REPORT
Emerging Self-Representation Presents a
Challenge When Perspectives Conflict
Emanuela Yeung
, Dimitrios Askitis, Velisar Manea, and Victoria Southgate
Department of Psychology, University of Copenhagen
Keywords: infancy, pupillometry, perspective tracking, self, inhibition
a n o p e n a c c e s s
j o u r n a l
ABSTRACT
The capacity to take another’s perspective appears to be present from early in life, with young
infants ostensibly able to predict others’ behaviour even when the self and other perspective
are at odds. Yet, infants’ abilities are difficult to reconcile with the well-known problems
that older children have with ignoring their own perspective. Here we show that it is the
development of the self-perspective, at around 18 months, that creates a perspective conflict
between self and other during a non-verbal perspective-tracking scenario. Using mirror
self-recognition as a measure of self-awareness and pupil dilation to index conflict processing,
our results show that mirror recognisers perceive greater conflict during action anticipation,
specifically in a high inhibitory demand condition, in which conflict between self and other
should be particularly salient.
INTRODUCTION
The capacity to take another’s perspective appears to be present from early in life, with young
infants are ostensibly able to predict others’ behaviour even when the self and other perspec-
tive are at odds (Baillargeon et al., 2010; Choi et al., 2018; Luo & Johnson, 2009; Southgate &
Vernetti, 2014). Yet, infants’ abilities are difficult to reconcile with the well-known problems
that 3-year-olds have with ignoring their own perspective (Birch & Bloom, 2003). A particular
challenge for explaining the processes that underlie infants’ abilities is to account for the role
that developmentally-dependent abilities like conflict monitoring and inhibitory control seem
to play in managing perspective conflict in older children (Carlson & Moses, 2001; Kloo &
Perner, 2003).
The false belief task is the paradigmatic case of perspective conflict because, to make the
correct inference, one cannot rely on one’s own (differing) representation and many studies
have demonstrated some involvement of inhibitory resources in success on verbal mentalizing
tasks (Devine & Hughes, 2014). This relationship likely stems from the assumed need to deal
with two conflicting representations: one derived from the child’s own knowledge of reality
and the other from the child’s encoding of the other’s perspective. To resolve this conflict,
various accounts appeal to conflict monitoring and management mechanisms (Leslie et al.,
2004). Neuroimaging work supports this view by demonstrating that brain regions implicated
in inhibition are required for success on perspective conflict tasks (Hartwright et al., 2015;
Samson et al., 2005) and recruited at a point where the participant needs to make their judge-
ment (McCleery et al., 2011). Given that young infant’s inhibitory skills are likely to be less
Citation: Yeung, E., Askitis, D., Manea,
V., & Southgate, V. (2022). Emerging
Self-Representation Presents a
Challenge When Perspectives Conflict.
Open Mind: Discoveries in Cognitive
Science, 6, 232–249. https://doi.org/10
.1162/opmi_a_00065
DOI:
https://doi.org/10.1162/opmi_a_00065
Supplemental Materials:
https://doi.org/10.1162/opmi_a_00065
Received: 1 March 2022
Accepted: 16 October 2022
Competing Interests: The authors
declare no conflict of interest.
Corresponding Author:
Emanuela Yeung
eyeung@psy.ku.dk
Copyright: © 2022
Massachusetts Institute of Technology
Published under a Creative Commons
Attribution 4.0 International
(CC BY 4.0) license
The MIT Press
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Yeung et al.
developed than those of preschoolers (Hendry et al., 2016; Müller & Kerns, 2015), it remains
unexplained how infants as young as 6 months of age seem to make predictions about
another’s behaviour when the infant and the other should have conflicting representations
(Luo & Baillargeon, 2007; Southgate & Vernetti, 2014).
One possible explanation could be that the non-verbal measures with which infants’ abil-
ities are measured do not place demands on inhibition, and thus enable infants to reveal their
perspective tracking ability by removing the need to inhibit their own perspective (Baillargeon
et al., 2010). While this would be a neat solution, it is unclear why non-verbal tasks should not
demand conflict resolution, especially in the scenarios described above (e.g., Luo & Baillargeon,
2007; Southgate & Vernetti, 2014) where the infant is still faced with two conflicting perspec-
tives and should need to ignore their own perspective to make the correct prediction. It seems
unlikely that the nonverbal nature of the task circumvents the need for inhibition since
dual-task manipulations, targeting executive functions, impair adults’ performance on an anal-
ogous nonverbal perspective conflict task (Schneider et al., 2012). Furthermore, manipulating
the presence or absence of the object, which targets inhibitory demands in adults (Hartwright
et al. 2015; Samson et al., 2005), impairs both children and adults’ ability to make belief-based
action predictions on a nonverbal task ( Wang & Leslie, 2016).
