have been deter- 
 mined at present, are of two sorts. We owe to J. 
 Ranke of Munich (1865) our first information con- 
 cerning them. In consequence of physical activity 
 there are formed in the muscles certain substances, 
 particularly lactic acid (the same substance found 
 in sour milk) and acid potassium phosphate. 
 
 These substances or waste products thrown off 
 from the muscles are poisons, or toxins (Mosso, 
 108 ff., 119 ff. ; Verworn, 500). If one injects into a 
 fresh muscle these products of the metabolism of a 
 fatigued muscle, these fatigue- sub stances, as they are 
 termed, then this fresh muscle, without having done 
 any work itself, at once suffers loss of its contracti- 
 bility and capacity for work. This Ranke demon- 
 strated for a single muscle, while Mosso (119 ff.) 
 strikingly confirmed the fact at Turin by injecting 
 into a live dog the blood of another dog whose ner- 
 vous system had been fatigued to a state of tetanus 
 contraction by a strong electric current. And the 
 same effect is produced — this is the second test — by 
 the injection of dilute phosphoric acid and acid po- 
 tassium phosphate (Landois, 612). 
 
 But, by flushing with dilute gas-free solution of 
 sodium chlorid (0.7 to 1.0 per cent.), these substances 
 are again eliminated, as experiments upon the 
 muscles of animals have likewise shown. By this 
 process the muscle for a short time regains its origi- 
 nal capacity. And, indeed, energetic movement, e. g., 
 shaking the hand fatigued by writing, massaging 
 fatigued limbs, as the runner often does, frequently 
 suffices to render the muscle efficient for some time. 
 
THE SYMPTOMS OF FATIGUE 11 
 
 The fatigue-substances — such is the most obvious in- 
 terpretation — are, by these means, eliminated from 
 the muscle. In the case of rest-pauses, the elimina- 
 tion is effected by the circulation of lymph and of 
 arterial blood. To be sure, this elimination of waste 
 products by the general circulation entails at the 
 same time a gradual poisoning of the whole body, 
 if the fatigue poisons that are thus distributed are 
 not absorbed and rendered ineffective by other sub- 
 stances or eliminated from the body through the skin 
 and kidneys. The question as to how this is accom- 
 plished need not concern us further. W. Weichardt 
 (Mun. Med. Wochenschrift, 1904),* we may note, 
 believes that he has at last discovered that the body 
 forms an antitoxin against the fatigue-toxin, and he 
 reports that he has succeeded in extracting this anti- 
 toxin and in rendering a mouse temporarily more 
 resistant to fatigue by its injection. What value 
 shall be attached to this interesting observation will 
 be better known when it has been confirmed. At 
 best, it offers only a means for partially overcoming 
 fatigue, not for cancelling it completely, because 
 the production of fatigue-substances is only one side 
 of muscular fatigue — the positive side. There still 
 remains the negative side. This, which is the more 
 important, consists in the fact that the fat, and finally 
 the muscle itself, is gradually absorbed during ac- 
 tivity, for the consumption, the dissimilation of the 
 materials of which the body is formed is, during ac- 
 tivity, more intense than their assimilation (dissimi- 
 lation and assimilation in the terminology of Hering ; 
 
 ♦See also his recent Ueoer Ermiidungstoffe, Stuttgart, 1910. — 
 Translator. 
 
12 MENTAL. FATIGUE 
 
 decomposition and recomposition in that of Her- 
 mann). That this using up of material is present in 
 addition to the accumulation of fatigue-substance is 
 shown by the circumstance that, in spite of repeated 
 removals of the fatigue products, the capacity of a 
 muscle that is subjected to repeated stimulation 
 diminishes, and finally reaches zero. 
 
 Max Verworn (500 fL), at Gottingen, has given an 
 exact demonstration of this fact for the central 
 nervous system by a celebrated experiment. The 
 blood of a living frog was replaced by an 0.8 per cent, 
 gas-free salt solution (i. e., a solution totally lacking 
 in nutritive substances) until the latter circulated 
 instead of blood in the veins of the animal. Violent 
 convulsions were then produced by a weak dose of 
 strychnine, while at the same time the circulation of 
 the neutral salt solution was discontinued. The pow- 
 erful excitation and the activity involved in the 
 violent contractions caused a rapid production of 
 fatigue-substances. On account of the checking of 
 the salt solution, these substances were not carried 
 away, and they soon induced a condition of non-ex- 
 citability of the nerves (rigor). So soon, however, 
 as these substances were washed away with the salt 
 solution, the excitability returned, though, it is true, 
 it finally disappeared, despite continued flushing out 
 of the poisons. Here, then, is fatigue without fatigue- 
 substances! If now, however, the frog be flushed 
 with oxygenated salt solution, he recuperates, and 
 the condition of excitability is once more restored. 
 Yet, still, after a time excitability again disap- 
 pears, despite continued flushing with the oxygenated 
 solution. Only when the frog has had injected in 
 
THE SYMPTOMS OF FATIGUE 13 
 
 place of this solution one of defibrinated ox blood 
 (blood that is freed of the solid constituents that are 
 precipitated by coagulation, and that contains, in 
 addition to oxygen, particularly carbon and sodium) 
 does it maintain its excitability during many hours 
 of strenuous activity. 
 
 Oxygen, carbon and sodium are, then, the sub- 
 stances that are especially required by living tissue 
 for its activity. The consumption of these materials 
 is the negative side of fatigue. Verworn prefers the 
 term * exhaustion' for this negative side, and un- 
 derstands by ' fatigue ' merely the positive produc- 
 tion of fatigue-substances — a usage that is followed 
 by W. Rivers and by E. Kraepelin of Munich (Psy- 
 chologische Arbeiten, I, 571 ; see also Hermann, 286). 
 In any event, these two phases of the fatigue effect 
 should be kept quite distinct in mind. To replenish 
 these exhausted materials in muscles and nerves is 
 the first task of nutrition and of rest, especially of 
 sleep, when the use of material (dissimilation or de- 
 composition) is so greatly reduced that the supply- 
 ing of material (assimilation or recomposition) so 
 far preponderates that there may take place an ac- 
 cumulation of surplus material — a storage of energy. 
 Nutrition and rest accordingly have, likewise, two 
 sides — a positive (the supplying of recuperative ma- 
 terial) and a negative (the removal of fatigue mate- 
 rials). 
 
 Symptoms of fatigue by mental work. The course 
 of fatigue by mental work is an analogous one. Effi- 
 ciency gradually diminishes; at first qualitatively 
 (we make more errors), then later on quantitatively 
 (we accomplish less than we did at first). Our atten- 
 
14 MENTAL. FATIGUE 
 
 tion exhibits marked fluctuations. We become more 
 easily distracted, and find it progressively more diffi- 
 cult to maintain a line of thought and to bury our- 
 selves in a problem. Children are then likely to be- 
 gin to play during school work. The child, in such a 
 case, may be said unconsciously to protect himself 
 from fatigue by inattention, and, following Kraepe- 
 lin, we may call his inattention a ' safety valve. ' 
 The observant teacher, who knows his pupils, pos- 
 sesses in this effect of fatigue a valuable sign of 
 warning. Our range of attention, at the best, is cir- 
 cumscribed, so that things come more and more to 
 escape our notice. Sense-perception functions both 
 more slowly and with less accuracy; sensitivity di- 
 minishes. Discrimination for every type of per- 
 ceptive content (acoustic, optic, tactual impressions, 
 weights, etc.) is less certain and more subject to er- 
 ror ; discriminative sensitivity is impaired. We learn 
 more slowly as the work continues, i. e., we learn a 
 less amount and with less exactness in a given time, 
 as is shown by the increase of errors revealed by sub- 
 sequent testing. ' Dispositions ' (in the sense used 
 by OfTner, 84) are less readily formed. In like man- 
 ner, the reproduction of what has been previously 
 acquired, i. e., the effectiveness of the ' disposi- 
 tions,' even of those that have been formed under 
 the most favorable conditions, is affected by con- 
 tinued mental activity. Eeproduction takes place 
 more slowly and less accurately. Our fancy be- 
 comes impoverished, and our thoughts come 'in 
 driblets' (Meumann, II, 122; OfTner, 122, 142). 
 
 Finally, the capacity of the voluntary muscles is 
 gradually affected, even though these are, during the 
 
THE SYMPTOMS OF FATIGUE 15 
 
 mental activity, brought into play little or not at all. 
 If, for example, bodily energy be tested by lifting a 
 weight over and over again to a fixed height, or by 
 contraction of the hand, repeated until the movement 
 is no longer possible, then the time at which the con- 
 tractions cease tends to appear much earlier after 
 severe mental work than when we are mentally quite 
 fresh (Cf. below, pp. 26 if.). Movements executed 
 after severe mental fatigue are also somewhat less 
 certain and slower, as is especially noted in the case 
 of accurately measureable movements of reaction, 
 and, indeed, not seldom in the case of speaking and 
 writing. Mosso (227, 254 f., and elsewhere) even 
 detected uncertainty in gait after long and arduous 
 mental activity in the laboratory and lecture room. 
 Moreover, the unconscious, or, as they are termed, 
 purely physiological processes, are affected by 
 fatigue through mental work. During such work, 
 respiration becomes shallower and faster, but after 
 it, deeper, as in rest ; finally, in the case of excessive 
 fatigue, respiration is again slower and shallower 
 (Binet and Henri, 33ff.). The pulse grows more 
 rapid, and may often increase until palpitation of 
 the heart appears (Mosso, 223), while, as is well 
 known, during bodily fatigue, pulse and respiration 
 are accelerated, and the respiration, in particular, be- 
 comes deeper. In addition, on account of the increase 
 in the blood supply of the active organ, the brain, 
 there is a rise of temperature in the head with a con- 
 comitant reduction of temperature in the extremities, 
 especially in the feet. Indeed, we all know the 
 cold feet and hot head that we develop at our desk, 
 and the college student who i sweats up' for ex- 
 
16 MENTAL FATIGUE 
 
 animations with a wet towel about his head is a 
 familiar figure. 
 
 In consciousness there appear subjective symp- 
 toms, like those accompanying bodily work — at first 
 a mood of indifference, then a disinclination to pur- 
 sue the fatiguing work, together with the desire for 
 a change. We are ' tired ' of this work. Then a 
 feeling of languor becomes evident, a feeling that we 
 can't get hold of things, though we still want to. We 
 feel weary for any kind of work (feeling of weari- 
 ness). Finally, we feel exhausted, and crave noth- 
 ing but rest and sleep. Then, not infrequently, head- 
 ache follows — analogously to the soreness of the 
 fatigued muscle; then restlessness and excitement, 
 heightened sensitivity to impressions (hyperes- 
 thesia), especially to noises, nervousness, irritabil- 
 ity, ill-humor and liability to passionate outbreaks. 
 Children are apt to behave badly and to whine. All 
 these are very important protective devices ; they are 
 warning signals that should admonish us to cease 
 work and to seek nourishment and rest. 
 
 The physiological processes that we assume to 
 underlie fatigue by mental work may be considered, 
 speaking generally, like those for fatigue produced 
 by bodily work, as a production of fatigue-substances 
 and a consumption of constitutive materials, espe- 
 cially in the central nervous system. From this sys- 
 tem, however, the fatigue-effect radiates, seeing 
 that, on the one hand, fatigue-poisons from the ac- 
 tively working brain are gradually disseminated 
 through the organism, while on the other hand, the 
 substances in the rest of the body come more and 
 more in demand, because no adequate replacement is 
 
THE SYMPTOMS OF FATIGUE 17 
 
 afforded by direct nutrition. This view is, I grant, 
 but an hypothesis, yet one that at present has a con- 
 siderable degree of probability, and against which 
 there is, at least, no serious objection. 
 
 It is scarcely necessary to say that the symptoms 
 are not the same in all persons. Age, sex, tempera- 
 ment, state of health, nutrition, and, more especially, 
 diathesis, play a considerable role. Neither is the 
 picture of the symptoms of fatigue always the same 
 in the same person. Thus, for instance, in most dis- 
 eases, especially in nervous diseases and during con- 
 valescence, the phenomena appear more quickly, 
 more intensely and more frequently than in a time 
 of good health, and the same thing is true of periods 
 of mental depression. 
 
THE MEASUREMENT OF FATIGUE 
 
 From what has preceded, it is seen that we have 
 at our disposal two methods of undertaking the 
 measurement of fatigue — of that reduction in ca- 
 pacity for work that ensues upon activity when in- 
 hibitory substances are generated, and when the 
 consumption of the constitutent substances of the 
 cells exceeds its immediate replacement by the pro- 
 cesses of nutrition. First, the subjective method, 
 that finds a standard of measurement in the sub- 
 jective symptoms of fatigue, i. e., in those that are 
 conscious only to the fatigued person himself, and 
 secondly, the objective method, that seeks a standard 
 of measurement in modifications in the physiological 
 functions and in the physical as well as the mental 
 efficiency, i. e., in modifications that are perceptible 
 to others as well as to the fatigued person himself. 
 
 Unreliability for the measurement of fatigue of 
 the subjective symptoms. It is evident that a sub- 
 jective factor cannot be a reliable measure, however 
 useful it may be as a signal. For our own mood, 
 which not seldom varies quite independently of the 
 consumption of energy, exercises an obvious in- 
 fluence. When we are happy we can perceive no 
 weariness. When we are sad and depressed, a task 
 to be done will all too soon engender that feeling 
 
 18 
 
THE MEASUREMENT OF FATIGUE 19 
 
 that we are accustomed to interpret as weariness. 
 If fear and anxiety attack us, we often forget all 
 weariness, however much exhausted we had felt be- 
 fore. 
 
 A swallow of wine, a cup of strong tea or coffee, 
 a few Kola pastilles banish the feeling of languor and 
 give us for a time the illusory feeling of renewed 
 freshness and undiminished capacity, even after the 
 hardest kind of work. 
 
 And a glass of beer, on the other hand, may, be- 
 fore we have done any work, induce a feeling of lan- 
 guor and render us as unfit for work as if we had been 
 through the most tiresome toil. 
 
 A short time after the chief meal of the day we are 
 least fit for mental work, but most fit for bodily work, 
 though we do not feel particularly disposed to un- 
 dertake it. 
 
 There are, too, many individuals who feel weary, 
 dull and ill-disposed at the outset of work, but who 
 gradually become fresher, more efficient and cheerful 
 as their work progresses. Yet there can be no such 
 thing as actual fatigue when the task is just begin- 
 ning. And there are yet other individuals who, un- 
 der protracted work when the consumption of energy 
 must have long exceeded the supply of fresh energy 
 available at the time, experience no feeling of weari- 
 less, and keep at work until they suddenly give up, 
 exhausted. In the former instance, therefore, there 
 is the feeling of weariness without fatigue; in the 
 latter, actual fatigue without the feeling of weari- 
 ness. Hence the relation between the feeling and the 
 psychophysical condition is anything but simple, and 
 the unraveling of the threads that are here inter- 
 
20 MENTAL FATIGUE 
 
 woven, and the discovery of unity and regularity in 
 this correlation, constitutes a special problem, whose 
 solution depends upon the general view that we hold 
 as to the nature of feeling. 
 
 The correspondence, then, between the subjective 
 symptoms, the feelings, and the psychophysical con- 
 dition is far too inexact and too ambiguous to afford 
 us a basis for the measurement of fatigue. And for 
 this reason no progress can be made in the under- 
 standing of the fatigue question so long as inquiry 
 is mainly confined to this well-meaning but unre- 
 liable witness, the weariness feeling — a witness, what 
 is more, that is inaccesible to experimental examina- 
 tion and impossible of exact measurement. Under 
 these conditions, too, the discussions concerning the 
 overburdening of school children can never rise above 
 the level of conjecture and guesswork, and are wholly 
 lacking in power to convince. 
 
 The objective procedure and the two chief groups 
 of measurement methods. We must, therefore, look 
 about for better measures, for symptoms that avoid 
 this uncertain judgment of the fatigued person him- 
 self, for objective symptoms that are susceptible both 
 of systematic experimentation and of mathematical 
 treatment. These are, primarily, the physiological 
 symptoms of fatigue that we have already cited. But 
 certain psychical symptoms also turn out to be sus- 
 ceptible of determination and of measurement by 
 objective, i. e., by external, observation. 
 
 Accordingly, the objective method subdivides into 
 two groups of measurement methods — the physio- 
 logical and the psychological. The physiological 
 
THE MEASUEEMENT OF FATIGUE 21 
 
 group measures the decrease of mental efficiency — 
 to the consideration of which we shall henceforth 
 limit ourselves — by means of alterations of physical 
 efficiency that it proceeds to test; in short, by tests 
 of physical capacity, and by means of observing 
 modifications that appear in specific physiological 
 functions. The psychological group, on the contrary, 
 confines itself to the psychical side, and observes and 
 measures the decrease of mental efficiency that re- 
 sults from mental activity, either in terms of the 
 changes that appear in the mental work itself that is 
 being continuously pursued, or by means of tests of 
 mental efficiency that are introduced at definite 
 stages of the fatigue-producing work. 
 
 When there are a large number of subjects, par- 
 ticularly in schoolroom tests, there are two forms 
 of procedure that are commonly followed. Either 
 tests are given to the class as a whole — in which case 
 there are needed several tasks of equal length and 
 difficulty, a requirement that is hard to fulfil — or the 
 class is divided on the basis of efficiency — putting 
 those of like attainment into the same group — into 
 as many groups as are wanted for tests, and one 
 group is tested at a time, e. g., as in the experiments 
 of Winch and of Thorndike. This admits the possibil- 
 ity, under certain experimental conditions, of apply- 
 ing the same test-work at different stages of fatigue 
 — a possibility of distinct advantage in extracting 
 conclusions from the experiment. But, since this pro- 
 cedure reduces the number of subjects, and since, 
 moreover, the same subject is tested less often — 
 under some circumstances but once in a day — there 
 is too much play given to the individual factor. And, 
 
22 MENTAL FATIGUE 
 
 at the same time, the chance of discovering this 
 factor, of making allowance for it in the determina- 
 tion of averages or of basing conclusions on these 
 averages is diminished or entirely lost. This is a 
 disadvantage of this form of procedure which, to 
 me, seems to more than outweigh the advantage that 
 accrues from the absolute standard of measurement 
 that it affords, unless the number of subjects or the 
 number of experiments be sufficiently large to permit 
 a change of the order of the groups, and unless the 
 preliminary tests of mental peculiarities on which 
 the distribution into groups is based be very precise. 
 
 The test methods rest at bottom upon two, or more 
 often, upon three assumptions, the justification for 
 which is, in the single case, usually probable, though 
 not capable of absolute proof. The first assumption 
 is that the work done really represents, both in quan- 
 tity and in quality, the work that can be done under 
 the conditions that prevail — that the work, in other 
 words, is a real test of capacity. 
 
 The second assumption — one that is commonly, 
 though not always made, and whose problematic na- 
 ture is usually well recognized — is that the test of 
 efficiency for the given type of work informs one also 
 of the efficiency for other, particularly for related, 
 types of work. 
 
 The third assumption is that the decrease of effi- 
 ciency during the course of the work is essentially a 
 fatigue phenomenon — an assumption that is indeed, 
 in most cases, both very obvious and very probable. 
 
THE PHYSIOLOGICAL METHODS 
 
 The dynamometer. The decrease of muscular 
 force, more exactly, of "the work that can be done 
 by the muscle under voluntary contraction ' ' (Eulen- 
 berg, 601), is a purely physiological symptom not 
 only of bodily, but also of mental fatigue, as we have 
 already shown. J. Loeb (1886) seems to have been 
 the first to investigate "muscular activity as a meas- 
 ure of mental activity." Soon afterwards (1890) 
 A. Mosso published his studies, "Ueber die Gesetze 
 der Ermudung ["On the Laws of Fatigue"], and 
 his well-known book, "La Fatica" (1891), translated 
 into German in 1892 [and into English, " Fatigue,' ' 
 1904] . Up to that time the Collin dynamometer had 
 been used for measuring muscular strength. This 
 instrument consists of a steel oval, which, when 
 gripped with the hand, indicates by a pointer the 
 pressure in kilograms exerted by the hand. Ul- 
 mann's dynamometer is another form that can be 
 used either for measuring pressure or traction. 
 
 These measurements that are secured by the use 
 of dynamometers possess, however, little accuracy, 
 in especial because the subjects are by no means apt 
 to exert in an equal degree all the muscles concerned, 
 so that when fatigue arises they may easily shift the 
 groups of muscles and introduce into the later meas- 
 urements groups of muscles that had relatively little 
 
 23 
 
24 MENTAL FATIGUE 
 
 share in the initial measurements. These and other 
 objections have been emphasized by Hirschlafr (192) : 
 GinefT (39) and Claparede (200 ff.) have, however, 
 expressed a more favorable opinion of the dynamo- 
 metric method, while Claviere ( Annee psychologique, 
 VII, 1901) and Schuyten have employed it for meas- 
 uring fatigue.* 
 
 The ergograph. Having these difficulties in mind, 
 Mosso constructed, on the plan of Helmholtz's myo- 
 graph, a new instrument, known as the ergograph, 
 and this piece has since been markedly improved by 
 later investigators, e. g., by Kemsies, Vaschide, 
 Kraepelin, and others. 
 
 In the ergograph, the forearm and hand, together 
 with the fingers, are firmly fixed in such a manner 
 that the hand is extended, palm uppermost, and with 
 only a single finger, usually the middle finger, left 
 free. The flexion of this finger lifts a weight that 
 is suspended by a cord, and the several lifts are in- 
 scribed accurately upon a rotating drum, producing 
 a record termed an ergogram. The number of lifts 
 that the subject can compass in a given period, and 
 also the sum-total of the heights of the several lifts — 
 for the automatic registration of which provision is 
 made upon the best forms of the instrument — are 
 taken as the measure of fatigue. The Belgian in- 
 vestigator, Mile. Joteyko, has contributed particu- 
 larly to the mathematical treatment and interpreta- 
 tion of the constituent factors of the ergographic 
 
 *The reader will find a fuller discussion of the dynamometric 
 method and its results in the translator's Manual of Mental and 
 Physical Tests, Warwick & York, Baltimore, 1910. Methods of con- 
 ducting most of the tests of fatigue hereinafter mentioned may be 
 found in the same volume. 
 
THE PHYSIOLOGICAL METHODS 25 
 
 curve (see her Lois de I'ergographie). Philippe 
 (Claviere, 204), made use of the ergometer, a sort 
 of non-registering ergograph, in the use of which 
 the experimenter himself must count the number of 
 lifts. 
 
 It is, of course, always presupposed in this type of 
 measurement that the subject of the test is firmly 
 resolved to continue flexing his finger or gripping 
 the dynamometer as long as he can possibly do so — 
 a presupposition that is not susceptible of objective 
 verification. 
 
 Furthermore, it is essential that the fastening of 
 the arm and hand and the nature of the connection 
 between the finger and the weight shall be absolutely 
 constant in every test — a requirement that is obvious 
 enough, but more easily stated than secured (Gineff, 
 47 if.). 
 
