Intersubjectivity and Understanding Motor Intentions: Evidence From Autism and Williams Syndrome

Background:  Many authors have underscored impairment in intention understanding in autistic spectrum disorders (ASD), but only recently has research outlined in ASD the presence of specific impairments in intention understanding at the motor level during the observation of others’ actions. Motor intention understanding is an essential component of social cognition, as it allows to be efficiently attuned and to establish reciprocal communicative interactions with others. Two types of motor understanding are enrolled during the observation of others’ actions: understanding what specific motor act is being performed and understanding why an act is being performed. The first offers immediate perceptual information on the observed motor act, while the second foreshadows the other’s future actions and contributes to intention understanding. Neurophysiological data have shown that two different mechanisms underlie what and why comprehension and behavioral studies have highlighted how these two abilities follow specific developmental patterns in typical development (TD). Furthermore two different studies highlighted a specific impairment in why understanding in children with high-functioning autism and an impairment in what understanding in Williams syndrome (WS), a deficit also affecting social cognition and intention understanding.

Objectives:  The main aim of this study was to better our understanding of what and why comprehension in ASD by comparing performance of younger children with low-functioning autism, children with WS and children with TD matched for mental age on a behavioral task. This would allow to evaluate whether impairment in motor intention understanding during the observation of simple motor acts: (a) proved to be different in ASD and in WS on comparable groups; (b) would present in ASD a similar developmental pattern to the one found in previous studies.

Methods:  Participants (17 children with ASD, chronological age 8;7 ± 2.9, mental age 6;6 ± 1.4; 17 children with WS, chronological age 13;7 ± 6.9, mental age 6;6 ± 2.0; 18 children with TD, chronological age 6;2 ± 1.5, mental age 6;6 ± 1.9), were shown pictures depicting hand-object interactions (i.e. touching, grasping to use, grasping to put away) and where asked to indicate what action was being performed (i.e. touching or grasping) and why it was being performed (i.e. grasping to use or grasping to put away) in presence or in absence of contextual cues.

Results: Results showed (a) differential impairment in ASD and WS, i.e. a significant difference emerged between the ASD and WS groups on error rate when perticipants were required to indicate what action was being performed, WS group performing significantly worse than both ASD and TD groups; (b) differing developmental pattern in ASD, especially considering performance when participants were required to answer why the action was being performed in relation to previous studies on TD.   

Conclusions: Behavioral data highlight a differential developmental pattern in the ability to understand others’ intentions at the level of simple motor actions in ASD, underscoring the importance of the distinction between what and why comprehension when considering understanding of specific differences in social skills present in ASD and WS.