Recently, an alternative account has instead argued that young infants’ precocious success
on tasks involving perspective conflict may be due to an altercentric – or other-centred – bias
in infant cognition (Southgate, 2020). According to this hypothesis, an altercentric bias
emerges from two features of early cognition. First, like adults, infants experience interference
from spontaneous encoding of the other’s perspective. For example, 7-month-old infants look
longer to the absence of a ball when another agent mistakenly believes it should be present,
even if the infant should know that it is absent, than they do when both they and the agent
both believe it to be absent (Kovács et al., 2010). Together with data from adults showing mod-
ulation by the others’ perspective (e.g., Kovács et al., 2010; Samson et al., 2010), this suggests
that both infants and adults spontaneously encode events from the perspective of other agents
who are present. Second, an initial absence of a competing self-perspective in the first year of
life reduces the potential for perspective conflict (when perspectives conflict), allowing the
altercentric encoding to be the dominant influence on infants’ memory. This hypothesis draws
on evidence for a late emergence of cognitive self-representation between 18 and 24 months
of age and proposes that self-awareness is a prerequisite for generating a self-perspective. It
also draws on the self-reference effect (Rogers, 1977; Symons & Johnson, 1997) and hypoth-
esizes that only when the child is able to generate a representation of their own perspective
(e.g., the ball is in the left-hand box) does this representation become a competitor to the rep-
resentation of the object that is highlighted or cued by another agent’s attention (the ball is in
the right-hand box). Thus, in the absence of the self-perspective, young infants are proposed to
have an altercentric bias that tracks the perspective (i.e., follows the attention) of another indi-
vidual, allowing infants to generate representations of events and make predictions about future
events, without the need to inhibit or control the conflicting self-perspective (Southgate, 2020).
While there is already evidence that infant’s encoding and memory of events can be
enhanced and changed by others’ attention (e.g., Reid & Striano, 2005; Yoon et al., 2008),
recent evidence suggests that when a conflict in perspectives exists, 8-month-old infants better
remember the event that was witnessed by the other agent, than they do the event witnessed
alone, evidencing a memory error for the object’s location that was co-witnessed with another
agent (Manea et al., 2022). Although these infants are well below the age at which self-
representation appears to emerge, and thus the data are consistent with the hypothesis that
an absence of self-representation reduces the experience of perspective conflict leading to a
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preferential encoding of events from the other’s perspective, it does not address the role of
emerging self-representation. In the present preregistered study, we tested the hypothesis that
the development of self-awareness between 18 and 24 months is instrumental in creating a
perspective conflict, and challenge, for young children. Based on the hypothesis that conflict
in a false-belief scenario arises because of a mismatch between the self-perspective and other-
perspective, we investigated whether experienced conflict was greater in infants who have
achieved self-awareness, a presumed prerequisite for awareness of the self-perspective. Our
main question was whether a manipulation aimed at increasing or decreasing the demands on
participants’ inhibitory resources in a perspective-conflict scenario, would a) be detected only
by infants who exhibit evidence of self-awareness and b) modulate belief-based action predic-
tions only in infants who exhibit evidence of self-awareness.
In line with previous work (Hartwright et al., 2015; Samson et al., 2005; Wang & Leslie,
2016), we manipulated demand on inhibitory resources by either transferring an object from
one box to another (high-conflict, HDfb) or removing the object from the scene altogether (low-
conflict, LDfb). In both cases, there is a conflict in perspectives between the child and the agent,
but that conflict is thought to be greater when the object remains in the scene as a salient
reminder of the participant’s own knowledge. We used the mirror self-recognition (MSR) test
as an index of self-awareness, categorizing infants as either recognisers or non-recognisers.
While MSR is a direct measure of physical self-recognition, there is considerable evidence that
it also indexes so-called ‘objective’ self-awareness, relating to self-other comparison (Kampis
et al., 2022), dyadic imitation (Asendorpf & Baudonnière, 1993), personal pronoun use (Lewis
& Ramsay, 2004), and brain indices of self-related processing (Bulgarelli et al., 2019).
We preregistered the prediction that recognisers would perceive greater conflict in the high-
than low-conflict scenario, whereas the perceived conflict between the two conditions would
be less for non-recognisers. To measure this, we used pupil size as an index of perceived con-
flict (Rondeel et al., 2015; Sirois & Brisson, 2014), predicting greater pupil dilation in the high
than low perspective conflict events, especially in infants who evidence mirror self-
recognition. Change in pupil diameter has been used as a marker of cognitive effort in both
adults and infants (Hess & Polt, 1960; Kahneman & Beatty, 1966; Kaldy & Blaser, 2020) and
pupillometry studies with young infants have shown that infants’ pupils dilate in response to
violations of expectation or prediction (Gredebäck & Melinder, 2010; Jackson & Sirois, 2009;
Pätzold & Liszkowski, 2019; Sirois & Jackson, 2012; Zhang & Emberson, 2020; Zhang et al.,
2019).
Secondly, we asked whether self-awareness would modulate belief-based action predic-
tion, reasoning that experiencing conflict between perspectives would impair children’s action
prediction capabilities in the absence of sufficient inhibitory resources. Thus, we preregistered
the prediction that infants who had achieved mirror self-recognition would show a greater
tendency towards incorrect action anticipation than those who had not. We further aimed
to test the prediction that there would be a relationship between inhibitory control and antic-
ipatory looking on the HDfb condition, but only in those infants who had achieved self-
awareness. In other words, we reasoned that for those infants who did experience the conflict
in perspectives, better inhibitory control ability would allow them to prioritise the other’s per-
spective and make the correct anticipation.
METHOD
This study was preregistered on the Open Science Framework and the description of the test-
ing protocol, stimuli, and planned analyses can be found here: https://osf.io/thr7y.
