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The Quarterly Journal of Experimental Psychology
ISSN: 1747-0218 (Print) 1747-0226 (Online) Journal homepage: http://www.tandfonline.com/loi/pqje20
Can gaze-contingent mirror-feedback from
unfamiliar faces alter self-recognition?
Alejandro J. Estudillo & Markus Bindemann
To cite this article: Alejandro J. Estudillo & Markus Bindemann (2016): Can gaze-contingent
mirror-feedback from unfamiliar faces alter self-recognition?, The Quarterly Journal of
Experimental Psychology, DOI: 10.1080/17470218.2016.1166253
To link to this article: http://dx.doi.org/10.1080/17470218.2016.1166253
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Mar 2016.
Published online: 07 Apr 2016.
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Can gaze-contingent mirror-feedback from unfamiliar faces alter
self-recognition?
Alejandro J. Estudillo and Markus Bindemann
School of Psychology, University of Kent, Canterbury, Kent, UK
ABSTRACT
This study focuses on learning of the self, by examining how human observers update
internal representations of their own face. For this purpose, we present a novel gaze-
contingent paradigm, in which an onscreen face mimics observers’own eye-gaze
behaviour (in the congruent condition), moves its eyes in different directions to
that of the observers (incongruent condition), or remains static and unresponsive
(neutral condition). Across three experiments, the mimicry of the onscreen face did
not affect observers’perceptual self-representations. However, this paradigm
influenced observers’reports of their own face. This effect was such that observers
felt the onscreen face to be their own and that, if the onscreen gaze had moved on
its own accord, observers expected their own eyes to move too. The theoretical
implications of these findings are discussed.
ARTICLE HISTORY
Received 17 July 2015
Accepted 23 February 2016
KEYWORDS
Self-face learning; Self-face
recognition; Mirror
recognition; Self-face
representation
The face is one of our most distinctive physical fea-
tures. It is considered the signature of the self
(McNeill, 1998) and plays an important role in self-
awareness (Morin, 2006). Therefore, it is not surprising
that self-face recognition has attracted researchers’
attention over the past two centuries (for a review,
see Keenan, Gallup, & Falk, 2003). Most studies in
this field have focused on the retrieval of the visual
representation of the own face (e.g., Brady, Campbell,
& Flaherty, 2004,2005; Brédart, 2003; Keenan,
Wheeler, Gallup, & Pascual-Leone, 2000; Tong &
Nakayama, 1999), the differences between the pro-
cesses involved in the recognition of our own and
other faces (e.g., Greenberg & Goshen-Gottstein,
2009), and the neural bases of self-face recognition
(for a review, see Devue & Brédart, 2011). In this
study, we want to explore one aspect of self-recog-
nition that has received comparatively little attention,
by examining how human observers might update
visual representations of their own face.
Recognition requires that a seen face is matched to
a stored, internal representation of that identity. The-
ories of face processing postulate that this internal
representation is not tied to a specific instance of a
seen face, but is activated by any image of this
person (see, e.g., Bruce & Young, 1986; Burton,
Bruce, & Johnston, 1990). Thus, this internal represen-
tation should be tolerant to some changes in the
appearance of a face, such as variation in lighting
direction (see, e.g., Bruce, 1982; Longmore, Liu, &
Young, 2008). A question that arises is how this
internal representation is created so that a previously
unfamiliar face, of someone that we have not met
before, becomes sufficiently familiar for recognition
to occur.
Current theorizing suggests one way to operationa-
lize this process could be the creation of face averages,
in which different instances of the same face are inte-
grated into a single representation (Burton, Jenkins,
Hancock, & White, 2005). In this process, information
that is relevant to the identity of a person, and there-
fore present consistently across encounters, is com-
bined to form a robust facial representation for
recognition. By contrast, variable visual information
that is irrelevant to identity, such as superficial
changes in the appearance of a particular face, is elimi-
nated naturally during averaging because their effect
will be cancelled out across different instances.
© 2016 The Experimental Psychology Society
CONTACT Alejandro J. Estudillo aje24@kent.ac.uk School of Psychology, University of Kent, Canterbury, Kent, CT2 7NP, UK
THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 2016
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This theoretical account can provide a robust
method to simulate face recognition (Burton,
Jenkins, & Schweinberger, 2011; Jenkins & Burton,
2008; Robertson, Kramer, & Burton, 2015). It also pro-
vides an account of face learning (see e.g., Burton,
Kramer, Ritchie, & Jenkins, 2016; Kramer, Ritchie, &
Burton, 2015; Leib et al., 2014). Accordingly, the
created internal representation of a face is tied in an
additive manner to the experience of that identity,
whereby every new exposure strengthens its
average and leads to a stronger internal represen-
tation (Burton et al., 2005,2011; Jenkins & Burton,
2008). Interestingly, this theoretical approach can
also explain two interrelated aspects of self-recog-
nition, namely how a visual representation of the
own face is created and how this representation
accommodates changes in physical appearance
during the lifespan. According to this perspective,
any new instance of the own face would be incorpor-
ated into the averaging process to naturally deal with
changes in the appearance.
However, current theories stop short of explaining
an important component of self-recognition, which is
the self-referential process of knowing that a particular
face is, in fact, one’s own (e.g., Devue & Brédart, 2011;
Morin, 2006). A potential answer to this question
emerges from the domain of body perception,
where research has shown the importance of body-
awareness for self-recognition (e.g., Botvinick &
Cohen, 1998; Tsakiris, 2010; Tsakiris & Haggard,
2005). Mental representations of our bodies are held
to be created through the interaction and integration
of different senses, such as visual, tactile, and proprio-
ceptive information (Blanke, Landis, Spinelli, & Seeck,
2004; Tsakiris & Haggard, 2005). This information
appears to be used not only in the formation of a rep-
resentation of our body, but also for updating and
modifying that representation when necessary (Botvi-
nick & Cohen, 1998; Lenggenhager, Tadi, Metzinger, &
Blanke, 2007; Petkova et al., 2011; Tsakiris & Haggard,
2005).