 But, even if the assumptions be actually realized, 
 the ergographs, even the improved patterns, do not 
 afford the reliable results that had been expected of 
 them. To be sure, the fact that the number of muscles 
 put into play in the use of the instrument is consid- 
 erably greater than the champions of the method 
 suppose does not constitute a prohibitive defect, pro- 
 vided only that these muscles are always the same. 
 But that is precisely the difficulty. It is true to a cer- 
 tain extent of all ergographs — as A. Hoch and E. 
 Kraepelin (Psychol. Arbeiten, I, 380 ff.) and E. Miil- 
 ler (Philos. Studien, XVII, 65 ff., 13 f.) showed defin- 
 itely for Mosso's instrument, and as Hirschlaff simi- 
 larly showed for the dynamometer — that, as fatigue 
 develops, the contractions radiate, until they finally 
 involve the musculature of the shoulder blade, so that 
 
26 MENTAL FATIGUE 
 
 the presupposition of permanent isolation of a few 
 muscles or permanent restriction of the muscular ac- 
 tivity to a single controllable group of muscles can- 
 not be attained.* And, what is more, the funda- 
 mental presupposition itself is not well enough estab- 
 lished. The decrease of bodily efficiency is, indeed, a 
 frequently-observed symptom of fatigue induced by 
 mental labor, yet, if we leave out of consideration 
 fatigue of an excessive degree with its consequences, 
 it is not an absolutely uniform symptom, so far at 
 least as experiment has, up to now, been able to de- 
 termine. Not infrequently persons are found whose 
 middle finger, to speak with a little exaggeration, 
 cannot be completely fatigued at all by such move- 
 ments as the ergograph demands, and this is equally 
 true, even after mental work (Gineff, 10 f., 49 f.). 
 And, even if we disregard exceptions of this sort, 
 and have in mind only those persons — and they form 
 the great majority — who are fatigued in body by 
 mental work, even so there exists no clear and re- 
 liable correspondence between the reduction of bod- 
 ily efficiency as measured by the ergograph and the 
 reduction of mental efficiency. Kraepelin (Psychol. 
 Arbeiten, I, 415, and Ueber die Messung, etc., 217) 
 found that his subject performed more work on the 
 ergograph from an hour to an hour and a half after 
 the principal meal — i. e., at a time notoriously unfav- 
 orable for mental work — than he did in the morn- 
 ing, and that he did best of all about 9 o'clock, after 
 his supper. With children Schuyten (On V6or-en- 
 
 *However, this objection has been almost, if not quite, completely 
 met in the elaborate instrument devised by Bergstrom (American 
 Journal of Psychology, XIV, 1903, 510-540).— Translator. 
 
THE PHYSIOLOGICAL METHODS 27 
 
 Namiddags, 184) found by means of the dynamom- 
 eter that their muscular strength was greater in the 
 afternoon than in the forenoon.* Further, neither 
 Kraepelin's pupil, T. L. Bolton (Psychol. Arbeiten, 
 IV, 200, 219, 232) nor Gineff (51 ff.) was able 
 to establish any definite relation between the 
 duration of mental work and the values ob- 
 tained from the ergograph. In fact, Bolton 
 noted one person whose ergogram was not re- 
 duced, but increased, by two hours of mental work. 
 In the same way, R. Keller of Winterthur (Zeits. f. 
 Sch. Hyg., X, 404 f.) found on one occasion a 50 per 
 cent, increase of muscular efficiency after two hours 
 and a half of forenoon instruction. In accord with 
 these instances are the observations of Oseretzkow- 
 sky (Psychol. Arbeiten, III, 612), who reported a 
 marked increase of muscular efficiency after severe 
 work in memorizing, and, indeed, similar observa- 
 tions were in some cases made by Mosso (287). 
 
 Finally, the will, and, still more, the feelings and 
 moods, may either reduce or increase the ergographic 
 performance — a well-known experience that has been 
 subjected to careful study by Fere (Travail et 
 plaisir) and by Meumann (II, 97 fT.). 
 
 Hence the method of measuring fatigue by the 
 ergograph, even if it should prove to be adapted for 
 exact measurement of bodily efficiency, has turned 
 out not to be sufficiently reliable for the measurement 
 of mental fatigue, at least not sufficiently reliable for 
 general use, though perhaps with some persons and 
 
 *A contrary result has, however, been reported in Smedley's 
 investigation made upon public-school children at Chicago; see 
 rny Manual of Mental and Physical Tests, p. 96. — Translator. 
 
28 MENTAL FATIGUE 
 
 in some degree the correspondence that is assumed 
 may obtain. 
 
 Measurement of fatigue by the respiration and by 
 the pulse. Still less feasible are other very fluctuat- 
 ing physiological symptoms that are affected by 
 many influences difficult of control, for example, to 
 name the most prominent, the retardation and dimi- 
 nution of the pulse and the shallowing of respiration 
 that frequently ensue upon mental work. Binet and 
 Henri (33 if.) have reported in some detail upon 
 these methods of measuring fatigue. Under some 
 circumstances, one can, to be sure, infer the presence 
 of mental fatigue from the presence of these phe- 
 nomena, but yet one does not always find them when 
 fatigue is present, and even if they are to be thought 
 of as symptoms of fatigue, still it is impossible to 
 argue from their magnitude to the magnitude of the 
 fatigue, since it is impossible to demonstrate any 
 proportionality between the two. 
 
 Beating time. Closely related to the ergographic 
 method is the method of beating time. This method, 
 which has been recommended by W. Stern (Biff. 
 Psych., 117 f., 122 fT.), has been much used by M. 
 Lobsien and W. A. Lay (especially 406 ff.) and has 
 found particular favor in America (Gilbert, Wells) 
 in tests of groups under the name, "the tapping 
 test."* 
 
 This method, like the preceding, tests efficiency by 
 resort to a physical process, which, like every bodily 
 activity, is naturally influenced by mental factors. 
 
 ♦The tapping test of Gilbert and Wells, however, is not identical 
 with the test of beating time here described, since in tapping the 
 subject is instructed to tap continuously at his maximal rate. See 
 reference, footnote, p. 24. — Translator. 
 
THE PHYSIOLOGICAL METHODS 29 
 
 The subjects are asked to beat time upon a tele- 
 graph key, following some assigned rhythm, e. g., a 
 three-beat measure, at whatever rate best suits them. 
 These movements are registered automatically upon 
 a rotating drum (kymograph). The number and the 
 rate of the movements are then used to measure the 
 amount of psychophysical energy. For every person 
 has his own rate — a natural individual rate of flow 
 of his psychical life (Stern, 115, and Meumann, II, 
 117). The slower the tapping is done in comparison 
 with this normal rate, the greater, so the inference 
 runs, is the fatigue. Here, again, it is true that men- 
 tal fatigue is not seldom accompanied by retardation 
 of other activities — in this instance, of the tapping. 
 But there is as little uniformity and certainty in the 
 relation of this decrease of rate to increase of fatigue 
 as there is between muscular efficiency and mental 
 fatigue, or between the spatial limen and mental 
 fatigue. Interest and will, mood, and so forth, play 
 a part, and, in addition, the rhythmic tapping itself 
 very often develops a condition of excitement that 
 for the time being can completely cancel the effects 
 of fatigue (Meumann, II, 101). 
 
 What is really measured in this test is only the 
 speed of beating time — an action that is primarily 
 physical in character — and, indirectly, through it the 
 physical energy of the subject. This energy is natur- 
 ally augmented during the period following meals. 
 Thus one critic of the method, E. Meumann (II, 117, 
 136), found that the rate of beating time was acceler- 
 ated after the mid-day meal, just as Kraepelin had 
 demonstrated an increase in ergographic perform- 
 ance after meals. 
 
30 MENTAL FATIGUE 
 
 Measurement of fatigue by means of the range of 
 accommodation of the eye. A. Baur, a training- 
 school physician of Gmiind, Swabia, has made use of 
 a new method of measuring mental or bodily fatigue 
 in terms of muscular efficiency. By means of Schem- 
 er 's experiment, he observed the very sensitive 
 muscle of accommodation, and found that the range 
 of accommodation, i. e., the distance between the far- 
 point and the near-point, is increased in conditions of 
 fatigue and exhaustion. Nevertheless, his investi- 
 gations have not yet been carried far enough to per- 
 mit the recognition of such a definite parallelism be- 
 tween increase of fatigue and increase of the range 
 of accommodation as must be demanded for exact 
 measurements of fatigue. We must await further 
 comparative investigations to gain insight on this 
 point.* 
 
 So far as the other physiological methods are con- 
 cerned, this insight, as we have seen, has already 
 been attained, and it has demonstrated that, despite 
 the many valuable suggestions that these methods 
 have afforded, they are so unreliable that, for the 
 present, they can be disregarded in our search for 
 exact measurements of mental fatigue. 
 
 * Since this was written, Baur has reported further results that 
 disclose, seemingly, a very close relation between the range of 
 accommodation and the condition of the central nervous system. 
 See Intern. Mag. of School Hygiene, VII, January, 1911, 52-92. — 
 Translator. 
 
THE PSYCHOLOGICAL METHODS 
 
 Methods of test-work. A better case may be made 
 out for the psychological methods. In the first group 
 of them the subject carries out some form of mental 
 work as a test of his efficiency (test-methods). Some 
 of these methods can be undertaken with very simple 
 and very short tests of efficiency. 
 
 Esthesiometry. In this category belongs the de- 
 termination of the degree of fatigue by the measure- 
 ment of cutaneous sensitivity. The discrimination 
 of two points, which forms the essential feature of 
 the measurement, is a mental, not a physical pro- 
 cess, as H. Griesbach in his later articles (Inter. 
 Archiv., 1, 1905) has attempted, in opposition to Hel- 
 ler (Wien. Med. Presse, 1899) and others, to main- 
 tain. And it is a mental magnitude — whether we 
 call it attention, as Griesbach himself originally 
 thought (Energetik, 8, 87), or whether we name it 
 mental energy, that is, the possibility that physical 
 processes appear in consciousness (Lipps, 60 ff. ; 
 OrTner, 44) — that is measured in this act of discrimi- 
 nation. It is, of course, true, as Motchoulsky espe- 
 cially emphasizes, that physical factors in the nerves 
 of the skin are also operative. But so, also, are 
 physical factors operative in the discrimination of 
 colors, of pitches, of tone intensities, in the estima- 
 tion of weights, of lengths, etc. In what mental pro- 
 
 31 
 
32 MENTAL FATIGUE 
 
 cess are they not, as a matter of fact, concerned? 
 But no one would think of calling such psychophysi- 
 cal investigations physiological, even though they 
 were first attacked by physiologists. 
 
 So, too, in this case, it was a physiologist, E. H. 
 Weber of Gottingen, who discovered long ago (1834) 
 that the shortest distance at which the contact of two 
 points is still felt as separate, i. e., as the contact of 
 two cutaneous points, that the spatial linien, as the 
 distance was named by Fechner,* varies at different 
 regions of the body, and on different persons in the 
 same region. The relative values of the spatial limen 
 for different regions are, however, approximately 
 constant for all persons. 
 
 Now, these liminal values are increased by physical 
 work. Griesbach (Energetik, 1895) appears to have 
 been the first to observe that, in a given individual, 
 the limen is also increased by strenuous mental work. 
 He found — and Eulenberg soon after confirmed the 
 observation on himself (Hyg. Rundschau, VIII, 600) 
 — that two closely approximated blunt compass 
 points applied gently to the skin at the same moment 
 are, as a rule, after fatiguing work, perceived as one 
 point, whereas they had been still perceived as two 
 before the work was begun. In general, the increase 
 of fatigue goes hand in hand with the increase of the 
 spatial limen, save that, under conditions of exces- 
 sive fatigue, combined with mental depression and 
 feelings of discomfort, there appears, for reasons as 
 
 *0. Ktilpe (Grundriss d. Psych., 38 f., 350 fie. [see English trans- 
 lation, Outlines of Psychology, pp. 36 f. and 337 ff.] ) and others have 
 shown that this determination does not afford a liminal value in 
 the strict sense of modern psychophysics. 
 
THE PSYCHOLOGICAL. METHODS 33 
 
 yet unexplained, a considerable diminution of the 
 spatial limen. These compasses and like instru- 
 ments, such as Eulenberg, Ziehen, Spearman, Eb- 
 binghaus, Binet, Abelson [Jastrow, Titchener] and 
 others have contrived for the same purpose, are 
 called esthesiometers, and, accordingly, the spatial 
 limen or the compass-point method is also termed the 
 esthesiometric method. 
 
 Griesbach's subjects were pupils in the Gymna- 
 sium and the Oberrealschule* (technical high school) 
 at Miihlhausen, as well as teachers in training, and, 
 in his later tests, teachers, soldiers and other adults 
 as well. He secured his measurements from several 
 regions of the body, e. g., the forehead, the cheek- 
 bone, the tip of the nose, the mucous membrane of 
 the lower lip, the ball of the right thumb and the tip 
 of the right forefinger. As he found that, in general, 
 the sensitivity of these regions varied in like manner, 
 he finally confined himself to the testing of a few re- 
 gions — at times, indeed, to a single region, particu- 
 larly to the cheek-bone, as being the most sensitive 
 place.t 
 
 Nevertheless, this correspondence of the different 
 regions held true only in a general way, as is shown 
 especially by the comparison of measurements taken 
 on symmetrical zones of the two halves of the body, 
 and these, too, are neither structurally nor func- 
 tionally absolutely alike. After more abstract ac- 
 
 *On the technical terms descriptive of the German school sys- 
 tem, consult Appendix II. — Translator. 
 
 f Schuyten of Antwerp prefers to test that part of the cheek that 
 lies vertically under the outer angle of the eye at the level of the 
 tip of the nose, and, with good reason, recommends that measure- 
 ments be taken on both sides of the face. 
 
34 MENTAL FATIGUE 
 
 tivities, e. g., after grammatical exercises, memoriz- 
 ing, arithmetic, and a great part of mathematics, as, 
 in general, after mental activity, it may be observed 
 that, with right-handed persons, the measurements 
 of the right side of the body — which, as is well known, 
 has its centers in the left half of the brain (that 
 hemisphere that is used in mental work, especially 
 when thinking in, and by means of, words) — have 
 yielded higher liminal values, even though the values 
 were identical for the two sides before the activity. 
 After activity that is predominatingly physical, on 
 the contrary, the liminal values are apt to be higher 
 on the left side. Finally, in the case of bodily activity 
 under concentrated attention, these liminal values 
 often differ but little from one another. With left- 
 handed persons all this, as a rule, is reversed. 
 
 Griesbach's method found many adherents. Thus, 
 his procedure was followed by E. Keller upon pupils 
 in the Gymnasium and industrial school at Winter- 
 thur ; by Th. Vannod upon pupils of a Bernese inter- 
 mediate school ; by L. Wagner in the Gymnasium at 
 Darmstadt; by B. Blazek in a Real gymnasium at 
 Lemberg ; by Th. Heller upon feeble-minded children 
 at Vienna, and by E. Schlesinger. These investiga- 
 tions led to results in the main accordant with those 
 of Griesbach. More recently Bonoff, a school phy- 
 sician at Sofia, has worked with this method upon 
 scholars of the Gymnasium, and Prof. P. M. Noikow 
 of Sofia upon teachers and candidates for teaching, 
 not to mention others, like Ferrari in Italy, Sakaki 
 in Japan, Ley, Schuyten and Michotte in Belgium. 
 A. Binet and J. Joteyko have also used and com- 
 mended the method. (Cf. also Griesbach, Int. Arch. 
 
THE PSYCHOLOGICAL METHODS 35 
 
 Schulhyg., I, 1905, and Verh. d. IX Jahresver., 233.) 
 And, last of all, there has appeared another success- 
 ful champion of Griesbach's method in the person of 
 W. R. Abelson, who has carried out very painstaking 
 and extensive experiments upon pupils at Rennes 
 and at London. The proof of a certain degree of 
 correlation between the esthesiometric records and 
 actual observation in the schoolroom has developed 
 confidence for the method, and has attracted a good 
 deal of attention. 
 
 On the other hand, the Griesbach method has been 
 sharply criticized by the Kraepelin school. In the 
 first place, Kraepelin (Ueber die Messung, etc.), and 
 especially Th. Bolton (Psychol. Arbeiten, IV), on the 
 basis of extensive laboratory tests that Bolton con- 
 ducted with an improved esthesiometer — though, to 
 be sure, upon a single observer — made it evident that 
 the procedure advised and adopted by Griesbach and 
 his adherents, when carried out in the hasty way that 
 they had followed, was quite inadequate for an exact 
 determination of the spatial limen, simply on ac- 
 count of the difficulty of applying the two points with 
 absolute simultaneity, and with the same pressure in 
 successive trials ; that, on the contrary, an absolutely 
 reliable determination of the spatial limen is such an 
 elaborate undertaking that the method cannot be 
 recommended for group tests. Secondly, and this is 
 a more weighty objection, Bolton insists (196 fT.) that 
 there exists no definite relation between degree of 
 fatigue and magnitude of the spatial limen, although 
 it is not unlikely, but ofttimes quite evident, that men- 
 tal fatigue does have some effect upon the limen. As 
 as matter of fact, discriminative sensitivity is often 
 
36 MENTAL FATIGUE 
 
 increased by emotional excitement, just as it is in the 
 condition of hyperesthesia that follows excessive 
 fatigue. "The experimental errors and the varia- 
 tions of the spatial limen set up by other causes are 
 so great that, despite weeks of the most painstaking 
 work with a subject trained in physiological experi- 
 mentation, we have not been able to determine defi- 
 nitely the effect of fatigue upon the limen. ' ' Similar 
 negative conclusions have been reached by other in- 
 vestigators, e. g., by J. H. Leuba (Psych. Rev., VI), 
 who worked with adults of both sexes, and with col- 
 lege students, and who was especially careful to 
 guard against disturbing conditions (thickness of the 
 skin, blood supply, skin temperature, general physi- 
 cal condition and the like), and by Prof. C. Eitter of 
 Ellwangen (Zeits., XXIV), who undertook fatigue 
 measurements upon Gymnasial students; by J. B. 
 Germann, who employed but a single observer, and 
 also by Gineff (15 ff.) and by Meumann (II, 91 if.). 
 
 Nevertheless, it cannot be denied that the measure- 
 ments of the decrease and increase of what we term 
 the spatial limen, as secured with this method by 
 Griesbach and many others after him, do show a de- 
 gree of accordance that cannot be entirely attributed 
 to bias, to autosuggestion on the part of the experi- 
 menter, or to that suggestion of the observer to which 
 Tawney in particular (Philos. Studien, XIII) calls 
 attention, even if this source of disturbance has been 
 present in every instance. Again, the inaccuracy of 
 procedure, for which Griesbach has been criticized, 
 could at the most result merely in concealing, or in 
 making less evident, the correspondence between the 
 degree of fatigue and the spatial limen, provided such 
 
THE PSYCHOLOGICAL METHODS 37 
 
 a correspondence were actually present ; it could not 
 have produced in so many instances an illusory ap- 
 pearance of a correspondence if no such thing existed 
 at all. It must be added that the method of Bolton and 
 others, as Griesbach shows in his later investigations 
 (Int. Arch. f. Schulhyg., I), is by no means free from 
 criticism, and that the results in many instances are 
 susceptible of another interpretation than that given 
 them by Bolton. Moreover, the coincidence, to which 
 we have referred, between the esthesiometric meas- 
 urements and common observation, especially in the 
 schoolroom, speaks for their utility as a measure of 
 fatigue, more correctly as a method of measurement 
 for one of the symptoms of fatigue. 
 
 And so it seems as if with this method we may, 
 after all, come very considerably nearer to mental 
 fatigue than with the ergographic or any other 
 method that is based upon physiological symptoms ; 
 and this will be so much the more the case when we 
 have succeeded in attaining technically satisfactory 
 measurements — e.#.,in especial, absolute simultaneity 
 of application of the compass-points, absolute equal- 
 ity of pressure in all applications (the more compli- 
 cated instruments already make this possible), and 
 equality of temperature of the instrument and of the 
 skin — and when we have also succeeded in avoiding 
 suggestion (which may affect the experimenter as 
 well as the subject) and in eliminating what is known 
 as the "paradoxical error," i. e., the perception of 
 two points when but one is applied.* 
 
 And when comparison is made of the values ob- 
 tained in different regions of the body of the same 
 
 *See Gineff (15ff.). 
 
38 MENTAL FATIGUE 
 
 person, it must be remembered that the richness of 
 the nerve-endings in the different organs varies, as 
 does also the thickness of the skin; and again, that 
 one organ or one region of the body may be more 
 practiced for this kind of discrimination than other 
 organs or regions. 
 
 Finally, when comparison is made of the esthesio- 
 metric values of the same regions of the body in dif- 
 ferent persons, it must be remembered that, in this 
 case, too, the thickness of the skin, the degree of 
 practice of the person in general, as well as of the 
 organ in question, condition individual differences, 
 and that, furthermore, age, sex, ability to observe, 
 sensory type, capacity for concentration, the general 
 level of mental development, as well as external 
 social relations (Vannod), all may be responsible for 
 individual differences that must be taken into account 
 before greater or lesser degree of fatigue, and thus 
 of the f atiguability of the several individuals, can be 
 determined in comparison one with another. All 
 these values have, however, so far only an individual 
 or relative value. 
 
 Measurements of fatigue by means of other liminal 
 values. The difficulties that appear in this determi- 
 nation of the spatial limen in consequence of the 
 variation in anatomical conditions in the same indi- 
 vidual do not appear in the determination of other 
 liminal values. 
 
 Meumann (II, 92) and Gineff (17) have, therefore, 
 good warrant for asserting that we might just as 
 well, and even better, use as an index of fatigue any 
 other limen, i. e., that we might measure fatigue in 
 terms of the magnitude (which varies with the degree 
 
THE PSYCHOLOGICAL METHODS 39 
 
 of mental freshness) of any other stimulus that is 
 just perceptible, and that just arouses a sensory ex- 
 perience, or the similarly varying magnitude of the 
 difference between any two stimuli that arouses two 
 just noticeably different sensory experiences, e. g., 
 the limen for weak auditory or for weak pressure 
 stimuli. This assertion, indeed, seems to be con- 
 firmed by Baur's experiments (Das kranke Schul- 
 kind, 175, note), for he found that the distance at 
 which a watch must be placed in order that its tick- 
 ing might still just be heard decreased as fatigue in- 
 creased ; similarly, he found symptoms of fatigue in 
 the pupillary reflex, in the decreasing size of the field 
 of vision and in certain variations in the recognition 
 of colors, although these symptoms have not as yet 
 been subjected to systematic study. 
 
 The kinematometer method. Nor have we as yet 
 any thorough examination of what may be termed 
 the kinematometer method. The kinematometer, or 
 movement measurer, is an instrument constructed 
 by G. W. Storring that indicates in angular degrees 
 the magnitude of the movement of a member that is 
 fastened in it. Meumann (II, 94) has worked with it, 
 but his pupil, D. Gineff, gives (63 if.) a more detailed 
 account of the method. Gineff caused his subject, 
 whose eyes were blindfolded, to execute for an hour 
 or two a given form of movement, e. g., a swing of 
 the forearm over a horizontal baseboard, with the 
 elbow as a fixed point of rotation. The extent of this 
 movement, which was known as the normal move- 
 ment, was regulated by two fixed terminal points or 
 stops. Then he removed one of these stops, and 
 directed the subject to make the movements that 
 
40 MENTAL FATIGUE 
 
 followed, the comparison movements, equal to the 
 first or normal movement, as judged by the sensa- 
 tions set up by the movement, i. e., to make the move- 
 ments of such an extent that no difference could be 
 detected between the 'feel' set up by it and the 
 'feel' set up by the normal movement. The more 
 delicate the differential sensitivity for sensations of 
 movement, the closer will the comparison move- 
 ments approximate to the normal movement, or the 
 smaller will be the error of estimation. In a fatigued 
 condition, larger errors are made, i. e., the compari- 
 son movements then exhibit greater deviations from 
 the normal movement than in a fresh condition, be- 
 cause the differential sensitivity (sensible discrimi- 
 nation) for sensations of movement suffers from 
 fatigue, just as we saw it to be affected in the case 
 of other sensory experiences. In this instance, the 
 error introduced by fatigue is not distributed evenly 
 to either side of the normal movement, but there is a 
 strong tendency to make the comparison movement 
 shorter than the normal movement, or, in other 
 words, to overestimate the former. The reason lies 
 in this, that, in fatigue and exhaustion, as we all 
 know, every movement is difficult and slow of execu- 
 tion ; small movements are accompanied by a feeling 
 of tension or activity (feeling of exertion of will) as 
 intense as that that accompanies larger movements 
 made in fresh condition. This feeling of effort, how- 
 ever, serves us as a secondary criterion of the magni- 
 tude of any movement that we make. Only occa- 
 sionally do the comparison movements show a tend- 
 ency to be much longer, viz., when the subject be- 
 comes cognizant of, and therefore strives to counter- 
 
THE PSYCHOLOGICAL METHODS 41 
 
 act, that first natural tendency to make the compari- 
 son movement shorter. 
 
 On the basis of his experiments (unfortunately 
 limited to a single subject), Gineff has reached the 
 conviction that this kinematometer method is more 
 reliable than the ergographic method. That his ex- 
 pectation will be confirmed is not improbable ; in any 
 case, the method is certainly simpler, and hence more 
 easily applied in individual school tests, than is the 
 ergographic method. 
 