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Participants
To reach our pre-registered sample of 50 infants (n = 25 in each group of mirror recognisers
and mirror non-recognisers) we tested 80 infants in total. Participants were included based on
providing sufficient eye-tracking data for analysis (described below) and completing the Mirror
Self-Recognition (MSR) task. Of the 50 infants included in the non-verbal perspective-tracking
task (Mage = 18.17 months, SD = 9.83 days, 20 females), n = 40 also successfully completed
the inhibition task. There was no significant age difference between mirror recognisers and
non-recognisers (Mrecognisers = 18.22 months ± 7.26 days, Mnon-recognisers = 18.12 months ±
11.83 days, t(39.84) = −1.10, p = .28, Welch’s test).
The study was approved by the Research Ethics Committee of the Faculty of Social Sciences
at the University of Copenhagen and parents provided informed consent prior to participation.
Procedure
Infants were most often accompanied by one parent, who was asked to maintain a neutral
presence throughout the session. The task order for all participants was the same: the non-
verbal perspective-tracking task (NVPT), the Early Childhood Inhibitory Touchscreen Task
(ECITT), and the Mirror Self-Recognition task (MSR).
Non-Verbal Perspective-Tracking Task
Apparatus. Gaze and pupil diameter data were recorded from both eyes at 500 Hz using an
Eyelink1000 Plus eye tracker (SR Research, Ontario, Canada). The stimuli were presented on a
17″ monitor.
Stimuli. Animations were created using Blender (Blender Online Community, 2018) and
Adobe Premiere Pro. We ensured that our stimuli were isoluminant across the duration of each
trial and between conditions, to minimize pupil changes caused by variations in luminosity.
Infants were seated in their parent’s lap, approximately 60cm from the
Design and Procedure.
screen and Eyelink’s 5-point calibration was used for each infant. Stimuli were presented using
MATLAB for Mac (R2016b) and Psychtoolbox (3.0.16 Beta, SVN revision 10420).
The sequence of events is shown in Figure 1. Infants were first presented with two famil-
iarization trials. On each trial, an agent observed a ball jumping into one of two boxes. Next,
two lights illuminated together with a sound cue, and the agent reached into the box to
retrieve the ball. Infants saw the agent reaching once into the left box and once into the right
box with order counterbalanced.
Following familiarization, test trials were presented in blocks, each consisting of 11 trials.
On each test trial, the agent witnessed a ball move into one of two boxes. A curtain was then
drawn shut, occluding the agent, and the ball then jumped into the other box (false belief –
high demand condition, HDfb, movie 1) or out of the scene (false belief – low demand con-
dition, LDfb, movie 2). The curtains reopened, revealing the agent, the boxes reopened, and
the lights on each box illuminated together with a sound cue1. In each block, participants saw
5 videos for each false belief condition, including 2 trials where the agent reached into the box
where they last saw the ball (the “outcome”) after the anticipation phase. In addition, infants
1 To address the possibility that infants might infer that the agent could see the location of the ball when the
boxes reopened, we asked a group of 30 adults to evaluate the stimuli. The majority of the sample did not think
the agent could see inside the box (see SI for more detail).
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Figure 1. Time course and structure of the Non-Verbal Perspective-Tracking Task.
also saw 1 “true belief” trial in each block in which the agent witnessed the ball moving into
the second box and then reached into the box where the ball was located. The purpose of the
“outcome” and true belief trials was to motivate infants to make anticipatory looks throughout
the block (see below), but the gaze and pupil data from these trials were not used for analysis.
Infants were excluded if they looked away during portions of the familiarization and/or test
trials that were critical for understanding the structure of the task (see supplementary
information for further details).
Pupil Diameter. The eye-tracking data was extracted from the eye-tracker using the Eyelink IDE
and custom MATLAB scripts. The raw pupil data was first converted from arbitrary units to
millimeters. Next, we examined the data obtained from each eye for each participant and
excluded data from one eye when the ratio of the pupil standard deviations between eyes
was less than 1.5. The subsequent steps of our pre-processing pipeline followed the procedure
described by Kret and Sjak-Shie (2019); for details, see the supplementary information. Due to
preprocessing, we removed 20.7% (SD = 15.4%) of pupil data on average for each participant.
We also removed trials with more than 30% of data missing, which resulted in acceptance of
835 out of 1086 trials. Our final sample consisted of infants who provided at least 3 trials per
condition after pre-processing, resulting in 707 trials included in total.
Our primary dependent measure was change in pupil dilation. We calculated the change in
pupil dilation by subtracting the pupil size at each timepoint from a baseline period. We
defined the baseline as the average pupil diameter between 2000–5000 ms, which corre-
sponds to the movement of the ball from the centre of the screen into the first box and is iden-
tical in both conditions. In order to ensure that pupil data was not contaminated by noise in the
baseline, we restricted the analysis of pupil data to trials that had no missing values in their
baseline. This resulted in a further exclusion of 51 trials, leaving 656 trials in total.
The test phase was the period between 6.5 to 17.5 s of each trial. Previous studies have
found that infants’ pupils react more slowly than those of adults’ and require more time to
adapt to changes in stimuli (Pätzold & Liszkowski, 2019; Verschoor et al., 2015). As such,
the time windows for analyses of change in pupil size were adjusted to 500 ms after event
boundaries. Because we did not have a priori information about when infants might experi-
ence a conflict between the self- and other-perspective, we pre-registered three possible
windows of analysis: 1) 6.5–11.5 s, when the ball moved from the first to the second box,
2) 11.5–14.5 s, when the agent returned and the boxes opened, and 3) 14.5–17.5 s, when
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the sound and light cued for action prediction and while the agent sat stationary behind the
boxes (see Figure 1 for an overview of our task design).
