Adults with autism spectrum disorder (ASD) show less surprise than adults without ASD when faced with something unexpected in their environment, and the level of this reduced surprise can predict the severity of ASD symptoms, reports a study published online this week in Nature Neuroscience. The study suggests that adults with ASD tend to overestimate how changeable an environment is and underestimate the likelihood of a specific change, thus making unexpected events less surprising.

Insistence on sameness and intolerance of change are part of the diagnostic criteria for ASD, but there is little research addressing how people with ASD represent and respond to changes to their environment. For instance, how surprised should a person be if they hit a key on their keyboard and hear a car-horn sound instead of a clacking sound- Ordinarily, the clacking sound would be expected, but if the person’s tech-savvy prankster teenage niece has been visiting, the person might adjust their expectations, owing to a more changeable (volatile) environment, and be less surprised. However, overestimating how changeable the environment is may impair the formation of prior expectations (of the key clack), thus making the car horn less surprising.

In this study, Rebecca Lawson and colleagues tested 24 adults with ASD and 25 age- and intelligence-matched neurotypical adults with a learning task and applied computational modelling to the data to characterize each person’s learning process. They find that adults with autism show a tendency to overestimate the volatility of the sensory environment, at the expense of learning to build stable expectations that lead to adaptive surprise. That is, after pressing a key on a keyboard, adults with autism might not be surprised by hearing a car horn. The authors conclude that their study offers novel insight into the behavioural, computational and physiological mechanisms that underlie how people with ASD to respond to changes to their environment.