 Method of time estimates. The estimation of time 
 has been applied to the measurement of fatigue by 
 M. Lobsien at Kiel {Ermudung u. Zeitschatzung). 
 A duration of one minute was filled by rapid metro- 
 nome beats. The subjects (10-year-old pupils of a 
 Kiel common school) had directly afterward to re- 
 cord their estimate of the length of this time. The 
 average estimation, as computed from the total of 
 the estimates, increased with some fluctuations from 
 the beginning of the first hour, when it averaged 2.43 
 miuutes, to the last hour, when it reached 4.03 
 minutes. In view, however, of the notorious unre- 
 liability of children and of many adults in estimating 
 time intervals, the estimation thus demanded on the 
 basis of a single presentation of the object to be 
 estimated seems to afford a very unreliable measure 
 of fatigue ; in any case, further and more extensive 
 tests must be carried out, and upon adults as well as 
 upon children. 
 
 The algesiometer method. The increase of sen- 
 sitivity to pain, or the magnitude of the pressure that 
 is necessary to arouse a sensation of pain (not a feel- 
 ing of unpleasantness) at a given point, has also 
 
42 MENTAL FATIGUE 
 
 been taken by Vannod {Fatigue Intel.) as a meas- 
 ure of fatigue. A prick-like pressure is applied to 
 the skin by means of an ' algesiometer, ' which is an 
 instrument closely similar to von Frey's hair esthesi- 
 ometer, and which consists essentially of a fine point 
 and a scale that indicates the pressure of the hand 
 upon the point, and consequently of the point upon 
 the skin. In his experiments, Vannod found that at 8 
 o'clock, before instruction began, a pressure of 45 
 grams set up a pain sensation, whereas at 10 o 'clock, 
 39 grams, and at noon only 29 grams sufficed. Swift 
 has carried on similar tests in American schools, and 
 Vaschide has confirmed Vannod 's report. Binet 
 (Annee psychologiqtie, XI), however, reached di- 
 rectly the opposite result, viz., that fatigue decreases, 
 not increases, pain sensitivity (Cf. Claparede, 199 f., 
 and Meumann, II, 109). 
 
 It must be repeated that in all these cases, with the 
 exception of these last — as to the real nature of 
 which we have as yet insufficient knowledge — what is 
 measured is not so much mental fatigue itself, as 
 rather a mental activity that is essentially condi- 
 tioned by the degree of attention that is given to it. 
 We are dealing, then, with a measurement of atten- 
 tion, the reduction of which we regard as the result 
 of the work that has been performed. But it is evi- 
 dent that the measure of the attention applied to a 
 given piece of work, or of the mental energy dis- 
 played in it, is conditioned not only by the amount 
 of mental energy available at the time, but also by 
 other factors, such as feelings, moods, general dis- 
 position, inclination, and the like. However, these 
 supplementary factors are not subject to regular 
 
THE PSYCHOLOGICAL METHODS 43 
 
 daily or weekly variations corresponding with the 
 amount of work done at the time, but are quite vari- 
 able in their appearance, so that, as investigations 
 increase in number, they assuredly tend to be elimi- 
 nated. The fund of mental energy, on the other 
 hand, is the most important factor that conditions 
 attention and psychical activity in general, so that 
 any reduction in it during or after a period of work 
 becomes very clearly and very uniformly evident. 
 On this fact rests the applicability of discriminative 
 sensitivity to the measurement of fatigue. 
 
 The measurement of fatigue by the measurement 
 of the duration of mental processes. We have already 
 made reference to the fact that the duration of men- 
 tal processes is affected by fatigue. The principle 
 has been turned to account experimentally by Keller. 
 In studying the development of fatigue during 
 lengthy gymnastic exercises, he had his pupils read 
 words at a fast rate, and found that the average time 
 of reading was increased by 13 per cent, for words 
 and by 16 per cent, for syllables, in comparison with 
 the average time in a fresh condition : even when the 
 same words or syllables were used, the time was in- 
 creased by 10 and by 9 per cent., respectively. In a 
 similar manner, Lobsien (Unt. u. Erm.) sought to de- 
 tect fatigue by the rate of reading and the number of 
 errors committed. 
 
 Following the demonstration by Axel Oehrn (Psy- 
 chol. Arbeit en, I) that speed of mental activities is 
 reduced by fatigue, S. Bettmann (Psychol. Arbeiten, 
 I) employed the more refined methods of the labora- 
 tory to determine the time necessary to react to a 
 presented impression or stimulus with one of two 
 
44 MENTAL FATIGUE 
 
 very simple movements, in accordance with a pre- 
 arranged combination of stimulus and movement — 
 in other words, to measure the time of the simplest 
 'choice reaction.' He found that this time was 
 longer when the subject was fatigued, and that this 
 retardation was more evident after mental, than 
 after bodily fatigue. Although Bettmann has called 
 special attention to the sensitivity of this method, it 
 does not seem, up to now, to have been employed fur- 
 ther for the determination and measurement of 
 fatigue, so that we cannot say at present whether or 
 to what extent it is feasible for more exact measure- 
 ments. In any event, the fact that, in the determina- 
 tion of fatigue by means of computation and other 
 similar tests, the speed of work increases at first, and 
 often continues to increase, though the quality is re- 
 duced, should warn us to be quite cautious in general- 
 izing about the relation between the speed of mental 
 activities and fatigue. 
 
 The method of test-problems in the narrower 
 sense. The discrimination of two points on the skin, 
 the perception of faint sensory stimuli, the compari- 
 son of the extent of two movements and similar pro- 
 cesses are all mental activities that are used to ascer- 
 tain how much of mental energy remains after some 
 other form of mental activity. The method of test- 
 problems in the narrower sense is based on the same 
 principle. In it, a test is introduced during or after 
 the mental activity that is creating fatigue. But this 
 test is now far less simple, less limited in its demands, 
 less dependent on physiological factors and more 
 akin to the fatiguing mental activity that it measures 
 than is the test of discriminative sensitivity, etc. The 
 
THE PSYCHOLOGICAL METHODS 45 
 
 test- work consists chiefly of such tests as taking dic- 
 tation, computing, counting letters, and other similar 
 activities which involve a series of mental processes 
 of a predominatingly intellectual character, like 
 those that constitute the higher mental processes in 
 general. 
 
 This method had its inception in the common ob- 
 servation that hard mental work renders us disin- 
 clined and unfit, at first for the kind of work we are 
 doing, then for similar work, and finally for any sort 
 of mental exertion. That is to say, we are in a state 
 of general fatigue. Nevertheless, we have reason 
 to suppose that this general reduction of mental effi- 
 ciency does not affect all phases of mental activity 
 equally, but rather in accordance with the degree of 
 similarity — that, in other words, the mind is the more 
 fatigued for a given form of new activity, the more 
 this new activity resembles the original fatigue-pro- 
 ducing activity.* 
 
 It follows that these tests of fatigue that prescribe 
 a form of work that is as similar as possible to the 
 fatigue-producing activity, particularly to school 
 work, really get at mental fatigue from more sides 
 than do such tests as esthesiometry and the like. 
 
 Still, they do not, by any means, get at it from all 
 sides, because a form of test that should be fully 
 equivalent to the activities involved in studying and 
 in school work generally would itself be so com- 
 plicated that it would be impossible to evaluate it ex- 
 actly, especially to determine and compute the errors, 
 and hence impossible to compare the different tests ; 
 
 ♦The disputed question of specific versus general fatigue must 
 be deferred for extended discussion in a subsequent section. 
 
46 MENTAL FATIGUE 
 
 moreover, it is impossible to devise absolutely equiva- 
 lent test-problems. Accordingly, if we want a form 
 of test that shall permit of ready quantitative treat- 
 ment, and that shall at the same time be exactly 
 equivalent to the fatiguing work, we must simplify 
 the fatiguing work, e. g., by the use of dictation, sim- 
 ple computation, and the like. By this plan, we secure 
 perfect comparability between the test-material and 
 the fatiguing work; on the other hand, we lose touch 
 with practical life, because the mental fatigue that 
 we wish to measure is commonly the result of a much 
 richer and more elaborate mental activity. 
 
 Schoolroom tests of fatigue seek a path between 
 these two extremes. The younger a class and the 
 simpler the mental work that is required of it, the 
 nearer can the test approximate to the fatiguing 
 school activity. But the more advanced the class and 
 the more manifold and complex the work that is done 
 by it, the less can the test be made to approximate to 
 this more elaborate fatiguing work. 
 
 The first investigator to employ considerable 
 amounts of work as test-materials for measuring 
 fatigue was the Eussian psychiatrist, J. Sikorski. 
 He had pupils write from dictation for a quarter of 
 an hour, both early in the day, before school work 
 began, and later in the afternoon, after school work 
 was over. He found 33 per cent, more errors in the 
 second exercise. It is understood, of course, that 
 here, as in other experiments of this kind, it is not a 
 question of errors that spring from lack of knowl- 
 edge, but only of errors that spring from slips of 
 attention. Naturally, Sikorski's method, like the 
 first trial of any such experiment, is susceptible of 
 
THE PSYCHOLOGICAL METHODS 47 
 
 improvement: it served, however, to break the 
 ground, and those who followed him, like Friedrich 
 at Wurzburg and Bellei at Bologna, have learned how 
 to avoid his difficulties. Yet there remains the great 
 difficulty of arranging material for dictation that 
 really presents uniform difficulty for the pupils, for 
 unity of the standard of measurement is a prime 
 necessity. 
 
 To circumvent this difficulty, H. Laser (Geist. 
 Erm.), following Burgerstein's example, selected 
 simple computation as a test-material. He had his 
 subjects, boys and girls of the middle classes of a 
 Konigsberg Biirgersckide, perform easy examples 
 in addition and multiplication for 10-minute periods 
 and as rapidly as possible. The periods he arranged 
 to fall at the opening of the morning session and at 
 the end of each one of the five following school hours. 
 He discovered a rapid increase in the total amount 
 of computation performed by the several classes dur- 
 ing the school session. This increase, however, is to 
 be explained as due, not to any augmentation of men- 
 tal energy toward the end of the session, but partly 
 to the development, during the work, of practice in 
 computing, and partly to the overcoming of the men- 
 tal inertia that prevailed at the outset. On the other 
 hand, the increasing fatigue of the classes found its 
 expression in the increase in the total number of 
 errors (except in the final period) and of corrections 
 (made by the pupils themselves), and in the decrease 
 in the number of pupils whose work was without 
 error. These results of Laser coincide substantially 
 with those obtained by Burgerstein by another form 
 of computation test, to which we shall refer later on. 
 
48 MENTAL FATIGUE 
 
 Ebbinghaus (Nene Methode, etc.) also used this 
 method, and obtained similar results. Computation 
 has been tried, likewise, by Richter, Friedrich, Kem- 
 sies, Dankwarth, Teljatnik and Bellei.* 
 
 The query may, however, be raised whether this 
 application of the computation test for 10 minutes 
 or longer is not unwise, for, as Ebbinghaus noted, 
 computation develops a considerable practice-effect 
 in a period of this length, and again, the computation 
 itself becomes a source of fatigue. Moreover, ennui, 
 with consequent carelessness and loss of interest, 
 brings it about that the quantity and quality of the 
 computation cannot be regarded as an unambiguous 
 expression of the fatigue induced by the school work 
 that has just preceded. But, by both shortening the 
 duration and increasing the difficulty of the computa- 
 tion exercises, it seems as if a measure of fatigue is 
 discovered for us here, though one that can be em- 
 ployed only along with others, because it involves 
 only a specific and limited form of mental activity. 
 
 What is called the memory method, as used by Eb- 
 binghaus (Neue Methode, etc.), and later on by the 
 Russian experimental psychologist, Netschajefr", by 
 Schuyten, and by others, seems to be less applicable 
 in the schoolroom. In Ebbinghaus' experiment, 
 series of one-syllabled digits (the numbers 1 to 12t), 
 arranged to supply two series each of 6, 7, 8, 9, and 
 10 places (i. e., 10 series in all) were read aloud, with 
 a single reading for each series, at the beginning and 
 at the end of a school period. The pupils, who in- 
 
 *For methods and results see also reference, p. 24, note (Cb. IX, 
 Test 35). — Translator. 
 
 fThe German term for eleven is monosyllabic. — Translator. 
 
THE PSYCHOLOGICAL METHODS 49 
 
 eluded Sexta to Untersekunda forms [ages 8 to 18] 
 of a Breslau Gymnasium and some classes of a higher 
 girls' school, were then asked to write down each 
 series as accurately as possible. Fatigue was to be 
 indicated by the number of errors. But, in almost 
 every case, the number of errors decreased toward 
 the end of the school session. Here, then, the effect of 
 fatigue was concealed by practice, by the confusion 
 incident to writing the digits, and perhaps also by the 
 method that Ebbinghaus chose for computing the 
 errors. And even if this method did afford a fairly 
 exact expression of fatigue, it would need, for the 
 same reasons as were cited for the computation 
 method, to be supplemented by some method that 
 would afford contact with other phases of mental 
 activity, since the retention of series of one and two- 
 place numbers is quite as limited and specific a form 
 of work as is long-continued adding and multiplying. 
 The same thing might be said, too, of tests of memory 
 for series of words, as employed by Eitter and Tel- 
 jatnik, and of memory for sentences, as employed by 
 Januschke. 
 
 What has been termed the 'completion method 9 
 was invented by Ebbinghaus (Neue Methode, etc.) 
 for the same purpose of testing fatigue. There were 
 laid before the pupils prose texts, as nearly as pos- 
 sible of the same difficulty, in which many of the 
 words were omitted entirely, and in which only por- 
 tions of others, e. g., some syllables or only the first 
 letters, were given, and the pupils were instructed to 
 fill out the gaps so as to make sense and with due re- 
 gard to the number of syllables demanded. Five 
 minutes were allowed. One text was taken from Net-* 
 
50 MENTAL FATIGUE 
 
 tlebeck's Description of the Siege of Colberg. A 
 single paragraph will suffice to illustrate the plan. 
 
 Wh. . Willy . . . two old, he red 
 
 farm-h th . yard . . front .... The dan 
 
 . . . were th. . . there ; so that lo 
 
 yellow instead of * The nature and number of 
 
 the errors and of the corrections were to be taken as 
 an index of fatigue. The result was not very clean- 
 cut: there appeared an increase in the quantity of 
 work done, i. e., in the number of elisions supplied, in 
 the upper classes, but a decrease in the lower classes. 
 Sexta and Quinta [9 to 11 years]. The quality of 
 work did, indeed, become poorer in all classes, al- 
 though the maximal number of errors was by no 
 means made in the last study period. The decline in 
 quality was also much more rapid in the lower than 
 in the higher classes. 
 
 The method is, of course, open to improvement. 
 Ebbinghaus is quite right, for instance, in conclud- 
 ing after his experiment that the time allowed for 
 supplying the elisions was too long. His experi- 
 ments, it must be remembered, were all preliminary 
 experiments, and, unfortunately, the test proper 
 that was to follow them was never carried out. 
 Moreover, despite Ebbinghaus' proposals (Neue 
 Methode, 47 f.), the most serious difficulty still re- 
 mains — that it is even less possible than in the case of 
 dictations to work out any very large number of 
 texts of equal difficulty, or to recognize and make due 
 allowance in computing results for either these un- 
 
 *This example, from the translator's Manual, p. 448, is substi- 
 tuted for the German text. Blank forms for conducting this test 
 may be purchased of C. H. Stoelting Company, 121 North Green 
 street, Chicago. 
 
THE PSYCHOLOGICAL METHODS 51 
 
 avoidable differences in the texts or for such differ- 
 ences as depend on the individuality of the pupils 
 tested.* These difficulties, coupled with certain of 
 those that have been cited in connection with the 
 methods previously discussed, will interfere with the 
 use of the Ebbinghaus method in extended school 
 tests. It has, moreover, been tried thus far only by 
 Bellei,f though it has the advantage over all other 
 methods of appealing to quite varied phases of men- 
 tal life, yet not, of course, to all phases. 
 
 A more difficult form of the completion method is 
 used by some French investigators. They give the 
 subject a number of words which are arranged to- 
 gether and written down as a whole in such a form 
 as to make sense. The method used by Emily Sharp,$ 
 in which as many sentences as possible are con- 
 structed from a limited number of words, is of similar 
 kind (Cf. Gaupp, 126). These methods have the evi- 
 dent advantage that they engage a considerable part 
 of the subject 's mentality, but they have also the de- 
 fect that they put at a disadvantage subjects of lesser 
 ability and of little practice, and that, furthermore, 
 even when merely inserted as tests, they are them- 
 selves extremely fatiguing. 
 
 When these objections are considered, the dicta- 
 tion and computation methods must, after all, be 
 
 *Cf. the criticisms of Lobsien, Pad. Psych., II, 365 f., and Binet, 
 316 ff. 
 
 fThis statement is not strictly accurate. Ebbinghaus' method 
 has been tried by Wiersma (1902), by Terman (1906), by Kriiger 
 and Spearman (1907), and with some modifications by Lipmann 
 and Wertheimer (1907), though only Wiersma was directly inter- 
 ested in testing fatigue by its use. — Translator. 
 
 $See American Journal of Psychology, X, 1899, 329-391; also 
 reference, footnote, p. 24 (Tests 46 and 47). 
 
52 MENTAL FATIGUE 
 
 given preference over the completion method, since 
 they are simple methods, but nevertheless have 
 fewer defects. Especially are they to be preferred 
 when their task is made somewhat more difficult, as 
 for example, the form of computation test employed 
 by Kemsies (Arbeitshygiene der Schule, 7), and by 
 Teljatnik, in which the computation is done wholly 
 mentally, and only the result written down. This 
 plan has the further advantage of reducing the physi- 
 cal work of writing, and thereby lessening the chance 
 of introducing some bodily fatigue in the computa- 
 tion itself. 
 
 Yet, the chance of inducing fatigue in this way 
 needs hardly to be considered when dealing with 
 maturer pupils, and especially with adults. With 
 such subjects, more difficult computations may be em- 
 ployed with success, as Winch has shown in the case 
 of evening school pupils, 15 to 27 years of age. 
 
 The advantage of easy administration and of a 
 certain breadth of activity — though not, of course, 
 of universality of appeal — attaches also to a method 
 used by Eitter (Zeits., XXIV, 424 fT.).* In this 
 (the cancellation method), specified letters or words 
 are to be crossed out or cancelled on a given printed 
 text as rapidly as possible. The assignment might 
 be, for example, to put a vertical mark through every 
 E and r and a horizontal mark through every form 
 of the definite article.t Only two minutes are allowed 
 
 ♦This method appears, however, to have originated in the work 
 of Bourdon (Revue philosophique, 1895). Hitter's article appeared 
 in 1900. For a more extended account of it see my Manual of Men- 
 tal and Physical Tests, pp. 254-270. — Translator. 
 
 fin German the article is declined, and hence appears in several 
 different forms. — Translator. 
 
THE PSYCHOLOGICAL METHODS 53 
 
 for one such test. The difficulty with this interesting 
 method lies in the selection of texts that shall afford, 
 for a full series of tests for a day, not to speak of a 
 week, an approximately equal distribution of the let- 
 ters or words to be cancelled.* The rapid develop- 
 ment of practice also tends oftentimes, at the begin- 
 ning, to conceal the effect of fatigue. 
 
 Still simpler is the copying method employed by 
 M. C. Schuyten, the conductor of the Pedological In- 
 stitute at Antwerp (Arch, de Psych., IV, and Paed. 
 Jaarb., VI, 160 ff.). The teacher writes on the black- 
 board a certain number of combinations of the letters 
 a, e, i, o, u, r, v, n. The pupils have five minutes in 
 which to copy them. The number of errors and [self- 
 made] corrections gives a measure of attention, and 
 hence of the mental efficiency prevailing at the time, 
 and the variation in this number at differ ent hours 
 of the day serves as a basis for estimating the course 
 of the fatigue developed by the day's work. 
 
 Perhaps the most suitable method, both because it 
 exacts activities that are neither too easy for the sub- 
 jects nor too difficult for evaluation by the experi- 
 menter, and because it entails manifold forms of men- 
 tal activity and so does not become monotonous and 
 irksome,t is the combined method by which Teljat- 
 nikj tested 25 Volhsschule girls, averaging 9 years of 
 age. 
 
 ♦Several plans for meeting this difficulty are now available. See 
 Manual, 256-7. — Translator. 
 
 fThe method, however, does take considerable time, some 20 
 minutes, when used for testing fatigue, and may thus itself become 
 a source of fatigue. 
 
 $See Teljatnik's report of his own researches as prepared for 
 Burgerstein's HandbucJi der Schulhygiene, 2d ed., pp. 462 ff. 
 
54 MENTAL FATIGUE 
 
 Every experiment was subdivided into four parts. 
 The first of these tested attention. The girls were 
 asked to count the letters in each of the first five lines 
 of a page of their readers, and to write down the five 
 sums upon a sheet of paper. They had next mentally 
 to add, or to substract, several pairs of two-place 
 numbers that were written for them on the black- 
 board, and to write the answers on their papers. To 
 test observation, or direct retention, as Meumann 
 likes to term it (or the capacity for immediate repro- 
 duction, as I prefer to say — Gedachtnis, 129), either 
 six one-to-three syllable words or four one-to-two 
 place numbers were used. These were either recited by 
 the teacher and then repeated by the pupils in concert, 
 or were written, shown, and then erased; in either 
 case, the pupils had immediately to write down as 
 many of them as they could remember. Eecollection, 
 or, more accurately, recognition, was tested by hand- 
 ing to the pupils sheets containing 100 words and 50 
 figures, among them those that had been previously 
 used in the test of immediate reproduction, and ask- 
 ing them to underline the words or numbers that they 
 had heard (or seen). Since, however, every act of 
 recognition is conditioned by two factors — the dis- 
 position (tendency) and the incitement of the dis- 
 position (Cf. Offner, Gedachtnis, 108) — it follows 
 that the recognition can fail, either on account of in- 
 sufficient strength of incitement, despite a very strong 
 tendency, or on account of a feeble tendency (poor 
 impression), despite a strong incitement. These two 
 factors, then, must be considered independently of 
 one another, because it is not certain whether the two 
 are equally affected by fatigue. 
 
THE PSYCHOLOGICAL METHODS 55 
 
 This four fold test was applied at the beginning, at 
 the end and twice in the course of a school session 
 that ran from 9 to 2 o 'clock, and that was broken by- 
 one long and several short pauses. By a special 
 method of treating the data, Teljatnik derived from 
 the four forms of tests an average value which he 
 termed an ' * index of general capacity for work, ' ' and 
 which he used to measure mental fatigue, together 
 with the effect of pauses in the school work (some 
 occupied in games, some spent in absolute rest), and 
 other similar phases of the problem. 
 
 We may, perhaps, think of better specific tests than 
 these ; we may criticize the plan of combining values 
 derived from the separate tests into a single one that 
 conceals the differences in the development of the 
 component factors; nevertheless, Teljatnik's method 
 seems to be the one that has, thus far, made the most 
 manifold appeal to mental life, and at the same time 
 the one that is characterized by the greatest ease of 
 administration and evaluation. 
 
 If we take a general survey of these experiments 
 with various forms of tests, from the method of 
 Griesbach to that of Teljatnik, we see that, despite 
 many defects that may perhaps be remedied, and 
 many difficulties that are inevitable, they supply us, 
 beyond any doubt, with serviceable average values 
 (particularly when, by frequent repetition, the er- 
 rors are gradually eliminated by the law of large 
 numbers), and afford reliable information as to the 
 effect and the degree of fatigue, and that they may, 
 therefore, be significant for us in the regulation of 
 our work. These methods are also, so far as we can 
 see, the only ones that can at the present time be ap- 
 
56 MENTAL FATIGUE 
 
 plied in schools, and so be of direct utility for prac- 
 tical schoolroom service. 
 
 Their theoretical value is, nevertheless, limited. 
 These forms of test-work do not permit us to follow 
 the course of fatigue accurately and step by step, 
 else the fatiguing work would be so frequently in- 
 terrupted by the inserted test-work that the effect of 
 the former would be concealed, since the test-work 
 itself would induce a high degree of fatigue. 
 
 Method of Continuous Work 
 
 It was, therefore, a happy thought to use the 
 fatiguing work as test- work, to observe uninterrupt- 
 edly the changes in quantity and quality of perform- 
 ance effected by the fatigue- work, and to take these 
 changes as an index of the fatigue or of the decrease 
 of mental efficiency caused by the work. 
 