Evidence for such accounts comes from the rubber
hand illusion. In this paradigm, observers watch a
rubber hand being stroked while their own hand is
stroked out of sight in synchrony. This simultaneous
stimulation produces the feeling that the rubber
hand is, in fact, one’s own hand (Botvinick & Cohen,
1998; Tsakiris & Haggard, 2005). This effect relies on
the multi-sensory combination of touch (of one’s
own hand) and sight (of the rubber hand being
stroked). However, a rubber-hand effect has also
been obtained without touching, for example, when
there is synchrony of movement between a rubber
and one’s own hand (e.g., Dummer, Picot-Annand,
Neal, & Moore, 2009; Riemer et al., 2014). Similar
effects have been reported with arms (Guterstam,
Petkova, & Ehrsson, 2011) and even with the whole
body (Lenggenhager et al., 2007;Petkova et al.,
2011; Petkova & Ehrsson, 2008).
With respect to face learning, these findings are
interesting in that they could provide a self-referential
process to update internal representations, by accom-
modating physical changes in a person’s appearance
due to, for example, cosmetics, styling or aging.
Accordingly, such updating could be supported if
observers can see and, through proprioceptive feed-
back, feel their own face move at the same time.
Outside of the laboratory, such feedback is available
daily from mirrors—for example, during hygiene
activities such as washing and grooming. In these con-
ditions, a person’s mirror reflection provides synchro-
nous visual feedback for motor, proprioceptive, and
tactile information (Botvinick & Cohen, 1998; Taja-
dura-Jiménez, Grehl, & Tsakiris, 2012; Tsakiris, 2008,
2010). This feedback provides direct evidence that a
looked-at face is, in fact, one’s own. The question
arises of whether this also contributes to the updating
of a person’s face, by accommodating external
changes in their physical appearance into existing
internal representations.
Studies of multi-sensory integration already
provide some evidence to support this idea. For
example, when observers’faces are stroked in syn-
chrony with a target that consists of a 50:50 morph
of their own face and that of another person, they sub-
sequently tend to see more of their own features in
the other person’s face (Tsakiris, 2008). This perceptual
effect is accompanied by a subjective illusion that the
other face belongs to the observer. This bias in self-rec-
ognition or “enfacement effect”(Sforza, Bufalari,
Haggard, & Aglioti, 2010) has been shown with
totally unfamiliar (Tajadura-Jiménez, Grehl et al.,
2012), familiar (Sforza et al., 2010), and other-race
faces (Bufalari, Lenggenhager, Porciello, Serra-
Holmes, & Aglioti, 2014; Fini, Cardini, Tajadura-
Jiménez, Serino, & Tsakiris, 2013).
While these findings point to a remarkably robust
effect, multi-sensory paradigms rely on observing
the tactile stimulation of another agent. This presents
a scenario that is not encountered outside of the lab-
oratory. In this study, we therefore wish to examine
whether a similar updating of observers’facial
2A. J. ESTUDILLO AND M. BINDEMANN
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representations occurs with a stimulation method that
is more similar to the experience of studying one’s
own reflection in a mirror. For this purpose, we
present a gaze-contingent paradigm, in which the
eye movements of a face on a computer screen
directly mimic the looking behaviour of an observer.
To measure the effect of this manipulation on self-
recognition, we compared several conditions. In
Experiment 1, the gaze behaviour of the onscreen
target face provided a direct “mirror-reflection”of
observers’gaze behaviour, by mimicking their eye
movements in the congruent condition. This was con-
trasted with an incongruent condition in which the
eyes of the onscreen face responded to observers
eye-gaze but moved in a different direction. If
mirror-reflection is used to update facial represen-
tations of the own face, then it should be possible to
induce an enfacement-type effect in this paradigm,
whereby the onscreen face should be perceived as
more similar to the own face. In line with studies of
multi-sensory stimulation (e.g., Fini et al., 2013;
Sforza et al., 2010; Tajadura-Jiménez, Grehl et al.,
2012; Tsakiris, 2008), this effect should be found in
the congruent gaze condition in comparison with
incongruent displays.
To assess this possibility, we adopted established
measures of the enfacement illusion from multi-
sensory stimulation paradigms (see, e.g., Keenan
et al., 1999; Maister, Tsiakkas, & Tsakiris, 2013; Taja-
dura-Jiménez, Grehl et al., 2012; Tsakiris, 2008). This
comprised a self–other discrimination task, in which
observers were shown a morphing sequence
between the onscreen face viewed in the stimulation
stage and the observer’s own face. In this task, obser-
vers were asked to determine at which point they
could perceive their own face in the sequence. This
measure was complemented with an enfacement
questionnaire, which assessed different aspects of
observers’phenomenological experience of identify-
ing with the onscreen face of the stimulation stage.
EXPERIMENT 1
In this experiment, observers watched an onscreen
face in a gaze-contingent paradigm, which was com-
posed of two conditions. In the congruent condition,
the eyes of this face mimicked observers’eye-gaze
direction to imitate, in this particular aspect, the
experience of looking in a mirror. Observers triggered
the eye-gaze of the onscreen face by moving their
own eyes, which were tracked concurrently, around
the display screen. To encourage such eye move-
ments, the onscreen face was surrounded by eight
boxes, which, upon being fixated, revealed a visual
icon. Performance in this task was contrasted with
an incongruent condition, in which the eyes of the
onscreen face moved in temporal synchrony with an
observer’s eye-gaze but in a different direction.
