Neuropsychology
2018, Vol. 32, No. 2, 123–137© 2018 American Psychological Association
0894-4105/18/$12.00 http://dx.doi.org/10.1037/neu0000414

Mapping Self-Face Recognition Strategies in Congenital Prosopagnosia
Manuela Malaspina and Andrea Albonico

Junpeng Lao and Roberto Caldara

Università degli studi di Milano-Bicocca and Milan Center for
Neuroscience, Milano, Italy

University of Fribourg

Roberta Daini

This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

Università degli studi di Milano-Bicocca, Italy
Objective: Recent evidence showed that individuals with congenital face processing impairment (congenital prosopagnosia [CP]) are highly accurate when they have to recognize their own face (self-faceadvantage) in an implicit matching task, with a preference for the right-half of the self-face (rightperceptual bias). Yet the perceptual strategies underlying this advantage are unclear. Here, we aimed toverify whether both the self-face advantage and the right perceptual bias emerge in an explicit task, andwhether those effects are linked to a different scanning strategy between the self-face and unfamiliar
faces. Method: Eye movements were recorded from 7 CPs and 13 controls, during a self/otherdiscrimination task of stimuli depicting the self-face and another unfamiliar face, presented upright andinverted. Results: Individuals with CP and controls differed significantly in how they explored faces. In
particular, compared with controls, CPs used a distinct eye movement sampling strategy for processing
inverted faces, by deploying significantly more fixations toward the nose and mouth areas, which resulted
in more efficient recognition. Moreover, the results confirmed the presence of a self-face advantage inboth groups, but the eye movement analyses failed to reveal any differences in the exploration of theself-face compared with the unfamiliar face. Finally, no bias toward the right-half of the self-face wasfound. Conclusions: Our data suggest that the self-face advantage emerges both in implicit and explicit
recognition tasks in CPs as much as in good recognizers, and it is not linked to any specific visual
exploration strategies.

General Scientific Summary
Individuals with face recognition impairment from birth (i.e., congenital prosopagnosia) shownormal accuracy when they have to recognize their own face (self-face advantage) both in implicit
and explicit identification tasks. In particular, this advantage does not depend on any specific visual
exploration strategies and it seems more likely related to a general self-recognition mechanism,
which allows them to overcome their deficit at least in the case of one’s own face.

Keywords: congenital prosopagnosia, self-face recognition, face inversion, eye movements
Supplemental materials: http://dx.doi.org/10.1037/neu0000414.supp

The term “prosopagnosia” refers to a selective deficit affecting
the recognition of both familiar and unfamiliar people by using
face information alone (Bodamer, 1947). This impairment has
been primarily described in individuals who have sustained cortical lesions in adulthood, often as a consequence of head trauma or
stroke. In its acquired form (acquired prosopagnosia), the facerecognition deficit is attributed to a lesion in the ventral occipito-

temporal cortex, limited to the right hemisphere (De Renzi & diPellegrino, 1998) or bilateral (Sergent & Signoret, 1992), and it isusually perceived by the patients as they start to encounter some
unexpected difficulties in recognizing familiar people after thetrauma. Congenital Prosopagnosia (CP; also known as “developmental prosopagnosia,” e.g., Susilo & Duchaine, 2013) insteadrefers to a face-processing impairment that is present at birth in the

Manuela Malaspina and Andrea Albonico, Dipartimento di Psicologia,
Università degli studi di Milano-Bicocca, and NeuroMI–Milan Center for
Neuroscience, Milano, Italy; Junpeng Lao and Roberto Caldara, Eye and Brain
Mapping Laboratory (iBMLab), Department of Psychology, University of
Fribourg; Roberta Daini, Psychology Department and COMiB – Optics andOptometry Research Center, Università degli studi di Milano-Bicocca.
Andrea Albonico is now at the Human Vision and Eye Movement
Laboratory, Departments of Medicine (Neurology), Ophthalmology

and Visual Sciences, University of British Columbia, Vancouver, Canada.
Correspondence concerning this article should be addressed to Manuela Malaspina, who is now at the Human Vision and Eye Movement
Laboratory, Departments of Medicine (Neurology), Ophthalmology
and Visual Sciences, University of British Columbia, 2550 Willow
Street, Vancouver, BC, Canada V5Z 3N9. E-mail: m.malaspina1@
campus.unimib.it
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124

MALASPINA, ALBONICO, LAO, CALDARA, AND DAINI

absence of brain damage and in the presence of preserved sensory
and intellectual functions (Ariel & Sadeh, 1996; McConachie,
1976; Schmalzl, Palermo, Green, Brunsdon, & Coltheart, 2008). In
accordance with previous evidence suggesting a genetic contribution to the impairment (Grüter, Grüter, & Carbon, 2008; Kennerknecht et al., 2006), recent preliminary findings indicate that
CP could be associated with the DNA polymorphism of the receptor gene of oxytocin (a hormone that regulates basic social andreproductive behaviors; Cattaneo et al., 2016). On the contrary ofacquired prosopagnosics, individuals with CP are often not evenaware of their impairment because face perception was nevernormal in the lifetime of these individuals (Behrmann & Avidan,2005), so that they are not able to compare their actual facerecognition abilities with previously normal abilities. Furthermore,congenital prosopagnosics have had the opportunity to develop
different compensatory strategies in their lifetime, so that they areoften able to recognize people by using different types of cues,
such aphysiognomic cues (e.g., clothing, posture, and style ofwalking) or acoustic cues (e.g., voice; Palermo et al., 2011).
Despite some heterogeneity in CP, most studies agree that there
is a relationship between the face recognition impairment of thispopulation and their anomalous scan path behavior during the
exploration of faces (Schmalzl et al., 2008; Schwarzer et al., 2007).
Although good recognizers focus their gaze primarily on central
facial features, suggesting that these regions are the most informative regions in a human face (Hsiao & Cottrell, 2008; Peterson& Eckstein, 2012; Schmalzl et al., 2008; Schwarzer et al., 2007),
individuals with CP tend to show a more dispersed gaze, directing
their attention not only on central features but also on externalfeatures with both unfamiliar and famous faces (Barton, Radcliffe,
Cherkasova, & Edelman, 2007; Schmalzl et al., 2008; Schwarzer
et al., 2007). Furthermore, congenital prosopagnosics typicallyshow no or weaker familiarity modulation in their scan pathbehavior: Whereas good recognizers use fewer fixations and lessviewing time to identify famous faces compared with unfamiliar
faces, individuals with CP typically use a similar number offixations and viewing time in exploring both unfamiliar and famous faces (Barton et al., 2007; Schmalzl et al., 2008; Schwarzer
et al., 2007). As a possible explanation for this behavior, it has
been suggested that the lack of a familiarity modulation in congenital prosopagnosics’ eye movements could be related to theabsence of residual facial memories or internal viewing schema inthese individuals (Barton et al., 2007; Lê, Raufaste, & Démonet,
2003; Schmalzl et al., 2008), because they never developed normal
face recognition abilities.
Thus, previous findings seem to support the idea that, along with
the inability to recognize familiar and unfamiliar faces and thepresence of an anomalous scan path behavior, individuals with CP
explore every face in the same way, independently of whether theface is familiar (or famous) to them or not. However, recent
findings have demonstrated that despite their face recognition
impairment, congenital prosopagnosics (Malaspina, Albonico &Daini, 2016) achieve considerable accuracy when they have torecognize their own face. Similarly, one study on an acquired
prosopagnosic patient showed preserved trait inferencing from theself-face but not from familiar faces (Klein, Gabriel, Gangi, &Robertson, 2008). These results seem consistent with previous
evidence in healthy controls suggesting that we have specificknowledge for the self, and that the processing of self-information