 In this method, then, it is the continuous work it- 
 self, not bits of test-work applied at different times, 
 that indicates to what extent and how rapidly mental 
 efficiency is affected by the work. 
 
 It is clear that any continuous mental work of a 
 complex nature, e. g., the reading and assimilation 
 of a paragraph from Kant's Critique of Pure Rea- 
 son, the working out of mathematical problems or 
 the prosecution of botanical observation and experi- 
 ments — that such complex work would exclude the 
 possibility of a detailed and exact determination of 
 the effect of fatigue. For this purpose such simpler 
 mental processes must be selected, processes that are 
 not only characterized by a high degree of uniform- 
 ity, but that also permit the quick recognition of the 
 effect of fatigue. The course of such an activity, e. g., 
 
THE PSYCHOLOGICAL METHODS 57 
 
 two-hour adding of one-place numbers, may also be 
 shown in graphic form. A horizontal line is divided 
 into 24 parts, each one of which (for the two-hour test 
 just mentioned) accordingly represents a five-minute 
 period. The additions made in each of the five-min- 
 ute periods are then indicated by a line of the proper 
 length erected as a perpendicular to the base-line. 
 By joining the tips of these perpendiculars, we ob- 
 tain a line that is known as a curve of work. 
 
 This method was used for the first time by the 
 Austrian schoolman, L. Burgerstein (Arbeitslcurve 
 einer Schulstunde), when, in 1891, he studied the 
 course of fatigue within a single school hour. He 
 caused his pupils, boys aged 11 to 13 years, to per- 
 form easy examples in addition and multiplication, in 
 periods of 10 minutes each. A pause of five minutes 
 was introduced after each of these work-periods. 
 In this case, he found that, on the average, the num- 
 ber of examples performed increased from one quar- 
 ter of an hour to the next, perhaps on account of aug- 
 menting practice, or, toward the end, from anxiety 
 of the boys lest they should not be ready, or because 
 at the start they were working under an inhibition 
 that was only overcome by the work itself. There 
 were, however, more errors and corrections made as 
 the work went on. 
 
 In a similar, though much less extended experi- 
 ment, using forms of Latin verbs as test-material, 
 H. Merian-Genast, in the Gymnasium at Jena 
 (Cf. Eichter in Lehrproben, XLV, 8, note), obtained 
 similar results. This method is feasible for school 
 use. 
 
 So far as Burgerstein's results are concerned, we 
 
58 MENTAL FATIGUE 
 
 may call attention to his rather questionable com- 
 putation of the errors (Binet and Henri, 300 ; Ebbing- 
 haus, 24), and we should note that the results can- 
 not be interpreted without qualification as an indica- 
 tion of the fatigue-effect of an ordinary or normal 
 school hour. For school work is hardly ever so ex- 
 tremely uniform in character, nor does it ever require 
 uniformly sustained attention of the sort exacted in 
 these computations, which, moreover, were carried 
 on under stress of maximal speed. This criticism 
 has already been urged, and with right, by Richter, 
 Uhlig and others, particularly against Kraepelin's 
 work. Demands like those in these tests are made 
 upon the pupil at most only when he is doing l sight 
 work' or school tasks, or when he is actually being 
 questioned, and the other pupils are then less actively 
 engaged. Moreover, continuous computation of an 
 hour 's duration is a monotonous work of a kind such 
 that, after a short time, ennui or aversion, or at least 
 indifference, appears, and this must be overcome by 
 plucking up fresh courage for attentive work : these 
 circumstances are naturally fatal to uniform work 
 of sustained quality, while, despite fatigue, the speed 
 of the work is increased by practice (Cf . Ebbinghaus, 
 6; Binet and Henri, 302). But even if these difficul- 
 ties did not exist, we should still be unable, as we have 
 already pointed out, to infer positively, and as a mat- 
 ter of course, that fatigue followed the same line of 
 development in other forms of mental work as it does 
 in the case of computation. That must first be 
 proved. For these reasons, Burgerstein 's results, 
 like those obtained with his method by others, e. g., 
 by Marion Holmes (Pedagogical Seminary, III) with 
 
THE PSYCHOLOGICAL METHODS 59 
 
 American students, have in every case only a limited 
 significance, namely, for that particular work upon 
 which they were based. 
 
 Within this limited field, however, the method of 
 continuous work undoubtedly affords information of 
 value so far as it applies, and its usefulness for school 
 practice becomes greater in proportion as the task 
 used for experimentation resembles the tasks of the 
 schoolroom itself. The best plan is simply to use 
 school work itself as the basis, though this, to be sure, 
 can be done only in the earlier grades. This plan 
 has been tried by L. Hopfner {Zeits., VI, 194 fL), 
 who conducted a dictation test with a class of boys 
 of the average age of 9 years. This test consisted of 
 19 sentences, each one containing approximately 30 
 letters. Each sentence was read to the class once, 
 then repeated once by a single pupil, and finally re- 
 peated by the entire class. After this, the children 
 were required to write the sentence from memory. 
 The work in this way took two hours in all. Hopfner 
 discovered a general, though very irregular increase 
 in the number of errors from sentence to sentence. 
 His psychological analysis of the errors showed that 
 the longer the dictation continued (and hence the 
 more wearied the pupils), the more prevalent became 
 errors due to the displacement, by colloquial speech, 
 of the literary phrases learned in the classroom. It 
 is, then, the later acquired bits of knowledge, the 
 more recent associations, that fail first — that first 
 show the effect of fatigue — while the older acquisi- 
 tions, the words, grammatical forms and expressions 
 of colloquial speech that have been learned earlier, 
 and hence much oftener used — in short, the older as- 
 
60 MENTAL FATIGUE 
 
 sociations — are thereby brought into function as sub- 
 stitutes for them. 
 
 The advantage of Hopfner's method over that of 
 Burgerstein consists in the fact that in it a regular 
 school activity has been studied for its fatigue-effect. 
 And two further points of advantage are that, since 
 a real test is in operation, the pupils, of their own 
 accord, exert their attention to the utmost — indiffer- 
 ence and negligence cannot, therefore, enter as dis- 
 turbing factors — and that efficiency cannot be so 
 markedly augmented by practice during the test, as 
 is so plainly the case with computation-work. There 
 is, to be sure, one source of trouble even in this test, 
 viz., the task of securing material for dictation that 
 shall offer equal difficulty throughout. 
 
 The method of continuous work has been used with 
 special success by Kraepelin. In addition to the 
 counting of letters, reading, and the committing to 
 memory of series of digits and syllables, he has 
 favored the use of the method of the continuous ad- 
 dition of one-place numbers, because adding has the 
 merit of being, after all, one of the higher forms of 
 mental activity, while at the same time it is psycho- 
 logically far more uniform than other mental activ- 
 ities. Moreover, verbal imagery and articulatory 
 movements play a relatively minor role in it. Kraepe- 
 lin has worked out a simple procedure for <this 
 method. The subject is required to add, for a long 
 time (sometimes several hours), numbers printed in 
 vertical columns in a specially prepared note-book.* 
 Whenever the sum exceeds 100, the hundred is 
 
 ♦American readers may purchase such prepared forms of C. H. 
 Stoelting Company, 121 North Green street, Chicago. — Translator. 
 
THE PSYCHOLOGICAL METHODS 61 
 
 dropped, and the remaining units are carried on for 
 further additions. A signal bell rings every five 
 minutes. As soon as the subject hears it, he makes 
 a mark after the last digit that he has added. By 
 this means it is easy to ascertain, after the experi- 
 ment is finished, just how many digits have been 
 added by each subject in each five-minute period 
 (Kraepelin, Geistige Arbeit, 4th ed., 8). This form 
 of the method of continuous work is, to be sure, ill- 
 adapted for use in the school, as Kraepelin himself 
 admits {U eb erbiir dung sf rage, 13), but he and his 
 followers have, by its exploitation, done pioneer serv- 
 ice in the investigation of fatigue. 
 
RESULTS 
 
 Various factors in addition to fatigue, that de- 
 termine efficiency. 
 
 To Kraepelin and his followers we are primarily 
 indebted for the insight that we possess into the 
 conrse of long-continued mental work. And this 
 brings us to discuss the results of the investigation 
 of fatigue. 
 
 These investigations have shown that there are 
 several factors, several psychophysical phenomena, 
 that are more or less commonly present in this kind 
 of work; that these phenomena are consequences, 
 just as fatigue is a consequence, of persistent mental 
 work, and that they, too, influence the outcome of the 
 work, influence our performance. Their influence is 
 however, largely opposite to that of fatigue, so that 
 they reduce or cancel the fatigue-effect, in part, and 
 render it for a time imperceptible. These same influ- 
 ences are also operative in muscular work (Oseretz- 
 kowsky), and must, if we would avoid a false inter- 
 pretation of the results, be kept constantly in mind 
 in all measurements of fatigue or measurements of 
 work done. 
 
 Practice. In the first place, there is practice. 
 Whenever we continue or repeat an activity, the con- 
 sequence is that, to a certain extent, the activity is 
 carried out progressively more easily, i. e., with a 
 
 62 
 
RESULTS 63 
 
 lesser expenditure of energy, with a lesser degree of 
 attention, and also both more speedily and more 
 accurately, i. e., with fewer mistakes and more eco- 
 nomically, in that it constantly comes nearer the way 
 we wish it to go to accomplish the result that we de- 
 sire. Although the work done should relatively soon 
 suffer quantitative, or at least qualitative impairment 
 on account of the gradual rise of fatigue due to the 
 consumption of the available supply of psychophysi- 
 cal energy and to the fatigue-substances, we soon 
 find, on the contrary, a distinct and fairly persistent 
 augmentation, both quantitative and qualitative, of 
 the work done. We learn, while we are working, to 
 master our tasks better: after a short period of 
 work, often, in fact, after a few minutes, we do arith- 
 metical work more accurately, and particularly more 
 rapidly than we did when we began. This process of 
 progressive improvement of performance we may 
 term the concurrent practice-effect, and the amount 
 by which, in a specified time, the performance excels 
 the initial performance, we may term the concurrent 
 practice- gain, or the practice-result. 
 
 This practice-effect does not, as one might be in- 
 clined to expect, increase in proportion to the dura- 
 tion of the activity that is being practiced, but is 
 greatest at the beginning, and becomes smaller and 
 smaller as the activity continues, most probably just 
 in consequence of fatigue. If the work be divided 
 into a number of sections, each section will be found 
 to have its practice-result or practice-effect, but it 
 will be less from section to section.* Yet, the per- 
 
 *Cf. in this connection my discussion of the significance of repe- 
 titions for impression (Das Gedachtnis, esp. pp. 47-59). 
 
64 MENTAL FATIGUE 
 
 formance will still show improvement until fatigue 
 tips the scales against it, so that the work done is 
 more and more reduced, at first qualitatively and 
 then quantitatively, until, as the feeling of fatigue 
 grows progressively clearer and stronger, it finally 
 falls below the level at which it started. Now, the 
 total practice-result of these several periods of work 
 is not a permanent possession that remains as large 
 as it was when it was set aside ; on the contrary, the 
 condition of practice begins to wane as soon as the 
 practicing activity stops. And, again, this process 
 is not proportional to the time elapsed, but is rapid 
 at first, then slower and slower, and often the state of 
 practice remains perceptible for a surprisingly long 
 time (Cf. OrTner, 103 f?.). This residual skill, this 
 practice-gain that persists, can be recognized in the 
 facilitation of the activity that it brings about when 
 the activity is resumed at some later time, i. e., in the 
 qualitatively and quantitatively better performance 
 of practiced, as contrasted with unpracticed work. 
 
 It is with this persisting practice-result that school 
 instruction has primarily to do. 
 
 Both these forms of practice-result, moreover, are 
 the more evident the less practiced we still are in the 
 activity, and the less evident the more frequently 
 we have had an opportunity to exercise the activity 
 (Cf. in this connection, OrTner, Das Gedachtnis, 50 
 ff.). And finally, there comes a time when, even if 
 fatigue is not present, there is no further practice 
 result, neither of concurrent nor of persisting prac- 
 tice : this is the moment of maximal practice. 
 
 Habituation. Hand in hand with practice goes 
 habituation. We cease to be struck with the novelty 
 
RESULTS 65 
 
 or peculiar character of the work. Many a bit of 
 work that was distasteful at the outset loses its char- 
 acter of unpleasantness. Ideas foreign to the task 
 become fewer and fewer, and we are able to give our- 
 selves over to our activity with more and more atten- 
 tion. But maximal habituation is soon attained. 
 
 This shows us how we can exclude, at least for ex- 
 perimental purposes, these effects of practice and 
 habituation, and so remove an obstacle to the deter- 
 mination of fatigue. In order to observe fatigue, we 
 can evidently select just those mental activities in 
 which we have become so trained by extended prac- 
 tice that no further increase of efficiency can be had 
 during the work — such activities, for example, as 
 counting or very simple computation, particularly if 
 they have been brought up to the highest attainable 
 degree of efficiency by a period of special practice. 
 Baade (39, 107), however, maintains that complete 
 elimination of the influence of practice is at present 
 impossible, and that its exact computation is scarcely 
 more to be expected. But we can partly avoid the 
 practice-error by constant change of the subjects, so 
 that at least no permanent practice-gain shall de- 
 velop in any of them. 
 
 Warming-up (Anlauf). Once again, in tasks such 
 as we are considering, the work done is by no means 
 at its maximum at the very beginning, but reaches 
 its best output both qualitatively and quantitatively 
 some time — usually, of course, a short time — after 
 the start. This is a matter of every-day observation. 
 We make use of such expressions as: "We haven't 
 got into the game yet ;" "We must get into the spirit 
 of the work ; ' ' " We must get warmed up first ; ' ' " The 
 
66 MENTAL FATIGUE 
 
 machine must settle down to work." This stage we 
 may term ' warming-up. ' It is a stage that is passed 
 quickly by some persons, but takes more time for 
 others. Children, it may be added, take longer than 
 adults to settle down to a new piece of work (Meu- 
 mann, II, 5 f.). The stage is particularly long if we 
 have been previously occupied in some other form of 
 interesting work. But when we are once properly 
 warmed up, when we once have ourselves in trim, 
 then we 'turn out' results with ease — then is the 
 time when we are doing our best work. 
 
 Swing or fitness for work. Henceforth the work 
 takes full possession of us. We are completely 
 'held' by it, or we find ourselves in a condition of 
 full 'swing' (Anregung), as E. Amberg (Psychol. 
 Arbeit en, I, 373 ff.), Kraepelin and his school term 
 this mental condition, or in a condition of complete 
 'fitness for work' (Arbeitsbereitschaft), as Meu- 
 mann in particular prefers to call it. It appears 
 now that, as in the case of fatigue, so here in the case 
 of swing, we must distinguish between a general and 
 a special form of the condition. Anyone knows that 
 a short walk in the morning puts us into the mood 
 for work, into a readiness for any kind of work, more 
 quickly than if we betook ourselves directly from the 
 breakfast table to the work. Thus, Axel Key found 
 nothing but good results for his pupils when they 
 walked one to two kilometers [half a mile to a mile] 
 to school.* I have noted in my own case that, after 
 teaching from 8 till 9, I feel much more disposed to 
 
 ♦However, walking to school from a longer distance or a long 
 trip by rail is fatiguing, and produces a noticeable effect upon 
 mental efficiency, as Wagner has clearly shown by esthesiometric 
 tests. 
 
RESULTS 67 
 
 enter upon an activity of quite another character than 
 if I had spent this hour at home in the ordinary lazy 
 way. Hence, the strenuous mental activity demanded 
 for the teaching, like the activity of the walk, brings 
 about a disposition, a fitness, for every kind of activ- 
 ity — brings one generally into swing. 
 
 If, thereafter, we settle down at some particular 
 new activity and get well into the work, there de- 
 velops along with, and on account of, our activity a 
 special swing for this particular activity. It is this 
 condition that Kraepelin and other investigators 
 have in mind when they speak of swing and loss of 
 swing. General fitness is a condition that is termi- 
 nated only by fairly long intervals of rest, for in- 
 stance, by a long noon-recess, by an afternoon nap, 
 and particularly by a night's sleep; special fitness, 
 however, is naturally terminated by a change of 
 work, or even by brief pauses. If, for example, the 
 work be interrupted by so short a time as 5 or 10 
 minutes only, our special fitness suffers at once from 
 the interruption, and, of course, the effect is the 
 greater the longer the interruption. It hardly needs 
 to be said that this deleterious effect is much more 
 noticeable if the pause is not a rest-pause, but occu- 
 pied in some other form of mental work. Hence, 
 even in the case of tasks in which we are maximally 
 practiced, and in which, therefore, there is no ques- 
 tion of a loss of a practice-effect for the activity with 
 which we are working — e. g., very simple problems 
 in adding — even in such a case, the introduction of a 
 pause that we might expect to bring about an im- 
 provement in our performance (because it indicates 
 recuperation and some reduction of the effect of 
 
68 MENTAL FATIGUE 
 
 1 
 
 fatigue) is more apt to have the contrary effect. 
 That is, when we first resume the activity in question, 
 our performance is not infrequently worse. Of 
 course, if there is no considerable degree of fatigue 
 present, this lessened efficiency does not last very 
 long. We shall come back again to this matter of 
 the loss of swing when we discuss the problem of 
 pauses. 
 
 Spurt. Now, it is by no means always the case that, 
 in shifting from one task to another, our initial per- 
 formance with the new task is by loss of swing in- 
 ferior to our performance in the work we had just 
 left. Often, on the contrary, the new work starts off 
 considerably better, even though the previous work 
 had left us quite fatigued, as in general we often note 
 that the very first stages of any work yield strikingly 
 good results. Here, then, we come upon yet another 
 new factor. The explanation of this outcome, which 
 differs, as is evident, from what we have described 
 heretofore, is to be sought in the effect of novelty. 
 This factor, it is to be noted, has an inhibitory effect 
 upon many persons, but affects others, on the con- 
 trary, as a spur and stimulant, making an especially 
 strong appeal to their attention — the stimulus of 
 novelty is a matter of common knowledge — and 
 bringing about the release of an exceptional amount 
 of psychophysical energy. Following Kraepelin and 
 his school, we speak of such a release of an excep- 
 tional amount of energy as a ' spurt' (Antrieb), 
 terming it an 'initial spurt' if it develops at the be- 
 ginning of the work, or a 'spurt of change' if at the 
 beginning of some new and different form of work. 
 
 As, in this instance, the spurt springs from the 
 
RESULTS 69 
 
 stimulus of novelty, so it disappears as soon as this 
 stimulus ceases — a condition of affairs that ordi- 
 narily comes to pass in a short time and with special 
 and noticeable quickness if we have been fatigued by 
 the previous work. Accordingly, a drop in the curve 
 of performance can be plainly made out, even quite 
 soon after the beginning of an activity — at a time 
 when fatigue is still out of the question. This drop, 
 it is true, lasts but a very short time. Then the curve 
 rises again, at first quickly, until the condition of 
 swing is fully developed, and afterwards more slowly, 
 in consequence of the practice-effect. After a certain 
 time, which, of course, varies with the kind and dura- 
 tion of the work, with individual capacity, and with 
 the prevailing mood, the performance falls off, both 
 in quality and quantity, if fatigue gradually exerts 
 its baneful influence, and if the favorable effect of 
 practice is nullified. But this is by no means always 
 the case ; much oftener the course of work is other- 
 wise. We can become more and more absorbed in our 
 work, particularly if it be not monotonous ; our inter- 
 est comes back again, as we say — or, what amounts 
 to the same thing in this instance, our attention, our 
 expenditure of energy — and hence our achievements 
 recover their former level. In this manner, the effect 
 of fatigue may be compensated for a time. 
 
 However, it is possible that quite the contrary 
 phenomenon may occur. It may happen that the 
 work, having now lost the stimulus of novelty, may 
 at once become tedious; that interest, or, more ex- 
 actly, attention, may quite disappear, so that finally 
 we work reluctantly. In this event, our performance, 
 which already suffers somewhat from fatigue, nat- 
 
70 MENTAL FATIGUE 
 
 urally falls off considerably, particularly in quality. 
 And the reduction in efficiency is much greater than 
 if fatigue alone were operative. But if, perchance, 
 we recover ourselves in consequence of a some en- 
 couraging word, or a rebuke or some similar in- 
 fluence, then our performance once more shows a 
 gain in quantity, and even more in quality. Soon, 
 however, fatigue again asserts its sway, and this shift 
 of efficiency may be repeated several times, until at 
 last fatigue takes full possession of us, and the qual- 
 ity and scope of our work is reduced to a minimum. 
 Except that, if we note that we are nearing the end 
 of our work, this circumstance often operates as yet 
 another and final stimulating and encouraging factor. 
 This phenomenon is known as the ' terminal spurt ' 
 (Schlussantrieb), and its effect is to improve our per- 
 formance, just as horses step out better when they 
 know that they are returning to their stable. If, on 
 the other hand, we plan, so to speak, to work without 
 stopping, i. e., with a firm resolution not to desist, 
 but spur ourselves on and ever force ourselves to 
 fresh exertion, then there comes a time when our 
 ability to work is completely exhausted ; we collapse 
 utterly, and hardly ever without doing some grave 
 injury to our health. 
 
 It is evident that it is the will,m different forms and 
 degrees, manifested as rising and falling attention 
 or interest, as indifference and recovery — whether it 
 springs from newly-awakened sense of duty or from 
 the sight of the approaching and long-wished-f or end, 
 or from fear of not being ready — it is the will that in 
 these cases is affecting the course of the work, and 
 that is, with more or less success, counteracting the 
 
RESULTS 71 
 
 effect of fatigue. What is thus demonstrated within 
 the narrow bounds of experimental investigation is, 
 moreover, a phenomenon with which we are all well 
 acquainted. 
 
 The traveler who has reached the top of a moun- 
 tain in an exhausted condition, and who has hardly a 
 wish but for rest, forgets his weariness all in a mo- 
 ment if he meets some of his best friends, or if he 
 spies some rare and long-sought plant. Or perhaps 
 he finds that he has taken the wrong road. The ap- 
 proach of night, the loneliness of a totally unknown 
 region, the fear of meeting with some accident, may 
 so excite him that he feels no trace of weariness, that 
 he seems to be filled anew with a vigor and an elas- 
 ticity that astonish him. He hurries on with marve- 
 lous speed and endurance until he finally thinks he 
 has found the right road. Then, indeed, weariness 
 sweeps over him with twofold intensity, because his 
 fear no longer spurs him on. 
 
 The will, it would appear, then, puts at our dis- 
 posal extra mental power. Not that it creates it, 
 simply that it releases an already existing capital, 
 that it opens the storehouse once more and takes out 
 what the organism needs for the work of the moment. 
 
 But this process reduces the supply of energy, for 
 it is not the will that furnishes the energy, but the 
 substances taken up and worked over by the organ- 
 ism. This is shown directly by the proportionately 
 greater reduction of performance and the propor- 
 tionately greater need of nutrition and rest that fol- 
 low the expenditure of energy necessitated by such 
 conditions. As Schuyten has been wise enough to 
 see, this powerful influence exerted upon perform- 
 
72 MENTAL FATIGUE 
 
 ance by the manifold forms of will has not had proper 
 recognition in the majority of experimental tests of 
 fatigue (Kraepelin's work excepted). 
 
 Naturally, it must not be forgotten, to make brief 
 reference to the matter, that, when longer tasks are 
 undertaken, certain internal physiological processes, 
 such as nourishment, digestion, need of food, affect 
 efficiency, and that variations in external conditions, 
 especially of temperature, likewise leave some trace 
 upon the mental condition. But the most important 
 disturbing factor, aside from loss of attention due 
 to intruding ideas and distracting stimuli, is, of 
 course, fatigue. 
 
