Abstract
Most individuals with fragile X syndrome (FXS) exhibit symptoms of autism spectrum disorder (ASD), suggesting a substantial overlap in social cognitive profiles. This cross-sectional study aimed to explore social cognitive abilities in children and adolescents with FXS in comparison with an age-matched heterogeneous ASD group and typically developing (TD) peers. Key domains assessed included basic visual social attention towards faces, autonomic arousal in reaction to conflicting emotional information and Theory of Mind (ToM). Participants comprised 14 children with FXS, 24 with ASD and 19 TD controls, aged 6–18 years. Visual attention and implicit emotion recognition were measured using an emotional oddball paradigm using gaze behaviour and pupillometric analysis, and ToM was assessed with the NEPSY-II neuropsychological test battery ToM subtest. Results indicated that children and adolescents with FXS directed their gaze less towards relevant social–emotional information (i.e., faces and especially eyes), compared with both the ASD and TD groups. Regarding implicit emotion recognition, the attentional disparity between the FXS group and the TD group was reduced when conflicting multisensory emotional information was presented, rather than congruent cues. Next, a diminished pupillary response to conflicting emotional information was found in the FXS group, as compared with the ASD group. Additionally, the FXS group showed difficulties with ToM, compared with the ASD and TD groups. These findings suggest that both deviations in basic and higher-order social cognitive abilities may contribute to the social difficulties experienced by individuals with FXS and may partly account for the high incidence of ASD diagnoses in this population.