An analysis of embedded figures test performance in individuals with austistic-like traits

[Truncated abstract] The Embedded Figures Test (EFT; Witkin, Oltman, Raskin, & Karp, 1971) is a search task that involves detecting a simple closed-contour shape hidden within a complex structure. Individuals with an autism spectrum disorder (ASD) are faster detecting embedded figures relative to typically developing controls (de Jonge, Kemner, & van Engeland, 2006; Jarrold, Gilchrist, & Bender, 2005; Jolliffe & Baron-Cohen, 1997; Pellicano, Gibson, Maybery, Durkin, & Badcock, 2005). Superior EFT performance is not only observed in ASD groups relative to controls; those in the typically developing population with high levels of autistic-like traits also demonstrate enhanced performance relative to those with low levels of such traits (Grinter, Maybery et al., 2009; Grinter, Van Beek, Maybery, & Badcock, 2009; Russell-Smith, Maybery, & Bayliss, 2010). Examining individuals in these latter groups can be a useful method to extend current knowledge of complex ASDs by avoiding confounds such as co-morbidity associated with ASD samples. While enhanced EFT performance linked to autism has been repeatedly observed, it is not clear what underlying mechanism(s) allow(s) for such superiority. The aim of this thesis was to examine which specific aspects of the stimuli employed in the EFT are critical to enable superior visual search performance by those with high levels of autistic-like traits. Four series of experiments compared performance of groups of individuals with either high or low levels of autistic-like characteristics, as determined by the Autism-Spectrum Quotient (AQ; Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001), on the EFT and on a number of novel visual tasks designed to systematically investigate potential critical components of the EFT.