 Independent fluctuations of psychophysical en- 
 ergy. There remains yet one thing to which we may 
 make allusion, tentatively. R. Schulze (PraM. Schul- 
 mann, XLIV, 351, cited by Burgerstein, 594) and, in- 
 dependently of him, Teljatnik (Burgerstein, 594 ft*.) 
 have been led by their observations to consider the 
 possibility that our diurnal mental efficiency is 
 subject further to rhythmic fluctuations that oc- 
 cur regardless of whether we work or rest, and 
 that do not coincide with the divisions of our work 
 that are determined by pauses for the taking of food 
 and its digestion. Then too, W. Stern (120), and 
 after him, Lay (417) proved what had long been as- 
 sumed as true, that there is a movement of energy 
 between two maxima that are separated by a mini- 
 mum at noon and in the early afternoon. But since 
 this depression of mental efficiency is plainly condi- 
 tioned by the midday meal, it is not an independent 
 and special factor. Schulze and Teljatnik, however, 
 have reference to a phenomenon which appears inde- 
 
EESULTS 73 
 
 pendently, and which, if it be confirmed by subse- 
 quent investigations, would add another new factor 
 to the already sufficiently large number of them. 
 
 What course a bit of work actually takes, i. e.. 
 what variations in efficiency actually appear in its 
 course, which factors are most in evidence, and which 
 most determine the form of the curve of work — all 
 this depends on the character of the work, on the 
 peculiarities of its subject-matter, on the manner of 
 its execution and likewise on the individuality of the 
 worker, on his general disposition and upon the 
 changing external conditions. To isolate these sev- 
 eral factors, to bring each one of them into play by 
 itself while the others are completely suppressed, is 
 something that is at present quite impossible of ac- 
 complishment. It is, however, feasible, theoretically, 
 to isolate these factors in the large and to study their 
 effects one by one. 
 
THE LAWS OF FATIGUE 
 
 The laws of fatigue, particularly, cau be laid down, 
 at least in a broad and general way, thanks to every- 
 day observation and to those experimental investiga- 
 tions of the last decade to which we have already 
 given attention. 
 
 The phases of fatigue. These observations have 
 shown that fatigue passes through different stages 
 or phases of development. A piece of work that has 
 at first shown improvement in quality and quantity, 
 gradually undergoes a change that we must ascribe 
 to fatigue. The fatigue may have been really pres- 
 ent for some time before — though it is questionable 
 whether we should assume that it began at the mo- 
 ment that the work began (Cf. Claparede's discus 
 sion, 241 ff.) — but we notice it now for the first time. 
 This is the first stage of fatigue. During it, the 
 speed of work, it is to be noted, continues to increase ; 
 we accomplish more, e. g., more computations or 
 more counting, in each unit of time ; but the quality 
 deteriorates; more mistakes are made. In the sec- 
 ond stage, the quantity of work done in a given unit 
 of time also decreases. In the third stage, with some 
 persons the work becomes slower and slower and 
 finally is given up entirely ; with other persons there 
 is developed a considerable excitement. Fere calls 
 this condition fatigue-intoxication. We again do 
 more work, but the work is hurried and irregular; 
 
 74 
 
THE LAWS OF FATIGUE 75 
 
 our pulse is rapid and weak ; our movements are un- 
 certain ; our sensitivity to pain is augmented (Van- 
 nod), as is the sensitivity of the sense-organs. Meu- 
 mann (II, 121), for instance, has shown that sensi- 
 tivity for noises is increased. And finally, this stage 
 is terminated, as we should expect, by exhaustion 
 and breakdown. 
 
 ^ Types of fatigue or types of work. This descrip- 
 tion applies to the ideal form of the development of 
 fatigue in the case of long-continued work. But the 
 variations in efficiency are not always as simple as 
 this, even in work of a constant character, still less 
 so in the multiform work of the schoolroom. 
 
 In this connection we may distinguish four types 
 of work-curve. The simplest or falling type is that 
 in which the application of the test-work reveals a 
 steady decline in efficiency and a steady rise in the 
 number of errors. Exactly opposite to this is the 
 rising type in which the test-work reveals a progres- 
 sive diminution in the number of errors, which are 
 fewest in the last hours of the forenoon. A variation 
 of the first or falling type is the ' convex ' type, i. e., 
 one in which the curve rises a little at first (decrease 
 in errors) and then shows an unbroken drop (con- 
 stant increase in errors). Finally, the fourth or 
 ' concave' type of curve may be considered as a vari- 
 ant of the second or rising type ; in it, efficiency falls 
 at first, then continues to rise to the end of the work, 
 i. e., the errors increase at first, and then steadily de- 
 crease (Cf. Blazek, also Kemsies, Arbeitshyg. 17 and 
 Arbeit sty pen). It is possible to regard these pecu- 
 liarities in the general shape of the work-curve as 
 due simply to individual differences in type of fa- 
 
76 MENTAL FATIGUE 
 
 tigue ; in that case, the curves would really be curves 
 of fatigue. Or we may regard them as caused by 
 individual differences in manner of working — differ- 
 ences in the degree to which work incites or interests 
 — and these differences would then be thought of as 
 added to the effect of fatigue. In that case we have a 
 more complicated work-curve, in which the decisive 
 element is the individually different pure curve of 
 work. This would be the case with the rising and 
 the concave type of curve, whereas with the falling 
 and convex curves fatigue would be the primary 
 factor. 
 
 It is, of course, to be remembered that these types, 
 as we have described them, are valid only for the 
 forenoon work of the school. What kinds of types 
 would be discovered if we took into consideration the 
 work of a whole day is yet to be ascertained. 
 
 Fatiguability is, therefore, a thing that shows 
 marked differences in different persons, even in 
 healthy persons of the same age. It is worth while 
 calling attention to Kraepelin's proposal {Arch. f. d. 
 ges. Psych., I) that, when there is a system of sec- 
 tions or parallel classes, the pupils should be divided, 
 on occasion and by way of experiment, on the basis 
 of their fatiguability, in order to render possible 
 treatment suited to their special type. M. Brahn has 
 argued in the same vein. Susceptibility to fatigue, 
 as is well known, is greater in those who are ill, par- 
 ticularly in those who suffer from traumatic neuro- 
 ses. With them the fatigue is considerably greater 
 than that experienced by the most easily fatigued 
 well persons, as W. Specht {Arch. f. d. ges. Psych., 
 Ill) has demonstrated by the use of the method of 
 
THE LAWS OF FATIGUE 77 
 
 continuous adding. By this experiment, Specht, and 
 later on Bonofr", showed how we might detect simu- 
 lation. 
 
 Age. Age is an important conditioning factor of 
 fatigue. Every father who has taken his youngest 
 out for a stroll knows well enough that little children 
 tire out extraordinarily quickly. Of course, it is 
 quite out of the question to carry out any exact deter- 
 mination of mental fatigue with them, because after 
 a very short time they simply won't do anything 
 more, and, according to all appearances, before they 
 are particularly fatigued. Older children, like the 
 six-year olds in our school, give plain evidence of 
 fatigue after an hour, indeed, often after half an 
 hour of school work that includes both bodily and 
 mental tasks. These signs of fatigue appear all the 
 sooner if the children have not previously been used 
 to continuous activity. It is not surprising that 
 school hygienists (Burger stein, Adsersen, Hertel) 
 have been able to discover a rise in the death-rate 
 during the first year of school life. And this fact 
 gives good warrant for the plan of Gr. Kerschen- 
 steiner, director of the Munich Volksschule, who 
 softens the transition to the more severe exactions 
 of the school by a freer method of instruction which 
 leads over gradually from the liberty of the nursery 
 to the strict discipline of the school. However, effi- 
 ciency increases rapidly with age ; most pupils of 14 
 and 15 and over show little trace of fatigue, even 
 after three hours of school work. Of course, it is to 
 be borne in mind that these pupils also help them- 
 selves out by relaxing their attention, and that class 
 instruction gives more chance for this than does indi- 
 
78 MENTAL FATIGUE 
 
 vidual instruction. During the period of the best 
 mental and physical efficiency, namely from 20 to 30, 
 or perhaps to 40, f atiguability is naturally relatively 
 the least of any time of life. Thereafter it slowly 
 increases again. 
 
 It would be a mistake to suppose that this decrease 
 of susceptibility to fatigue, or this increase of effi- 
 ciency, keeps pace uniformly with increase of age. 
 Gilbert found by the use of the tapping test, which, 
 to be sure, is not especially accurate, that the in- 
 crease of efficiency with age is interrupted by periods 
 of special fatiguability, more specifically at 8, 13-14 
 and 16 years — the years, then, of more rapid phys- 
 ical growth (in Claperede, 208 f.). 
 
 Puberty. Mental growth, like bodily growth, is 
 especially influenced by puberty, and much more so 
 in girls than in boys. During this period, fatigua- 
 bility, to speak of that alone, is, as a rule, distinctly 
 increased. The school should then reduce its scho- 
 lastic requirements.* But, in our German Gymnasia, 
 the work of the Quinta, which, as everyone knows, 
 makes unusual exactions upon the pupils, falls in the 
 beginning of this period. Intelligent schoolmen, like 
 Eichter (Lehrproben, XV, 29) have for some time 
 called attention to this evil. Since pubertal develop- 
 ment, on the average, sets in with girls at the 13th 
 year, but with boys only at the 15th year, it will not 
 do to educate the two sexes together during the 12th 
 to the 17th years. For, from 12 to 15, the require- 
 
 *H6fler (29 f., 39, 60 f., 176 ff.) has shown us how this can be 
 done in the case of mathematics by limiting (rather than omitting) 
 certain definition and demonstration work as given in Euclidian 
 geometry, and how this more hasty treatment of the subject may 
 be carried out without doing any lasting damage by lack of thor- 
 oughness. 
 
THE LAWS OF FATIGUE 79 
 
 ments would be too high for the girls, if the average 
 efficiency of boys of this age were taken as the stand- 
 ard ; while from 15 to 17, they would perhaps be too 
 high for the boys, if they were based upon the aver- 
 age efficiency of the girls ; or else the requirements 
 would have to be reduced, at first in the interest of 
 the girls, in which case the boys would not be ade- 
 quately stimulated; later on in the interest of the 
 boys, in Which case, again, the efficiency of the girls 
 would not be turned completely to account. This is 
 an argument advanced by Burger stein (524 rr\) 
 against coeducation in the German middle schools, 
 and it is worthy of serious consideration. For the 
 rest, the relations between sex and fatiguability are 
 still quite as uncertain as those between intelligence 
 and fatiguability. The greater susceptibility to 
 fatigue of younger children is to be met by 
 shorter lesson-periods, fewer hours of study and 
 more frequent pauses, particularly in the primary 
 grades. 
 
 Length of lesson-periods. In dealing with the mat- 
 ter of the length of lesson-periods we may as well 
 see clearly at the start that human nature gives us no 
 absolute warrant whatsoever for making a lesson- 
 period exactly an hour, exactly 60 minutes. The fact 
 that this is the most usual length [in Germany] is 
 due to the simple fact that the clock is divided into 
 12 sections; in other words, we use hours in school 
 just because we have got used to dividing up our day 
 into twice twelve parts. And we divide our day by 
 twelves for the same reason that we buy our collars, 
 our handkerchiefs, and our candles by the dozen 
 rather than by tens, just because of a preference for 
 
80 MENTAL FATIGUE 
 
 the number twelve that even the ancient Babylonians 
 were conscious of. This preference, or special fond- 
 ness, for the number twelve is to be traced to the 
 astronomical fact that the moon encircles the earth 
 twelve times in one year. To take such a purely ex- 
 traneously determined custom, however ancient it 
 may be, as a basis for the division of work, and on 
 the basis of it to make every portion of work the 
 same for persons of every age, for every kind of 
 material, for every method of procedure, and for 
 every time of the day, as our school programs, taken 
 as a whole, have done down to the most recent times, 
 is perfectly absurd. The only rational time at which 
 to stop work and to indulge in a restorative pause 
 is the time at which the worker feels that he is get- 
 ting tired, or at which, if he does not notice his 
 fatigue himself, he nevertheless displays easily rec- 
 ognizable signs of fatigue, e. g., in addition to the 
 poorer quality of his work (which is of special im- 
 portance in experimental investigation), particularly 
 signs of uneasiness, decrease of attention, and a 
 tendency to dawdle — symptoms which may even be 
 seen, not only in ordinarily attentive and conscien- 
 tious children, but also in adults These and other 
 like symptoms should obviously not be regarded, as 
 is all too often the case, as invariably punishable 
 offenses, but as signals of fatigue, as signs that the 
 work ought now to be stopped and opportunity given 
 for rest.* To decide when the pupil has reached this 
 stage in his work is precisely the teacher's problem. 
 To do it he needs psychological understanding. 
 
 *F. Galton, Jour. Anthrop. Inst, and Revue scient., XVII (1889) ; 
 also A. M. Boubier, Arch, de Psych., I (1902). 
 
THE LAWS OF FATIGUE 81 
 
 Moreover, the teacher can make allowance, without 
 introducing any pause, within any given part of the 
 school program, for the fatigue (which, as we know, 
 does not exactly conform to the program divisions) ; 
 he can check the too rapid development of fatigue 
 by changing his manner of treating the subject-mat- 
 ter of the lesson, by making a transition to some 
 other phase of the same subject-matter, and by other 
 similar variations. In this way he can fit the length 
 of the lesson-period specified in the school program 
 to the individual needs of his classes. 
 
 On the other hand, the length of the lesson-period 
 in general cannot, of course, so far as the public 
 schools are concerned, be cut to fit the special needs 
 of a single class, but must be arranged to suit the 
 average efficiency of all the classes of the same 
 grade. It would need only a few well distributed ex- 
 perimental tests to secure the information necessary 
 for this purpose. It is only in the last 15 years that 
 we have brought about what the investigations of the 
 school hygienists have been demanding for the past 
 40 years, that here and there authorities have shaken 
 themselves free from the bonds of the customary 
 distribution of time into hours and have granted to 
 the younger pupils, or at least to the more easily 
 fatigued elementary grades, the shorter lesson- 
 periods which the maturer pupils of the higher 
 schools have long enjoyed. For feeble-minded chil- 
 dren, indeed, a half-hour ought to be regarded as 
 long enough for a period (Heller). 
 
 Thus, in the middle schools of Norway (Gymnasia 
 and the like) the lesson-period, since 1896, has been 
 limited to 45 minutes, and in Berlin, since 1898, the 
 
82 MENTAL FATIGUE 
 
 period lias been set at 30 minutes, at least for the 
 lowest grades of the Volksschule. Like improve- 
 ments have been tried in other cities (Cf. Burger- 
 stein, 543 if.). It is to be recommended, however, 
 that, for the upper grades of the Volksschule, and 
 still more for the more exacting Mittelschule, the 
 lesson-period be increased to 45-50 minutes (the so- 
 called ' short-hour' ), and that a pause of increasing 
 length be introduced after every period. At Karls- 
 ruhe, since 1894, the limitation of the class-period to 
 50 minutes in the Oberrealschule and the Realgym- 
 nasium has yielded good results and has made it pos- 
 sible to have a continuous five-hour session (Treut- 
 lein). And E. Keller (Intern. Archiv., II, 297 fT.), 
 according to the unanimous verdict of his school- 
 board (which was at first distrustful of the idea), 
 has, by the use of a 40-minute period, attained excel- 
 lent results, especially in the lower classes, in the 
 Realgymnasium and the trade school at Winterthur. 
 Nevertheless, it will sometimes be found worth while, 
 for the sake of school work, to extend the lesson over 
 the hour period. To this point we shall return later 
 on. Eeducing everything to rule, however desirable 
 it may be, is more likely to work injury in educa- 
 tional work than it is in any other field. W. Hellpach, 
 of Karlsruhe, proposes as a regular weekly schedule 
 the introduction, in addition to the ordinary short- 
 hours of 45 minutes, of six ' long-hours' of 80 min- 
 utes each — this, however, only for the upper grades 
 whose members have passed the period of puberty, 
 and only for review work. But even this type of 
 work, if the pupils co-operate actively, makes inten- 
 sive demands upon time, as may be noted in every bit 
 
THE LAWS OF FATIGUE 83 
 
 of assigned work or class work that lasts more than 
 an hour. To use such long hours as a regular sched- 
 ule would be a debatable proposition. 
 
 Number of periods per day and per week. A new 
 question arises when we discuss the total number of 
 class-exercises per day. Instinctively, and quite prop 
 erly, most schools are inclined to limit the formal 
 program to three forenoon and two afternoon periods 
 [hours], and to allow a maximum of four, or at most 
 five periods, only in the case of exclusively forenoon 
 sessions. At the Hamburg Gymnasium, however, as 
 many as six periods have, for some time, been com- 
 bined into a single t morning ' session — from 9 to 3 
 in the winter and from 8 to 2 in the summer — though, 
 of course, in conjunction with suitable rest-pauses 
 (Treutlein, 20). And the same arrangement is often 
 followed in Sweden (Burger stein, Handbuch, 590). 
 A similar experiment ( six periods of 45 minutes each) 
 was made at Elberfeld in 1899, but after several 
 years' trial, they returned to a five-period schedule, 
 because the higher school authorities, who could not 
 convince themselves of the advantage of the plan, for- 
 bade it, and with right. Even the fifth period, despite 
 longer pauses, is, at least with industrious pupils, of 
 little value. When the pupils co-operate actively, 
 four successive hours of required work constitute the 
 maximum. Anyone who, in his student days, has at- 
 tended lectures for four hours in succession will re- 
 member that he was unable to take in anything more 
 after the fourth lecture — and here all the periods 
 were ' short hours ' and he himself was a grown man. 
 Kemsies' observations are in accord with these state- 
 ments, and he proposes ( Arbeit shy giene, 64) four 
 
84 MENTAL FATIGUE 
 
 hours for younger and five for maturer pupils as the 
 maximum per day. G. Heberich and K. Schmid-Mon- 
 nard (292 fT.) demand that the maximal number of 
 hours per week shall be 24 regular hours. This figure 
 is least exceeded by the humanistic Gymnasia of Ba- 
 varia, with their 27 periods in the highest classes, 
 as compared with 31 in the Real gymnasium. It is 
 another question how much time should be permitted 
 for optional work. It can hardly be denied that very 
 many pupils do too much for their good, and that 
 many teachers do not restrain them from it, as if this 
 elective work made no demands on nervous energy. 
 For this type of work, too, a maximum time should be 
 allotted ; three periods a week in science, three or four 
 in music, two or three for drawing and stenography 
 should be the maximum for elective hours. If the 
 home throws a burden of added hours on the pupil, 
 then it must itself take the responsibility for it. But 
 it would, however, be well for the school to warn the 
 parents over and over again of the dangers of such 
 overburdening of their children and to show them 
 very clearly what their responsibility is in this mat- 
 ter, for they are seldom sufficiently well aware of it 
 ^see also Dornberger, Med. Prax., 13). 
 
 Days of the week. Another debated question is: 
 What days of the week are most favorable for mental 
 work? School authorities are apt, as a rule, to think 
 little of the days, or at least of the first half of the 
 days, that follow Sundays and holidays, and it is, in- 
 deed, out of kindly consideration of this circumstance 
 that in many places it is forbidden to assign written 
 tests or problems on these days. Kemsies (Arbeits- 
 hygiene) reached, however, somewhat different re- 
 
THE LAWS OF FATIGUE 85 
 
 suits, for he found the best days of the week to be the 
 first two after a holiday, i. e., Monday and Tuesday, 
 though to be sure, Monday was good only in the third 
 and fourth periods. It takes, then, somewhat longer 
 than usual to get back the general swing that has been 
 lost during the holiday. This difference of opinion 
 can be settled only by further and more extensive in- 
 vestigations. In any case, efficiency falls off plainly 
 from Wednesday on. And most school programs 
 take cognizance of this fact by inserting a half-holi- 
 day on Wednesday, though this, to be sure, does not 
 prevent the evasion of the purpose of this half -holi- 
 day in some places by the introduction of optional in- 
 struction. In France and in parts of Austria, Thurs- 
 day is left entirely free (in the celebrated Schulpforta 
 Gymnasium, all of Wednesday) ; here the expectation 
 is that the day will be devoted to elective work, not be 
 spent in doing nothing. 
 
 Pauses in school work. And this has brought us 
 naturally to discuss the problem of pauses. Let us 
 first consider the short pauses. What for purposes 
 of instruction is lost by these pauses in time is made 
 up in quality. This is shown clearly by the experi- 
 mental tests with exercises in dictation and computa- 
 tion that J. Friedrich (Zeits. XIII) , at Kiilpe's insti- 
 gation, applied to the pupils of the fourth class of a 
 Wtirzburg Volksschule. As has been known for a 
 long time, the pause has a recuperative effect — though 
 naturally only when it is actually used for rest, for 
 non-compulsory activity (especially in fresh air), or 
 for taking a moderate amount of nourishment, not 
 when it is taken up with studying or with gymnastic 
 exercises or strenuous games, as is so often the case 
 
86 MENTAL FATIGUE 
 
 in England (Abelson, 484). That this rest-pause is 
 the more beneficial and the more recuperative, the 
 longer it lasts, and that its effect is the more notice- 
 able, the longer the previous work had been,* is no 
 less certain than that the rest-pause must be made so 
 much the longer, the more fatiguing had been the pre- 
 vious work, the more the psychophysical energy had 
 been drawn opon. From this it follows that — if we 
 take no account of differences in difficulty of the vari- 
 ous subjects in the curriculum — the first pause should 
 be the shortest, and that the pauses should be made 
 longer and longer in order to prevent a too rapid low- 
 ering of efficiency, e. g., 15 minutes at 10 o'clock, 15 
 to 20 minutes at 11 o 'clock, and finally, at least 20 min- 
 utes at 12 o'clock. In working with feeble-minded 
 children, the pauses must be made still longer, since 
 these children are much more liable to fatigue (Hel- 
 ler). What holds good for the way the shorter pauses 
 are occupied, holds good also for the long ones. 
 
 That gymnastic exercises are really work, and 
 therefore out of place in rest-pauses, will be brought 
 out clearly later on. 
 
 The noon intermission is a pause of special signifi- 
 cance. As our day is at present divided, this pause 
 serves to secure an abundant supply of nourishment. 
 The organism is so much concerned in the subsequent 
 processes of digestion that it has little energy to 
 spare for mental work. The organism demands 
 quiet. "Plenus venter non studet libenter" is a well- 
 established maxim, and if it be not heeded, the work 
 is done less successfully and with greater effort, as 
 
 ♦The experimental confirmation of this and of similar observa- 
 tions has been supplied by G. Heiimann {Psychol. Arbeiten, IV). 
 
THE LAWS OF FATIGUE 87 
 
 I 
 
 Abelson (434) has clearly shown by esthesiometric 
 tests. And so the schools have been very properly 
 forbidden to set tasks that can be completed only by 
 working over the noon hour. The school cannot pre- 
 vent some pupils from preparing a part of their 
 afternoon lessons and other eager pupils from run- 
 ning over their assigned work once more during re- 
 cesses and intermissions. This undesirable kind of 
 work during the noon hour can be entirely avoided 
 only by giving up all informational instruction in the 
 afternoon. Besides, the noon intermission, which, as 
 scheduled, is already much too short, and which is 
 frequently misused by being put to other mental 
 work, is yet further shortened, and to a considerable 
 extent, by external conditions. In the larger cities it 
 is unfortunately impossible for all of the pupils, 
 whose instruction, on account of elective work, often 
 runs to 12 o'clock, to get to their dinner table by half- 
 past 12 and to finish the digestion of their dinner and 
 to regain sufficient mental freshness by 2 o'clock, 
 when the afternoon work ordinarily begins — to say 
 nothing of the fatigue set up by the morning's work 
 that should be eliminated so far as possible. The in- 
 disposition for mental work that every teacher, even 
 the youngest of us, notes after eating, and that many 
 persons can drive away only by the use of coffee, is 
 fe]t by the pupil, too, especially during periods of 
 rapid growth and also when the weather is hot. And 
 the ability of the school child to do mental work is 
 fully restored at the beginning of the afternoon ses- 
 sion only in the rarest cases (Griesbach, Vannod, 
 Wagner, Friedrich, and Burgerstein in his Hand- 
 buck, 581 fL). It is, accordingly, one of the most jus- 
 
88 MENTAL FATIGUE 
 
 tifiable demands of school hygiene that the afternoon 
 session, if it be not done away with entirely, should 
 begin at the very least two hours after the noon meal, 
 i. e., at 3 o'clock, and not at 2 o'clock, which would be 
 justifiable at most only if all the pupils sat down to 
 their dinner at 12 o 'clock — a custom that is becoming 
 less and less common in our larger cities as the years 
 go by.* 
 
 The pause that yields most abundant recuperation 
 is, of course, sleep, during which, if it be quiet and 
 dreamless, it may be assumed, no fatigue-substances 
 are produced at all, while assimilation far preponder- 
 ates over dissimilation. Without recounting in detail 
 the laws of sleep discovered by Romer, we may point 
 out simply that, in general, the same laws that hold 
 for pauses of all kinds hold also for sleep. Sleep 
 must, accordingly, be the longer, the more strenuous 
 has been the work that has preceded it, and the more 
 easily fatigued the organism is. It follows that the 
 need of sleep is the greater, the farther the person is 
 from the stage of mental and physical maturity. 
 Babies spend, or should spend, the greater part of the 
 time in sleep. And Axel Key (166 ff.), the Swedish 
 school hygienist, is right when he demands 11 hours 
 of sleep for 7 to 9 years old children. 10 hours for 10 
 to 13 year old children, and as many as 9 hours for 
 older pupils. Adult mental workers need from 7 to 8 
 hours. It must not be forgotten in this connection 
 that the need of sleep is less in summer than in win- 
 ter. Unfortunately, we know full well that very many 
 school children tend to spend in sleep fewer hours 
 
 *The Max-Gymnasium at Munich begins afternoon instruction in 
 summer anyway as late as 3 o'clock. 
 
