The Naturalness of Biological Movement by Individuals with Autism Spectrum Conditions: Taking Neurotypical Individuals' Viewpoint.

backgroundWhen an action is being observed, it is matched to the observer's internal representation of the action. The more similar, the more the action is perceived as natural. A factor influencing judgement of naturalness is the kinematic features of a movement. However, these features could be altered due to certain conditions that can modify movement such as Autism Spectrum Disorders. As a result, neurotypical observers may fail to interpret the action due to impaired naturalness.

aimThis work aims to investigate (1) whether neurotypical observers judge the autistic individuals' movement as less natural, (2) which kinematic factors (jerk, acceleration, velocity and size) contribute to their perception and (3) whether cue reliance correlates with autistic traits.

methodsThirty neurotypical participants (20 - 33 years old; 15 males) completed autistic trait screening questionnaires (ADC, TAS-20, AQ). They completed a computer task showing 2D side-to-side arm movements recorded from neurotypical and autistic individuals. Finally, they rated the naturalness of the observed movements, and how certain they were with their answer.

resultsThere was a significant difference between the participants' perception of naturalness of the two movement groups. Jerk, acceleration and velocity contributed to shaping the participants' perception with a jerk as the most significant factor. The correlation between the participants' autistic trait and both their perception of naturalness as well as of each kinematic cue were not significant.

conclusionOur neurotypical participants perceived the autistic movements as less natural. Their perceptions were influenced mainly by the jerk as well as acceleration and velocity of the autistic movements. Autistic traits in the participants did not correlate to their perception of movement naturalness nor to any of the kinematic factors.