People with autism perceive drastic illusory changes for repeated verbal stimuli.

A core symptom of autism spectrum disorder (ASD) is restricted and repetitive behavior, characterized partly by insistence on sameness and excessively focused interest. This behavior has often been interpreted as a manifestation of anxiety and fear triggered by resistance to change. The implicit assumption underlying this interpretation is that perception per se (such as the judgment of sameness and changes in sensory stimuli) is not different between ASD and typically developed (TD) individuals, but that only the emotional response to the same amount of perceived change is. However, few studies have examined how individuals with ASD actually perceive a repeated presentation of the same sensory stimulus. To explore this issue, we conducted a listening test to compare perception of a repeated sound pattern, namely a spoken word, between ASD and TD groups. Prolonged listening to a repeated word without a pause may induce perceptual changes, which is known as the verbal transformation effect. We discovered that individuals with ASD tend to perceive more drastic changes or differences for the same repeated auditory pattern. This suggests that such variable perception incites individuals with ASD to persist for sameness.