Gaze and Anticipatory Looking. Fixations were computed online by the Eyelink system using
the cognitive configuration (see Eyelink manual 2017, 4.3.9), and fixations from both eyes
were used when available to assess fixation on areas of interest (AOIs) or on the screen.
We preregistered two dependent measures to analyse our anticipatory looking data. Our
first dependent measure, “first fixations”, was binary: it expressed whether the first box AOI
that the participant fixated on within the time window of interest was the correct side. We
defined an AOI that included the two boxes (see supplementary information). The time win-
dow of interest was initially defined as the 3000 ms interval starting from the sound and light
cue onset. However upon reviewing the gaze data and video recordings from our participants,
we found that many infants already made anticipatory saccades when the boxes reopened,
835 ms prior to the light cues on the boxes. Thus, we adjusted our time window of interest
to begin when the boxes opened. First fixation scores were averaged across all trials per con-
dition for each participant.
The second dependent variable was a differential looking score (DLS) calculated for each
participant as cumulative fixation time to correct box AOI divided by the sum of cumulative
fixation times to the two box AOIs. The cumulative fixation times were calculated within
3000 ms from the box opening cue onset. DLS scores were averaged across all trials per
condition for each participant. In addition to the exclusion criteria described above, we also
excluded trials where the child did not make fixations in either box AOI within the 3000 ms
from cue onset.
Early Childhood Inhibition Touch Screen Task
The Early Childhood Inhibitory Touchscreen Task (ECITT; (Holmboe et al., 2021) is a comput-
erized touchscreen task designed to assess inhibitory control in infants and toddlers (see
supplementary information for additional details regarding the materials and procedure).
Mirror Self-Recognition Task
Procedure. We conducted a mirror self-recognition task (following the procedure of Bulgarelli
et al., 2019; see also Amsterdam, 1972) to assess children’s ability to recognize themselves in
the mirror. The testing procedure included four phases: 1) children were first exposed to and
familiarized with the mirror prior to application of the mark, 2) the mark was applied to the
child’s nose surreptitiously after mirror was occluded, 3) the child was exposed to the mirror
again after the mark was on their nose, and 4) the experimenter pointed to the child’s reflection
in the mirror and asked “Who is that?”.
Coding. Children’s reactions in the mirror were coded by a trained research assistant with
respect to whether they touched the mark on their nose during phase 3 (mark-directed behav-
iour) and whether they verbalized any self-reference when seeing themselves in the mirror
during phase 3 or upon request during phase 4. Children were considered to have passed
the mirror test (“mirror recognisers”) if they showed mark-directed behaviour, used a first-
person pronoun, or used their own name. Children who did not exhibit these behaviours were
considered “mirror non-recognisers”. None of the children touched the mark during the sec-
ond phase before seeing themselves in the mirror. A subset of participants (50%) were double-
coded by a second independent coder. Coders agreed in 86% of all cases (κ = .72). In cases of
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disagreement, a third coder was involved, and the final score was decided by the majority. All
coders were blind to children’s performance on the NVPT and ECITT.
RESULTS
Pupil Dilation
After pre-processing, infants in our sample watched a mean of 5.46 ± 2.05 HDfb and 5.44 ±
1.82 LDfb trials. There was no significant difference in the number of trials included per con-
dition (t(49) = 0.10, p = 0.92). When split by MSR status, there were also no differences in
number of trials included in both the HDfb (Mrecognisers = 5.00 ± 1.98, Mnon-recognisers = 5.92 ±
2.06, t(48) = 1.61, p = 0.11), and LDfb conditions (Mrecognisers = 5.04 ± 1.65, Mnon-recognisers =
5.84 ± 1.93, t(48) = 1.58, p = .12).
Figure 2 shows the mean baseline-corrected pupil diameter for the duration of the trial for
both groups of participants across the two conditions. To analyse differences in pupil dilation,
we pre-registered analyses using both ANOVA and functional data analysis (FDA). One par-
ticipant (a mirror recogniser) did not have sufficient data in window 3 and was excluded from
the ANOVA for this time window and the FDA analysis.
First we looked at differences in dilation using a 2 (condition) × 2 (MSR status) repeated-
measures ANOVA, with pupil dilation averaged within each of the 3 pre-registered time
windows. However, there were no significant main effects or interactions in any of the time
windows (see supplementary information for details). Although averaging across time windows
or trials is common practice for other measures of gaze data, this approach may not be optimal
for pupil data due to loss of information ( Jackson & Sirois, 2009). For this reason, we also pre-
registered FDA (Ramsay & Silverman, 2002) to assess whether the change in pupil dilation
over time differed between our two groups and to determine the specific time windows in
which differences could be observed.
The data was fitted using B-spline functions of order 4 with 58 bases. We performed a func-
tional two by two mixed ANOVA (Ramsay & Silverman, 2002) with mirror status as the
between groups factor and demand condition (HDfb and LDfb) as the repeated measure. To
determine statistical significance thresholds, we performed permutation analysis at 0.05 signif-
icance level and 10000 permutations, where the mirror and demand conditions were
Figure 2. Baseline-corrected change in pupil size across the duration of the trial. The panel on the left shows the HDfb condition, the panel
on the right shows the LDfb condition. Shaded regions show 95% confidence intervals. The dashed vertical lines demarcate the beginning of
each pre-registered time window.