is distinct from the processing of other-information (Frassinetti,
Ferri, Maini, Benassi, & Gallese, 2011; Kircher et al., 2000). In
particular, the existence of a specific advantage for the self-face(i.e., the self-face advantage [SFA]) has already been proven, andit consists of faster response times (RTs) when participants have torecognize their own face compared with unfamiliar or familiar
faces (Ma & Han, 2010; Sugiura et al., 2005). This advantage also
seems to be present with both upright and inverted faces (Keyes &Brady, 2010), despite the difficulty that characterizes the recognition of the latter ones because of the unusual orientation of presentation (i.e., the face inversion effect (IE), which consists ofbetter performance for upright compared with inverted faces; e.g.,
Farah, Wilson, Drain, & Tanaka, 1995).
As further proof of the specificity of the self-face, although therecognition of familiar and unfamiliar faces seems characterized
by a tendency to visually process the hemi-face that falls in theobserver’s left visual hemi-space (i.e., a left perceptual bias),
self-face recognition seems to be related to the opposite bias. Bothgood recognizers and individuals with CP, indeed, tend to rely
more on the right half-side of their face (i.e., a right perceptualbias), which falls in the right visual hemi-space looking at themirror, when they are asked to recognize themselves (Brady,
Campbell, & Flaherty, 2004; Malaspina et al., 2016), thus suggesting the existence of an asymmetry in the perception of the selfface, and that the SFA might be related to a preference for theright-half of the self-face. However, the possibility that the rightperceptual bias could be detected also in terms of eye movements
has still to be determined.
The first aim of the present studies was to investigate whether
the SFA showed by good recognizers and individuals with CP
during self-face recognition is also reflected in their scan pathbehavior. For this reason, we recruited a group of congenital
prosopagnosics and healthy controls who underwent a simple
recognition task involving different facial stimuli depicting theparticipant’s self-face and another unfamiliar face. We wanted tocompare the eye movements made by the two groups on these two
types of stimuli and investigate whether the SFA is detectable also
as a change in gaze behavior. Moreover, because the existing study
showing the advantage in the congenital prosopagnosic population
used an indirect task (Malaspina et al., 2016), here, by means of adirect task, “me/not me,” we tested whether these individuals also
still show the same advantage when asked to consciously identify
themselves. In particular, in this case, the use of both eye movement and behavioral measurements could allow us to obtain information on both the online visual processing of the stimulus aswell as on the resulting outcome. Eye movements can give us
information about how the efficiency and distribution of gazecontrol affect the perception (and recognition) of a stimulus(Bloom & Mudd, 1991), and provide insights into how prosopagnosic individuals process the information in faces (Barton et al.,2007). Finally, because the advantage for the self-face has been
demonstrated with both upright and inverted faces (Keyes &Brady, 2010), here, we decided to test both orientations of presentation as well.
Finally, we asked whether the rightward bias characterizing“indirect” self-face perception is also detectable in a “direct” task,
and whether it is linked to a different visual exploration of the two
halves of the facial stimulus. Thus, we used chimeric stimuli
created from the original picture of the face of each participant

HOW CONGENITAL PROSOPAGNOSICS LOOK AT THEMSELVES?

(i.e., a composite face made of two right half-faces and a composite face made of two left half-faces) in addition to the original faceand mirror-reversed face. In particular, we would expect the rightperceptual bias to be present and reflected in an increased visual
exploration of the right self-hemi-face, independently of its position in the visual field.

MethodThis document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

Participant Selection
A total of 38 participants (recruited as described in the next
section) took part in the experiment. All participants had normal orcorrected-to-normal vision, and each of them received course
credits for participation in two 1-hr sessions. An informed consent
form for the processing of personal data and for the use of theirphotographs was obtained from all participants before testing, andthe ethical approval for this study was specifically granted by the
Ethics Committee of the University of Milano-Bicocca.
Control participants. In order to select individuals with noface recognition difficulties, 31 undergraduate students of the
University of Milano-Bicocca (all females, right-handed, age
range ⫽ 19 –27 years, mean age ⫽ 22.23 ⫾ 2.43) were recruited
through the Milano-Bicocca Sona System and underwent a batteryof tests assessing face and object recognition (see below).
After the screening phase, on the basis of the participants’agreement to come back to undergo the second part of the study(because participants were receiving course credit for their participation, roughly half of them did not return for the second part ofthe experiment, as they had already completed their course requirement), 13 of the initial group of 31 participants returned for themain experiment and served as the final control group for theexperimental phase (CG group; all females, right-handed, age
range ⫽ 19 –23 years, mean age ⫽ 21.46 ⫾ 1.56). None of themexperienced face recognition difficulties during their lives.
Congenital prosopagnosics. Seven females (all right-handed,
age range ⫽ 20 –25 years, mean age ⫽ 21.23 ⫾ 1.89) with CP took
part in this study and composed our experimental group (CPgroup). They were recalled from previous studies (Cattaneo et al.,2016; Malaspina et al., 2016; Malaspina, Albonico, Toneatto &Daini, 2017) because of their verified impairments in recognizing
unfamiliar and familiar faces. Furthermore, all these individuals
showed a DNA polymorphism of the receptor gene of oxytocin ina previous study (Cattaneo et al., 2016), further confirming thediagnosis of the congenital form of the face recognition impairment.
As the controls, all the CP participants underwent a battery oftests investigating face and object recognition, and a semistructured interview conducted by an experienced neuropsychologist inorder to assess the presence of CP and to exclude possible alternative explanations for face recognition impairment. All congenital prosopagnosics reported significant difficulty in recognizing
people starting from face information alone and provided detailed
examples about it. They also reported that they did not have any
history of brain damage, that their impairment was present frombirth and other common symptoms of prosopagnosia, as theirstrategy of relying on nonfacial cues to recognize the others.

125

Face and Object Recognition Abilities Assessment
All participants underwent a first screening session during
which their face and object recognition abilities were assessed. In
particular, our battery was composed of five tests: the Benton
Facial Recognition Test (BFRT; Benton, 1994; Benton & Van
Allen, 1968), the Cambridge Face Memory Test (CFMT; Duchaine & Nakayama, 2006), the Boston Naming Test (BNT; Kaplan,
Goodglass, & Weintraub, 1983), a Famous Faces Recognition Test
(FFRT), and a Famous Monuments Recognition Test (FMRT).
These tests were selected to determine the presence of prosopagnosia by assessing participants’ ability to recognize unfamiliar andfamiliar faces (i.e., BFRT, CFMT and FFRT, respectively), andtheir visual object recognition and general visual processing abilities (i.e., BNT, FMRT).
The CFMT (Duchaine & Nakayama, 2006) is one of the mostcommonly used tests for assessing prosopagnosia (Wilmer et al.,2012). It has been proven to be the most sensitive test for detecting
face recognition impairment and to have impressive test–retest
reliability (Bowles et al., 2009; Duchaine & Nakayama, 2004,
2006; Wilmer et al., 2010). In addition, we calculated an additional
index from the CFMT: the IE (Yin, 1969). The IE is the difference
between the total score of the upright and inverted faces (i.e., the“cost” for recognizing inverted faces) and was included as afurther criterion of face recognition impairment because it represents a qualitative index of face processing, which is often notpresent or inverted in participants with prosopagnosia (e.g.,Behrmann & Avidan, 2005). The BFRT (Benton, 1994; Benton &Van Allen, 1968) was included as part of the neuropsychologicalbattery in order to investigate the perceptual aspects of face recognition in our participants, as some studies have suggested that
some, but not all, individuals with CP can experience face discrimination difficulties in addition to face memory impairment(Ariel & Sadeh, 1996; de Gelder & Rouw, 2000). The FFRT was
administered in order to assess participants’ ability to identify
famous people from their faces (see Malaspina et al., 2017 formore details). Lastly, participants also underwent two control tests
on object recognition: an FMRT (described in Cattaneo et al.,2016), asking participants to name pictures of national and international monuments taken in their most conventional perspective(all pictures were taken from the Internet and labeled for reuse
with modification), and the BNT (Kaplan et al., 1983), in order toassess each participant’s visual object recognition and visual naming ability by using black-and-white line drawings.
The scores obtained in these tests by the 31 initial healthy
participants who took part in the screening phase formed thesample for the calculation of z scores for the CP and CG participants. The mean scores for each test (⫾ 1 SE) were as follows:
47.61 ⫾ 3.12 for the BFRT, 58.29 ⫾ 8.99 for the upright versionof the CFMT, 43.39 ⫾ 5.95 for the inverted version of the CFMT,
14.90 ⫾ 6.44 for the IE, 31.39 ⫾ 5.76 for the FFRT, 20.68 ⫾ 5.42
for the FMRT, and 55.55 ⫾ 3.13 for the BNT. In Table 1, theindividual test scores for each congenital prosopagnosic and the zscores calculated for each individual CP against the data from theinitial group of 31 participants are reported. In addition, to further
confirm the presence of prosopagnosia in the CP group, our zscores were compared with the published control scores for thistest (Duchaine & Nakayama, 2006).

