A central diagnostic criteria for autism spectrum disorder (ASD) is the qualitative impairment in reciprocal social interaction and a prominent hypotheses that tried to explain this impairment is the Theory of Mind (ToM) deficit hypotheses. On a behavioral level the critical test for having a ToM, the understanding of false beliefs (FB), is often used for testing ToM abilities in individuals with ASD. Investigating the neural underpinnings several neuroimaging studies revealed a network of areas involved in FB reasoning in neurotypical individuals. For ASD individuals the neural correlates of false belief processing are largely unknown. Using functional magnetic resonance imaging and an adapted unexpected transfer task, that makes it possible to distinguish between the computation of diverging beliefs and the selection of a belief-associated response, we investigated a group of adult high-functioning individuals with ASD (N = 15) and an age and IQ matched group of neurotypical adults (NT; N = 15). On the behavioral level we found no group differences. On the neural level, results were two-fold: In the story phase, in which participants had to compute whether the character's belief is congruent or incongruent to their own belief, there were no differences between neurotypical participants and those diagnosed with ASD. But, in the subsequent question phase, participants with ASD showed increased activity in the bilateral anterior prefrontal cortex, the left posterior frontal cortex, the left superior temporal gyrus, and the left temporoparietal area. These results suggest that during the story phase in which the participants processed observable actions the neural correlates do not differ between adult individuals with ASD and NT individuals. But in the question phase in which participants had to infer an unobservable mental state results revealed neural differences between the two groups. Possibly, these subtle neural processing differences may contribute to the fact that adult ASD individuals are able to master explicit false belief tasks but fail to apply their strategies during everyday social interaction.

This study aimed to validate the short‐story‐task (SST) based on Dodell‐Feder et al. as an instrument to quantify the ability of mentalizing and to differentiate between non‐autistic adults and autistic adults, who may have acquired rules to interpret the actions of non‐autistic individuals. Autistic (N = 32) and non‐autistic (N = 32) adult participants were asked to read “The End of Something” by Ernest Hemingway and to answer implicit and explicit mentalizing questions, and comprehension questions. Furthermore, verbal and nonverbal IQ was measured and participants were asked how much fiction they read each month. Mentalizing performance was normally distributed for autistic and non‐autistic participants with autistic participants scoring in the lower third of the distribution. ROC (receiver operator curve) analysis revealed the task to be an excellent discriminator between autistic and non‐autistic participants. A linear regression analysis identified number of books read, years of education and group as significant predictors. Overall, the SST is a promising measure of mentalizing. On the one hand, it differentiates among non‐autistic individuals and on the other hand it is sensitive towards performance differences in mentalizing among autistic adults. Implications for interventions are discussed.