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Functional F-test (ANOVA) with MSR status as the between-subjects factor. Statistical
Figure 3a.
significance was detected during the outcome phase, between 15918–16384 and 16544–
16904 milliseconds.
randomly shuffled. For each permutation, the computed F-statistics were used to form null
distributions, against which our original values were compared. When we examined mirror
status (the between groups factor), we detected a significant difference in pupil dilation
between mirror groups in the anticipation window between 15918–16384 ms and 16544–
16904 ms. When we compared dilation between conditions, there was a statistical difference
in the time period that differed visually between the conditions (i.e., when the ball jumps out
of the scene or into the second box). We did not find any other statistical differences in pupil
dilation between the demand conditions, nor in their interaction with the mirror factor (see
Figures 3a–3c). When looking only in the HDfb condition, a functional t-test also showed that
baseline-corrected pupil dilation differed between groups in the anticipation phase, specifi-
cally between 15790–16990 milliseconds. No differences between pupil dilation were
detected in the LDfb condition (see Figures 4a–4b).
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Figure 3b.
Functional F-test (ANOVA) with condition (HDfb vs. LDfb) as the between-subjects
factor. Statistical significance was detected only around the time period when the two conditions
differed visually (i.e., the ball jumping into the second box or jumping out of the screen).
OPEN MIND: Discoveries in Cognitive Science
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Figure 3c.
condition. No statistical significance was detected.
Functional F-test (ANOVA) for the interaction between MSR status and demand
Exploratory Analyses
Growth Curve Analysis. To provide further support for the effect of MSR status detected in the
third pre-registered time window (14.5 s–17.5 s) on pupil dilation, we performed a post hoc
growth curve analysis (GCA) to examine how the pupil reactions deviated over time. GCA is a
multilevel regression model that fits orthogonal polynomials to time series data to model var-
iations in the curve shape (Mirman, 2017). It has been increasingly used in modelling pupil
data time series (Kuchinsky et al., 2013; McGarrigle et al., 2017; Wagner et al., 2019; Winn,
2016) and is ideal for investigating the temporal dynamics of pupil data that can be obscured
in a time window averaging approach.
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Functional t-test for mirror recognisers vs non-recognisers within the high demand
Figure 4a.
condition. Statistically significant differences were observed during the outcome phase, from
15790 to 16990 milliseconds.
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Figure 4b.
condition. No statistically significant differences were observed across the test phase.
Functional t-test for mirror recognisers vs. non-recognisers within the low demand
We used normalised orthogonal polynomial terms up to degree 4 to model the pupil data
from 14.5 s to 17.5 s (see supplementary information for further details). Given that our FDA
analysis revealed effects only in the HDfb condition, we restricted our analysis in this condi-
tion. We considered the full model with mirror status as a main effect and all its interactions
with polynomial terms (see Table 1). Based on a Likelihood Ratio Test, the full model fit the
data better than the null model (i.e., the one consisting of the polynomial predictors but with-
out the mirror factor; χ2 = 11.521, dDF = 5, p < 0.05). Following Mirman (2017), we examined
each individual interaction by dropping it from the full model and evaluated its unique effect
by the reduction in the model fit.
We detected a significant effect of the MSR factor on the linear and quadratic term (see
Table 2). This reflects the overall increase of pupil size in the recognisers compared to the
non-recognisers (i.e., the effect on linear term), that is faster in the beginning (the effect on
quadratic term), as we can observe in Figure 5. The difference in the pupil dynamics is indic-
ative of the mirror recognisers, but not the non-recognisers, experiencing perspective conflict
during the anticipation phase.
Early Effect. Through visual inspection of the data, we observed a difference in pupil reaction
between the two mirror-status groups before our preregistered test period, at approximately the
time the agent begins to be occluded (∼5–6 s). To explore this further, we conducted a func-
tional t-test from 5 s to 6.5 s using permutation analysis at 0.05 significance level and 10000
permutations (see Figure 6), combining the data from both the HDfb and LDfb conditions as
they are identical during this time period. We detected a statistically significant difference
between the two groups from 5498 ms to 5820 ms. Taking into account the pupil responsivity
delay, this suggests that the mirror recognisers showed greater pupil dilation in anticipation of
the agent becoming occluded than mirror non-recognisers2.
2 As infants saw multiple trials, they could in principle anticipate the forthcoming disappearance of the agent
at the same time on each trial.
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The full model within the high demand condition, with pupil ∼ mirror * (op1 + op2 +
Table 1.
op3 + op4) + (op1 + op2 + op3 + op4|subj). For the calculation of the p-values the z-distribution
was used as an approximation to the t-distribution (see Mirman, 2017). We saw effects of MSR status
on the linear and quadratic term.
