Brightness local bias in children with autism spectrum disorder

Autism spectrum disorder (ASD) has long been associated with a detail-oriented visual perception. Local-perceptual bias might be partially responsible also to the "core" deficits in the social domain, such as face processing and biological motion detection. There is a large literature describing this "local-perceptual bias" in ASD, which results, sometimes, in superior performances compared to typically developing (TD) children. However nothing is known about the lightness-perception (brightness) in children with ASD. We investigated the lightness-perception in 21 children, 11 TD and 10 children with ASD matched for age and IQ. Lightness-induction can occur on the basis of the immediate surround of a region (local interactions) and also on the basis of global factors of perceptual organization. We employed a stimulus set proved to differentiate the contributions of these two factors. In TD adults, according to the literature, when higher-level and lower-level factors act contemporaneously, the contrast effect induced by the global-organization principle of perceptual belongingness overcomes the local effect due to retinal lateral inhibition. In the Experiment 1, a grey scale matching task, the TD children confirmed the results obtained with adults: the brightness was a consequence of the global factors. On the contrary the children with ASD completely ignored the global information provided by the display. In the Experiment 2, we "simulate" the lightness-perception of the ASD children varying the time exposure of the stimulus in TD university students. The result was that the TD students’ brightness was comparable to what observed in the children with ASD when visual stimulus was masked after 150 ms, suggesting that brightness processing in ASD is restricted to the low-level visual areas . In conclusion also the lightness perception in children with ASD is peculiar: a local bias affects their final percept and it could have consequences in their high-level social-communicative development.