Before and after this task, observers performed a
self–other discrimination task. This consisted of a
morphing sequence between the onscreen face
from the stimulation stage and observers’own faces.
This sequence always began with the onscreen face,
which was gradually morphed into the observer’s
face. Observers had to stop this sequence as soon as
they felt that the face resembled their own face
more than that of the stimulation face. In addition,
observers’phenomenological experience of the
gaze-contingent task was assessed with an estab-
lished enfacement questionnaire.
If this gaze-contingent mirror-reflection paradigm
can be used to update observers’representations of
their own face, then the onscreen face should
become integrated into this representation in the con-
gruent condition. As a consequence, observers should
detect their own face earlier in the morphing
sequence in the congruent than in the incongruent
condition. This effect should also be evident from
the questionnaire, with observers reporting a greater
resemblance with the stimulation face in the congru-
ent condition.
Method
Participants
Twenty Caucasian students (13 females) from the Uni-
versity of Kent, with a mean age of 22 years (SD = 4.2),
participated in this study. All provided informed
consent prior to taking part and received course
credits or a small fee for participation. All reported
normal or corrected-to-normal vision.
Stimuli
Gaze-contingent stimulation displays
For the stimuli of the gaze-contingent task, a male and
a female frontal face were taken from the Glasgow
Face Database (Burton, White, & McNeill, 2010).
These faces were digitized with FaceGen Modeller
software (Singular inversions Inc., Toronto). The result-
ing faces provided artificial representations of the
original stimuli, in which gaze direction can be
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controlled with the same software. This was used to
create nine images of each face, in which the eye-
gaze systematically varied across three horizontal
(left, middle, right) and three vertical positions (up,
middle, down). To enhance the salience of these
gaze directions, the brightness of the sclera was
increased by 25% using Adobe Photoshop.
In the experiment, each of these faces was pre-
sented at a width and height of 325 × 420 pixels at a
resolution of 72 ppi in the centre of a white display.
These faces were surrounded by eight boxes, which
measured 220 × 220 pixels. When fixated, these
boxes were replaced by images of objects (e.g., a
radio, cd, glove), which measured maximally 200 ×
200 pixels. These displays are illustrated in Figure 1.
Self–other discrimination task
For the self–other discrimination task, a digital photo-
graph of each observer was taken prior to the exper-
iment. For consistency with the model’s face, these
pictures were also modelled with FaceGen. The result-
ing images were morphed with the stimulation face
that matched the observer’s sex in 1% steps using Fan-
tamorph (Abrasoft) software. This resulted in a
sequence of 100 images, which provided a smooth
continuum between the stimulation face and an
observer’s own face. Each of these images was pre-
sented at a size of 254 × 313 pixels at a resolution of
96 ppi.
Enfacement questionnaire
A questionnaire was administered to assess observers’
subjective experience of the gaze-contingent para-
digm. This questionnaire was adapted from studies
of the enfacement effect (Tajadura-Jiménez, Grehl
et al., 2012; see also Maister et al., 2013) and consisted
of 11 items (see Table 1). The first seven questions
assessed observers’enfacement experience and
included items such as “I felt like the onscreen face
was my face”and “I felt like I was looking at my own
face in the mirror”. A high score in these items indi-
cates that observers felt that the stimulation face
had become integrated with the internal presentation
of their own face during the experiment (see Tajadura-
Jiménez, Longo, Coleman, & Tsakiris, 2012). The four
remaining items assessed whether observers per-
ceived the eye-gaze of the stimulation face, with state-
ments such as “I felt like the onscreen face’s eyes
followed my eyes”, to provide a manipulation check.
Responses to all items were recorded on 7-point
Likert scales, which ranged from “strongly disagree”
to “strongly agree”.
Procedure
In the experiment, observers participated in the self–
other discrimination task first to obtain a baseline
Figure 1. Example stimuli of the congruent condition for Experiments 1 and 2, showing direct eye-gaze (left panel) and the eyes pointing up
(centre) or down (right). In the neutral condition, the eye-gaze remained direct and static throughout. In the incongruent condition, the eyes of
the onscreen face pointed in a different direction to observers’own eye-gaze and therefore did not point at the revealed object.
Source: Face was taken from the Glasgow Face Database.
Table 1. The enfacement questionnaire
Type of item Enfacement item
Enfacement 1. I felt like the onscreen face was my face
2. I felt like the onscreen face belonged to me
3. I felt like I was looking at my own face reflected in
a mirror
4. I felt like my own face was out of my control
5. I felt like my face began to resemble the onscreen
face
6. I felt like the onscreen face began to resemble my
face
7. I felt like if the onscreen face’s eyes had moved, my
eyes would have moved too
Verification 8. I felt like the onscreen face’s eyes followed my eyes
9. I felt like if I had moved my eyes, the onscreen
face’s eyes would have moved too
10. The onscreen face’s eyes moved in the same
direction as my eyes
11. The onscreen face’s eyes moved in a different
direction as my eyes
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measure of self-recognition (the pre-test), which was
conducted using E-prime on a computer with a 21′′
screen. In this task, observers viewed the sequence
of the morphed faces. This sequence always began
with the stimulation face (100% stimulation face, 0%
observer), which was gradually morphed, in 1% seg-
ments, into an observer’s own face. This sequence
was presented at a rate of one segment per second.