Term
(Intercept)
mirror
op1
op2
op3
op4
mirror:op1
mirror:op2
mirror:op3
mirror:op4
Estimate
−0.059381
−0.246222
0.246440
−0.148520
0.125062
0.046273
0.158428
−0.127158
−0.050750
0.047509
SE
0.029130
0.078655
0.058157
0.041083
0.034271
0.029130
0.078655
0.058157
0.041083
0.034271
t
−2.038456
−3.130421
4.237516
−3.615159
3.649185
1.588465
2.014229
−2.186473
−1.235310
1.386270
p
0.041504
0.001746
0.000023
0.000300
0.000263
0.112181
0.043985*
0.028781*
0.216715
0.165665
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Anticipatory Looking & Inhibitory Control
We examined whether conflict between perspectives would impair children’s action predic-
tion capabilities in the absence of sufficient inhibitory resources, predicting that infants who
had achieved mirror self-recognition would show a greater tendency towards incorrect action
anticipation than those who had not. We also predicted that there would be a relationship
between inhibitory control and anticipatory looking on the HDfb condition, but only in those
infants who had achieved self-awareness.
After pre-processing, infants in our sample watched a mean of 5.22 ± 1.93 HDfb and 5.08 ±
1.84 LDfb trials. There was no significant difference in the number of trials included per con-
dition (t(98) = 0.37, p = 0.71). When split by MSR status, mirror non-recognisers had more
trials included in both the HDfb condition (Mrecognisers = 4.68 ± 1.95, Mnon-recognisers = 5.76 ±
1.79, t(48) = 2.04, p = .05), and LDfb condition (Mrecognisers = 4.44 ± 1.47, Mnon-recognisers =
5.72 ± 1.97, t(48) = 2.60, p = .01). Both recognisers and non-recognisers anticipated in the
same proportion of trials in both conditions (HDfb: Mrecognisers = 0.84 ± 0.21, Mnon-recognisers =
0.92 ± 0.11, t(36) = 1.76, p = .09, Welch’s test; LDfb: Mrecognisers = 0.81 ± 0.20, Mnon-recognisers =
0.88 ± 0.15, t(44) = 1.36, p = .18, Welch’s test).
The effect of dropping each single interaction of a polynomial term with MSR status to
Table 2.
model fitness. Because we dropped only one term each time, the degree of freedom is one. We see
that dropping the first two terms resulted in worse fitting models, which allowed us to conclude that
these terms are significant.
Interaction term dropped
linear
quadratic
cubic
quartic
χ2
3.8979
4.5615
1.5027
1.8850
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0.0483*
0.0327*
0.2203
0.1698
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Figure 5. Plotted fit of the full model, between MSR groups and within the high demand condition.
We analysed two indicators of whether infants anticipated correctly: i) first fixation scores
(i.e., whether after the cue onset, the first box they fixated on was the side where the agent should
have expected to find the ball given their false belief ) and ii) DLS score during the anticipation
period. As our predictions differed by MSR status, we analysed each group separately.
For first fixation, recognisers were at chance in the HDfb condition and below chance in
the LDfb condition (MHDfb = 0.45 ± 0.28, t(24) = −0.88, p = .38; MLDfb = 0.38 ± 0.24, t(24) =
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Figure 6. Functional t-test for mirror recognisers vs. non-recognisers in both conditions in the
early period around agent occlusion. We detected a significant difference from 5498 ms to 5820 ms.
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−2.60, p = .02; both tests are one-sample t-tests on first fixation scores equal to chance (.5)),
and non-recognisers were below chance in the HDfb condition and at chance for the LDfb
condition (MHDfb = 0.36 ± 0.26, t(49) = −3.70, p < .001; MLDfb = 0.41 ± 0.23, t(49) = −2.82,
p = .003; both tests are one-sample t-tests on first fixation scores below chance (.5)).
For DLS score, recognisers were at chance in the HDfb condition and below chance in the
LDfb condition (MHDfb = −0.08 ± 0.49, t(24) = −0.77, p = .45; MLDfb = −0.22 ± 0.47, t(24) =
−2.40, p = .03; both tests are one-sample t-tests on DLS scores equal to chance (0), and non-
recognisers were below chance in the HDfb condition and at chance in the LDfb condition
(MHDfb = −0.28 ± 0.35, t(24) = −4.03, p < .01; MLDfb = −0.11 ± 0.28, t(24) = −1.99, p = .06;
both tests are one-sample t-tests on DLS scores equal to chance (0). Thus, neither measure
provided evidence for correct action prediction.
Given that our predictions regarding the relationship between anticipatory looking and
inhibitory control assumed evidence of correct prediction with anticipatory looking, it is not
informative to examine the relationship with inhibitory control abilities. We nonetheless
include the preregistered analyses in the supplementary information. Of note, there were no
differences in performance on the ECITT task between mirror recognisers and non-recognisers
based on accuracy on prepotent trials (t(38) = −0.84, p = .41), accuracy on inhibition trials
(t(38) = 0.32, p = .75), or ADS score (t(38) = −0.61, p = 0.55), indicating that inhibitory control
was not related to recogniser status.
Exploratory Analyses
Latency - Anticipation Phase. Although infants did not correctly anticipate, we considered
post hoc whether examining differences in latency to make anticipatory looks would allow us
to better interpret the differences in pupil dilation during the anticipation phase. Saccades during
the anticipation window could reflect either simply a reaction to exogenous cues (e.g., the lids
on the box opening or the lights on the boxes that appear at the start of this window to prompt
anticipation), or in addition, could reflect infants’ expectation concerning in which box they
think the agent will search. While neither group provided evidence that they correctly antici-
pated the agent’s search, we reasoned that latency to make the initial saccade could provide
information on whether anticipatory saccades were exogenously or endogenously mediated.
