Proceedings of the Annual Meeting of the Cognitive Science Society

The bystander effect, reduced helping in the presence of others, has been linked to automatic neural processes that inhibit action preparation. Recent work using the Drift-Diffusion Model (DDM) showed that human faces slow evidence accumulation during emergency classification tasks. We examined whether face pareidolia stimuli (objects in which illusory faces are perceived) produce similar effects, and whether autistic traits predict decision-making parameters. Participants (N = 65) classified scenes as safe or dangerous while viewing human faces, face-like objects, or non-face-like objects. Human faces significantly slowed drift rate, replicating prior findings; face pareidolia showed a similar but non-significant trend. In this non-clinical sample, Autism-Spectrum Quotient (AQ) scores predicted slower drift rates for both scene types, with modest effect sizes (r = .26 to .28), suggesting reduced excitatory efficiency with higher autistic traits. These findings extend the implicit bystander effect to individual differences and link autistic traits to evidence accumulation.