While watching this sequence, observers were asked
to press the space bar as soon as they felt that the dis-
played face resembled their own face more than that
of the stimulation phase. Prior to this pre-test, obser-
vers were trained on this discrimination task by watch-
ing a sequence that morphed the face of David
Cameron (British Prime Minister) into Barack Obama
(American President).
The pre-test was followed by the gaze-contingent
stimulation task. For this task, observers’eye move-
ments were tracked using the SR-Research Eyelink
1000 desk-mounted eye tracking system. Observers
sat at a distance of 50 cm from a 21′′ screen, which
was held constant by a chinrest. Although viewing
was binocular, only the left eye was tracked. To
calibrate eye-gaze, the standard nine-point Eyelink
procedure was used. Thus, observers fixated a set of
nine fixations targets, which was followed by a
second sequence of nine targets to validate cali-
bration. If this procedure indicated poor measurement
accuracy (i.e., a measurement error of >1°of visual
angle), calibration was repeated.
At the beginning of the stimulation task, observers
fixated a central dot so that an automatic drift correc-
tion could be performed. The stimulation face was
then displayed in the centre of the screen. The sex
of this face was always kept congruent with that of
the observer. The stimulation face was surrounded
by eight boxes, which were depicted in different
colours (see Figure 1). Each of these boxes hid an
object, which was revealed when it was fixated by
the observers, to provide a task demand that would
encourage eye movements around these displays.
Observers were asked to look at these boxes and to
memorize their contents. Crucially, the onscreen
location of these boxes served as trigger regions to
manipulate the eye-gaze direction of the stimulation
face, which changed only 150 ms after a trigger
region was fixated. This task lasted for 2 min and, to
assess any effects of this stimulation on self-recog-
nition, was followed by a repetition of the self–other
discrimination task and the enfacement questionnaire.
Observers were then presented with a second block of
the stimulation task, which was followed by a further
repetition of the discrimination task and the
questionnaire.
One of the stimulation blocks comprised congruent
stimulation (i.e., the gaze of the stimulation face was
always congruent with observers’own eye-gaze direc-
tion) and the other block incongruent stimulation (i.e.,
the gaze of the stimulation face was always incongru-
ent with observers’own eye-gaze direction). This
spatial incongruence was created by randomly assign-
ing a different gaze direction to the stimulation face
for each of the observer’s possible gaze directions.
Over the course of the experiment, the presentation
order of the congruent and incongruent conditions
was counterbalanced across observers.
Results
Self–other discrimination task
Performance in the discrimination task was assessed
first. Figure 2 shows the mean percentage of frames
that were perceived as the stimulation face and as
observers’own face in the morphing sequence.
These data are given for the initial baseline measure
and after the gaze-congruent and incongruent stimu-
lation conditions were administered. A one-factor
analysis of variance (ANOVA; baseline, congruent,
incongruent condition) of these data showed a main
effect of condition, F(1, 19) = 7.13, p< .01, h2
p= .27.
Paired sample t-tests (Bonferroni-corrected) revealed
that observers perceived their own face earlier in the
morphing sequence after the application of the
gaze-congruent condition in comparison with the
baseline, t(19) = 2.80, p< .05. However, a similar
Figure 2. Performance in the self–other discrimination task in Exper-
iment 1, expressed as the number of frames that observers judged to
show their own face or that of the onscreen face, for the baseline
measure and after congruent and incongruent stimulation.
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effect was observed also in the incongruent condition
in comparison to baseline, t(19) = 3.44, p< .01, and the
congruent and incongruent condition did not differ
from each other, t(19) = 0.50, p= .98. Taken together,
these results suggest a practice effect as observers
perceived their own face earlier in both the congruent
and incongruent conditions compared with the base-
line. However, the equivalent performance in the con-
gruent and incongruent conditions also indicates that
gaze-contingent stimulation did not affect observers’
perceptual self-representations.
Enfacement questionnaire
We also assessed observers’questionnaire responses to
determine whether this paradigm affected how they
felt regarding the stimulation face. These data are pro-
vided in Figure 3 as mean Likert responses to each of
the enfacement items, for the congruent and incongru-
ent conditions. Four of the questionnaire items are ver-
ification items, which assess whether observers were
sensitive to the gaze-contingent task. The differences
in ratings for these verification items show that obser-
vers were aware that the stimulation face followed
their own eye-gaze in the congruent compared to the
incongruent condition (Items 8 and 9), both ts(19) ≥
4.00, ps < .001. The ratings also show a clear difference
between conditions in terms of the directionality of the
eye-gaze (Items 10 and 11), whereby observers were
more likely to report that the eyes of the stimulation
face moved in the same direction as their own eyes
in the congruent condition, t(19) = 7.28, p< .001. In con-
trast, observers noted that the eyes of the stimulation
face moved in a different direction to their own in
incongruent displays, t(19) = 5.98, p<.001. However,
when the ratings for Items 10 (eyes moved in the
same direction) and 11 (eyes moved in a different direc-
tion) are compared directly, it emerges that these are
more similar in the incongruent condition, t(19) =
1.60, p= .12, than in the congruent condition, t(19) ≥
15.79, p< .001. This suggests that observers always per-
ceived movement of the stimulation face’s eyes, but
were less sensitive to the direction of these movements
in the incongruent condition.
A comparison of the congruent and incongruent
conditions also shows that the gaze-contingent para-
digm did not affect observers’feelings about the onsc-
reen face, which were comparable across these
conditions in all enfacement questions (Items 1–7),
Figure 3. Mean Likert responses to each enfacement item for the congruent (black bars) and the incongruent (grey bars) conditions in Exper-
iment 1. ***p< .001.
