Pupillary responses for social versus non-social stimuli in autism: a systematic review and meta-analysis

Pupillometry has gained attention as a valuable tool for assessing autonomic nervous system activity and studying phasic changes in pupil size to comprehend underlying neurocognitive mechanisms. However, knowledge regarding pupillary responses to social processing in autism is limited. We conducted a systematic review and meta-analysis, examining research studies on pupil size changes that compare social and non-social stimuli in autism. Electronic searches were performed for articles up to September 2023 and relevant studies were evaluated following PRISMA guidelines. Out of 284 articles screened, 14 studies were eligible for systematic review. The results indicated that non-autistic individuals showed larger pupil size for social compared to non-social stimuli (g = 0.54; 95% CI [0.25 0.82]), whereas autistic individuals seemed to exhibit no differences between the two conditions. However, high heterogeneity was observed between studies in autistic populations, compromising interpretability. Despite such limitations, pupillary responses may constitute an objective physiological marker of social processing in autism. This review emphasizes the need for further investigations into pupillary responses in autism across different life stages.