Specifically, we reasoned that a longer latency to generate a saccade to a box in the anticipa-
tory window could reflect a delay related to managing two conflicting representations, if sac-
cades were endogenously mediated. To examine latency, we computed the time from the box
opening cue to the first saccade to one of the box AOIs. Independent samples t-tests (with
unequal variances) revealed that mirror recognisers were indeed slower (M = 879.05 ±
495.64 ms) than non-recognisers (M = 652.97 ± 254.00 ms) in the HDfb condition (t(35.79) =
−2.03, p = .05). Latency was not significantly different in the LDfb condition (Mrecognisers =
810.13 ± 453.00; Mnon-recognisers = 723.23 ± 250.41; t(37.42) = −0.84, p = .41).
Latency - Early Effect. We also considered posthoc whether examining differences in latency to
making a saccade to the agent would allow us to better interpret the differences in pupil dila-
tion during the earlier time window, just before the agent is occluded. We reasoned that if
pupil dilation reflects anticipation of the agent being occluded, we may observe differences
in how quickly infants saccade to the agent. Latency was computed as the time from the
curtains beginning to close to the first saccade to the agent AOI in both the HDfb and LDfb
conditions combined. An independent samples t-test revealed that mirror recognisers were
faster (M = 540.71 ± 270.58 ms) than non-recognisers (M = 712.38 ± 248.22 ms) to saccade
to the agent (t(48) = 2.34, p = .02, d = .66).
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DISCUSSION
This study tested the hypothesis that the emergence of self-representation, between 18 and 24
months, presents a challenge for young children when they are presented with a situation in
which the self and other should hold conflicting perspectives (Southgate, 2020). Under this
account, self-representation enables children to represent their own perspective as the self-
perspective, and in doing so, this representation can compete with the representation of an
event that is generated from tracking the other’s perspective. Thus, we preregistered the pre-
diction that infants who had achieved self-awareness, as indexed by mirror self-recognition,
would experience greater conflict, as indexed by pupil dilation, while watching events in
which conflict between self and other perspectives is high. We further predicted that this con-
flict would manifest in a reduced ability to make anticipatory saccades towards a location
congruent with an agent’s false belief in infants who evidenced mirror self-recognition, and
that this may be modulated by infants’ capacity for inhibitory control.
Our results suggest that mirror recognisers did perceive greater conflict during the late pre-
registered time window (corresponding to the action anticipation phase), which reached sig-
nificance only in the high demand condition in which the conflict between self and other
should be particularly salient. Within this condition, mirror recognisers also took longer to
saccade to a box during anticipation. While latency was not a pre-registered variable, it
may provide additional support for our interpretation of the pupil dilation data. Specifically,
taking longer to generate a saccade would be consistent with our interpretation that it is the
mirror recognisers who detect the perspective conflict. Nevertheless, the main effect of mirror
status suggests that mirror recognisers detected a conflict in both low and high demand trials.
While work with adults has found that only high demand trials seem to require intact inhib-
itory control (Hartwright et al., 2015; Samson et al., 2005), for 18-month-olds, even the low-
demand trials where they do not know the real location of the object, present a challenge.
Similar to findings in adults showing that conflict manifests at the point where a response is
needed (McCleery et al., 2011), the presence of a difference in pupil dilation only in this final
window may imply that the perceived conflict between perspectives only emerges when the
infant is prompted—albeit implicitly—to make a prediction about what the other person will
likely do.
However, while we found the expected pupil dilation for recognisers in the high conflict
condition, suggesting that it was only in this group and in this condition that the conflict
between the two perspectives was perceived, we did not find support for our hypothesis that
the non-recognisers would surpass the recognisers in correct action anticipation. To correctly
anticipate, infants would ostensibly need to inhibit their own conflicting perspective. In the
current study, we found either at-chance or below-chance performance on both anticipatory
looking measures, depending on MSR status and trial type, suggesting that neither group pre-
dicted correctly where the agent would reach for the ball.
Considering the pupil and anticipatory looking data together, one possibility is that 18-
month-olds who have achieved self-awareness begin to perceive a conflict but are, as yet,
unable to overcome this conflict. However, the failure to correctly anticipate in the non-
recognisers is more difficult to explain because the pupillometry data suggests that they do
not perceive a conflict to the extent that recognisers do and so we predicted that they would
be better able to generate correct predictions, regardless of inhibitory control capacity. We see
a number of possible explanations.
First, it may be that, contrary to the altercentric bias hypothesis, infants’ failure to accurately
predict is unrelated to the emergence of self-representation and what is captured here—at least
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on the high demand trials for non-recognisers—is evidence of a reality bias where the infant’s
representation of the ball’s location is strongest from the self-perspective. However, in our
exploratory analysis, we also found that non-recognisers were significantly faster than recog-
nisers to generate a first saccade after cue onset. We ran this analysis because we reasoned that
a first saccade may reflect two things: i) an attempt by the participant to predict where the
agent will reach or ii) an evoked reaction to the light/sound cues and box opening, which
could be random or influenced by priming of something having previously happened at
one box over the other. While this analysis was exploratory and the data should be interpreted
with caution, it is consistent with anticipatory looking reflecting different underlying processes
in the two groups. If the recognisers perceived greater conflict, the slower latency to saccade is
consistent with a genuine—if ultimately incorrect—attempt to generate a prediction. On the
other hand, if the non-recognisers perceived less conflict, but still failed to correctly anticipate,
it is possible that they simply default to where they know the object to be. However, given that
our main prediction, that the emergence of self-representation is related to perceived conflict,
was confirmed, it seems unlikely that the reason why non-recognisers perceive less conflict is
because they have a clear representation of the actual location of the ball.