6A. J. ESTUDILLO AND M. BINDEMANN
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all ts(19) ≤1.65, ps > .07. An overall enfacement score,
which was calculated by averaging across Items 1 to 7,
also shows that the congruent (M= 20.4, SD = 8.2) and
incongruent (M= 17.9, SD = 9.1) conditions did not
differ, t(19) = 1.14, p= .14.
Discussion
Experiment 1 explored whether it would be possible
to update the internal representation of one’s own
face with a gaze-contingent paradigm that simulates
the mirror-reflection experience. This was investigated
by comparing a congruent condition, in which the
eye-gaze of an onscreen face follows that of the obser-
ver, with an incongruent condition, in which the gaze
of the onscreen face was spatially incongruent. To
assess whether this stimulation affected observers’
self-representation, they were asked to detect their
face in an image sequence that began with the onsc-
reen face and gradually morphed into their own face.
In comparison with a baseline measure, which was
obtained prior to the administration of the stimulation
task, a shift in self-recognition was found in the con-
gruent condition, whereby observers recognized
their own face at an earlier stage of the morphing
sequence. However, the same effect was also
observed after the administration of the incongruent
condition. Taken together, these results suggest that
the gaze-congruent condition did not affect observers’
self-recognition per se. Instead, these findings hint at a
practice effect whereby observers perceived their own
face earlier in the morphing sequence of the congru-
ent and incongruent conditions in comparison to
the initial baseline measure. In line with these findings,
the results indicate also that the gaze-contingent
paradigm did not affect how observers feel about
the onscreen face and their own face.
A possible explanation for these findings is that the
difference in eye-gaze between the congruent and
incongruent conditions was insufficient to elicit a
mirror effect that can alter self-recognition. The verifi-
cation items of the questionnaire reveal that observers
were sensitive to the eye movements of the stimu-
lation face in the congruent condition. However, this
effect was considerably smaller with incongruent dis-
plays. Here, observers showed some false agreement
that the stimulation face followed their eyes (see
Item 8 in Figure 3), and a direct comparison of Items
10 and 11 indicates limited insight into whether the
onscreen gaze was moving in the same or a different
direction to observers’own eyes.
This situation might arise because eye-gaze direction
cannot be perceived easily outside the focus of attention
(Burton, Bindemann, Langton, Schweinberger, & Jenkins,
2009; Hermens, Bindemann, & Burton, in press). In the
current paradigm, observers have to explore the boxes
surrounding the stimulation face to trigger its eye move-
ments. As a result of this, however, this face is unattended
when any changes in its gaze direction occur. If observers
have limited awareness of these changes, then this might
not produce the mirror-type effects that are required to
affect self-recognition.To explore this possibility, we con-
ducted a further experiment in which the incongruent
condition was replaced with a neutral display, in which
the eyes of the onscreen face looked straight ahead
regardless of the observers’gaze behaviour. Such direct
gaze is more salient than averted gaze outside the
focusofattention(Yokoyama,Sakai,Noguchi,&Kita,
2014) and should therefore produce a stronger contrast
to the congruent eye-gaze condition.
EXPERIMENT 2
In contrast to Experiment 1, which compared congru-
ent gaze-contingent displays with an incongruent
condition, this experiment compared congruent with
neutral displays, in which the gaze of the onscreen
face remained static and unresponsive. Based on pre-
vious research, we predicted that this condition
should provide a stronger contrast to the moving
eye-gaze of the congruent condition, particularly
when the stimulation face is not attended (see
Burton et al., 2009; Hermens et al., in press; Yokoyama
et al., 2014). If it is possible to update the represen-
tation of the own face using a gaze-contingent para-
digm, then such an effect might now be observed
here, by comparing observers’self-representations
after the congruent and neutral displays.
Method
Participants
Twenty new Caucasian students (10 female) from the
University of Kent, with a mean age of 21 years (SD =
5.1), participated in this study. All provided informed
consent prior to taking part, received course credits
or a small fee for participation, and reported normal
or corrected-to-normal vision.
Stimuli and procedure
The stimuli and procedure were identical to those in
Experiment 1, except that the incongruent condition
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was replaced with neutral gaze displays. In this con-
dition, the eye-gaze of the onscreen face was always
directed straight at the observers and was unrespon-
sive. As in Experiment 1, the self–other discrimination
task was administered initially to obtain a baseline
measure of self-recognition. Observers then per-
formed two blocks, one for the congruent condition
and one for the neutral condition, which comprised
the stimulation phase, the self–other discrimination
task, and the enfacement questionnaire. The order of
these blocks was counterbalanced across observers.
Results
Self–other discrimination task
Figure 4 illustrates performance in the self–other dis-
crimination task for the baseline condition and after
the administration of the congruent and neutral dis-
plays. A one-factor ANOVA (baseline, congruent,
neutral condition) showed a main effect of condition,
F(1, 19) = 20.37, p<.001, h2
p= .51. Paired sample t-
tests (Bonferroni-corrected) show that observers per-
ceived their own face earlier in the morphing sequence
after the application of both the congruent and neutral
conditionsin comparison with the baseline, t(19) = 6.68,
p< .001, and t(19) = 4.51, p< .001, respectively. Dis-
crimination performance in the congruent and neutral
conditions did not differ, t(19) = 0.75, p=1.00.
Enfacement questionnaire
Observers’questionnaire responses are summarized in
Figure 5. The difference in mean ratings for the verifi-
cation items between the congruent and neutral con-
ditions demonstrates that observers were aware that
the onscreen face followed their own eye-gaze (see
Items 8–10 in Figure 5), all ts(19) ≥6.55, ps < .001.In
addition, when asked whether the onscreen face’s
eyes moved in a different direction to observers’
own (Item 11), ratings were low in both conditions,
and no difference was found, t(19) = 0.92, p=.36.