53
⫺.81
58
1.10
56
.46
54
⫺.50
58
1.10
55
⫺.18
57
.78
55.86 ⫾ 1.95
56.00 ⫾ 2.20
20
⫺.13
18
⫺.49
17
⫺.68
18
⫺.49
27
1.17
18
⫺.49
24
.61
20.29 ⫾ 3.77
20.85 ⫾ 5.56
14
⫺3.02
11
⫺3.53a14⫺3.02a17⫺2.50a18⫺2.32a12⫺3.37a18⫺2.32a14.86 ⫾ 2.85
32.08 ⫾ 5.95

z score

22
25
20
19
19
22
20
A.D.
C.R.
E.B.
G.M.
M.B.
R.B.
S.E.
CP mean ⫾ SD
CG mean ⫾ SD

45
⫺.84
40
⫺2.44a40⫺2.44a
50
.77
47
⫺.20
46
⫺.52
46
⫺.52
44.86 ⫾ 3.67
48.62 ⫾ 2.99

40
⫺2.03
36
⫺2.48a36⫺2.48a37⫺2.37a34⫺2.70a40⫺2.03a37⫺2.37a37.14 ⫾ 2.19
65.62 ⫾ 4.68

⫺2.14
⫺2.77a⫺2.77a⫺2.65a⫺3.03a⫺2.27a⫺2.37a34⫺1.58
30⫺2.25a35⫺1.41
31⫺2.08a
37
⫺1.07
44
.10
44
.10
36.43 ⫾ 5.68
46.54 ⫾ 3.71

6
⫺1.38
6
⫺1.38
1
⫺2.16a6⫺1.38⫺3⫺2.78a⫺4⫺2.93a⫺7⫺3.30a.71 ⫾ 5.47
19.08 ⫾ 4.77

a
a
a

Age
Participant

Raw
score

z scoreRaw
score

z scorez score (Duchaine& Nakayama, 2006)

Raw
score

z scoreRaw
score

z scoreRaw
score

z scoreRaw
score

z score

Raw
score

BNT
FMRT
FFRT
Inversion effect
CFMT Inverted
CFMT Upright
BFRT

Table 1
Demographic Details and Scores (Raw and z Scores) at the Tests Investigating Face and Nonface Object Recognition for the 7 Congenital Prosopagnosics (CP) and
Average Score for the Control Group (CG)This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

Note. BFRT ⫽ Benton Facial Recognition Test; CFMT ⫽ Cambridge Face Memory Test; FFRT ⫽ Famous Face Recognition Test; FMRT ⫽ Famous Monuments Recognition Test; BNT ⫽ Boston
Naming Test.
aPathological score.

MALASPINA, ALBONICO, LAO, CALDARA, AND DAINI126

All seven of the congenital prosopagnosics were impaired inface recognition; indeed, they all performed poorly (i.e., 2 SD
below the mean of the control group) in the upright version of the
CFMT (both considering our control sample and the publisheddata of the controls from Duchaine & Nakayama, 2006) and the
FFRT. Furthermore, all congenital prosopagnosics showed asmaller IE and, particularly, four of them had an IE score twostandard deviations lower than controls. In the BFRT, only two ofseven congenital prosopagnosics performed pathologically, consistently with other studies proving that some individuals with CP
can experience difficulty with face discrimination in addition to
face memory (Ariel & Sadeh, 1996; de Gelder & Rouw, 2000).
Moreover, previous studies have also highlighted that individuals
with prosopagnosia may achieve normal score on the BFRT,
thanks to the availability of external cues in this test (Duchaine &Nakayama, 2004).
By contrast, in the tests investigating object recognition abilities(FMRT and BNT), all congenital prosopagnosics performed in thenormal range, further confirming the selectivity of their impairment. None of the controls who agreed to come back for thesecond part of the study (13 females) showed any impaired performance in any tests.

Material and Stimuli
Apparatus and procedure. Participants sat in a comfortablechair approximately 57 cm from a Sony Trinitron monitor (27-in.,
1920 ⫻ 1080 pixels, refresh rate of 120 Hz in 32-bit color) in asilent room and with their head stabilized with a chin and foreheadrest. Participant’s eye movements were monitored at a rate of
1,000 Hz with a spatial resolution of 0.2° by an Eye-Link 1000 eye
tracking system (SR Research, Mississauga, Canada). Althoughviewing was binocular, only the right eye was tracked. Before theexperiment began, participants underwent a 5-point calibration(calibration target of 0.15° diameter black circle overlaid on a
0.35° diameter white circle). The calibration was accepted when
the worst error point in the calibration was less than 0.75° and theaverage error for the 5 points less than 0.5°.
The experiment was controlled by MATLAB R2012a, and a
Microsoft video-game controller was used to collect participants’
responses. The instructions of the task were displayed by using aself-paced presentation on the screen at the beginning of theexperiment. Each trial began with a central drift correction circle(0.5°), which participants were asked to accurately fixate on, inorder to check fixation drift for minor changes in head position (inthe case that the drift correction error was larger than 0.5°, thecalibration procedure was repeated). When the participant’s fixation remained stable within 0.75° of this drift correction circle forat least 200 ms, one of the possible facial stimuli (see the Stimuli
section) appeared on a black background and remained on thescreen for as long as the participant responded. Participants were
instructed to freely look at the stimulus and to decide whether the
chimeric face represented the self-face or another individual’s faceby pressing one of two keys on the video-game controller. They
were asked to be as accurate and as fast as possible. Participant’s
response was then followed by a 500-ms random noise mask, inorder to eliminate any possible afterimage before the beginning of
the next trial. Although viewing was binocular, only the right eyeThis document is copyrighted by the American Psychological Association or one of its allied publishers.
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HOW CONGENITAL PROSOPAGNOSICS LOOK AT THEMSELVES?

