Atypical Attentional Effort During Visual Search in Autistic Adults: Evidence From Task-Evoked Pupillary Responses

According to prevalent views, autistic individuals have a stronger tendency to allocate attention to details, as supported by reports of enhanced visual search performance. However, both the dynamics and the types of information involved in attentional guidance in autism are not fully understood. We addressed this issue by testing the influence of search history on visual search performance and pupil size in a long search display (Experiment 1) and on accuracy in a brief and masked-more attentionally demanding-search display (Experiment 2). Autistic (N = 48) and non-autistic (N = 45) participants searched for a color singleton target (all equiluminant colors) and responded by identifying its shape. In each trial, the target and distractor colors could be repeated, switched, or novel with respect to the previous trial. In Experiment 1, while overall reaction time was comparable across groups, the task-evoked pupillary responses (TEPRs) were smaller in the autistic group, indicating reduced attentional effort in autism. In Experiment 2, in a more attentionally demanding display, autistic individuals showed superior search accuracy. In both experiments, both groups showed a reliable effect of recent search history on performance, indicating that, similar to non-autistic individuals, autistic individuals rely on recent experience during attentional allocation. Alterations in attentional allocation and its interaction with recent experience in autism were reflected in pupil responses. These alterations may provide a sensitive marker of differences in the dynamics of attentional allocation in autism, which are reflected in behavioral measurements when display conditions are more attentionally demanding.