A comparison of the congruent and neutral con-
ditions also shows that the gaze-contingent paradigm
affected how observers felt about the stimulation face.
Observers were more likely to report that this face
looked like their own in the congruent than in the
neutral condition (Items 1 and 2), both ts(19) ≥2.87,
ps < .01, and also reported a closer resemblance
between their own face and that of the onscreen
face in the congruent than in the neutral condition
(Items 5 and 6), both ts(19) ≥2.44, ps < .05. This
effect was such that, if the eyes of the onscreen face
had moved, they expected their own eyes to move
too in the congruent condition (Item 7), t(19) = 2.72,
p< .05. However, an effect of condition was not uni-
versally found. Observers did not report that their
own face felt out of control (Item 4), t(19) = 0.19, p
= .84, or, despite the clear convergence in felt resem-
blance between their own and the onscreen face,
that they were looking at their own face in a mirror
(Item 3), t(19) = 0.98, p= .33.
Finally, an overall enfacement score was also calcu-
lated for each observer, by averaging across Items 1 to
7. This enfacement score was higher in the congruent
(M= 22.8, SD = 10.6) than in the neutral condition (M
= 16.9, SD = 8.4), t(19) = 3.24, p< .01.
Discussion
This experiment investigated whether it is possible to
update the representation of one’s own face with a
gaze-contingent paradigm by comparing a congruent
condition, in which the eye-gaze of an onscreen face
followed that of the observer, with a neutral condition,
in which the onscreen face was static and unrespon-
sive. As in Experiment 1, observers were sensitive to
the eye movements of the onscreen faces and their
directionality in the congruent condition. However, a
clearer contrast between conditions was now found,
by replacing incongruent with neutral gaze displays
(cf. Items 8–10 in Figures 3 and 5). Once again,
however, this did not affect observers’self-recognition
in the discrimination task, which revealed identical
effects after congruent and neutral stimulation.
Despite the absence of an effect on self-recognition
in the visual discrimination task, the gaze-contingent
paradigm affected observers’reports of how they
Figure 4. Performance in the self–other discrimination task in Exper-
iment 2, expressed as the number of frames that observers judged to
show their own face or that of the onscreen face, for the baseline
measure and after congruent and neutral stimulation.
8A. J. ESTUDILLO AND M. BINDEMANN
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felt about the onscreen and their own face. These
reports revealed that observers felt that the onscreen
face “was”their own face and “belonged”to them, and
also that both faces began to resemble each other.
This effect was such that, if the eyes of the onscreen
face had moved, observers expected their own eyes
to move too.
These results indicate that this mirror-like gaze-
contingent paradigm can affect how observers feel
about their own faces. This finding converges with
recent enfacement experiments, in which similar
effects are found when observers view the tactile
stimulation of another agent while their own face is
also stimulated (e.g., Maister et al., 2013; Tajadura-
Jiménez, Grehl et al., 2012; Tajadura-Jiménez, Longo
et al., 2012; Tsakiris, 2008). However, in these studies
a concurrent effect in the self–other discrimination
task is typically also found (e.g., Tajadura-Jiménez,
Grehl et al., 2012; Tsakiris, 2008).
A possible explanation for the absence of such an
effect here might relate to the objects surrounding
the onscreen face, which acted as trigger-regions to
change its gaze-direction and were required to elicit
mirror-like responses. As a result of this manipulation,
observers were actually drawn away from the onsc-
reen face during stimulation. If this limits the encoding
of the stimulation faces in our visual displays, by pre-
senting these outside of foveal vision (see, e.g., Rous-
selet, Husk, Bennett, & Sekuler, 2005; Rousselet,
Thorpe, & Fabre-Thorpe, 2004), then this could limit
the integration of the stimulation face into observers’
self-representations. To explore this possibility, we
conducted a third experiment in which the eight
boxes surrounding the onscreen face were replaced
with the same face. The aim of this manipulation
was to maximize encoding of this identity even
when observers were not viewing the central stimu-
lation face directly.
EXPERIMENT 3
In this experiment, we sought to maximize the encod-
ing of the face identity in the stimulation task. As in
the preceding experiments, an unfamiliar face was
placed in the centre of the screen and responded to
observers’eye-gaze. However, to increase the encod-
ing of this identity, the eight surrounding boxes
were replaced with copies of the same face. In contrast
Figure 5. Mean Likert responses to each enfacement item for the congruent (black bars) and the neutral (grey bars) conditions in Experiment
2. *p< .05; **p< .01; ***p< .001.
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to Experiments 1 and 2, observers were therefore able
to view the stimulation face directly, in the centre of
the screen or one of the surrounding locations,
throughout this task. These surrounding faces also
responded to observers’eye-gaze by copying the
actions of the central face. This manipulation over-
comes the potential limitations of Experiment 1, in
which eye-gaze direction could be perceived only
from the unattended central face. In the current exper-
iment, this allowed us to revert to incongruent gaze
displays, in which the onscreen gaze moves in tem-
poral synchrony but a different direction to observers’
own eye-gaze. To introduce a task demand, one of the
surrounding faces would close its eyes after the 2-min
stimulation period, and observers were asked to
detect this change. If it is possible to update self-rep-
resentations with this gaze-contingent paradigm, then
such an effect should be more likely under these con-
ditions, which maximize encoding of the stimulation
face, than in the preceding experiments.
Method
Participants
Twenty new Caucasian students (17 female) from the
University of Kent, with a mean age of 22 years (SD =
8.5), participated in this study. All provided informed
consent prior to taking part, received course credits
or a small fee for participation, and reported normal
or corrected-to-normal vision.