was tracked, and the eye movements were recorded from thestimulus onset until participant’s response.
The experiment consisted of two blocks: a first block (uprightcondition), during which the original mirror image and two composite faces of the participant and matched control were presented
in the upright perspective, and a second block (inverted condition),
involving the same stimuli but presented upside-down. Each condition (upright and inverted) consisted of 80 randomized trials
depicting the four facial stimuli of the participant and four facial
stimuli of the control unknown to the participant. The order of thetwo tasks was counterbalanced across participants. Furthermore, inorder to avoid possible differences related to stimulus–response
spatial compatibility, response key buttons were also counterbalanced across participants.
Before each condition, a practice session was run in order to let
the participants familiarize themselves with the task and to practice
making responses. This practice session consisted of eight trials
depicting all the possible facial stimuli used for the experiment andgave the participants the opportunity to take a first look at each ofthem. Practice trials were not counted for statistical analysis.
Stimuli. A unique set of face stimuli was created for eachparticipant. This set included four facial stimuli, built starting fromthe participant’s own face and four facial stimuli, created startingfrom a control face (unknown to the participant). A participant’s
face could also be used as control face for another participant. In
this case, it was verified that our participants did not know one
another before the experiment. Moreover, the control face wasalways matched so that it looked as similar as possible to theparticipant’s face (i.e., eyes and eyebrows color, skin texture).
All participants agreed to be photographed under symmetricalambient light on a white background in order to create the facial
stimuli needed for the experiment (see Malaspina et al., 2016 formore details). Participants were asked to look directly at thecamera (Nikon d5100) with a neutral expression. At a later stage,
each photograph was converted into grayscale using Adobe Photoshop CS4, and, if necessary, the whole image (3648 ⫻ 2736
pixels) was rotated between ⫺1° and 1° and scaled in order toadjust eye collinearity between the two hemi-faces. Then, eachface was cropped into an oval shape so that external features suchas hair were excluded; any specific traits (e.g., pimples, moles andscars) that could facilitate self-recognition were also removed. A
vertical line passing through the face midline was used to crop theoval faces exactly at midpoint in order to obtain the right and left
sides of the face (192 ⫻ 243 pixels), which were afterward
duplicated and mirror-reversed in order to create four facial stimuli
for each participant: an original face (R_L, as people know theirown face as a photograph image), a mirror face (L_R, as people
know their own face as a mirror image), a composite face made by
two left half-faces (L_L chimeric), and a composite face made by
two right half-faces (R_R chimeric; see Figure 1). The final images
were fully included in a 384 ⫻ 486 pixel rectangle (approximately
12 cm ⫻ 14.5 cm and 12° ⫻ 15° of visual angle).
Summarizing, all these steps resulted in four images (originalface-R_L, mirror face-L_R, left-chimeric-L_L, and right-chimericR_R) of each person’s face (participant and matched control) for a
total of eight images in each unique stimulus set—four images ofthe participant’s face and four of the matched control—which
could also be presented upside-down depending on the block of theexperiment. The facial stimuli needed for the inverted condition127

were created by vertically flipping each of the four facial stimuli of
the participant and matched control.
Stimuli nomenclature. Stimuli nomenclature was based on
the observer’s point of view. In order to better assess which of thetwo hemi-faces and which of the two visual hemi-spaces weremore relevant for self and others’ recognition, we followed thefollowing rules: The first letter of the stimulus indicated which
half-face was falling in the observer’s left visual space, and thesecond one indicated which half-face was falling in the observer’s
right visual space (e.g., “R_L” means that the stimulus was composed on the left side by the right half-face falling and on the rightside by the left half-face).

Results
Behavioral Data
Proportion of correct responses and RTs from correct trials wereadopted as dependent measures. RTs were measured from thestimulus onset until the participant’s response. RT outliers (2.5 SD
above or below the mean for each participant) were discarded andnot analyzed (less than 1% for each participant). In order toprovide a better summary of our findings, we also analyzed theinverse efficiency score (IES), defined as RT/accuracy (Bruyer &Brysbaert, 2011).
The behavioral data (i.e., accuracy, RTs, and IES) from thecontrol and congenital prosopagnosic groups were analyzed using
a linear mixed model with the lme4 package (Bates et al., 2014) in
R (R Core Team, 2014). A first model was run including thefactors Face Identity (self vs. other), Orientation (upright vs.
inverted), Group (CG vs. CP), and a random intercept for eachparticipant. Then, a second model was run in order to investigate
any possible effect of the four facial stimuli (L_L, L_R, R_R, and
R_R) on participants’ performance only in the self-condition (i.e.,in the familiar face condition, as no effect should be expected in
the case of an unfamiliar face). Thus, in this second model, thefactors included were Stimulus (L_L, L_R, R_R, and R_R), Orientation (upright and inverted), Group (CG and CP), and a random
intercept for each participant. For both models, F tests from the
LMER results are presented (Type III with Satterthwaite approximation for degrees of freedom), and significant differences were
further explored by Bonferroni post hoc multiple comparisons(corrected p values are reported). Effect sizes were also calculated
as Cohen’s f 2 following the procedure described in Selya, Rose,
Dierker, Hedeker, and Mermelstein (2012).
Accuracy analysis failed to reveal a significant effect of Group,
F(1, 18) ⫽ 0.07, p ⫽ .79, f 2 ⫽ 0.017, but revealed significant main
effects of Orientation, F(1, 294) ⫽ 22.80, p ⬍ .001, f 2 ⫽ 0.074,
and Face Identity, F(1, 294) ⫽ 8.65, p ⬍ .01, f 2 ⫽ 0.031, showing
that, overall, both groups were more accurate in recognizing upright than inverted faces (0.966 ⫾ 0.01 and 0.914 ⫾ 0.03, respectively) and in recognizing the self-face compared with the otherface (0.951 ⫾ 0.02 and 0.928 ⫾ 0.03, respectively). Theinteraction between the Face Identity and the Group was alsosignificant, F(1, 294) ⫽ 4.99, p ⬍ .05, f 2 ⫽ 0.016, highlighting
that, in terms of accuracy, the SFA (i.e., the difference between theaccuracy in the self- and the other-condition) was significant onlyin the CP group (control group ⫽ .007, p ⫽ 1.00; CP group ⫽.053, p ⫽ .02).

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MALASPINA, ALBONICO, LAO, CALDARA, AND DAINI

Figure 1. Examples of facial stimuli. (A) Letters “R” and “L” refer to side of the model’s face from the model’s
perspective. For example, the farthest left image in A1 demonstrates the layout of an original photograph. withthe right side of the models face in the observer’s left visual space and the left side of the models face in theobserver’s right visual space (“R–L” means that the stimulus was composed of the right half-face falling in theobserver’s left visual space and the left half-face falling in the observer’s right visual space). Images A2 to A4
demonstrate how each image was modified relative to the original layout (A1). (B) Examples of four stimuli usedin the experiment for one model: (B1) The original photograph; (B2) the left-right reversal, or mirror image, ofthe original photograph; (B3) a right-half-of-model’s-face chimeric; and (B4) the left-half-of-model’s-facechimeric. (C) The labels used for each type of stimulus (adapted from “Right perceptual bias and self-facerecognition in individuals with congenital prosopagnosia” by M. Malaspina, A. Albonico, & R. Daini, 2016,
Laterality: Asymmetries of Body, Brain, and Cognition, 21, Copyright 2016 by Taylor & Francis pp. 118 –142.
Reprinted with permission.).

Analysis on RTs failed to reveal a significant effect of Group,
F(1, 18) ⫽ 2.76, p ⫽ .11, f 2 ⫽ 0.119, but showed that the main
effects of Face Identity, F(1, 294.13) ⫽ 71.11, p ⬍ .001, f 2 ⫽0.110, and Orientation, F(1, 294.13) ⫽ 165.79, p ⬍ .001, f 2 ⫽0.243, were significant: Both groups were faster in responding totheir own face (637 ⫾ 24 ms) than to the other-face (693 ⫾ 26 ms),
and they were also faster in responding to upright faces (619 ⫾ 19ms) than to inverted faces (711 ⫾ 27 ms). More interestingly, theinteraction between Group and Face Identity, F(1, 294.13) ⫽18.34, p ⬍ .001, f 2 ⫽ 0.029, was also significant: The SFA (i.e.,the difference between the RTs in the other- and self-conditions)
was significant for both groups (control group ⫽ 32 ms, p ⬍ .001;
CP group ⫽ 98 ms, p ⬍ .001), and the CP group was significantly
slower than the control group only in the Other condition (751 ⫾50 ms and 661 ⫾ 25 ms, respectively, p ⬍ .001) but not in the Self
condition (653 ⫾ 39 ms and 629 ⫾ 29 ms, respectively, p ⫽ 1.00).
This result suggests that in the self-condition, participants with CP
improved their performance to the point that it could be comparable with one of controls. Finally, the interaction between Groupand Orientation was significant, F(1, 294.13) ⫽ 11.85, p ⬍ .001,
f 2 ⫽ 0.020, showing that congenital prosopagnosics were signif-

