Autism spectrum disorder is a developmental disorder characterised by persistent atypicalities in communication and social interaction, and restricted and repetitive interests (American Psychiatric Association, 2013). While not a diagnostic criterion for autism, differences in mentalising, that is the ability to correctly identify the mental states (e.g. seducing, mocking) of others, are wide-spread and have been argued to lie at the heart of many of the social challenges that autistic people face (e.g., Frith, 2001). Difficulties inferring mental states have been shown in experiments using the Frith-Happé animation task, where participants are asked to make judgements about actions and mental states shown in animated interactions between triangles (Abell et al., 2000; Heider & Simmel, 1944). Abell et al. (2000), for example, found that high-functioning children with autism used mentalising descriptions less frequently than neurotypical eight-year olds when describing animations and that these were often less accurate. A similar pattern has been found using the task with adults, where fewer and less appropriate descriptions of mental state animations are contrasted with descriptions of action words comparable in accuracy to a control group (Castelli et al., 2002).
While social difficulties comprise a primary focus of autism research, atypical movement has also been shown to be an important component of autism (Cook, 2016). There is a marked difference between autistic and neurotypical people in terms of movement kinematics, with increased jerkiness being a characteristic feature of autistic kinematics (Cook et al., 2013; Fukui et al., 2018). The presence of atypical movement in autism is important because of the role that movement kinematics play in social cognition. For example, (Edey et al., 2017) found that neurotypical fast walkers rate slower emotions (e.g. sadness) more intensely than faster movements (e.g. anger), due to the fact that slower movements are further away from their own kinematic profile. This has important implications for understanding communication difficulties in autism because it raises the possibility that communicative difficulties between autistic and neurotypical people may not be wholly explained by limited mentalising abilities on the part of the autistic individual. Instead, it may be that the different kinematic profiles of autistic and neurotypical individuals cause difficulties inferring mental states in both directions (Cook, 2016; Edey et al., 2016).
In a previous study, we used an adapted version of the Frith-Happé animation task (Abell et al., 2000; Heider & Simmel, 1944) to investigate neurotypical participants’ accuracy in attributing mental states to autistic movements and vice versa. In a modified version of the task, neurotypical and autistic participants were asked to manually direct triangles to generate their own animations depicting mental state and action words. Participants were then asked to judge animations that had been generated by other autistic and non-autistic participants. As predicted, it was found that neurotypical participants were more accurate in attributing mental states to animations created by other neurotypical participants compared to those generated by autistic participants. However, autistic participants did not show a same group advantage, scoring comparatively for both groups (Edey et al., 2016). This finding provides mixed results. On the one hand, it demonstrates that neurotypical individuals are not adept at inferring mental states of people with autism, a finding that is likely due to the atypically jerky kinematics in the autistic animations. On the other hand, if autistic people are no better at inferring mental states in animations made by autistic individuals than by neurotypical individuals, it is not possible to say that atypicalities in mentalising in autism are due to their atypical kinematic profile since, if this were the case, autistic participants should be able to correctly attribute mental states to animations which move ‘like them’.
One could argue that our previous results provide strong evidence of mentalising difficulties in adults with autism. That is, autistic participants were less accurate in attributing mental states even when animations moved in a way that was similar to their own movement kinematics. However, an alternative explanation is that there were greater between-individual differences in kinematics in our autism, compared to neurotypical, group; meaning that autistic participants were less likely than neurotypical participants to see animations that truly matched their own kinematic profile. The present study will probe this alternative explanation by employing a completely digital version of the animations task. Our digital version efficiently indexes the jerkiness of animations generated by a participant and intelligently selects stimuli, from a pre-existing database, such that participants are presented with a tailored selection comprising animations that are highly similar, and highly dissimilar, to their own movements. Our digital version therefore enables us to test whether autistic participants are less accurate in attributing mental states even when animations move in a way that is similar to their own movement kinematics.