Face individual identity recognition: a potential endophenotype in autism

Abstract

Background: Face individual identity recognition skill is heritable and independent of intellectual ability. Difficulties in face individual identity recognition are present in autistic individuals and their family members and are possibly linked to oxytocin polymorphisms in families with an autistic child. While it is reported that developmental prosopagnosia (i.e., impaired face identity recognition) occurs in 2-3% of the general population, no prosopagnosia prevalence estimate is available for autism. Furthermore, an autism within-group approach has not been reported towards characterizing impaired face memory and to investigate its possible links to social and communication difficulties.

Methods: The present study estimated the prevalence of prosopagnosia in 80 autistic adults with no intellectual disability, investigated its cognitive characteristics and links to autism symptoms' severity, personality traits, and mental state understanding from the eye region by using standardized tests and questionnaires.

Results: More than one third of autistic participants showed prosopagnosia. Their face memory skill was not associated with their symptom's severity, empathy, alexithymia, or general intelligence. Face identity recognition was instead linked to mental state recognition from the eye region only in autistic individuals who had prosopagnosia, and this relationship did not depend on participants' basic face perception skills. Importantly, we found that autistic participants were not aware of their face memory skills.

Limitations: We did not test an epidemiological sample, and additional work is necessary to establish whether these results generalize to the entire autism spectrum.

Conclusions: Impaired face individual identity recognition meets the criteria to be a potential endophenotype in autism. In the future, testing for face memory could be used to stratify autistic individuals into genetically meaningful subgroups and be translatable to autism animal models.

Keywords: Autism; Emotion recognition; Endophenotype; Face memory; Heterogeneity; Individual identity recognition; Prosopagnosia; Social memory; Theory of mind.

Fig. 1

The prevalence of prosopagnosia in autism. Performance (number of correct responses) at the Cambridge Face Memory Test (CFMT) for 160 participants plotted as a function of their diagnostic group (autistic-AUT vs. neurotypical-NT) and prosopagnosia (prosopagnosic-P vs. non-prosopagnosic-NP). Thicker horizontal lines represent the medians, boxes the interquartile ranges, and whiskers the maximum and minimum values. The solid horizontal black line is the CFMT clinical cut-off for prosopagnosia (i.e., 42). AUT-P: dark blue, AUT-NP: light blue, NT-P: dark red, NT-NP: light red boxes. Black dots represent individual data points

Fig. 2

Prosopagnosia moderates the influence of identity recognition on mental state understanding. In autistic participants who are prosopagnosic (AUT-P, dark blue circles), face memory skill at the CFMT predicted their ability to understand another person’s mental states at the RMET, while this was not the case for autistic participants who are not prosopagnosic (AUT-NP, light blue circles). The dark blue solid line represents a significant regression line for the AUT-P group, while the light blue line represents nonsignificant regression line for the AUT-NP group. The black solid line represents CFMT cut-off score (i.e., 42)

Fig. 3

Autistic prosopagnosics do not show face inversion effect and have no general memory impairment. Non-prosopagnosic autistic participants (AUT-NP, N = 42, light blue dots) showed a face inversion effect, that is they performed better on upright (gray bars) vs. inverted (white bars) faces, while prosopagnosic autistic participants (AUT-P, N = 22, dark blue dots) did not. AUT-P did not show a general memory impairment, that is, although they performed worse than AUT-NP on upright faces, they did not differ from AUT-NP on inverted faces. The red asterisk indicates that AUT-NP performance at the upright CFMT differs from all other conditions (ps < 0.05). The dashed horizontal line indicates the CFMT chance level which corresponds to 24 correct responses

Fig. 4

a General intelligence does not correlate with face memory skill in autism. In autistic participants, IQ level (percentile) does not significantly correlate with face memory skill (number of correct responses) at the Cambridge Face Memory Test (CFMT). Light blue dots represent nonprosopagnosic autistic participants (AUT-NP) while the dark blue dots represent prosopagnosic autistic participants (AUT-P). The dashed black line represents the nonsignificant regression line, while the surrounding gray-shaded area represents a 95% confidence interval. b Subjective face memory awareness does not predict objective face memory performance in autistic individuals. In autistic participants self-reported prosopagnosia traits at the prosopagnosia index questionnaires (PI20) do not correlate with their objective performance at the Cambridge Face Memory Test (CFMT). The light blue dots represent non-prosopagnosic autistic participants (AUT-NP) while the dark blue dots represent prosopagnosic autistic participants (AUT-P). The dashed black line represents the nonsignificant regression line, while the surrounding gray-shaded area represents a 95% confidence interval