THE LAWS OF FATIGUE 89 
 
 than they should.* The blame attaches sometimes to 
 the home, sometimes to the school and frequently the 
 trouble lies in external conditions, such as poverty 
 and the like, over which neither school nor home has 
 control (Cf. Burgerstein, 680 f.) The recuperative 
 effect of sleep is, of course, the greater, the less the 
 organism's activity is continued in it, the less, in 
 other words, the sleep is disturbed — whether by out- 
 ward impressions, by dreams, by the after-effects of 
 strenuous mental work undertaken just before going 
 to bed, or finally, by indigestible or stimulating sup- 
 pers. It is, therefore, essential that pupils should not 
 be allowed to continue their study up to the time they 
 go to bed, but should be busied with light reading, 
 simple music or games and the like. All the school 
 can do in this connection is, of course, to give good 
 advice to the parents. The school has still more in- 
 terest in — but, unfortunately, has still less influence 
 upon — the external conditions under which children 
 get their sleep — conditions Which, as Friedrich has 
 shown for Wiirzburg, Bernhard for Berlin, and Ka- 
 venhill for English elementary schools, are often the 
 worst conceivable. If a full amount of sleep is not 
 sufficient to restore the capacity for work completely 
 by the next morning, then the demands made on the 
 organism by the work of the previous day were too 
 great for its efficiency. This might occur either be- 
 cause the efficiency had itself been weakened (per- 
 haps by illness or inadequate nutrition), or because 
 excessive demands had been made upon a person of 
 perfectly normal efficiency, i. e., upon an efficiency 
 
 *D6rnberger and Grassniann (12) found, however, that pupils 
 in the Gymnasia at Munich had enough sleep. 
 
90 MENTAL FATIGUE 
 
 that had not been reduced by any otherwise unfavor- 
 able circumstances. In the first instance, we have 
 over- fatigue as a result of an abnormal and especially 
 pathological f atiguability ; in the second case, we have 
 over-fatigue as over-burdening, i. e. y as a result of 
 activity that exceeded the normal capacity. It is 
 hard to prevent occasional over-fatigue, and we need 
 not take that very tragically. But if it is repeated, 
 or if it persists, and if, for weeks at a time, sleep and 
 the other rest-pauses that interrupt the work do not 
 completely restore the efficiency available at the be- 
 ginning of the periods of work, if the periods of men- 
 tal freshness become shorter and shorter, and if fa- 
 tigue sets in earlier and earlier — as both teachers and 
 pupils frequently experience after a hard year of 
 school work, or as mental workers in general experi- 
 ence in the form of the well-known ' year's fatigue' — 
 then, indeed, we have a condition that calls for seri- 
 ous consideration. These symptoms show that, just 
 in these longer periods of work, the consumption of 
 nervous energy has gone so far that the ordinary 
 rest-pauses no longer suffice to restore it completely. 
 Quite often, even in a case like this, a still longer 
 pause, one of several days or weeks, especially a 
 vacation, may bring energy back to the height at 
 which it usually stands in the first weeks of the school 
 year. If the restoration of the original efficiency is 
 not brought about even then, we have undoubtedly to 
 do with exhaustion. Schuyten (Overlading, etc.), 
 unfortunately, did not apply this final and decisive 
 test. 
 
 If this sign of over-fatigue, or exhaustion, appears 
 in the majority of its pupils, the school must make a 
 considerable reduction in its demands and change its 
 
THE LAWS OF FATIGUE 91 
 
 methods. If, on the contrary, it appears in only a 
 few pupils, the home must realize the fact that the 
 task has become too hard for the pupil, and must per- 
 mit him to repeat the grade in order to give his body 
 and mind a chance to develop the physical efficiency 
 and the mental maturity that is absolutely necessary. 
 Or, if even the longer rest-pauses of the vacations do 
 not restore his old-time vigor, there may be some dis- 
 ease or the after-effect of an excessive degree of ex- 
 haustion. To hold a pupil thus afflicted down to men- 
 tal work is as great a crime as to load him with over- 
 Work to the same degree. Sleep, therefore, affords 
 us a reliable criterion for the differentiation of nor- 
 mal fatigue from that which is induced by patho- 
 logical or other unfavorable conditions or by over- 
 burdening. 
 
 There is better agreement as to the significance of 
 sleep than as to the most advantageous length and 
 distribution of the longer pauses in school work, i. e., 
 the vacations. In southern Germany the usual ar- 
 rangement calls for nine weeks of vacation in the 
 summer, 10 days at Christmas and 16 days at Easter, 
 with no long vacation at Pentecost, but in northern 
 Germany there is a vacation at Pentecost, and the 
 somewhat shorter summer vacation is divided into 
 two parts, though, it must be admitted, not without 
 much opposition. The Christmas and Easter vaca- 
 tions are here approximately as long as in southern 
 Germany.* 
 
 Again, many observers feel sure that relatively 
 
 *Burgerstein points out that hygienic considerations other than 
 fatigue favor a threefold division (Die zweckmassigste Begelung 
 d. Ferienordnung, in Bericht u. d. Ik Intern. Kong. f. Hygiene u. 
 Demographie, Berlin, 1907, Vol. II). 
 
92 MENTAL FATIGUE 
 
 short and frequent vacations are more favorable for 
 school work than relatively longer and fewer ones. 
 Certain it is that, during long vacations of several 
 weeks duration, the pupils drift farther away from 
 the spirit of school work than they do during short 
 intermissions of only one or two weeks. Yet this is no 
 disadvantage from the hygienic point of view. It is 
 a good thing for pupils completely to forget their 
 school cares and duties once in a while, and this they 
 can scarcely do in one or two weeks. Of course, it is 
 equally true that they forget a good deal of what they 
 have learned as well. But systematic drill, with repe- 
 tition, can re-create this lost material in the first 
 weeks of the new term, without delaying entrance 
 upon the new work for which the pupils are eager. 
 However, this is a matter that has not been suffi- 
 ciently tested scientifically as yet. 
 
 Even if the loss occasioned by the long vacation 
 could not be easily recovered, nevertheless the ar- 
 rangements of vacation periods already made by the 
 school authorities and in other social and business 
 circles would have to be considered. To make new 
 vacation arrangements at the risk of rendering more 
 difficult the gathering together of the whole family (a 
 custom that leads to the arousal of a multitude of 
 stimulating ideas in the new surroundings of country 
 life and that affords both children and parents oppor- 
 tunity for a more intimate mental intercourse than 
 the busy days of the remainder of the year) would be 
 to administer a serious setback to the development of 
 family life that already suffers manifold restrictions 
 in other ways. In this matter school hygiene will 
 have to give way somewhat to social and ethical con- 
 
THE LAWS OF FATIGUE 93 
 
 siderations, to the hygiene of the spirit of family- 
 life, and this it can do without undue anxiety, since, 
 so far at least, no serious hygienic disadvantages 
 have been shown to follow the long vacation. 
 
 The shorter pauses, too, have their disadvantages. 
 They break up the work, and this interruption means 
 loss of swing, of fitness for work, or of the pupil's 
 adjustment for the particular work on which he is 
 engaged ; and if the interruption is longer, this means 
 the loss as well of the readiness for mental work of 
 any kind, the loss, in other words, of what we have 
 termed ' general swing.' The experiments of W. H. 
 Eivers and Kraepelin (Psych. Arbeit en, I), of E. 
 Lindley (Psych. Arbeit en, III), and of Heiimann 
 (Psych. Arbeiten, IV) teach us that the loss is the 
 greater, the longer the interruption lasts and the 
 more our attention was adapted to these objects, was 
 accommodated for the one particular work. 
 
 It is clear that the loss of special fitness is not in- 
 jurious, provided the new lesson deals with a totally 
 different kind of material, but that it is very disad- 
 vantageous if the same lesson is continued or if the 
 new lesson is closely related with the subject-matter 
 of the preceding one, i. e., if it is pedagogically allied 
 to it — as, for example, if the material of a lesson in 
 history was to be worked over for a bit of composi- 
 tion work in the German lesson that followed it. 
 Since, in a case like this, the ideas that had been 
 gained in the first lesson would have to be developed 
 again in the next one, it is better to make the transi- 
 tion without any pause, as is, in fact, usually done in 
 the case of German composition work. It is assumed, 
 however, that lessons thus prolonged are followed by 
 
94 MENTAL FATIGUE 
 
 longer pauses for recuperation, and that they should 
 be limited in use to the upper grades. In these upper 
 grades, where, for the sake of pedagogic unity, a les- 
 son must often present and work over a considerable 
 number of ideas, the lesson-period in general must 
 frequently be longer than in the lower grades. And 
 the lessened susceptibility to fatigue of these maturer 
 pupils makes such an arrangement permissible. 
 
 Naturally, the loss of general swing is another mat- 
 ter. To lose it works injury even when the subject- 
 matter of the new lesson is quite different. The first 
 five or ten minutes will always be handicapped by the 
 very unfavorable influence of an incomplete fitness 
 for work. The school would best be served by short 
 pauses which would permit the general swing to be 
 maintained, though specific fitness would be lost, and 
 at the same time a certain amount of recuperation 
 would take place. To select just the best length for 
 pauses — a length such that the loss of swing and the 
 gain in recuperation would balance one another — is, 
 on account of the many contributory factors, a prob- 
 lem by itself, the solution of which still presents so 
 many difficulties to experimental psychology that it 
 would be safer and better for the school to choose the 
 lesser evil, the loss of swing, so that it may at least 
 avoid the greater evil, overburdening. 
 
 Change of work: special and general fatigue. 
 Change of work also brings about recuperation often- 
 times. If we mean by this statement that, when we 
 resume a task that we have interrupted by some other 
 form of activity, we then work considerably better 
 than before the interruption — that, to speak more ac- 
 curately, we enter upon the task again with a fresh 
 
THE LAWS OF FATIGUE 95 
 
 supply of energy — then the statement, in view of the 
 preceding discussion, is very much to be doubted. It 
 cannot be supposed that, in our complicated psycho- 
 physical organism, an activity of appreciable inten- 
 sity can run its course in any part of our complicated 
 psychophysical organism without thereby affecting 
 the functions of the other portions of the organism, 
 and hence of the whole organism. And the more man- 
 ifold, the more intimate the connection of the one part 
 with the remaining parts, the more rapidly and the 
 more extensively will the fatigue make itself evident 
 in these parts as well. 
 
 Conversely, the less the active part be connected 
 with the remainder of the organism, the more it is 
 possible to limit its functioning to itself, the more 
 slowly will the fatigue spread to the other parts, and 
 the more possible will it be for the fatigue to take on 
 the semblance of localized and isolated fatigue. This 
 is shown by Urbantschitsch's observation that a con- 
 tinuous tuning-fork tone after a time becomes inaud- 
 ible, although the striking of any other fork readily 
 evokes its proper auditory sensation, The organ, 
 then, — whether as a whole or in some definite part we 
 need not try to decide — fatigues for just that one 
 tone, but not — or more exactly, not yet — for the 
 others. This is substantially the same thing as J. J. 
 Muller discovered, when he proved that overtones be- 
 come ineffective if they have been given intensely 
 just beforehand. Another example of fatigue by 
 and for a very specific activity is the negative after- 
 image, for this — at least in terms of the Young-Helm- 
 holtz theory of color sensations — is an instance of 
 fatigue for the color previously seen (or the light- 
 
96 MENTAL FATIGUE 
 
 waves that correspond to this color), coupled with 
 continued sensitivity for other colors (or other light- 
 waves).* Finally, the marked unreliability of the 
 physiological methods of measuring fatigue, especi- 
 ally in the case of mild degrees of the fatigue set up 
 by mental work, is most easily explained by the as- 
 sumption that the active parts of the organism fa- 
 tigue first of all, and that the organism as a whole, 
 especially the musculature, is only gradually sympa- 
 thetically affected. The same assumption, too, en- 
 ables us to see how there may be a general, as well as 
 a special fitness for work. There is, then, such a thing 
 as special fatigue, which we must look upon as a 
 consumption of the constitutive materials of the act- 
 ive organ — a process that in the very nature of the 
 case is limited to the organ in question — and as a 
 secretion of fatigue-substances that accumulate at 
 first at the point where the work is done. 
 
 Nevertheless, there is no isolated fatigue. The fa- 
 tigue-substances do not remain where they are se- 
 creted, but are carried forth through the whole body 
 by the ceaseless circulation of the blood. Thus, there 
 appears a general as well as a special fatigue. More- 
 over, the fact that the part of the body that is vigor- 
 ously at work is continuously and extensively draw- 
 ing recuperative materials from the circulation must 
 bring it about that a lesser amount of these materials 
 remain at the disposal of the other organs. And 
 Mosso even believes that an organ draws upon the 
 supplies of other organs as well, that it uses up their 
 reserves, so to speak, e. g., that the brain, during its 
 activity, draws upon the muscles for recuperative 
 
 *Cf. L. Hermann, Lehrbuch der Physiologic, 2d ed., 523 f. 
 
THE LAWS OF FATIGUE 97 
 
 substances. This is the second way in which fatigue 
 may spread from the active organ. It follows quite 
 clearly from this that, when one organ is intensely 
 active, there cannot well be any storage of recupera- 
 tive materials in the other organs, but that, on the 
 contrary, these organs must also in time be exhausted. 
 And, of course, the same thing is true if vigorous 
 activity is discontinued in one organ, but set up in 
 some other with equal intensity. Accordingly, change 
 of work, or more properly, changing the organ that 
 works, does not bring about recuperation as long as 
 the consumption of materials continues at the same 
 rate. 
 
 If, however, the work to which we change is con- 
 siderably easier — if it is of such a kind that, to put it 
 in the terms of our discussion, it generates a smaller 
 amount of fatigue-substances and makes smaller de- 
 mands on the available supply of material, and if the 
 supply of material, at least by respiration, goes on 
 unchecked — then change of work may, it must be ad- 
 mitted, bring about recuperation. Whether and to 
 what extent a given piece of work is easier depends, 
 naturally, on the kind of work that it is. and also upon 
 the individuality of the worker, his knowledge, his 
 native ability, his susceptibility to practice, his skill, 
 his interests, and the like — in short, on the manner 
 and method in which he takes his work. 
 
 But we think, too, that we can often discern a recu- 
 perative effect when we change from one form of ac- 
 tivity to another of equal intensity. Here, however, 
 it does not appear that we are dealing with recupera- 
 tion in the strict sense of the term. The work that is 
 resumed is not essentially better than it was before 
 
98 MENTAL FATIGUE 
 
 the interruption. Not essentially better, we must 
 say, for the inevitable slight pauses do actually exert 
 some slight recuperative effect, and our fresh start is 
 affected favorably by an initial spurt, here the spurt 
 of change, as we have termed it. Our work, however, 
 is certainly much better than it would have been had 
 we continued without any interruption to the same 
 moment of time. It is, then, not really bettered, but 
 has simply not grown any worse. Obviously, because 
 the consumption of material in the organ in question 
 ceased during the interruption, whereas in the second 
 case, it would have continued uninterruptedly. 
 
 The experiments conducted by Weygandt (Psychol. 
 Arbeiten, II and Kraepelin, Ub erbur dungs f rage, 9 
 ff.), that are often cited as decisive against the recu- 
 perative effect of a change, do not, of course, really 
 suffice to refute this assumption or that of the exist- 
 ence of partial fatigue. His experiments merely 
 prove that if an easy piece of work interrupts a more 
 difficult one, the result is that we do better when we 
 resume the difficult work than we would have done if 
 we had worked on with the difficult task for the same 
 length of time without the interruption — a result 
 that is perfectly intelligible for us from what we have 
 already seen. His results do not, however, prove any- 
 thing against the idea of special fatigue or anything 
 against that of an advantageous effect arising from 
 the change in kind of work (neither do the experi- 
 ments of Schulze, in which changes were arranged 
 between adding and copying letters), for the forms 
 of work used for the shifts of activity (adding, memo- 
 rizing of series of numbers and syllables, cancella- 
 tion, the reading of texts in a foreign language, etc.) 
 
THE LAWS OF FATIGUE 99 
 
 are too much alike. Of course, they are different 
 sorts of operations, but they involve either the same 
 or similar elements. Physiologically considered, 
 they are processes that run their course very largely 
 in the same brain regions. Different brain regions 
 will always be brought into action in some measure, 
 if the subject-matter of a lesson is treated in quite 
 different ways — if, for instance, the subject is pre- 
 sented at first pictorially and concretely, then de- 
 scriptively and more abstractly. By such a method 
 the pupiPs efficiency can be put to use more ration- 
 ally. The points at dispute hinge on such questions 
 as whether a specific region of the brain can fatigue 
 without affecting other regions also; whether an 
 activity that we think of as exclusively — or, since this 
 is hardly conceivable, as predominantly — centered in 
 a specific part of the brain, and that we must con- 
 sider as being predominantly an activity of a single 
 or of certain determinate phases of mental life, fa- 
 tigues quite by itself and leaves our mind in full effi- 
 ciency for such other activities as we ascribe to other 
 regions of the brain and as are evidently other phases 
 of mental life ; whether, then, a fatigue can not only 
 be special when it begins, but can remain special, 
 isolated, and localized, or whether it spreads gradu- 
 ally over the entire psychophysical organism, or 
 whether, finally, it induces from the very beginning 
 an equal amount of impairment of efficiency in all 
 parts of the organism. Our discussions have shown 
 that we must admit a special fatigue, but deny its iso- 
 lation. But it follows from this that change of Work 
 brings about for the regions of the brain freed from 
 work a cessation in the consumption of the materials 
 
100 MENTAL FATIGUE 
 
 of which the nerve cells are built up, so that, when the 
 former activity is resumed, this fact, taken together 
 with the spurt of change, results in better perform- 
 ances than before the interruption of the activity, 
 and in this way there seems to be a recuperation. 
 
 And the fact that in the new work, i. e., in what 
 might be called the l change-work, ' more is accom- 
 plished than at the end of the previous work, despite 
 the general reduction of efficiency to be expected from 
 the distribution of the fatigue-substances, is intel- 
 ligible. On the one hand, the stimulus of novelty re- 
 awakens interest and incites us to a greater expendi- 
 ture of energy (the effect of mood). On the other 
 hand, the parts of the organism that are set into ac- 
 tivity by the new work have not yet been concerned in 
 work ; their store of energy has not yet been assailed. 
 
 It is, of course, presupposed that the previous work 
 had fatigued the organism only moderately, and that 
 the new work is essentially different from that that 
 had preceded it.* On this account, the form of change 
 that most effectually slows the progress of fatigue, 
 though it does not, of course, entirely check it, is the 
 change from mental and bodily work. All in all, the 
 view frequently held by educators (e. g., Eichter, 
 Lehrproben, XLV, 14) that change means recupera- 
 tion appears to be but the psychologically and physi- 
 ologically unjustifiable interpretation of observations 
 that of themselves are not incorrect. 
 
 Social activities. What we have said about the ef- 
 
 *Special (partial) and general fatigue are distinguished also by 
 Mosso (244), Kraepelin (UberMr dungs f rage, 16) and, apparently, 
 by Claparede (236, but see 218 ff. and 268 f.), only that these 
 writers lay more emphasis upon the general effect, while Teljatnik 
 (in Burger stein, 467) emphasizes rather the partial fatigue effect. 
 
THE LAWS OF FATIGUE 101 
 
 feet of change of work holds true in the main for the 
 effect of social life. If the pupil's social activities 
 make only slight demands on his mental life, if they 
 call forth only a moderate degree of interest, if they 
 serve to divert and amuse rather than to excite, then 
 they are good things to conclude the day's work with, 
 particularly because they prevent the carrying over 
 (perseveration) of the thoughts and worries of the 
 day.* But if these social activities fetter our atten- 
 tion and render us 'all stirred up/ then they are 
 really another kind of work — quite apart from cut- 
 ting short our time for sleep — and then we must ask 
 ourselves seriously the question whether the satis- 
 faction that we hope to gain from them is enough to 
 compensate for the loss of mental efficiency on the 
 following day. 
 
 The home will see to it that school children at least 
 are kept from strenuous social activities, if it is all 
 desirous that their studying shall not be interfered 
 with. 
 
 Gyrh/nastics. The same general principles apply to 
 every sort of bodily movement, and especially to gym- 
 nastics and active games. When these are pursued 
 vigorously, they are distinctly fatiguing, and are, in 
 any event, not recuperative, as used to be generally 
 believed. Anybody who has done intensive gymnas- 
 tic work or played tennis or enjoyed sport on the ice 
 knows how little inclined he was afterward for mental 
 work. Griesbach, Wagner and Vannod found a con- 
 siderable reduction in the sensitivity of the skin 
 under such conditions. And other investigators have 
 
 *On perseveration, see Offner, Das Gedachtnis, 23 f. and else- 
 where. 
 
102 MENTAL. FATIGUE 
 
 in other ways proved that gymnastics exert a strong 
 fatigue-effect; in fact, all who have used scientific 
 methods of measurement have come to striking 
 agreement on this point (Cf. Burgerstein, 570 if.)-* 
 However, this kind of fatigue-effect, when of moder- 
 ate degree, has the merit that one speedily recovers 
 from it, so that, even after an hour's rest, especially 
 if nourishment be taken during that time, one feels 
 again prepared for mental work and one may ac- 
 complish very good results in it (Cf. Abelson, 414, 
 486). The reason for this is that there are operative 
 here other favorable factors which can soon cancel 
 the fatigue-effect. The vigorous exercise, especially 
 when taken in fresh air, the augmented metabolism 
 and the consequent augmented supply of the mate- 
 rials that build up the body, particularly the aug- 
 mented supply of oxygen through the quickening and 
 deepening of respiration and of nutritive material 
 through the quickening of appetite, the hastening of 
 the elimination or the oxidization of the fatigue- 
 products, all these are factors that condition a rapid 
 renewal of the stock of psychophysical energy used 
 up by the strenuous bodily activity. So that gymnas- 
 tics may, after all, possess indirectly an unquestioned 
 recuperative value, not merely an apparent one, as 
 Gaupp (118) thinks. When interpreted in this way, 
 there is justification for the general opinion of the 
 value of exercise — an opinion in which no distinction 
 is made between the direct and the indirect effect of 
 exercise. If, however, the subsidiary effects which 
 
 ♦See also the results of Smedley at Chicago, in Rept Dept. Child- 
 Study and Pedagogic Investigation (4Gth An. Rept Brd. Educ, 
 Chicago), 1899-1900.— Translator. 
 