Interpreting the behaviour of non-recognisers as indicating that they simply fail to predict is
also difficult to reconcile with data from younger infants showing that they likely do generate
expectations about where someone else with a false belief will search (Onishi & Baillargeon,
2005; Southgate & Vernetti, 2014, but see non-replications such as Dörrenberg et al., 2018;
Poulin-Dubois et al., 2013). Thus, while this finding requires further investigation, we believe a
plausible explanation is that non-recognisers’ incorrect prediction reflects a reaction to the
onset of the visual cues rather than a genuine attempt to make a prediction about where
the agent will reach, and this is consistent with the faster generation of saccades in the non-
recognisers. As recent studies have cast doubt on the reliability and validity of anticipatory
looking as a measure of action prediction, even in simple cases where no belief evaluation
is required (Kampis et al., 2021), this remains a viable interpretation.
Although we categorised infants as “recognisers” and “non-recognisers” for the purposes of
this study, and our data differentiated infants on this basis, it is likely that the emergence of self-
representation is gradual and protracted (de Waal, 2019; Rochat, 2003) and may be captured
with other measures at an earlier time point. While self-awareness is a multi-faceted concept
with different manifestations of self-awareness emerging at different time points, there is a gen-
eral distinction in the literature between subjective and objective self-representation (e.g.,
Duval & Wicklund, 1972). For the capacity that is proposed important here, the ability to rep-
resent what one has seen as the self-perspective, it would seem likely that an objective self-
representation is required. Given that mirror self-recognition is related to various behaviours
that would imply an objective self-representation including the ability to see oneself in relation
to others and be motivated to align with others (Kampis et al., 2022), we suggest that the ability
to represent the self-perspective presupposes an objective self-representation (Southgate,
2020). It remains likely that while recognisers experienced greater conflict than non-
recognisers, the non-recognisers were not devoid of self-representation entirely, and the
absence of reliable belief-based action prediction in the non-recognisers may reflect this shift-
ing balance away from an altercentric bias.
While we chose pupil dilation as a measure because of its relationship with conflict, it is
important to note that we cannot be sure that pupil dilation itself reflects the process of per-
ceiving or experiencing conflict. Pupil dilation has also been associated with both violation of
expectation ( Jackson & Sirois, 2009) and effort (Kaldy & Blaser, 2020) and it is unclear whether
these processes are independent (Laeng et al., 2012). As we find this difference during the
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anticipatory time window, an alternative possibility is that it reflects the anticipatory process
itself. While infants’ tendency to make anticipatory saccades did not differ between recogni-
sers and non-recognisers nor between high and low conflict trials, it is possible that the effort
involved in anticipating was greater in recognisers on the high-demand condition, precisely
because this is where recognisers perceived greatest conflict. However, even if this were the
case, it would still provide support for our interpretation that the emergence of self-awareness
is required for infants to experience a conflict when the self and other perspectives diverge.
Finally, a finding that emerged from our exploratory analyses is that recognisers also show
significantly greater pupil dilation than non-recognisers at an earlier time point which was
outside of our preregistered time-windows. During this early time window, infants see the cur-
tains begin to occlude the agent from the scene, suggesting that recognisers and non-
recognisers react to the disappearance of the agent differently. While we made no a priori
predictions, there are at least two possible ways of interpreting this finding. First, it may be
that only the recognisers understand the significance of the disappearance of the agent, and
it may be that this event is only worthy of attention if we understand the contrast with our own
continued visual access. Alternatively, the difference between the recognisers and non-
recognisers in pupil size during this time window could be driven by the non-recognisers’
decreased interest in events that occur in the absence of other agents. According to the alter-
centric hypothesis, infants encode events better when they are co-witnessed with another
agent, and thus events witnessed in the absence of others receive relatively less attention
(Manea et al., 2022). Whether either of these explanations has traction should be the subject
of future studies.
ACKNOWLEDGMENTS
This work was supported by a Consolidator Grant from the European Research Council
(DEVOMIND 726114) to V. Southgate. The authors thank Maria Bolding Eskildsen, Kathrine
Habdank, Marie Louise Krogsgård Nielsen, and Kathrine Søndergaard Christensen for their
assistance with data collection, Karla Holmboe and Henrik Dvergsdal for their assistance with
implementing the ECITT, and three anonymous reviewers for their helpful comments on this
manuscript.
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AUTHOR CONTRIBUTIONS
E. Yeung and V. Southgate developed the study concept. All authors contributed to the study
design. V. Manea and E. Yeung designed the stimuli. Data collection was performed by E.
Yeung. D. Askitis and E. Yeung performed the data analysis and interpretation under the super-
vision of V. Southgate. E. Yeung, D. Askitis, and V. Southgate wrote the manuscript. All authors
approved the final version of the manuscript for submission.
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