Atypical cross-modal calibration of sensory evidence in autism

Sensory perception is often characterized by altered calibration to contextual regularities, but the basis of this difference remains unclear. We tested whether temporal magnitude perception in autism relies on modality-specific or amodal calibration using an adapted range-of-standards paradigm. Autistic and non-autistic adults completed separate auditory and visual duration-discrimination tasks. Across blocks, we manipulated the contextual duration range and whether the standards establishing that range were presented in the same modality as, or a different modality from the target stimulus. Non-autistic participants showed an auditory advantage in duration discrimination and stronger context effects within than across modalities, consistent with modality-specific temporal coding. In contrast, autistic adults exhibited reduced auditory advantage and comparable context effects across modalities, suggesting broader and less differentiated temporal calibration. To examine whether these patterns reflected synesthetic cross-modal tendencies, we tested an additional group of adults with synesthesia. Synesthetes showed calibration patterns resembling the non-autistic group, indicating that the cross-modal effects observed in autism cannot be attributed to synesthetic mechanisms. The study included only adults, limiting conclusions about developmental trajectories and whether atypical temporal calibration emerges early or reflects lifelong adaptation. Autistic individuals demonstrate enhanced cross-modal context effects that exceed those observed in synesthesia, consistent with a more amodal temporal magnitude code in autism.