icantly slower than controls only with inverted faces (765 and 682
ms, respectively).
The analysis on the IES confirmed the presence of a significant
effect of Orientation, F(1, 291.42) ⫽ 26.99, p ⬍ .001, f 2 ⫽ 0.086,
and Face Identity, F(1, 291.42) ⫽ 13.69, p ⬍ .001, f 2 ⫽ 0.055: Bothgroups performed better with upright than inverted faces (647 ⫾ 27
ms and 810 ⫾ 97 ms, respectively), and in the self-condition compared with the other-condition (678 ⫾ 32 ms and 787 ⫾ 101 ms,
respectively). The main effect of Group was not significant, F(1,18) ⫽ 2.73, p ⫽ .12, f 2 ⫽ 0.053; however, once again, theinteraction between Group and Face Identity was significant, F(1,291.42) ⫽ 6.94, p ⬍ .01, f 2 ⫽ 0.026, highlighting that congenital
prosopagnosics showed a performance comparable with controls inthe self-condition (control group ⫽ 677 ⫾ 45; CP group ⫽ 681 ⫾ 42;
p ⫽ 1.00), whereas in the other-condition, they performed significantly worse than controls (control group ⫽ 713 ⫾ 38; CP group ⫽925 ⫾ 69; p ⬍ .001; see Figure 2).
The type of facial stimulus (L_L, L_R, R_R, and R_R) did notseem to influence participant’s performance neither in terms ofaccuracy, F(3, 126) ⫽ 1.11, p ⫽ .348, f 2 ⫽ 0.053, nor RTs, F(3,This document is copyrighted by the American Psychological Association or one of its allied publishers.
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HOW CONGENITAL PROSOPAGNOSICS LOOK AT THEMSELVES?

Figure 2. Mean inverse efficiency score of the control group (CG) andcongenital prosopagnosia group (CP) for the other- and self-conditions.
Vertical lines indicate ⫾1 standard error. IES ⫽ inverse efficiency score.
ⴱp ⬍ .05.

125.93, f 2 ⫽ 0.004) ⫽ 0.274, p ⫽ .844, or IES, F(3, 125.98) ⫽1.01, p ⫽ .392, f 2 ⫽ 0.024.
Taken together, these results confirmed the findings of previous
studies showing that the SFA is detectable both in good recognizers and individuals with CP. In particular, the SFA is detectable interms of RTs in the control group and in terms of accuracy, RTs
and IES in the CP group. Moreover, the SFA in the CP group is soeffective that in the self-face condition, their performance is comparable with controls.

Eye Movement Data
Eye movement data were preprocessed using EyeLink Data
Viewer software (SR Research Ltd., Mississauga, Canada). All
fixations were recorded from the beginning to the end of each trial.
Because the initial fixation was always at the center of the screen,superimposed on the fixation dot, it was discarded, and the fixation
following this first fixation was taken as the onset of the scanningsequence.
First, we looked at the basic characteristics of the eye movements made by participants while they were encoding the face. The
total scan time per stimulus (i.e., the sum of the durations of all
fixations) was analyzed in order to investigate the amount ofscanning the participants needed to recognize the face; mean
fixation number and duration per stimulus were also examined todetermine whether any change in total scan time was related to anincrease in the number or the length of fixations. Finally, mean
first fixation duration was also analyzed as indicator of participants’ preference when starting to explore the facial stimulus.
Second, we explored the scanning distribution over the facestimulus. Fixation distribution was analyzed by iMap4 (Lao, Miellet, Pernet, Sokhn, & Caldara, 2017), which has the advantage to
avoid any issues related to the use of predefined regions of interest

129(Caldara & Miellet, 2011) by providing a completely data-driven
way to analyze the scanning distribution.
Fixation features. Eye movement data were analyzed using alinear mixed model with the lme4 package (Bates et al., 2014) in
R (R Core Team, 2014). The same models tested on the behavioral
results were run also on the eye movement data. Again, for bothmodels, F tests from the linear mixed-effects model (LMER)
results are presented (Type III with Satterthwaite approximation
for degrees of freedom), and significant differences were further
explored by Bonferroni post hoc multiple (corrected p values arereported).
The main effect of the Group was significant in the total scantime, F(1, 18) ⫽ 5.13, p ⬍ .05, f 2 ⫽ 0.122, in the mean numberof fixations per stimulus, F(1, 18) ⫽ 6.50, p ⬍ .05, f 2 ⫽ 0.235, andin the mean first fixation duration, F(1, 18) ⫽ 7.02, p ⬍ .05, f 2 ⫽0.200, showing that overall congenital prosopagnosics differed in
the way they explored the facial stimulus (see Figure 3). Indeed,participants with CP needed more time (735 ⫾ 39 ms) and more
fixations (3.70 ⫾ 0.25) to encode the stimulus compared with
controls (668 ⫾ 26 ms and 3.06 ⫾ 0.17, respectively); accordingly, they also made shorter first fixations (253 ⫾ 40 ms) andoverall fixations (307 ⫾ 29 ms) than controls (356 ⫾ 31 ms and361 ⫾ 24 ms, respectively).
The main effect of the Orientation was significant in the total
scan time, F(1, 294.2) ⫽ 28.99, p ⬍ .001, f 2 ⫽ 0.055, in the mean
number of fixations, F(1, 294) ⫽ 71.28, p ⬍ .001, f 2 ⫽ 0.070, in
the mean fixation duration, F(1, 294.02) ⫽ 22.29, p ⬍ .001, f 2 ⫽0.031, and in the mean first fixation duration, F(1, 294.11) ⫽12.92, p ⬍ .001, f 2 ⫽ 0.024. Both congenital prosopagnosics andcontrols used more scan time and more (and shorter) fixations in
the inverted conditions (scan time ⫽ 713 ⫾ 23 ms; mean fixation
number ⫽ 3.45 ⫾ 0.16; mean fixation duration ⫽ 328 ⫾ 83 ms;
mean first fixation duration ⫽ 304 ⫾ 25 ms) compared with the
upright one (scan time ⫽ 670 ⫾ 22 ms; mean fixation number ⫽3.12 ⫾ 0.14; mean fixation duration ⫽ 356 ⫾ 91 ms; mean first
fixation duration ⫽ 337 ⫾ 28 ms). The interaction between Groupand Orientation was also significant in the mean number of fixations per stimulus, F(1, 294) ⫽ 6.06, p ⬍ .01, f 2 ⫽ 0.015, showingthat the increase in the number of fixations in the inverted condition was greater in the CP group (control group ⫽ 0.25; CPgroup ⫽ 0.45).
Finally, the Face Identity factor significantly influenced the total
scan time, F(1, 294.2) ⫽ 18.87, p ⬍ .001, f 2 ⫽ 0.036, and themean number of fixation per stimulus, F(1, 294) ⫽ 6.82, p ⬍ .01,
f 2 ⫽ 0.014, highlighting that the SFA is evident also in terms ofeye movements (see Figure 3). Indeed, participants needed lesstime and less fixations in order to recognize their own face (675
⫾ 21 and 3.24 ⫾ 0.16) compared with an unfamiliar face (708⫾ 23 ms and 3.33 ⫾ 0.15). By contrast, the analysis on the
fixation duration did not show any difference between the selfand other-conditions, suggesting that even though the self-facerequires less information in order to be recognized, the amount of
information extracted with each fixation is similar in the two
conditions.
Interestingly, the interaction between Group and Face Identity
was nearly significant in the total scan time, F(1, 294.2) ⫽ 3.19,
p ⫽ .07, f 2 ⫽ 0.009, showing that, similar to the IES results, thedifference between CPs and controls was bigger in the othercondition (762 ⫾ 39 and 679 ⫾ 26 ms) than in the self-condition

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Figure 3. Eye movements data for (A) the control group (CG) and congenital prosopagnosia group (CP);(B) the inverted and upright conditions; and (C) the other- and self-conditions. ⴱ p ⬍ .05.

