People with autism spectrum disorders (ASD) often take longer to make decisions. The Autism-Psychosis Model proposes that people with autism and psychosis show the opposite pattern of results on cognitive tasks. As those with psychosis show a jump-to-conclusions reasoning bias, those with ASD should show a circumspect reasoning bias. Jumping-to-conclusions was assessed in a sample of 20 adolescents with ASD and 23 age-matched controls using the jumping-to-conclusions beads task. Both groups demonstrated equivalent levels of confidence in decision-making, however the ASD group required more beads than controls before making their decision. Furthermore, there was a positive correlation between the beads required and degree of autism symptoms. Consistent with the Autism-Psychosis Model, a more circumspect reasoning bias was evident in ASD.