Abstract/Summary

Autistic individuals respond to sensory information in perceptual tasks differently than non-autistic individuals. However, it is unclear which component processes are altered, and how other aspects of neurodiversity (e.g., ADHD traits) affect these processing stages. Here, we applied diffusion models to decompose numerosity task performance into distinct processing stages, across two pre-registered studies with rigorous blinded analyses. In Study 1, we validated our approach and investigated relationships between diffusion-model parameters and autism- and ADHD-related traits in the general population ( n = 130). Study 2 investigated group differences between diagnosed autistic ( n = 100) and non-autistic ( n = 100) adults with comparable non-verbal reasoning ability, and assessed relationships with ADHD traits. Study 1 found no relationships between diffusion-model parameters and autism and ADHD-related traits in the general population. Study 2 revealed that autistic individuals had shorter non-decision times than non-autistic individuals, reflecting less time taken for sensory encoding and/or response generation, with no group differences in sensory evidence accumulation or response caution. We also found that individuals with higher motor hyperactivity-impulsivity had lower non-decision times and that individuals with higher verbal hyperactivity-impulsivity accumulated evidence more slowly. The diffusion model, therefore, reveals the convergence and divergence of processing stages in autism and across ADHD-related traits.