THE LAWS OF FATIGUE 103 
 
 bring about this rapid compensation of the fatigue 
 were to be restricted, then the fatigue-effect of bodily- 
 exercise would assume large proportions. Thus, 
 gymnastics in closed or poorly ventilated rooms have 
 very little value. Since these beneficial secondary 
 factors are not immediately effective, it is easy to 
 understand why we are not in a position to do inten- 
 sive mental work directly after active physical exer- 
 cise, but only after a rest of three-quarters of an 
 hour or an hour. In cases, however, like that cited by 
 Holmes (Ped. Seminary, III), who found, by means 
 of the addition test and a test of bisection of lines, 
 that a moderate walk and a brief four-minute calis- 
 thenic exercise in the school room were directly stim- 
 ulating to mental work, and like that cited by Dorn- 
 bliith, who noted a similar result after a gymnastic 
 lesson that did not make great demand on energy or 
 attention — in these cases, we must conclude that the 
 consumption of energy by the physical activity is 
 more than compensated by those indirect effects that 
 augment the supply of energy. Moreover, in the case 
 of walking, rhythm is a factor that is not to be under- 
 estimated, since it exerts a favorable influence upon 
 our mood (Cf. Offner, Das Gedachtnis. 84, 86, 190). 
 That a short walk might have a stimulating effect we 
 showed previously, in our discussion of swing. There 
 are, then, considerable differences in the effect on 
 mental efficiency of different kinds and degrees of 
 bodily movement, and variations in the bodily consti- 
 tution of the individual introduce yet other differ- 
 ences. 
 
 Science can only lay down general principles. It 
 will be the business of the home and of the school to 
 
104 MENTAL FATIGUE 
 
 determine for particular children, or groups of chil- 
 dren, by dint of careful observation, in what way, to 
 what degree, and at what time physical activity is a 
 healthy counteractivity for mental work : as it will be 
 also their business to determine how gymnastics, that 
 obviously serve not only hygienic, but also pedagog- 
 ical purposes (training in discipline, order, vigor and 
 physical development), shall be given due place along 
 with the studies of the school, and how neither physi- 
 cal nor mental training shall suffer from the other, 
 but shall be of mutual advantage. The working out 
 of this problem is the art of pedagogic diplomacy. 
 Theory can supply only certain guiding principles, 
 the most important of which are : Physical activity is 
 also fatiguing work. It cannot, therefore, afford re- 
 cuperation after mental work, but itself demands a 
 period of rest. It is, however, accompanied by sec- 
 ondary results that are extremely helpful for recu- 
 peration after mental work. These secondary results 
 are best realized when there is no activity of any kind 
 directly after the physical activity; for this reason, 
 it is well to have the exercise come at the end of the 
 formal school instruction, particularly because it 
 then satisfies the desire for movement that comes 
 from sitting still for a long time. If the exercise be 
 carried out with less intensity, it has a stimulating 
 effect, and then, but only then, it can be taken be- 
 tween, or even before, the period of formal instruc- 
 tion. 
 
 Fatigue-coefficient of the studies. We see, then, 
 that gymnastics and similar physical activities have 
 a special relation to fatigue. But, in the same way, 
 every discipline, every subject-matter, has its own 
 
THE LAWS OF FATIGUE 105 
 
 peculiar way of setting the mind into action, and 
 hence the fatigue-effect is different for each of them. 
 One of the special chapters in the investigation of 
 fatigue — Griesbach is, in fact, the first to state the 
 problem — has to do with determining which subject 
 fatigues the most and in what direction the most ; in 
 other words, with determining, at least quantita- 
 tively, the specific degree of the fatigue-effect of each 
 study (other conditions being equal). This we may 
 term the fatigue-coefficient. It affects the outcome of 
 mental work as the friction of machines, indicated by 
 their coefficient of friction, lessens their mechanical 
 efficiency. By the use of this fatigue-coefficient, there 
 might be made out a fatigue-scale of the several 
 school subjects that could apply either to the ability 
 and disposition of the single pupil or to the average 
 capacity of an entire class, and to a given age or stage 
 of development as well. The experience of the school- 
 room has taught us for a long time that certain 
 studies strain and fatigue some more than others of 
 the pupils, and that there are certain lessons and cer- 
 tain subjects that make greater demands than others 
 upon at least the average of the class. The results 
 obtained by Griesbach with the esthesiometer accord 
 pretty well with this schoolroom experience, as they 
 show that mathematics and memorization-exercises 
 are very fatiguing, much more so than geography or 
 drawing. Similar, though not identical results have 
 been obtained by Wagner, Sakaki and Blazek, with 
 the same method, and by Kemsies with the ergograph 
 (Deutsch. Med. Wochenschrift, 1896). Both Vannod 
 and Vaschide showed by the use of the esthesiometer 
 that mathematics and ancient languages are more 
 
106 MENTAL FATIGUE 
 
 fatiguing than geography and French (here the 
 mother tongue). But it is interesting to note that 
 Vannod found drawing to be strongly fatiguing, also. 
 Quite in accord, again, with schoolroom experience is 
 Bitter's observation that exercises in sight transla- 
 tion are more exacting than the reading of the au- 
 thors. There is no reason to be surprised that these 
 experimental results do not show more exact agree- 
 ment when we consider the inequality of the conduct 
 of class instruction and of the requirements of 
 schools of different, and even of those of the same 
 type, and when we remember, further, that the meas- 
 urements were not all taken by the same method 
 and that the subjects in question were conducted at 
 different lesson-periods (before or after a pause, 
 before noon or after noon, at the beginning and at 
 the end of the school day), and that this discrepancy 
 has not been allowed for. There are also involved 
 here certain other factors that we shall discuss later. 
 Afternoon instruction. The specific fatigue-effect 
 of afternoon instruction is still undetermined. 
 Sakaki, Vaschide and Vannod, on the basis of their 
 esthesiometric tests, made out that afternoon instruc- 
 tion fatigues much more than forenoon instruction. 
 Similarly, Schuyten found (Voor- en Nam) that in 
 afternoon sessions more errors were made in copying 
 and poorer results were exhibited in learning two- 
 place numbers. But it is not certain how much the 
 physiological factor, digestion, may have affected 
 this result. We may assume, on the other hand, that 
 the taking in of nourishment brings with it a restora- 
 tion of the supply of energy. The ergograph, and 
 likewise the dynamometer (Schuyten), shows that 
 
THE LAWS OF FATIGUE 107 
 
 bodily strength is increased thereby. Ritter con- 
 cluded from his use of the word-learning method that 
 his gymnasial pupils at Ellwangen were somewhat, 
 though not much more fatigued by a two to three- 
 hour afternoon session than by a four-hour morning 
 session. It depends entirely on the length and use of 
 the noon intermission. 
 
 In view of the fact that the time from 4 or 5 o 'clock 
 to 8 o 'clock or later is the best part of the day for very 
 many mental workers, and that of 64 mathematicians 
 who replied to a questionary, 24 asserted that the 
 evening was their best time for work, while seven 
 rated morning and evening as equally good (Clapa- 
 rede, in L'enseignernent math., 1908, pp. 216 f.), we 
 certainly cannot urge any theoretical objections 
 against instruction that begins late in the afternoon, 
 provided care be taken that the process of digestion 
 is entirely finished. Or, if we may disregard entirely 
 the disputed question of one-session or two-session 
 plan (a question complicated by other and quite dif- 
 ferent issues, e. g. y possibility of adequate physical 
 activity, distance of the home from the school, time- 
 consuming and wearying trips on rail and street cars, 
 and in winter, too, the problem of illumination,* and, 
 furthermore, the oversight of pupils that have no 
 afternoon instruction and the question of meal-hours 
 as they are affected by parental occupation and other 
 local customs) — if we disregard this question, we 
 should like to put the matter quite generally by say- 
 ing: Eeadiness for mental work is renewed in the 
 second part of the day at two to three hours after 
 
 ♦Consult the judicious treatment of the question in Burgerstein, 
 578 ff., and in Treutlein's Progr. d. Realgymn., Karlsruhe, 1906. 
 
108 MENTAL FATIGUE 
 
 eating the noon meal. This second work-period is, in 
 fact, more favorable than the morning period for 
 many persons (Cf., also, Schuyten, Paed. Jaarboek, 
 VII). The most satisfactory plan for giving proper 
 weight to all the pertinent factors appears to be to 
 put formal school exercises so far as possible in the 
 forenoon, to use the afternoon for comprehensive, 
 but not formal physical activity, and then, after a rest 
 of half an hour to an hour, with nourishment, to de- 
 vote the evening hours from 5 to 8 to mental work 
 again, using this time for the pupils' studies, for 
 reading, and for review and preparation of home- 
 work — the abolition of which, as desired by many per- 
 sons, including some teachers, would not be at all 
 favorable to training in independent mental work; 
 as even Kraepelin (Ueberb. 37) admits. From these 
 considerations, there appears justification of evening 
 schools for apprentices, for whom, as a rule, such 
 courses are more of a recreation than an exaction of 
 further effort (Schuyten).* 
 
 School program. These considerations of the value 
 of forenoon and afternoon sessions and of the fa- 
 tigue-value of the several studies are naturally of sig- 
 nificance in the arrangement of the school program, 
 as well as for the choice of the total number of pe- 
 riods, and particularly for the division of these 
 periods. We shall have to try to put the most difficult 
 subjects in the first two periods of the day, to put 
 some easier subjects between difficult subjects, and to 
 put gymnastics at the end of the forenoon session, or 
 
 *See, however, Winch, Some measurements of mental fatigue in 
 adolescent pupils in evening schools, Jour. Educ. Psychol. I, 1910, 
 13-24, 83-100, where different conclusions are reached. — Translator. 
 
THE LAWS OF FATIGUE 
 
 109 
 
 even better, to defer these until the afternoon, as had, 
 indeed, been done, so far as feasible, in many places, 
 before these questions were attacked by experimen- 
 tal investigation. One of the worst obstacles encoun- 
 tered in the attempt to make such arrangements is 
 the system of departmental instruction. 
 
 Schiller (1897) was the first to try to adjust a 
 school program in conformity with the results of ex- 
 perimental psychology. But it is clear that this was 
 only a preliminary attempt, which did not, and could 
 not, claim to afford an ultimate solution. The inves- 
 tigations of the fatigue-value of the several studies 
 are still far from reaching results that are in any 
 way conclusive. Nor can they ever afford us univer- 
 sally valid conclusions. Strictly interpreted, even 
 when the difficulty of the fatigue-effect at different 
 hours is obviated by making a large number of ex 
 periments, they are valid only for the average of a 
 class actually compounded of good, average and poor 
 pupils, animated by varied specific lines of interest. 
 But this changes in proportion as this composition of 
 the class changes by entrance or loss of pupils and in 
 proportion as the pupils themselves change, for we 
 must remember that their mental development does 
 not, in any case, proceed with entire uniformity. Fur- 
 thermore, the results must differ in other classes that 
 differ in composition according to the endowment 
 and propensities of the pupils. And it is well known, 
 too, that the same subject is not equally difficult in 
 every class— that, for instance, the geography of Ger- 
 many, which is the assignment for the first and sec- 
 ond classes of the Gymnasium, makes very much less 
 demand on the pupil, at least when skillfully man- 
 
110 MENTAL FATIGUE 
 
 aged, than the geography of countries outside of Eu- 
 rope, which is assigned in the fourth class, and which 
 is commonly compressed into a single year's work. 
 So we cannot simply say: geography is Jess fatiguing 
 than, perhaps, a linguistic study. Then, again, a 
 school lesson is more exacting if the number of pu- 
 pils in the class is small, because then the pupils are 
 called on oftener and have to know their lesson 
 better. 
 
 Fatigue-coefficient of the teacher. One more fac- 
 tor is to be noted that appreciably complicates the 
 determination of the fatigue-coefficient of any study, 
 namely, the fatigue-coefficient of the teacher. The 
 more stimulating is a teacher's instruction, the more 
 skillful he is in riveting the attention of his pupils, 
 the more fatiguing is his instruction. The interest 
 aroused by the teacher may banish the feeling of 
 fatigue in the pupils, but, as Griesbach {Intern. 
 Archiv., V) properly remarks, this interest can as lit- 
 tle remove the actual fatigue of the pupils as can the 
 music of the regimental band banish the fatigue of a 
 marching troop. This everyday observation has been 
 confirmed by Wagner (Unterricht und Ermudung, 
 115 rT.) by means of esthesiometric tests. And he is 
 right when he estimates this factor as of more impor- 
 tance than the fatigue-value of the subject-matter. 
 Moreover, a teacher who has little capacity for sus- 
 taining his pupil's attention can compel them to more 
 active participation by harsh disciplinary measures. 
 In such cases, the pupils exert their whole energy 
 from fear. 
 
 Fatigue-coefficient of the method of teaching and 
 learning. Besides the fatigue-coefficient of the 
 
THE LAWS OF FATIGUE 111 
 
 teacher and that of the subject-matter, there is also 
 a fatigue-coefficient of the method of teaching and 
 learning. Thus far scarcely any attempt has been 
 made to evaluate it; only Eulenburg and Bach (p. 
 1239) mention it. But it is evident that, even from 
 the standpoint of the economy of mental force, it is 
 not a matter of indifference whether I acquire certain 
 information, e. g., in the history of civilization, in 
 botany, in physics, or in chemistry, by merely listen- 
 ing to a verbal description, or by reading about it, or 
 by observation. Again, in the observation itself it is 
 not a matter of indifference whether, in my consider- 
 ation of the object or of the pictorial representation 
 of it, I am guided by an accompanying description 
 of the teacher, or whether I have quite by myself to 
 pick out the essential features and separate them 
 from the unessential ones. And it certainly makes 
 some difference in the demands on mental efficiency 
 whether a poem or a prose selection is learned by 
 heart without adequate explanation of its meaning, 
 or only after there has been gained complete under- 
 standing and adequate survey of the thing as a whole 
 and after some emotional reaction has thus been 
 awakened for the piece. Again, it will make a dis- 
 tinct difference whether a principle in physics has 
 chanced to be worked out deductively and developed 
 by mathematical formulas, or whether it has been dis- 
 covered inductively by the introduction of experi- 
 ments, whether the course of thought of a problem in 
 philosophy, ethics, or natural science has been sim- 
 ply assimilated in a purely receptive manner, or has 
 been developed by means of free exchange of ideas 
 between pupils and teacher. These statements are, 
 
112 MENTAL FATIGUE 
 
 of course, only opinions. In general, the problems 
 that are raised by them are, unfortunately, in large 
 measure so complex in nature that their solution by 
 experiment is still a far-distant matter. Meantime, 
 we must rely for the working out of such problems 
 entirely upon the keen sensitivity of the teacher who 
 keeps watch on the effects of his teaching. 
 
 Individual instruction and class instruction. It 
 is also clear that the economy of mental energy is dif- 
 ferent in individual, from that in class instruction, 
 and that this difference plays a very decisive influ- 
 ence in the division of the subject-matter and the ar- 
 rangements of the school program. Class instruc- 
 tion makes distinctly fewer demands on the attention 
 of the pupils, for it permits those pupils who are not 
 actually called on for recitation to work at half-atten- 
 tion. Kraepelin (Geistige Arbeit, 18) sees in this 
 very fact a safety-valve, an automatic protective de- 
 vice against the over-exactions of the school. If, he 
 means, the pupil were compelled to work at maximal 
 attention during the whole school session, he would 
 break down. But, as we have already asserted once 
 before, class instruction does not really presuppose 
 this. Because, if it could ever be brought about that 
 the pupils followed the whole lesson with undivided 
 attention, then we could certainly get on with a much 
 shorter school session. Individual instruction dem- 
 onstrates the truth of this statement. But, since the 
 school cannot compel this intensive concentration of 
 attention, it must extend the duration of the school 
 day to make up for it. From the point of view of the 
 teacher, however, the relations are just the reverse. 
 For him, individual instruction is much less exacting 
 
THE LAWS OF FATIGUE 113 
 
 than class instruction, which, as the class increases in 
 size, demands that just so much louder speech and 
 just so much more careful watching of the behavior 
 and of the attention of the pupils be added to the task 
 of teaching itself. The most exacting kind of school 
 work, as is well known, is preparation for an exam- 
 ination; this Griesbach has demonstrated by tests 
 with the esthesiometer. 
 
 Fatiguability of the teacher. This leads us now to 
 speak briefly of the teacher, since we have thus far 
 treated almost exclusively of the fatigue of pupils. 
 We noted once before that fatiguability reaches its 
 minimum, or mental efficiency its maximum, at the 
 beginning of the twenties. If other conditions are 
 favorable, we appear to remain in this stage some 
 ten or fifteen years, often still longer. As we reach 
 our fourth decade, efficiency slowly declines, and from 
 the age of 50 on, this decline becomes quite manifest 
 in many persons. From this, the conclusion may be 
 drawn that the teacher — like every mental and physi- 
 cal worker — ought, as he grows older, to have his 
 load lightened, not increased, as is at present so often 
 the case ; thus, for example, the teachers of the two 
 upper classes (the two Prima), who are frequently 
 the oldest of the staff, often have the hardest work — 
 with the possible exception of the teachers of the fifth 
 and sixth classes (the two Tertia). The opposite ar- 
 rangement would be more rational from the stand- 
 point of economy of energy. Basing their action on 
 this same argument, the Austrian association of 
 teachers of the middle schools has incorporated into 
 their program a movement for the reduction of hours 
 of service as the age of the teacher increases — a posi- 
 
114 MENTAL FATIGUE 
 
 tion for which Burger stein (p. 721) has pleaded for a 
 long time. It must be admitted that in Bavaria, as 
 the work is now distributed, there can, in general, be 
 no complaint that the teachers are overburdened, at 
 least so far as the number of hours of required in- 
 struction are concerned. And it is not only the right, 
 but the duty of those in charge of the schools to take 
 proper steps to insure that the teachers do not ex- 
 haust their energies all too soon by giving extra in- 
 struction outside the required school hours. The 
 maximal number of pupils for the middle and upper 
 classes seems, however, to be too great, when we con- 
 sider the labor of correcting the pupils ' work, and this 
 becomes particularly important in the cases, which 
 are many, in which the regular enrollment is the max- 
 imal number allowed. In the matter of number of 
 hours, only the teachers of the fourth and fifth classes 
 are overloaded in schools in which, as is still quite 
 often the case, they carry all the class instruction 
 save that in mathematics. 
 
 But even when the maximally permissible number 
 of hours are not assigned, the academically trained 
 teacher nevertheless finds that his capacity for work 
 is well taxed, more so than in most other academic 
 callings. Here, as ever, exceptions prove the rule. 
 Unstinted praise belongs to H. Schroder for having 
 proved incontestably by statistical inquiry that the 
 notion that the teacher, on account of his constant 
 association with youth, rejoices in unusual vitality is 
 a naive fable, that, as a matter of fact, the academi- 
 cally trained teacher, in particular, exhausts his pow- 
 ers sooner than do other officials of like training, and 
 that his liability to disease and his mortality exceeds 
 
THE LAWS OF FATIGUE 115 
 
 that of other public servants. Subsequent inquiries 
 have showed that he was right. The teacher of the 
 Volksschule works under still more unfavorable con- 
 ditions.* From a purely business point of view, 
 therefore, the teacher's capacity to work should be 
 economized, to the end that it may be rendered avail- 
 able for longer service. To say nothing at all of the 
 enormous importance for the success of teaching and 
 education that the teacher shall confront his pupils 
 with perfect freshness of mind and spirit, not with 
 the irritability and ill-humor of a neurasthenic. 
 
 *Cf. R. Wichmann's lecture on the health of teachers in the Ver- 
 handlungen der VII. Jahresversammlung des deutschen Vereines 
 fiir Schulgesundheitspflege, 1906, at Dresden, also the Erganzung- 
 sheft to Gesunde Jugend, VI, 1906, 27 ff., and the very noteworthy- 
 chapter on the hygiene of the teacher in Burgerstein, 718 ff., as 
 well as L. Wagner's comments in his translation of M. V. Mana- 
 ceine's he surmenage mental dans la civilisation moderne. 
 
CONCLUSION 
 
 There are many other questions that may be raised 
 in connection with this subject. And we might at- 
 tempt, in summarizing, to work out a unitary theory 
 of fatigue. But this would be possible only by dis- 
 cussing the general energetics of mental life, the gen- 
 eral theory of the forces operative in our psychical 
 life, their amounts, their origins, their consumption, 
 and the laws of their interaction. We have been led, 
 indeed, to do this on more than one occasion, as, for 
 instance, when — in our earlier presentation of the 
 problem of memory along Lippsian lines — we made 
 use of the concept of mental energy and its supply, 
 and when we said of it that it increases with rest and 
 nutrition, but is used up during work. But it would 
 lead us farther into the field of psychological theo- 
 ries and hypotheses than would M the purpose of the 
 present discussion were we to pursue these consider- 
 ations any longer. 
 
 7s it permissible that pupils be fatigued? But we 
 must first answer another question of importance to 
 the teacher. Is it permissible that pupils should be 
 fatigued by work, or more exactly, since there is no 
 work of any sort that does not fatigue, is it permis- 
 sible that pupils should be held to their work so long 
 that positive signs of fatigue, especially weariness 
 and reduction of work, appear? 
 
 116 
 
CONCLUSION 117 
 
 Perhaps this question will be answered by an anx- 
 ious negative, for fear lest the youthful nervous sys- 
 tem might otherwise suffer injury, and it will be cer- 
 tainly pointed out that the work that is done under 
 the stress of oncoming fatigue is surely of less value. 
 
 We need not be too anxious, even if we do not stop 
 to note that a piece of work done, though it may be 
 inferior to some other, is nevertheless better than 
 none at all. So long as the youthful worker, by dint 
 of adequate nutrition and abundant rest, especially 
 plenty of sleep, regains every morning his capacity 
 for, and pleasure in, work, so long there is no danger, 
 and we may unconcernedly let him work till he is 
 fatigued. Only, we should not neglect at the same 
 time to make clear to him the significance, as a pro- 
 tector of his health, of the feeling of weariness, and 
 to train him in this way to restore his powers and to 
 recuperate his energy rationally. 
 
 But I go farther than this. We may, indeed we 
 ought, off and on, to let him work a good bit under 
 the pressure of fatigue. We ought, now and then, to 
 induce him to take himself in hand and to draw on all 
 his reserve strength, so as to force him, as a test of 
 power and strength of will, to do more than he ordi- 
 narily does. Often enough, our life brings us into 
 situations where we have to put forth more than our 
 customary effort — situations that oblige us for some 
 time, and unfortunately often for no short time, 
 either, to turn a deaf ear to the kindly warnings of 
 that faithful guardian of our health. 
 
 A man must be trained to meet such situations as 
 these, too. He must learn by his own experience how 
 much strength he has laid by, in saving, for emergen- 
 
118 MENTAL FATIGUE 
 
 cies ; but he must also learn as well how to expend this 
 reserve prudently, and how he can restore it once 
 more. To learn the first lesson brings him assurance 
 and consciousness of power ; to learn the second de- 
 ters from foolish use of his reserve capital. To shield 
 the pupil from these tests of strength is to rear him 
 in weakness and timidity. And in this sense, we 
 agree with Zielinski when he says : " An easy school 
 is a social crime" (see Hofler, 39 f.). 
 
 In the same way, physical training develops in the 
 growing being the capacity for resistance that is 
 requisite for life, not by timidly sheltering him from 
 the harshness of the elements, but by gradual habitu- 
 ation to them, by a process of hardening. In this 
 physical training, he is compelled — not every day, 
 but from time to time — to undertake trying marches 
 and fatiguing athletic games, to endure thirst and 
 hunger, heat and cold, weariness and pain of limb, 
 to exercise self-control by deferring the gratification 
 of his desires (perfectly justifiable intrinsically) un- 
 til the resting place has been reached, the journey's 
 end attained. Then, to be sure, he is allowed to re- 
 store himself, but he is taught, even then, to choose 
 the proper kinds of food, to observe moderation, and 
 to take his repose in a rational manner. And if we 
 do this systematically and with due deliberation, if 
 we bring up our youth to proper care of their bodies, 
 more by strict training than by fine talking, we know 
 that we are thereby doing them a greater kindness 
 than if, out of weak sympathy, we had let them give 
 heed to every trivial call of their bodily needs. 
 
 Training in mental hygiene. Now. training in 
 mental hygiene must follow precisely the same plan, 
 
CONCLUSION 119 
 
 if it is to train up hardy and persistent workers, and 
 not dawdling weaklings, in the fields of mental effort. 
 It must occasionally exact a hard bit of work of the 
 youth. It is to be assumed, however, that it will make 
 these demands of him only when it can afford him a 
 proportionately longer time for subsequent rest and 
 recovery, and when, moreover, it teaches him method- 
 ically how the stint that is set may be done with the 
 available amount of strength, and how he may work 
 most economically and with maximal profit. This 
 kind of training in mental hygiene is peculiarly neces- 
 sary in these days, when large numbers of our 
 youths, especially in the cities, no longer bring with 
 them to the school the same unweakened nervous en- 
 ergy that our father and grandfathers displayed, when 
 life outside the school makes greater demands on the 
 pupils than formerly, and when, too — we must not 
 deceive ourselves on the point — the requirements of 
 the school, despite the fact that many a grammar has 
 become thinner, are certainly not less, when they are 
 all fully satisfied, than they were forty or fifty years 
 ago. For our school work today, as Keller rightly 
 declares, is less restricted and unitary, and to be sure 
 less monotonous, too, but rather of a kind to appeal 
 to more varied interests ; it is richer in content and 
 more intensive in treatment, since it proceeds less 
 mechanically, less by mere passive reception, but im- 
 pels the entire person to greater activity. 
 
