Objective: Two-alternative forced-choice tasks are widely used to gain insight into specific areas of enhancement or impairment in individuals with autism spectrum disorder (ASD).Data arising from these tasks have been used to support myriad theories regarding the integrity, or otherwise, of particular brain areas or cognitive processes in ASD. The drift diffusion model (DDM) provides an account of the underlying processes which give rise to accuracy and reaction time distributions, and parameterises these processes in terms which have direct psychological interpretation. Importantly, the DDM provides further insight into the origin of potential group differences in task performance. Here, for the first time, we used the DDM to investigate perceptual decision making in ASD.Method: Adults with (N = 25) and without ASD (N = 32) performed an orientation discrimination task. A drift diffusion model was applied to the full RT distributions. Results:Participants with ASD responded more slowly than controls, the groups did not differ in accuracy. Modelled parameters indicated that: (i) participants with ASD were more cautious than controls (wider boundary separation); (ii) non-decision time was increased in ASD; and (iii) the quality of evidence extracted from the stimulus (drift rate) did not vary between groups.Conclusions: Taking the behavioural data in isolation would suggest reduced perceptual sensitivity in ASD. However, DDM results indicated that despite response slowing, there was no evidence of differential perceptual sensitivity between participants with and without ASD.Future use of the DDM in investigations of perception and cognition in ASD is highly recommended.

including the URL of the record and the reason for the withdrawal request.

Circuit level brain dysfunction has been suggested as a common mechanism through which diverse genetic risk factors and neurobiological sequelae lead to the core features of autism spectrum disorder (Geschwind 2009; Port et al. 2014). An important mediator of circuit level brain activity is lateral inhibition, and a number of authors have suggested that lateral inhibition may be atypical in ASD. However, evidence regarding putative atypical lateral connections in ASD is mixed. Here we employed a steady state visual evoked potential (SSVEP) paradigm to further investigate lateral connections within a group of high functioning adults with ASD. At a group level, we found no evidence of altered lateral interactions in ASD. Exploratory analyses reveal that greater ASD symptom severity (increased ADOS score) is associated with increased short range lateral inhibition. These results suggest that lateral interactions are not altered in ASD at a group-level, but that subtle alterations in such neurobiological processes may underlie the heterogeneity seen in the autism spectrum in terms of sensory perception and behavioral phenotype.