(709 ⫾ 37 and 657 ⫾ 25 ms). In accordance with the behavioral
results, the type of facial stimulus (L_L, L_R, R_R, and R_R) did
not seem to influence participant’s eye movements neither in termsof total scan time, F(3, 126.08) ⫽ 0.33, p ⫽ .804, f 2 ⫽ 0.013, nor
in mean number of fixations, F(3, 126) ⫽ 0.27, p ⫽ .848, f 2 ⫽0.0001, or in fixation duration (first fixation duration, F[3,126.01] ⫽ 1.65, p ⫽ .18, f 2 ⫽ 0.008; overall fixations duration,
F[3, 125.93] ⫽ 0.37, p ⫽ .77, f 2 ⫽ 0.021).
Taken together, these results showed that congenital prosopagnosics required longer scan times to recognize faces, and it seems
that this could be largely not related to the fact that their fixations
lasted longer, but it could happen because they used more fixations. Furthermore, confirming previous findings, both groups
made fewer fixations and had shorter scan time with upright faces
than inverted faces, reflecting the presence of an IE in the characteristics of their eye movements. Finally, all participants re-quired fewer fixations and less viewing time to recognize theirown face than the unfamiliar face—that is, they showed an SFA.
Spatial fixation mapping using iMap4. The spatial mappingof the fixation distribution was performed using iMap4 (Caldara &Miellet, 2011; Lao et al., 2017). iMap4 is a data-driven analysis
framework for statistical fixation mapping, in which fixation distribution is modeled using linear mixed model and hypothesis
testing is performed using nonparametric statistics based on resampling and spatial clustering (Lao et al., 2017).
iMap4 projects the fixation durations into two-dimensional
space according to the x- and y-coordinates at the single-trial level.
The sparse fixation duration maps were then smoothed with a 2D
Gaussian kernel function of full width at half maximum around 1°of visual angle. The smoothed fixation map for each condition isthen estimated within each participant by taking the mean of thetrials in the same condition. To model the spatial pattern of fixation

HOW CONGENITAL PROSOPAGNOSICS LOOK AT THEMSELVES?

pattern, the conditional mean fixation maps were normalized using
the z score (Figure 4A). The resulting 3D matrix (Trials ⫻x-Size ⫻ y-Size) was then modeled as the response variable iniMap4. Each pixel in the smoothed fixation map was fitted with alinear mixed model using the following formula:Fixation Intensity(s,y) ~ 1 ⫹ Group ⫹ Face Indentity⫹ Face Orientation ⫹ Group ⴱ Face Identity⫹ Group ⴱ Face Orientation⫹ Face Identity ⴱ Face Orientation

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⫹ GroupⴱFace Identity ⴱ Face Orientation⫹ (1ⱍSubject), 1 ⱕ x ⱕ x Size, 1 ⱕ y ⱕ ySize
Thus, the fixation duration at different spatial location (e.g.,eyes, nose, or mouth) was fitted as a linear function of Group (CGor CP), Face Identity (self or other), Face Orientation (upright orinverted face), and their interactions. The effect of subject was
fitted as a random intercept. iMap4 uses the LinearMixedModelclass from the Statistics Toolbox in MATLAB for model fitting.
The linear mixed model coefficients were estimated using restricted maximal likelihood with the default iMap4 settings. A
bootstrap spatial clustering procedure threshold on the cluster size
was applied for the null hypothesis significance testing and for
multiple comparison corrections (Lao et al., 2017).
An ANOVA on the linear mixed model revealed a significant
main effect of Face Orientation on the right eye and the mouth131

region, and a significant interaction of Group and Face Orientation
around the right eye and nose (see Figure 4B). The effect of Face
Identity does not modulate the fixation pattern, as its main effectand interaction are not significant after multiple comparison correction using bootstrap clustering. Overall, participants fixatedmore the mouth and nose areas with inverted faces compared withupright faces (local maximum within the significant cluster, F[1,280] ⫽ 33.88, ␤upright ⫽ 0.17 [⫺0.338, 0.670], and ␤inverted ⫽1.08 [0.577, 1.586]; local minimum, F[1, 280] ⫽ 3.88,
␤upright ⫽ ⫺0.09 [⫺0.202, 0.022], and ␤inverted ⫽ 0.07 [⫺0.043,
0.181]; p ⬍ .05 cluster corrected; brackets show 95% confidence
intervals), whereas the eye region was fixated more in the uprightthan in the inverted condition (local maximum within the significant cluster, F[1, 280] ⫽ 53.99, ␤upright ⫽ 1.07 [0.570, 1.568], and␤inverted ⫽ 0.08 [⫺0.418, 0.579]; local minimum, F[1, 280] ⫽3.90, ␤upright ⫽ 2.93 [2.062, 3.796], and ␤inverted ⫽ 2.34 [1.472,
3.206]; p ⬍ .05 cluster corrected; brackets show 95% confidence
intervals).
To clarify the significant main effect and interaction, we
mapped the fixation area above chance level of the following
predictors: CG_upright, CG_inverted, CP_upright, and CP_inverted, and then performed linear contrasts among these conditions (see Figure 4A). The main effect of face orientation was
mostly driven by the change of fixation pattern between the
upright and inverted condition in CP: They fixated more on
the nose and mouth area in the inverted condition, whereas in

Figure 4. iMap4 results of the spatial fixation pattern. (A) Conditional z score fixation duration map estimatedfrom the linear mixed model: control group (CG) viewing upright and inverted faces, and congenital prosopagnosics (CP) viewing upright and inverted faces. Linear contrasts of the conditional fixation maps were
performed for all the possible 2 ⫻ 2 combinations. Significant clusters are outlined with black lines in the map(cluster corrected p ⬍ .05). (B) ANOVA result output from iMap4: F value map of the significant main effectof Group and significant interaction of Group and Face Orientation. n.s. ⫽ not significant. See the online article
for the color version of this figure.

MALASPINA, ALBONICO, LAO, CALDARA, AND DAINI132

the upright condition, they were heavily biased toward the eyeregion only. Moreover, as shown in Figure 1 of the online
supplemental material, the significant Group ⫻ Face Orientation interaction around the nose region (Fmax [1, 280] ⫽ 27.93,
and Fmin [1, 280] ⫽ 3.88, within the significant cluster; p ⬍ .05
cluster corrected) was driven by the higher fixation duration in
the upright condition compared with the inverted one in CG,
and the reverse pattern in CP.

