Abstract
The systemizing trait of autism has recently been found to covary with susceptibility to visual illusions driven by contextually-induced distortions of an observer’s egocentric frame of reference (Walter et al., 2009). The current study sought to determine whether the relationship between systemizing and illusion susceptibility can be attributed to a heightened processing of local cues, attenuated processing of global cues, or some combination of the two. Scores on the Systemizing Quotient-Revised (SQ-R, Wheelwright et al., 2006) were compared to measures of susceptibility to the Rod-and-Frame illusion (RFI) in a large neurotypical sample. Depending on the size of the illusion-inducing frame, the RFI is thought to be driven by a weighted combination of local, low-level orientation contrast effects (prominent with small frames) and globally-induced distortions of the observer’s egocentric reference frame (prominent with large frames). Susceptibilities to these two components of the illusion were measured using recently-developed techniques designed to isolate the two (Dassonville & Williamson, 2010). Higher SQ-R scores were found to be associated with both a decreased tendency to use global contextual cues, and an increased tendency to use local orientation cues. However, susceptibilities to the local and global RFI effects were uncorrelated, suggesting that local processing biases do not necessitate attenuated use of global contextual information. Furthermore, a principal components analysis indicated a two-factor structure to the SQ-R that was differentially predictive of illusion susceptibility. Higher scores on the ‘analytical tendencies’ factor were associated with decreased global effects of the RFI, while higher scores on the ‘need for sameness’ factor were associated with increased local effects. These results suggest that the systemizing trait of autism contains a two-factor structure that is differentially predictive of a shift from reliance on global to local visual cues and that, while comorbid in autism, these may be two orthogonal perceptual processes.
Meeting abstract presented at VSS 2012