 More intensive physical development. In point of 
 fact, the school cannot stop short at this training in 
 mental hygiene. It will ultimately be compelled in 
 some measure to reduce its scholastic requirements, 
 in order to give an opportunity for a serious and sys- 
 
120 MENTAL FATIGUE 
 
 tematic plan of physical development. For it cannot 
 be denied that our cultured classes are now retro- 
 grading physically, and this means that ultimately 
 they will lose in mental efficiency as well. The school 
 is certainly much less to blame for this condition of 
 affairs than people are apt to think. Only an excep- 
 tionally strong nervous system can withstand our 
 complex life, ever becoming more intensive, the de- 
 mands of our professional and our public career, as 
 well as the manifold claims arising from other aspects 
 of our life — claims that we might avoid if we wished, 
 but to which we tend more and more to give way from, 
 lack of moral force to decline them. Most of us suf- 
 fer, and our nervous vigor is seriously impaired by 
 this stress of life. 
 
 Nor is this all. The weakness of the parents is 
 handed down as a handicap of inheritance to the chil- 
 dren. These are facts to which we cannot close our 
 eyes. Rather must we keep the situation clearly be- 
 fore us, and use every endeavor to better faulty con- 
 ditions. 
 
 The edict of the Bavarian ministry of public in- 
 struction, which, several years ago, required the cul- 
 tivation of athletic games, has shown the right road. 
 We need only keep on in this direction. We must 
 make participation in games a duty, so that no pupils, 
 at least none of those who need them most, the weak- 
 lings, can fail to take part in them. And we must 
 make room for such games in our school program by 
 reducing the demands for intellectual work, so that 
 even the most industrious and conscientious, who are 
 the very ones that stand most in need of a counter- 
 actant to their mental effort, shall be able to indulge 
 
CONCLUSION 121 
 
 i 
 
 in games with an easy conscience and with no lack 
 of enthusiasm.* 
 
 Finally, we must undertake seriously to revise our 
 views of the relation of bodily and mental work. We 
 must reach the conviction that bodily life and mental 
 life are not separate systems, but that they spring 
 from the same sources ; that they do not keep separate 
 accounts, like married folks who divide their goods, 
 but work together, like husband and wife who hold 
 the funds in common, when whatever the one takes 
 out of the bank is no longer at the disposal of the 
 other. 
 
 If this exposition assists teachers to a fuller under- 
 standing of the close connections between the two 
 sides of our human nature and of the limits of their 
 efficiency, and if it stimulates them to make applica- 
 tion of this understanding, it will have served its 
 purpose. 
 
 *On the lack of adequate participation in athletic games, con- 
 sult Dornberger (Dtsch. Med. Prax., 13) and Grassmann (p. 170), 
 who demands compulsory participation to remedy this faulty con- 
 dition. 
 
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 A. J. Ph. — American Journal of Physiology. 
 
 A. P. — Annee psycho logique. 
 
 Ar. P. — Archives de Psychologie. 
 
 I. M. — International Magazine of School Hygiene. 
 
 I. K. — International Kongress. 
 
 J. E. P. — Journal of Educational Psychology. 
 
 P. A. — Psychologische Arbeiten. 
 
 P. J. — Paedologisch Jaarboek. 
 
 P. R. — Psychological Review. 
 
 P. S. — Pedagogical Seminary. 
 
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 S. Z. — Schiller-Ziehen, Sammlung von Abhandlungen aus dem 
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 Z. P. — Zeitschrift fur Psychologie und Physiologie der Sinnes- 
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BIBLIOGRAPHY 123 
 
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 M. C. Scbuyten, Onderzoekingen over estbesiometriscbe variatie 
 
 bij kinderen gedurende bet scbooljaar, in P. J., 5 : 1906-7. 
 M. C. Scbuyten, On voor-en namiddags onderwijs, in P. J., 6: 
 
 1907-8. 
 M. C. Scbuyten, Wat is over lading? Ontstaat sij door een te veel of 
 
 door eenzijdigelading? In P. J., 7: 1908-9. 
 M. C. Scbuyten, Estbesiometriscbe onderzoekingen op volwassen 
 
 leerlingen die een avondkursus f olgen, in P. J., 7 : 1908-9. 
 M. C. Scbuyten, Mesure de la fatigue intellectuelle cbez les enfants 
 
 des deux sexes avec l'esthesionietre, in Revue de psycbiatrie, 
 
 1908, taken from his Education de la femme. Paris, 1909. 
 J. Sikorski, Sur les effets de la lassitude provoquee par les travaux 
 
 intellectuels cbez les enfants & l'age scolaire, in Ann. d'byg. 
 
 publ., 2 : 1879. 
 W. Specbt, Ueber kliniscbe Ermudungsmessungen, in A. G. P., 3: 
 
 1904. 
 W. Stern, Ueber Psychologie der individuellen Differenzen. 1900. 
 G. Tawney und V. Henri, Die Trugwahrnehmung zweier Punkte, 
 
 in Ph. S., 11 : 1895. 
 O. Teljatnik, Review in Burgerstein und Netolitzky (462 ff.) of his 
 
 own experiments, published first in Vjestnik psichiatri- 
 
 nevropatologi, 12: 1897 (St. Petersburg). 
 Th. Vannod, La fatigue intellectuelle et son influence sur la sen- 
 
 sibilite cutanee, in Rev. Med. de la Suisse Romande, 17 : 1897. 
 Th. Vannod, La methode esthesioinetrique pour la mensuration de 
 
 la fatigue intellectuelle, in Report 1st Int. Cong, on School 
 
 Hygiene, Nurnberg, 1904, vol. II. 
 
BIBLIOGRAPHY 127 
 
 N. Vaschide, Les recherches experimentelles sur la fatigue intel- 
 
 lectuelle, in Revue de Philos., 5: 1905. 
 M. Verworn, Allgemeine Physiologie. 4th ed., 1903. 
 L. Wagner, Unterricht und Ermiidungsmessungen an Scbulern des 
 
 neuen Gymnasiums in Darmstadt, in S. Z., 1 : 1898, Hft. 4. 
 L. Wagner, Die geistige Ueberburdung in den boberen Scbulen, in 
 
 his translation of Marie v. Manaceine, Le surmenage mental 
 
 dans la civilisation moderne. 1905. 
 W. Weichardt, Ueber Ermudungstoxine und Antitoxine, in Miinch- 
 
 ener Medizinische Wochenschrift, 51 : 1904. 
 W. Weichardt, Ueber Ermudungstoxine und deren Hemmungs- 
 
 korper. Klinik, 2 : 1906. 
 W. Weygandt, Ueber den Einfluss des Arbeitswechsels auf fort- 
 
 laufende geistige Arbeit, in P. A., 2 : 1899. 
 B. Wichmann, Der Stand der akademisch gebildeten Lehrer und 
 
 die Hygiene, in Gesunde Jugend, 6 : 1906, Erganzungshef t. 
 B. Wichmann, Die Ueberburdung der Lehrinnen, in Rept. 1st In- 
 tern. Cong. School Hygiene, Nurnberg, 1908. 
 W. H. Winch, Some measurements of mental fatigue in adolescent 
 
 pupils in evening schools, in J. E. P., 1 : 1910, 13-24, 83-100. 
 
 For other literature on the fatigue problem, consult Baade, 
 Baginsky, Burgerstein, Claparede, Dornberger und Wunderer, 
 Eulenburg, Gineff, Joteyko (Fatigue), Meumann, and Kraepelin's 
 works.* 
 
 For criticisms of the methods for measuring fatigue, consult, 
 besides these authors, R. Tiimpel, Ueber die Versuche die geistige 
 Ermudung durch mechanische Messungen zu untersuchen, in Zeits. 
 f. Philosophic und Padagogik, 5: 1908, J. Larguier des Bancels, 
 Essai de comparison des differentes methodes proposees pour la 
 mesure de la fatigue intellectuelle, in A. P., 5 : 1899, E. L. Thorn- 
 dike, Mental fatigue, in P. R., 7 : 1900, and R. Altschul, Wert der 
 Experimente bei Schuluntersuchungen, in Rept. 1st Intern. Cong. 
 School Hygiene, Nurnberg, 1904, Vol. II. 
 
 *A comprehensive bibliography on fatigue up to the year 1903, prepared 
 by Mile. Joteyko, will be found in the Dictionnaire de Physiologic— 
 Translator. 
 
APPENDIX I. 
 
 Selected References on Fatigue fob English Readers. 
 
 J. A. Bergstrom, A new type of ergograph, with a discussion of 
 
 ergographic experimentation, in A. J. P., 14: 1903, 510-510. 
 H. G. Beyer, The relation between physical and mental work, in 
 
 Jour. Boston Soc. Med. Sci., 4 : 1900, 121-132. 
 T. Bolton, The reliability of certain methods for measuring the 
 
 degree of fatigue in school children, in P. R., 7 : 1900, 136-7. 
 T. Bolton and Eleanora Miller, On the validity of the ergograph 
 
 as a measurer of work capacity, in Nebraska Univ. Studies, 
 
 1904, 79, 128. 
 
 A. C. Ellis and Maud Shipe, A study of the accuracy of the present 
 methods of testing fatigue, in A. J. P., 14 : 1903, 496-509. 
 
 S. I. Franz, On the methods of estimating the force of voluntary 
 muscular contractions and on fatigue, in A. J. Ph., 4: 1900, 
 348-372. 
 
 F. Galton, see Offner's bibliography. 
 
 C. F. Hodge, Some effects of electrically stimulating ganglion cells, 
 in A. J. P., 2 : 1889, 376-402. 
 
 Marion E. Holmes, see Offner's bibliography. 
 
 T. Hough, Ergographic studies in neuro-muscular fatigue, in A. 
 J. Ph., 5 : 1901, 240-266. 
 
 Wm James, The energies of men, in Philos. Rev., 16 : 1907, 1-20. 
 
 F. S. Lee, Fatigue, in the Harvey Lectures, Phila., 1906, 169-194; 
 also in J. Amer. Med. Ass., 46: 1906, 1491, and in Studies in 
 Physiology, Columbia University, 1902-7. 
 
 F. S. Lee, The action of normal fatigue substances on muscle, in 
 A. J. Ph., 20 : 1907, 170-179. 
 
 F. S. Lee, The nature of fatigue, in Pop. Sci. Mo., 76: Feb., 19 L0, 
 182-195. 
 
 J. H. Leuba, see Offner's bibliography. 
 
 W. P. Lombard, The effect of fatigue on voluntary muscular con- 
 tractions, in A. J. P., 3 : 1890, 24-42. 
 
 W. P. Lombard, Some of the influences which affect the power of 
 voluntary muscular contractions, in J. of Physiol., 13: 1892, 
 1-58. 
 
 A. MacDonald, Experimental study of school children, etc. Re- 
 print of chs. 21 and 25 of Rept. U. S. Comsnr. of Educ, 1899. 
 
 W. MacDougall, On a new method for the study of concurrent men- 
 tal operations and of mental fatigue, in Brit. J. of Psych., 1 : 
 
 1905, 435-445. 
 
 W. MacDougall, The conditions of fatigue in the nervous system, in 
 
 Brain, Nov., 1909, 256-268. 
 H. D. Marsh, The diurnal course of efficiency, Columbia Univ. diss., 
 
 N. Y., 1906. Pp. 99. 
 
 128 
 
APPENDIX I 129 
 
 S. W. Mitchell, Wear and tear, or hints for the overworked. 5th 
 
 ed., Phila., 1887. Pp. 76. 
 J. M. Moore, Studies in fatigue, in Studies from the Yale Psych. 
 
 Laboratory, 3: 1895, 68-95. 
 A. Mosso, Fatigue. Eng. tr., N. Y., 1904. Pp. 334. 
 M. V. O'Shea, Mental fatigue, in Pop. Sci. Mo., 55 : 1899, 511-524. 
 W. B. Pillsbury, Attention waves as a means of measuring fatigue, 
 
 in A. J. P., 14 : 1903. 
 G. T. Patrick, Fatigue in school children : a review of the experi- 
 ments of Friedrich and Ebbinghaus, in Univ. of Iowa Studies 
 
 in Psych., 1 : 1897, 77-86. 
 W. H. Rivers, On mental fatigue and recovery, in J. of Mental 
 
 Science, 42: 1896, 525-529. 
 C. E. Seashore, A method of measuring mental work: the psy- 
 
 cherograph, in Univ. of Iowa Studies in Psych., 3 : 1902, 1-17. 
 C. E. Seashore, The experimental study of mental fatigue, in 
 
 Psych. Bulletin, 1 : 1904, 97-101. 
 C. E. Seashore and G. H. Kent, Periodicity and progressive change 
 
 in continuous mental work, in P. R. Mon. Supp., No. 28 : 1905, 
 
 46-101. 
 C. S. Sherrington. The integrative action of the nervous system, 
 
 N. Y., 1906. Especially 214-221. 
 F. W. Smedley, Rept. dept. child-study and pedagogic investigation, 
 
 Chicago, 1898-1899 and 1899-1900. Also reprinted in Rept. 
 
 U. S. Comsnr. of Educ, 1902, vol. 1. 
 Carrie R. Squire, Fatigue: suggestions for a new method of in- 
 vestigation, in P. R., 10: 1903, 248-267. 
 T. Storey, The influence of fatigue upon the speed of voluntary 
 
 contraction of human muscle, in A. J. Ph., 8 : 1903, 355. 
 E. Swift, Sensibility to pain, in A. J. P., 11 : 1900, 312-7. 
 E. L. Thorndike, Mental fatigue, in P. R., 7 : 1900, 466-482, 547-579. 
 
 E. L. Thorndike, Mental fatigue, in J. E. P., 2 : 1911, 61-80. 
 
 A. D. Waller, The sense of effort: an objective study, in Brain, 
 14 : 1891, 218-249. 
 
 F. L. Wells, (a) A neglected measure of fatigue, in A. J. P., 19: 
 
 1908, 345-358. (b) Normal performance in the tapping test 
 before and during practice, with special reference to fatigue, 
 in A. J. P., 19: 1908, 437-483. (c) Studies in retardation as 
 given in the fatigue phenomena of the tapping test, in A. J. P., 
 20: 1909, 38-59. (d) Sex differences in the tapping test: an 
 interpretation, in A. J. P., 20 : 1909, 353-363. 
 
 J. H. Wimms, The relation of fatigue and practice produced by 
 different kinds of mental work, in Brit. J. of Psych., 2 : 1907, 
 153-195. 
 
 W. H. Winch, see Offner's bibliography. 
 
 W. R. Wright, Some effects of incentives on work and fatigue, in 
 P. R., 13 : 1906, 23-34. 
 
 C. S. Yoakum, An experimental study, of fatigue, in P. R. Mon. 
 Supp., 11 : 1909, whole No. 46. Pp. 131. 
 
APPENDIX II. 
 The Terminology of the Geeman School System. 
 
 No attempt has been made in the translation to find English 
 equivalents for Volksschule, Gymnasium and other types of Ger- 
 man schools, because there are no exact English equivalents. A 
 brief explanation of the German school system is therefore in 
 order. Each German state has its own system, yet there is a gen- 
 eral similarity of organization. The Prussian system may be taken 
 as typical. In that state, what would correspond to our public 
 schools are divided into two sections, which are often termed the 
 elementary and the secondary schools, respectively, though these 
 designations convey the false idea of an 'educational ladder,' like 
 our own system, that does not exist in Germany. 
 
 The elementary schools include the Volksschule, the Mittel- 
 schule and the Fortbildungsschule. These three schools serve to 
 train children of the laboring or lower business classes. Attend- 
 ance in the Volksschule is absolutely compulsory from six to four- 
 teen years, unless the child is otherwise instructed. The Mittel- 
 schule includes instruction in French and English, exacts a mod- 
 erate tuition fee, is patronized by the lower middle classes, and 
 hence draws pupils of better ability and home training. The mod- 
 ern Mittelschule may be considered a substitute for the earlier 
 Burgerschule. The Fortbildungsschule (continuation school) is a 
 short course, required or optional, giving vocational and industrial 
 instruction to pupils who have finished the Volksschule or Mittel- 
 schule. 
 
 The higher or secondary schools include the Vorschule and 
 various types of Gymnasium and Realschule, as well as the 
 Hbhere Mddchenschule or Tochterschule. The Vorschule is vir- 
 tually an elementary preparatory school, entered at six, and turn- 
 ing its pupils into higher schools proper at the age of nine. Prac- 
 tically all German children destined for higher education use the 
 Vorschule in place of the Volksschule or Mittelschule. Of the 
 higher schools proper, the Gymnasium, the Realgymnasium and the 
 Oberrealschule represents three co-ordinate, but independent, insti- 
 tutions, each with a prescribed nine-year curriculum. Pupils com- 
 monly enter, then, at nine, and are graduated at eighteen, so that 
 the course virtually includes the first two years of the ordinary 
 American college. Pupils may, subject to geographical limitations, 
 elect the type of school, and may in theory elect certain optional 
 supplementary work in them, but in practice, the required work 
 is heavy enough for most pupils. The nine classes, beginning at 
 the last, or senior, year are known as Oberprima, Unterprima,, 
 Obersecunda, Untersecunda, Obertertia, Untertertia, Quarta, 
 Quinta and Sexta, respectively. 
 
 130 
 
APPENDIX II 131 
 
 The Reformgymnasium and the Refwmrealgymnasium have 
 practically the same curricula as the Gymnasium and the Real- 
 gymnasium, only so arranged that the pupil need not decide finally 
 upon his course of study until the age of twelve, instead of at nine. 
 
 The Progymnasium, the Realprogymnasium and the Realschule 
 are three schools, corresponding to those indicated by their names, 
 but offering only six of the nine years' course; they are found 
 oftenest in smaller cities that cannot afford the nine-year courses. 
 
 The Hohere Mddchenschule, or Tochtcrschule, is a ten-year 
 school for girls (thus allowing them one year more than boys) 
 and covering as a rule the ages six to sixteen. A very recent 
 movement (since 1908) provides for the enlargement of these 
 courses by the addition of three more years, which will give girls 
 an education equal to that offered boys. 
 
 For a description of the Frauenanstalt, or school for women, 
 and the Lehrerinnenseminar, or normal school for female teachers, 
 as well as for further details concerning the schools mentioned 
 above, the reader may consult J. F. Brown, The Training of 
 Teachers for Secondary Schools m Germany and the United 
 States, Ch. I. 
 
INDEX OF NAMES 
 
 Abelson, 33, 35, 85 f., 102. 
 Adsersen, 77. 
 Amberg, 66. 
 
 Baade, 65. 
 
 Bach, 111. 
 
 Baur, 30, 39. 
 
 Bellei, 47 f., 51. 
 
 Bernhard, 89. 
 
 Bettman, 43 f. 
 
 Binet, 8, 15, 28, 33 f ., 42, 51, 58. 
 
 Blazek, 34, 75, 105. 
 
 Bolton, 27, 35, 37. 
 
 Bonoff, 34, 77. 
 
 Boubier, 80. 
 
 Bourdon, 52. 
 
 Brann, 76. 
 
 Burgerstein, 47, 57, 60, 72, 77, 
 
 79, 82 f., 87, 89, 91, 100, 102, 
 
 107, 114 f. 
 
 Claparede, 24, 42, 74, 78, 100, 107. 
 ClaviSre, 24 f. 
 
 Dankwarth, 48. 
 Dornberger, 84, 89, 121. 
 Dornbltith, 103. 
 
 Ebbinghaus, 33, 48 ff., 58. 
 Eulenberg, 23, 32 f., 111. 
 
 Fechner, 32. 
 
 Fere, 9, 27, 74. 
 
 Ferrari, 34. 
 
 Friedrich, 47 f., 85, 87, 89. 
 
 Galton, 80. 
 
 Gaupp, 51, 102. 
 
 Germann, 36. 
 
 Gilbert, 28. 
 
 Gineff, 24 ff., 36 ff., 41. 
 
 Grassmann, 89, 121. 
 
 Griesbach, 31, 33 ff., 55, 87, 101, 
 
 105, 110, 113. 
 Heller, 31, 34, 81, 86. 
 Hellpach, 82. 
 Helmholtz, 24. 
 Henri, 8, 15, 28, 58. 
 Herberich, 84. 
 Hering, 11. 
 Hermann, 12 f., 96. 
 Hertel, 77. 
 Heumann, 86, 93. 
 Hirscblaff, 24 f . 
 Hoch, 25. 
 Hofler, 78, 118. 
 Holmes, 58, 103. 
 Hopfner, 59 f . 
 
 Januschke, 49. 
 Joteyko, 24, 34. 
 
 Keller, 27, 34, 43, 82, 119. 
 
 Kemsies, 24, 48, 52, 75, 83 f., 105. 
 
 Kerschensteiner, 77. 
 
 Key, 66, 88. 
 
 Kraepelin, 13, 24 ff., 35, 58, 60 ff., 
 
 66 ff., 72, 76, 93, 98, 100, 108, 
 
 112. 
 Kiilpe, 32. 
 
 Landois, 10. 
 Laser, 47. 
 Lay, 28, 72. 
 Leuba, 36. 
 Ley, 34. 
 Lindley, 93. 
 Lipmann, 51. 
 Lipps, 31. 
 Loeb, 23. 
 Lobsien, 28, 41, 43. 
 
 Manaeeine, 115. 
 Merian-Genast, 57. 
 
 132 
 
INDEX OF NAMES 
 
 133 
 
 Meumann, 14, 27, 29, 36, 38 f., 
 
 42, 54, 66, 75. 
 Michotte, 34. 
 
 Mosso, 8 ff., 15, 23 f., 27, 96, 100. 
 Motchoulsky, 31. 
 Muller, J. J., 95. 
 Muller, R., 25. 
 
 Netschajeff, 48. 
 Noikow, 34. 
 
 Offner, 14, 31, 54, 64, 101, 103. 
 Oehrn, 43. 
 Oseretzkowsky, 27, 62. 
 
 Philippe, 25. 
 
 Ranke, 10. 
 Ravenhill, 89. 
 Richter, 48, 57 f ., 78, 100. 
 Ritter, 36, 49, 52, 106 f. 
 Rivers, 13, 93. 
 Romer, 88. 
 
 Sakaki, 34, 105 f. 
 
 Schiller, 109. 
 
 Schlesinger, 34. 
 
 Schinid-Monnard, 84. 
 
 Schroder, 114. 
 
 Schulze, 72, 98. 
 
 Schuyten, 24, 26, 34, 48, 53, 71, 
 
 90, 106, 108. 
 Sharp, 51. 
 Sikorski, 5, 46. 
 Smedley, 102. 
 Spearman, 33, 51. 
 
 Specht, 76 f. 
 Stern, 28 f., 72. 
 Storring, 39. 
 Swift, 42. 
 
 Tawney, 36. 
 
 Teljatnik, 48 f., 52 f., 55, 72, 100. 
 
 Terman, 51. 
 
 Thorndike, 21. 
 
 Treutlein, 82 f., 107. 
 
 Uhlig, 58. 
 Ulmann, 23. 
 Urbantschitsch, 95. 
 
 Vannod, 34, 38, 42, 75, 87, 101, 
 
 105 f. 
 Vaschide, 24, 42, 105 f . 
 Verworn, 8, 10, 12 f. 
 
 Wagner, 34, 66, 87, 101, 105, 110, 
 
 115. 
 Weber, 32. 
 Weichardt, 11. 
 Wells, 28. 
 Wertheimer, 51. 
 Weygandt, 98. 
 Wichmann, 115. 
 Wiersma, 51. 
 Winch, 21, 52, 108. 
 
 Young, 95. 
 
 Ziehen, 33. 
 Zielinski, 118. 
 
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