doi:10.1016/j.cub.2006.11.043


Magazine
R7

but can be mundane. Many 
beginning faculty members want 
their first papers to be ‘home 
runs’. But, ‘home runs’ come after 
the lab has momentum, and the 
way to gain that momentum is 
to start producing as quickly as 
possible. 

Do you think there is an 
increased trend towards 
translational research? 
Throughout the history of 
modern science there have been 
times when political or societal 
needs have set the agenda for 
scientific research. For example, 
World War II accelerated 
research in a number of areas 
related to communications 
and weapon systems. So the 
present push towards finding 
cures for the major illnesses 
that plague humankind today 
is understandable. That said, 
I find the extent of the present 
translational rhetoric a bit 
troubling for two reasons. First, 
there is a phenomenal amount of 
human suffering that today could 
be alleviated with the knowledge, 
medicines and technology that 
we already have, if the political 
will were there. Second, I 
believe that much of what drives 
discovery by scientists is sheer 
curiosity, and the desire to 
solve puzzles. It is a mistake to 
forget that the creation of new 
knowledge, for its own sake, is 
an important part of what makes 
us human. At the same time, 
science is increasingly expensive 
and technologically demanding, 
and our fellow citizens pay for 
it. Therefore, each of us has the 
responsibility to honestly, to the 
best of our ability, attempt to 
create new knowledge. Some 
of this new knowledge will be 
directly relevant to curing human 
disease or other important 
society issues in the short-term. 
Some of the new knowledge may 
change conceptual frameworks in 
ways that are unpredictable, with 
unpredictable consequences, on 
both short-term and long-term 
timescales. 

Volen Center and Biology Department, 
Brandeis University, Waltham, 
Massachusetts 02454-9��0, USA.  
E-mail: marder@brandeis.edu
Quick guide

Prosopagnosia

Alison M. Harris and  
Geoffrey K. Aguirre

What is prosopagnosia? 
Prosopagnosia — from the Greek 
prosop for ‘face’ and agnosia 
for ‘ignorance’ — also known as 
face-blindness, is an impairment 
in the ability to recognize other 
individuals by their faces, 
sometimes even those of parents, 
siblings and spouses (Figure �). 
Despite its potentially distressing 
social consequences for sufferers, 
this disorder has proved a boon 
to cognitive neuropsychology 
research, providing some of the 
earliest and strongest evidence for 
the existence of ‘face- selective’ 
processing in the human 
visual system. Although first 
systematically observed only 60 
years ago by Joachim Bodamer, 
prosopagnosia is now the subject 
of an extensive literature. Despite 
what you may have heard, 
prosopagnosics seldom mistake 
their wives for hats.

What causes prosopagnosia? 
Prosopagnosia can be ‘acquired’ 
as a result of brain damage, 
specifically from lesions to 
the occipito-temporal region. 
In recent years, there has 
also been growing interest in 
quantifying lifelong impairments 
in face recognition, known as 
developmental or congenital 
prosopagnosia. In such cases, 
the etiology is often unknown, but 
evidence of familial inheritance 
suggests a genetic component 
in at least some individuals. 
Recent research has also 
examined whether links exist 
between congenital impairments 
in face perception and social 
developmental disorders like 
autism.

What cognitive systems are 
affected in prosopagnosia? 
Impairment of any number 
of cognitive systems, from 
perception to memory, could 
result in a failure to recognize 
familiar faces. Yet, although 
prosopagnosia is often 
accompanied by mild to moderate 
difficulties in object recognition, 
prosopagnosics may learn to rely 
on non-face visual cues, such as 
hairstyle or gait, for recognition, 
as well as information from other 
modalities, such as voice. This 
allows many prosopagnosics to 
discern facial characteristics such 
as gender, age, and emotion. 
Prosopagnosia is therefore 
commonly conceptualized as 
reflecting damage to a cognitive 
system specific to visual 
processing of facial identity. 
Supporting this idea, Moscovitch 
and colleagues (�997) described a 
patient, CK, with a severe deficit in 
general object perception whose 
face recognition was nonetheless 
intact. This ‘double dissociation’ 
between prosopagnosics and 
object agnosics like CK supports 
the existence of two separate 
visual processing streams for 
faces and other objects.

What neural systems are 
affected in prosopagnosia? 
Acquired prosopagnosia is 
frequently associated with 
bilateral (occasionally unilateral, 
right) damage to extrastriate 
visual cortex, particularly the 

Figure �. Prosopagnosia.

In Giuseppe Arcimboldo’s The Vegeta-
ble Gardener (Natura), prosopagnosics 
can see the vegetables, but not the face. 
 Object agnosic CK, on the other hand, 
 easily perceives the face but not its un-
usual composition. (Sistema Museale 
della Città di Cremona — Museo Civico 
“Ala Ponzone”.)