Stimuli and procedure
The stimuli and procedure were identical to those in
Experiment 1, except for the following changes. In
the stimulation task, the eight boxes surrounding
the central face, and the objects within, were now
replaced by copies of the stimulation face (see
Figure 6). Each of these peripheral faces measured
160 × 210 pixels at a resolution of 72 ppi. In the con-
gruent condition, the central face and each of these
peripheral copies mirror-mimicked observers’eye-
gaze direction. In the incongruent condition, the
eye-gaze direction of the central face and the periph-
eral copies was spatially incongruent with observers’
gaze. After a two-minute stimulation period, one of
the surrounding faces closed its eyes. Observers
were asked to scan the surrounding faces and to
press the spacebar as soon as they detected this
change.
Results
Self–other discrimination task
Figure 7 summarizes performance in the self–other
discrimination task for the baseline condition and
after the administration of the congruent and incon-
gruent stimulation displays. A one-factor ANOVA
(baseline, congruent, incongruent) showed a main
effect of condition, F(1, 19) = 11.57, p< .001, h2
p= .38.
Paired sample t-tests (Bonferroni-corrected) show
that observers perceived their own face earlier in the
discrimination sequence in the congruent condition
compared to the baseline, t(19) = 3.12, p< .05.
However, a similar effect was observed in the incon-
gruent condition, t(19) = 3.40, p< .05, and perform-
ance was indistinguishable when the congruent and
incongruent conditions were compared directly, t
(19) = 0.95, p= 1.00.
Figure 6. Example stimuli for Experiment 3, showing direct and averted eye-gaze.
Source: Face was taken from the Glasgow Face Database.
10 A. J. ESTUDILLO AND M. BINDEMANN
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Enfacement questionnaire
The questionnaire responses indicate that observers
were aware of the onscreen face following their own
eye-gaze in the congruent compared to the incongru-
ent condition (see Items 8 and 9 in Figure 8), both ts
(19) ≥2.19, ps < .05. Observers were also more likely
to report that the target’s eyes moved in the same
direction as their own in the congruent condition
(Item 10), t(19) = 7.13, p< .001, and in a different direc-
tion in the incongruent condition (Item 11), t(19) =
6.66, p< .001. In addition, a direct comparison of the
ratings for Items 10 (eyes moved in the same direc-
tion) and 11 (eyes moved in a different direction) con-
firmed that observers discriminated the directionality
of the onscreen eye movements in both the congru-
ent, t(19) = 12.15, p< .001, and the incongruent con-
dition, t(19) = 3.10, p< .001.
The gaze-contingent paradigm also influenced
how observers felt about the onscreen face. In the
congruent compared to the incongruent condition,
observers were more likely to report that the onscreen
face looked like their own face (Item 1), that it
belonged to them (Item 2), and that they felt they
were looking at their own face in a mirror (Item 3),
all ts(19) ≥2.06, ps < .05. This effect was such that
observers expected their own eyes to move too if
the eyes of the target face had moved (Item 7), t(19)
= 2.96, p< .01.
However, an effect of condition was not universally
found. Despite the clear convergence in felt resem-
blance between observers’own and the onscreen
face, they did not report that these faces actually
began to resemble each other (Items 5 and 6), both
ts(19) ≤1.65, ps > .07. In addition, observers also did
not report that their own face felt out of control
(Item 4), t(19) = 0.19, p= 1.67. Despite these similarities
across conditions, observers’overall ratings, which
combine Items 1 to 7, also revealed a higher enface-
ment score in the congruent (M= 25.5, SD = 9.1) than
in the incongruent condition (M= 19.7, SD = 8.8), t
(19) = 3.42, p< .01.
Discussion
In this experiment, the objects surrounding the onsc-
reen face during the stimulation phase were replaced
with further images of this identity to maximize its
encoding. In this context, observers were clearly sensi-
tive to the onscreen face’s eye movements in the con-
gruent and incongruent conditions. As in Experiment 2,
the gaze-contingent stimulation paradigm also influ-
enced how observers felt about the onscreen face,
such that they were more likely to report that the onsc-
reen face looked like their own face and that it
belonged to them in the congruent than in the incon-
gruent condition. This effect was sufficiently strong for
observers to be more likely to report that they felt as if
they were looking at their own face in a mirror in the
congruent condition, and that their own eyes might
move to mimic the actions of the onscreen face.
Despite this impact on observers’reports, the gaze-
contingent task did not produce separable effects for
the congruent and incongruent conditions in the per-
ceptual self–other discrimination task. This converges
with the findings of Experiments 1 and 2 to suggest
that the gaze-contingent paradigm does not influence
observers’facial self-representations.
GENERAL DISCUSSION
In this paper, we have presented a new paradigm to
study how human observers might update mental
representations of their own face. This paradigm simu-
lates the mirror reflection experience by mimicking
observers’eye-gaze behaviour with an onscreen
face. In Experiment 1, observers were exposed to con-
gruent stimulation, in which the movement of the
onscreen face was synchronized with their own gaze
behaviour, and an incongruent condition, in which
the eyes of the onscreen face moved in a different
direction to observers’eye-gaze. This experiment did
not reveal an effect of gaze stimulation in the self–
other discrimination task or on observers’subjective
reports. The verification items of the questionnaire
suggest that observers were sensitive to onscreen
eye-gaze in the congruent condition. By contrast,
Figure 7. Performance in the self–other discrimination task in Exper-
iment 3, expressed as the number of frames that observers judged to
show their own face or that of the onscreen face, for the baseline
measure and after congruent and incongruent stimulation.
THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY 11
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however, observers did not report a clear directional-
ity effect for the onscreen face’s eye movements in
the incongruent condition. This suggests that they
misperceived the direction of the onscreen face’s
eye movements, which might have undermined any
stimulation effects of the gaze-contingent task.
Subsequent experiments explored whether the
gaze-contingent paradigm can be modified to elicit
such effects. Experiment 2 replaced the incongruent
condition with neutral displays, in which the onscreen
eye-gaze was static and unresponsive, to provide a
stronger contrast with congruent displays (see
Burton et al., 2009; Hermens et al., in press; Yokoyama
et al., 2014). Observers’self-reports showed that they
were sensitive to the difference in the eye movements
between conditions, and also the mimicry that these
eye-movements exerted in the congruent condition.
This was accompanied by a feeling that the onscreen
face “was”their own face and “belonged”to them, and
that both faces began to resemble each other. This
effect was such that, if the eyes of the onscreen face
had moved, observers would have expected their
own eyes to move too. Once again, however, these
changes were not accompanied by a corresponding
effect in the self–other discrimination task, which indi-
cates that the gaze-contingent task did not modify
observers’perceptual representations of their own
face.
It is possible that the encoding of the onscreen face
was limited in these experiments because observers
were drawn from its location to the peripheral
object-triggers during the stimulation phase. We
therefore conducted a third experiment in which
these peripheral objects were replaced with further
photos of the onscreen face to promote further
encoding of this identity. These additional face
images also responded to observers’gaze in an
attempt to further enhance this manipulation. In con-
trast to Experiment 1, observers were now clearly sen-
sitive to gaze direction in both the congruent and the
incongruent condition. As in Experiment 2, this was
accompanied by stronger reports in the congruent
condition that the onscreen face was the observer’s
own face than with incongruent displays, and that
observers felt like they were looking at their own
face in a mirror. Once again, however, the stimulation
conditions did not affect the perceptual discrimination
task.
Figure 8. Mean Likert responses to each enfacement item for the congruent (black bars) and incongruent (grey bars) conditions in Experiment 3. *p
< .05; **p< .01; ***p< .001.
12 A. J. ESTUDILLO AND M. BINDEMANN
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Taken together, these results indicate that our
gaze-contingent mirror-experience paradigm can
alter observers’subjective reports about their own
face, by creating a “felt”resemblance between their
own face and an onscreen target. This effect is remark-
able considering it followed a short stimulation period
of only 2 min. At the same time, this stimulation was
not effective in altering observers’perceptual self-rep-
resentations, as measured with the self–other discrimi-
nation task. A possible explanation for these
differences between observers’subjective reports
and their perceptual performance could be that
these reflect partially independent pathways in the
cognitive face recognition system. One of these is
responsible for the perceptual recognition of a face,
whereas the other might provide an accompanying
affective familiarity response, which can be expressed
through changes in electrodermal activity (i.e., skin
conductance responses, see Ellis & Young, 1990;
Schweinberger & Burton, 2003). This idea derives
from the study of Capgras delusion and prosopagno-
sia. In the former, observers can identify familiar
faces but do not exhibit the appropriate correspond-
ing feelings of familiarity and related skin conduc-
tance responses. As a consequence, people with
Capgras delusion believe that familiar persons have
been replaced by impostors or aliens (Ellis, 1997). Pro-
sopagnosic observers, on the other hand, are impaired
in overt recognition but can still exhibit arousal
responses to familiar faces (see, e.g., Ellis, Quayle, &
Young, 1999). It is possible that our findings also tap
into these dissociable processes, by manipulating
affective evaluations of the own face but not percep-
tual representations.
This idea receives some support from explorations
of the enfacement effect, where visuotactile stimu-
lation mediates arousal responses to target faces (e.
g., Bufalari et al., 2014; Fini et al., 2013; Maister et al.,
2013; Paladino, Mazzurega, Pavani, & Schubert, 2010;
Tajadura-Jiménez, Grehl et al., 2012). These physiologi-
cal changes are similar to skin conductance responses
during familiar face recognition (Ellis, Young, &
Koenken, 1993; Tranel & Damasio, 1985,1988)and
have been observed after synchronous, but not asyn-
chronous, tactile stimulation with an unfamiliar face
(see Tajadura-Jiménez, Grehl et al., 2012). However,
in contrast to the current experiments, this enface-
ment effect is also accompanied by changes in the
perceptual processing of faces.
It remains unresolved why perceptual processing
was not affected as well in the current experiments,
but one possibility is that a stimulation phase of only
2 min is insufficient to manipulate self-representations
that have been build-up over 20 years in our partici-
pants. This explanation would be consistent with the-
ories of face recognition, such as average-based
accounts, in which different instances of the same
face are integrated into a single representation
(Burton et al., 2005). Such averages appear to be
remarkably resistant to contamination by other identi-
ties. For example, changes to the average of a person’s
face appear to be imperceptible even when 20% of
the source images are photographs of the wrong
person (Jenkins & Burton, 2011). If this approach corre-
sponds to the cognitive system for face recognition,
then one would also expect internal facial represen-
tations to be immune to the brief perceptual stimu-
lation that is applied in the experiments here.
In future studies, this could be explored further by
extending the stimulation phase or by applying this
paradigm to developmental populations, in which
self-representations have been established for fewer
years, and facial appearance is undergoing more pro-
nounced age-related changes. Future studies could
also examine whether the effect of mirror-feedback
might be enhanced by mimicking more than obser-
vers’eye-gaze, such as facial expression and speech.
By encompassing further facial information in this
way, the mirror-mimicry may exert more direct
effects on visual encoding and the updating of rep-
resentations of the own face.
Disclosure statement
No potential conflict of interest was reported by the authors.
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