Decoding Social Information from Biological Motion in the Broad Autism Phenotype: An Eye-Tracking Study

Abstract

The term broad autism phenotype (BAP) refers to individuals who do not meet the diagnostic criteria for autism but share some of its features, including social difficulties and atypicalities in visual perception and attention that have been linked to a detail-oriented cognitive style. To examine both the cognitive and social aspects of BAP, we employed a biological motion paradigm combined with eye-tracking technology. Participants with high (n = 20) and low (n = 22) levels of autistic traits, grouped by their Autism Spectrum Quotient scores, viewed point-light displays depicting emotional expressions and dyadic interactions and identified them by keypress in a forced-choice task. Although both groups performed with near-ceiling accuracy (>90%), high-trait individuals responded significantly slower in both tasks. No group differences emerged in global eye-movement metrics such as the number and characteristics of fixations and saccades. However, the spatial allocation of attention revealed more finegrained effects: high-trait individuals made more fixations on non-social background regions in the emotion task and showed a less centralized gaze pattern when viewing dyadic interactions. These findings suggest that individuals with elevated autistic traits process the social information carried by biological motion with reduced efficiency relative to their low-trait counterparts, which is reflected in slower responses and less focused attention to socially relevant regions of the display. The results are consistent with a graded, efficiency-based account of social perception in the broad autism phenotype.