The Shepard Illusion Is Reduced in Children With an Autism Spectrum Disorder Because of Perceptual Rather Than Attentional Mechanisms

Abstract

Earlier studies demonstrate reduced illusion strength in the Shepard illusion in adults and adolescents with an autism spectrum disorder (ASD) and in typically developing (TD) adults with high levels of autistic traits. We measured the strength of the Shepard illusion in ASD and TD children and tested if ten different eye-tracking measurements could predict group differences in illusion strength. The ASD children demonstrated reduced illusion strength relative to the TD group. Despite this, there were no mean differences on any of the eye-tracking measurements between groups. Even though none of the eye-tracking measurements revealed mean differences between the two groups, the degree to which spatial attention was directed toward the standard stimulus, as indexed by the number of saccades within and toward this stimulus, predicted the strength of the illusion in the overall sample. Furthermore, this active scanning of the standard stimulus was found to enhance illusion strength more strongly in the ASD than the TD group. Together, we conclude that scan patterns and the degree to which participants are able to shift between different locations in a visual scene did not account for group differences in illusion strength. Thus, the reduced strength of the Shepard illusion in ASD does not appear to be driven by how attention shifts or is spatially allocated. Rather, differences may relate instead to perceptual mechanisms that integrate visual information. Strategies that may aid ASD individuals to see this illusion more strongly could have them make even more eye movements within and between the stimuli presented in the illusion display.

Exploring how material cues drive sensorimotor prediction across different levels of autistic-like traits

“…Although seemingly contradictive of various sensorimotor research (e.g., Mosconi et al 2013; Buckingham et al 2016), this corresponds with a meaningful body of clinical evidence which has shown broad prediction-dependent capabilities to be typical in autistic people (Mostofsky et al 2004; Gidley-Larson et al 2008; Ego et al 2016; Tewolde et al 2018). Findings also align with recent evidence that autistic and neurotypical individuals attend to similar information when presented with visual illusions (Chouinard et al 2018). Consequently, in contrast to broad predictive accounts of autism (e.g., Pellicano and Burr 2012; Sinha et al 2014), our data indicate that links between sensorimotor prediction and autistic-like traits may not be due to any generic processing abnormalities, but rather due to context-sensitive ‘high-level’ mechanisms.…”

The strength of the Shepard illusion in children coincides with age and cognitive skills but not perceptual abilities

“…Second, we know that the strength of the illusion increases as participants actively attend and scan the displaynamely the illusion strengthens with the number of saccades made between different elements in the display (Chouinard et al, 2018). This contrasts with other illusions, such as the verticalhorizontal illusion, that increase in strength as participants make less saccades and the image of the display is more stable on the retina (Chouinard et al, 2017).…”

“…This method of normalising is used in many illusion studies (Chouinard et al, 2019;Chouinard et al, 2013;Chouinard et al, 2016;Chouinard et al, 2017;Chouinard et al, 2018;Schwarzkopf et al 2011;Sherman & Chouinard 2016) and allows for meaningful comparisons across studies.…”

“…In addition, we assessed receptive language using the Peabody Picture Vocabulary Test (PPVT) (4th Edition) (Dunn & Dunn, 2007) and abstract reasoning using the Raven's Progressive Matrices (RPM) (Raven et al, 2003). A small subset of the data has been published previously for the purposes of matching an ASD sample who performed similar tasks (Chouinard et al, 2018). This earlier study did not examine the effects of age, which was the primary purpose of the present investigation.…”

“…We also examined verbal and other non-verbal abilities using the Peabody Picture Vocabulary Test (PPVT) (4th Edition) (Dunn & Dunn, 2007) and Raven's Progressive Matrices (RPM) (Raven et al, 2003), respectively. Both measures are quick to administer and have been used in other developmental studies as a way to provide an estimate of verbal and non-verbal intelligence in children (Chouinard et al, 2018(Chouinard et al, , 2019Landry et al 2019). The RPM also offered the advantage of testing Piaget's ideas that reasoning skills need to be developed before a child can experience illusions in the same way as adults (Piaget, 1969(Piaget, , 1999.…”