Linearly integrating speed and accuracy to measure individual differences in theory of mind: Evidence from autistic and neurotypical adults

It has long been theorised that there is a direct link between individual differences in social cognition and behaviour. One of the most popular tests of this theory has involved examination of Theory of Mind (ToM) difficulties in Autism Spectrum Disorder (ASD). However, evidence for associations between ToM and social behaviour is mixed, both when testing the ToM explanation of ASD and when investigating individual differences in ToM in the general population. We argue that this is due to methodological limitations of many ToM measures, such as a lack of variability in task performance, inappropriate non-ToM control tasks, and a failure to account for general mental ability. To overcome these issues, we designed a novel task, which probed individual differences in ToM fluency through mental state attribution in response to cartoons (Cartoons Theory of Mind [CarToM] task). This task, enabling the linear combination of speed and accuracy, was used to quantify ToM ability and its association with self-reported (a)typical social behaviour in adults with and without ASD. In a large sample (N = 237), we found that having an ASD diagnosis and higher autistic traits predicted lower ToM ability, even after accounting for performance on a well-matched non-ToM condition and general mental ability. Overall, our findings provide fresh support for the existence of a link between individual differences in social cognition (specifically, ToM) and behaviour (specifically, autism). This has implications for social-cognitive theory and research, allowing large-scale, online assessment of individual differences in ToM in clinical groups and the general population.