Current Biology Vol �7 No �
R8

Correspondences

Mediaeval 
artists: Masters 
in directing the 
observers’ gaze

Ute Leonards1, Roland 
Baddeley1, Iain D. Gilchrist1,  
Tom Troscianko1, Patrick Ledda2 
and Beth Williamson3

The gold leaf in early 
Renaissance paintings such as 
Duccio’s “The Annunciation” 
(�3��) appears to glow when lit 
by candles as the artist would 
have expected. Subjectively, 
the candle-lit painting appears 
drastically different from the 
same painting illuminated with 
diffuse daylight typical of modern 
art galleries. By analysing 
the density of observers’ eye 
fixations when looking at this 
painting under these two lighting 
conditions, we found objective 
differences in where in the 
painting observers attended: 
specifically, the glow of the gold 
induced shifts in fixations to 
symbolically important regions of 
the painting.

To investigate the effects of 
illumination on the perception 
of mediaeval paintings, we first 
constructed an area of gold 
leaf, using the techniques of the 
Italian Renaissance painters, 
and measured its reflectance 
properties. We also measured 
the spectral characteristics 
of beeswax candle light and 
daylight illumination. This 
allowed us to mimic the effects 
of such light sources on gold. 
On the basis of these data, 
we then used photorealistic 
computer graphics to render 
a high resolution digital scan 
of the original painting under 
both beeswax candle illuminant 
and daylight illuminant (see 
Supplemental experimental 
procedures in the Supplemental 
data available on-line with 
this issue). In the behavioural 
experiment, we had two groups 
of human participants view one 

of the two rendered pictures 
while we measured their eye 
movements. Figure � shows 
how the nature of the illuminant 
affected where in the picture the 
participants fixated in the picture.

The gold leaf, which is used 
so extensively in paintings of 
this era, creates a dramatic 
glow effect when lit by candles, 
which would have been the 
contemporary illuminant for these 
paintings. This glow effect leads 
the eye to fixate in a different part 
of the image than when ordinary 
diffuse daylight illumination is 
used. In the case of Duccio’s 
Annunciation, observers look 
less at the faces of the Angel 
and the Virgin and more towards 
the Virgin’s hand. One might 
speculate that this is the eyes 
being directed away from the 
faces (looking at them directly 
might have been considered 
irreverent). Alternatively, the 
eyes could have been directed 
towards the Virgin’s hand, which 
she uses to grasp her veil and 
to gather her mantle around 
herself protectively. Her gesture 
has been claimed to reflect 
a state of mind somewhere 
between disquiet and reflection, 
consistent with the early stages 
of the Angelic Colloquy or the 
interaction between the Angel 
and the Virgin [�]. The methods 
used by this great Italian painter 
appear to exploit the effect 
of ‘glowing’ gold to direct the 
viewer’s eyes. 

Our results raise two important 
scientific issues. First, why does 
the subtle induction of ‘glow’ 
have such a significant effect 
on eye movements? Sources of 
illumination are often the most 
perceptually visible regions 
in a visual scene. Traditional 
low- level salience models of 
eye movement control [2] would 
predict a high fixation probability 
of these regions. In the current 
experiment, however, eye 
movements were not directed 
toward the brightest parts of the 
image, such as the gold- covered 
garments or windows under 
candle-light conditions, as 
predicted if fixations were driven 
by either brightness or the global 
effect in which saccades are 
directed to the centre of gravity 
fusiform gyrus. This relatively 
posterior locus of injury 
buttresses the view of acquired 
prosopagnosia as a disorder 
of visual processing. Although 
people with developmental 
prosopagnosia have no obvious 
lesion in the fusiform gyrus, 
recent work suggests that there 
is a subtle alteration of the white 
matter connections in this region 
of the brain. Neurons in this area 
have been shown to respond 
vigorously, and selectively, to the 
visual image of faces.

Aren’t faces just harder to 
recognize? Or the subject 
of greater experience? In 
fact, several such alternative 
explanations have been proposed. 
Many are variants on the 
‘individuation’ account, which 
holds that special processing 
for faces is not specific to 
this visual stimulus category. 
Proponents of this view note that 
faces are a special category of 
object for which we constantly 
identify individual exemplars, 
whereas such ‘subordinate-level’ 
processing is seldom necessary 
for recognition of other classes of 
object. In line with this view, some 
prosopagnosics demonstrate 
impairments in individuation 
of other object classes, such 
as specific animals. But this 
within- category impairment 
may reflect damage to adjacent 
but separate cortical areas. 
Furthermore, some experiments 
have still found specific 
impairment for faces versus other 
object classes in prosopagnosic 
subjects when the difficulty of 
individuation for these stimulus 
sets is matched. The issue of 
the specificity of the deficit in 
prosopagnosia remains an active 
area of debate. 

Where can I find out more?
Barton, J.J. (2003). Disorders of face 

perception and recognition. Neurology 
Clinic 21, 52�–548.

Moscovitch, M., Winocur, G., and Behrmann, 
M. (�997). What is special about face 
recognition? Nineteen experiments on 
a person with visual object agnosia and 
dyslexia but normal face recognition. J. 
Cognitive Neurosci. 9, 555–604.

Department of Neurology, University 
of Pennsylvania, Philadelphia, 
Pennsylvania �9�04, USA.  
E-mail: aguirreg@mail.med.upenn.edu

mailto:aguirreg@mail.med.upenn.edu

	Prosopagnosia
	What causes prosopagnosia?
	What cognitive systems are affected in prosopagnosia?
	What neural systems are affected in prosopagnosia?
	Aren’t faces just harder to recognize? Or the subject of greater experience? 
	Where can I find out more?