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Discussion
The aim of the present study was to test whether the SFA
showed by congenital prosopagnosics in an indirect task
(Malaspina et al., 2016) could also be detected by asking
participants an explicit recognition of their face, and, if so,whether this advantage would be reflected by a specific gazebehavior, distinct from the one characterizing the exploration of
unfamiliar faces. In the present study, we asked the participants
to explicitly discriminate the face stimuli and to judge them as“me”/”not me,” whereas previous evidence of the advantage incongenital prosopagnosics was obtained by means of a matching task in which the discrimination between the self- andother-faces was indirectly required. In particular, in order tostudy the possible presence of the SFA during this explicit task,
we took advantage of both behavioral and eye movement measurements because although the former could confirm the presence of the advantage also during explicit self-face recognition,
the latter could provide us information about how efficiency
and distribution of gaze could account for its possible existence.
As a first result, our data confirm previous evidence (Malaspina
et al., 2017; Schmalzl et al., 2008; Schwarzer et al., 2007) proving
that, overall, individuals with CP show abnormal gaze behavior
compared with good recognizers during the exploration of facial
stimuli. Indeed, congenital prosopagnosics needed more time to
explore the face, making more and shorter fixations. These results
seem to suggest that individuals with CP need to sample more
information to encode the stimulus properly compared with goodrecognizers. In particular, the difference between the two groups in
the first fixation duration might be crucial; indeed, previous evidence (e.g., Hsiao & Cottrell, 2008) suggested that the first fixation is the most crucial during face recognition, with the second
fixation providing a little more evidence about face identity. Accordingly, in order to maximize the amount of information extracted, usually the first fixation is placed in the center of thestimulus, that is, the area between the eyes (Hsiao & Cottrell,
2008; Sadr, Jarudi, & Sinha, 2003; Vinette, Gosselin, & Schyns,
2004). Thus, the fact that congenital prosopagnosics made shorter
first fixations and that, especially in the upright condition, they
never focused on the central areas might suggest that these individuals are not able to extract information easily enough within thefirst fixation. As a consequence, all their fixations are shorter andthey quickly move their gaze within single features in order toencode the face stimulus. However, despite these differences, theanalyses on the spatial distribution of the fixations failed to reveal
a significant main effect of the group in the upright condition,
whereas congenital prosopagnosics tended to fixate more on themouth area compared with controls in the inverted condition. The
lack of difference between controls and congenital prosopagnosics
when faces are presented upright might be quite surprising con-sidering previous evidence showing that individuals with prosopagnosia have a more dispersed gaze distribution compared with
controls (Malaspina et al., 2017; Schmalzl et al., 2008; Schwarzer
et al., 2007). However, a critical difference between previous
studies and the present one lies in the duration of the stimulus
presentation: Whereas in the present study the eye movements
were recorded from the appearance of the face stimulus to theparticipant’s response (and the total scan time averaged around
700 ms for both groups), in the other studies the face stimulus waspresented for a fixed and longer amount of time (1,500 ms in
Malaspina et al., 2017; 5,000 ms in Schmalzl et al., 2008; and7,000 ms in Schwarzer et al., 2007).
Thus, it seems possible that the different presentation times
could play a critical role in determining the different results
reported in the literature on upright faces, and that the differencein the spatial distribution of the fixations between congenital
prosopagnosics and controls could emerge as the stimulus duration
increases. In particular, we believe that when congenital prosopagnosics have more time to explore the facial stimulus, they tend
to make more dispersed fixations, probably in the attempt tosample more information in order to properly encode the face. By
contrast, the difference between individuals with congenital prosopagnosics and controls in the fixation features (i.e., the tendency
to make more and shorter fixations in the prosopagnosic population) seems to be present independently of the stimulus duration, as
it has been demonstrated in both the present and previous studies(Malaspina et al., 2017; Schmalzl et al., 2008; Schwarzer et al.,2007).
Finally, congenital prosopagnosics tended to fixate more on themouth area compared with controls in the inverted condition, andthis result seems to confirm that these individuals tend to process
the face stimulus by focusing on single features and not on thecentral area. This tendency seems more evident when faces arepresented upside-down and might be because face inversion disrupts not only long-range spatial relations but also low-range
spatial relations across different facial features (Sekunova & Barton, 2008).
A newer and significant result of this study concerns face
inversion. Indeed, in accordance with previous evidence (Barton,
Radcliffe, Cherkasova, Edelman, & Intriligator, 2006; Farah et al.,1995), for all participants, upright faces were easier to recognize
compared with inverted faces and required fewer fixations andshorter scanning time. Surprisingly, in this case, individuals withCP showed an IE similar to controls both in terms of accuracy and
RTs. However, despite congenital prosopagnosics typically showing lack of IE, and, thus, a similar performance between uprightand inverted faces (de Gelder & Rouw, 2000; Righart & de Gelder,2007), it is worth mentioning that the studies reporting this effectin these individuals usually have used only unfamiliar faces asstimuli. By contrast, in this case, both the inclusion of the self-facein the experimental paradigm, and, thus, the presence of a SFA in
the congenital prosopagnosic group, might have played as a confound factor, preventing the absence of an IE in these individuals.
Moreover, the analysis on the spatial fixation mapping revealed
that face inversion affected the two groups differently.
In particular, controls tried to encode both upright and inverted
faces in a similar way, that is, by focusing their fixations on theeyes and nose areas in both conditions. This is in accordance withprevious evidence showing that the eye region contains the mostThis document is copyrighted by the American Psychological Association or one of its allied publishers.
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HOW CONGENITAL PROSOPAGNOSICS LOOK AT THEMSELVES?

diagnostic information for face identification (Hsiao & Cottrell,
2008; Sadr et al., 2003; Vinette et al., 2004), and that goodWestern recognizers look mostly at the eyes and scan the upper
half-face more than the lower half when recognizing faces (Barton
et al., 2006; Blais, Jack, Scheepers, Fiset, & Caldara, 2008; Henderson, Williams, & Falk, 2005; Miellet, Vizioli, He, Zhou, &Caldara, 2013). However, previous evidence in good recognizers
has also shown that the face IE is not strictly a consequence of
anomalous eye movements (Williams & Henderson, 2007),
whereas it might be linked to a different efficiency in the extraction of information between the two conditions (Sekuler, Gaspar,
Gold, & Bennett, 2004), and our data seem to point in the same
direction. In fact, in our experiment, the control group did notshow any anomalous eye movement pattern with inverted faces,
but continued to focus on the same eye region, and because thisarea does not seem to be so informative in this specific orientation,
they showed behaviorally a typical IE.
By contrast, our CPs changed their fixation pattern between the
upright and inverted conditions, focusing only on each one of theeyes, in the first case, but extending their exploration to the noseand mouth areas in the latter one. Despite that face inversion is oneof the most powerful arguments used to support the presence of
face-specific impairment in CP, to the best of our knowledge, only
one study investigated in detail how face inversion affects the gazebehavior of congenital prosopagnosics (Malaspina et al., 2017).
Specifically, results from that study showed that individuals withCP tended to explore both upright and inverted faces in a very
similar way, that is, by focusing only on facial features. Despitesome differences, probably related to the additional inclusion of
the self-face and the different timing of the stimulus exposure here,
the results of both studies seem coherent. Indeed, during this task,
overall, the congenital prosopagnosic group directed their eyes on
the single features of the face (eye, nose, or mouth) while ignoring
the region between the eyes, crucial for expert holistic processing.
In particular, as also suggested by a previous study (Righart & deGelder, 2007), the use of a same feature-based strategy with both
upright and inverted faces could partially explain why congenital
prosopagnosics often show a similar accuracy in recognizing upright and inverted faces. Specifically, whereas the feature-based
strategy could also be optimal in the inverted condition, the same
is not true for upright faces, which require holistic processing, andeven though face recognition can be achieved also by using afeature-based strategy, this kind of processing is typically lessefficient, requires more time, and could explain why congenital
prosopagnosics struggle so much with upright faces.
Regarding the processing of the self-face, our behavioral data
corroborated previous findings (Keyes & Brady, 2010; Malaspina
et al., 2016; Ma & Han, 2010) showing that the SFA is detectable
both in people with good recognition abilities and individuals with
CP, with both groups performing better and faster in the self-facecondition. In particular, although congenital prosopagnosics performed significantly worse than controls with unfamiliar faces,
their performance was comparable with controls with the self-face,suggesting that the SFA may act as a compensatory process toovercome their face recognition impairment. It should be mentioned that a small set of stimuli was used for both the own and theother- conditions; because previous studies (Burton, 2013; Jenkins,
White, Van Montfort, & Burton, 2011; White, Rivolta, Burton,
Al-Janabi, & Palermo, 2017) have shown that increasing within-133

person variability can affect the performance of both normal
recognizer and individuals with CP in face recognition tasks, theresults might change when a larger sample of stimuli for bothconditions are used. Nevertheless, we might expect to find aquantitative but not qualitative change in the pattern of results, asboth groups appear to be affected by the increased within-person
variability. Furthermore, we used only gray-scale images, which
could reduce the texture information contained in the images.
Previous studies (Andrews, Baseler, Jenkins, Burton, & Young,
2016; Itz, Golle, Luttmann, Schweinberger, & Kaufmann, 2017)
have shown that texture information is critical in both face matching and recognition tasks, and that poor face recognizers rely lesson this kind of information than good recognizers. It follows thatusing gray-scale images might decrease the differences between
the two groups by impoverishing the performance of the control
group. However, this should be true for both the own- and theother-face conditions, so that the choice of discarding color information did not introduce any qualitative distortion on the results.
Our results on the self-face are also in accordance with aprevious study showing that individuals with CP have also normal
neural responses (N250 and P600f components) to the identity ofthe own face (Parketny, Towler, & Eimer, 2015). Moreover, bothgroups exhibited an SFA in their gaze behavior; indeed, all ourparticipants required less time and fewer fixations in order torecognize their self-face compared with the unfamiliar face. Interestingly, this advantage was not associated with a different spatial
distribution of their fixations, suggesting that, whereas the information from the self and other was sampled in a similar way (samespatial fixation mapping), the processing of the information extracted within each fixation must have been different in the two
conditions in order to give the different behavioral results. Thisevidence seems to support the idea that what is special about theself could be not “what” is processed but “how” efficiently the
information sampled is processed. Indeed, even though the exploration of familiar faces is usually characterized by a different
distribution of fixations (i.e., more sampling of the internal areas)
compared with unfamiliar faces in good recognizers (Heisz &Shore, 2008; Stacey, Walker, & Underwood, 2005), in our study,
the distribution of scanning during the recognition of the self-face
was similar to the one of the unfamiliar face. Moreover, despite
congenital prosopagnosics usually do not show any familiarity
effect in terms of eye movements during the visual exploration of
faces, here, we could still detect a different gaze behavior (fewer
fixations and less scan time) in the case of the self-face. Taken
together, both these results allow us to discard the possibility thatoverexposure to the self-face during life could play a critical rolein determining the SFA we found in both behavioral and eye
movement data.
Accordingly, the possibility that the self-face could be characterized by a specific processing has been already addressed in theliterature, but the evidence collected so far is mixed. Indeed,
whereas some studies found that the SFA might be part of aright-dominated neural network devoted to the processing of selfinformation (Devue et al., 2007; Platek, Keenan, Gallup, & Mohamed, 2004; Platek et al., 2006; Uddin, Kaplan, Molnar-Szakacs,
Zaidel, & Iacoboni, 2005), other studies have provided evidence
for a specific bilateral representation of one’s own face, suggestingthat the advantage might be related to a more robust representationof the global and local aspects of the self-face across the brain

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134

MALASPINA, ALBONICO, LAO, CALDARA, AND DAINI(Brady et al., 2004; Brady, Campbell, & Flaherty, 2005; Keyes &Brady, 2010). In particular, according to this last hypothesis,
although the right hemisphere would be responsible for the global
aspects of the self-face, the left hemisphere might contribute byemphasizing the local aspects of it (Keyes & Brady, 2010). The
results of the present study seem to support the first hypothesis
emphasizing that the self-face could be characterized by an enhanced processing of self-information, and, in particular, we believe that the SFA could reflect a more general enhanced processing of self-related information. In fact, the advantage for the
self-face affected the performance of controls and congenital prosopagnosics similarly in terms of behavioral and eye movement
data, and, because of the face recognition impairment characterizing the latter ones, this lack of difference between the two groups
seems to suggest that the advantage could be not related to any
face-specific mechanisms. Accordingly, if the SFA was facespecific, we would have expected a different modulation of it in
the two groups, which we could not find. Furthermore, althoughsome authors (Brady et al., 2004, 2005; Keyes & Brady, 2010)
interpreted the presence of the SFA in both upright and inverted
faces as proof of the more robust and bilateral representation of thelocal and global aspects of the face, we believe that this evidence
could actually support the opposite hypothesis. In fact, it is well
accepted that face inversion disrupts the expert face recognition
processing and that, when inverted, faces are processed like anyother object, that is, feature by feature (Tanaka & Farah, 1993);
thus, for this reason, the presence of an advantage for the self-facein the inverted condition does not seem to be attributable to aface-specific mechanism, but, by contrast, it seems more in favorof a generic self-advantage. In particular, as suggested by others(Blanke, 2012; Frassinetti et al., 2011; Frassinetti, Maini, Romualdi, Galante, & Avanzi, 2008), the self-advantage may rely
upon the integration of multisensory signs of the self-body involving a frontoparietal network in the right hemisphere, and, in ourcase, this multisensory representation of the self could act as acompensatory process to overcome the face recognition impairment in individuals with CP at least when they have to recognize
their own face. However, additional studies will be needed tofurther investigate whether the SFA is face-specific or linked toself-related material in general; specifically, because previous
studies have demonstrated that prosopagnosics can be impaired inbody and body motion perception (Kolers, 1968; Lange et al.,2009; Moro et al., 2012; Righart & de Gelder, 2007; Rivolta,
Lawson, & Palermo, 2017), it might be critical to investigate
whether these individuals show also a self-advantage for theirbody parts, and, if so, if this advantage differs from the one
characterizing the self-face. Lastly, because previous studies suggested that the SFA could be linked to the preference for the righthalf of the face (Brady et al., 2004; Malaspina et al., 2016), anotheraim of this study was to investigate whether the right perceptual
bias described in the literature in both good recognizers andcongenital prosopagnosics would be detectable also in terms of eye
movements. However, the analyses on the chimeras did not prove
any influence of the type of chimeric stimulus on the behavioral
performance of the two groups in the self-condition, so that nopreference for one specific half of the self-face was found. In
particular, we could not find a right perceptual bias in the behavioral or eye movement results of the two groups. Nevertheless, thelack of right perceptual bias is still very informative about, at least,

two aspects: (a) Because neither of the two groups showed apreference for the right-half of the self-face despite showing asignificant SFA, this could suggest that the two effects are independent of each other and further support the hypothesis that the
SFA can be related to a more general enhanced processing ofself-related information; and (b) furthermore, the lack of rightperceptual bias in a task requiring a direct and explicit recognitionof the self-face could also suggest that the bias toward the righthalf of the self-face could be sensitive to the task demand. Indeed,
whereas the previous studies demonstrating the existence of therightward bias have used indirect tasks, not requiring an explicit
recognition of the self-face (Brady et al., 2004; Malaspina et al.,2016), in this study, participants had to explicitly judge the facestimulus as “me”/”not me.” Accordingly, a previous study thatused an explicit task to test self-face recognition failed to observea right perceptual bias in good recognizers (Brady et al., 2005),
suggesting that the rightward bias characterizing the self-facemight be detectable only during indirect tasks, probably because
they require maintaining a short memory representation of theself-face, which might elicit a different exploration of this stimulus.
In conclusion, the present study further corroborated the presence of an SFA in both congenital prosopagnosics and goodrecognizers during an explicit recognition task, and both in thecase of upright and inverted face processing; in particular, the SFA
was not related to any change in the spatial fixation distribution,suggesting that it could be related to a more general enhancementof the self-information processing, instead of being related toface-specific mechanisms. However, contrary to what found inprevious studies (Malaspina et al., 2016; Brady et al., 2004, 2005),
the SFA was not driven by the preference to the right-half face,suggesting that these two effects are separate and independent ofeach other, and that the right perceptual bias characterizing theself-face is sensitive to the task demand, being more evident whenan explicit recognition of the self-face is not required. Finally, we
showed that face inversion differently affects controls and congenital prosopagnosics. On the contrary, of controls who mostly
explored the eyes and the area between them in both conditions oforientation, congenital prosopagnosics made more distributed fixations in the noncanonical inverted condition, by focusing more on
the nose and the mouth in this orientation. This observation could
explain why congenital prosopagnosics sometimes perform evenbetter with inverted compared with upright faces. Altogether, ourdata revealed a new oculomotor signature of the congenital faceprocessing deficit.

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Received March 9, 2017
Revision received August 11, 2017
Accepted August 14, 2017 䡲