Joint Action Coordination in Children with Autism Spectrum Disorder

Background:  Impaired motor skills are seen in a large majority of children with Autism Spectrum Disorder (ASD) and are considered a possible origin of the social and communicative deficit characterizing the disorder. The different views on the origin of motor deficit in ASD range from the impairment in action planning to predictive mechanisms supporting action execution. A specific deficit in anticipating the perceptual consequences of their own and others movements may lead ASD children to experience difficulties in interpersonal interactions that include joint-actions, namely those motor interactions whereby two people coordinate their actions to achieve a change in the environment. Studying the movement during motor interaction tasks could help in elucidating the motor control mechanisms possibly altered in ASD, providing cues for novel intervention strategies.

Objectives:  To analyze, in TD and ASD children, the reach-to-grasp movements in a joint-action task, and elucidate the influence of action context on movement performance and kinematics.

Methods: Five high-functioning ASD children (mean [SD] age = 94 [10.8] months) and five TD children (mean [SD] age = 92.5 [8.9] months, SD) participated in a joint-action task with the experimenter. Children were required to execute the same action - reaching and grasping little objects - in two contexts (cooperative CP vs. competitive CM). Each session was video recorded, and a magneto-inertial sensor was fixed through a support on both children and experimenter wrists. Five measures were obtained: (a) reaction time (RT); (b) movement time (MT); (c) peak acceleration (peak Acc); (d) time of peak acceleration (peak Acc Time); and (e) time at which each child started reaching as a function of the experimenter movement (ExMT%). Each variable was analyzed using RM ANOVAs to test group differences and the effect of the social context. Significance was setted at p<0.05.

Results:  Analysis of RTs and ExMT% showed a significant interaction between group (ASD, TD) and social context (CP, CM). Both groups showed faster RTs (p<0.001) and lower ExMT% (p<0.001) in CM than in CP context. However, RTs and ExMT% in CM were respectively slower (p = 0.04) and higher (p<0.001) in ASD with respect to TD group. A main effect of social context (p<0.001) reflecting faster MTs in CM than CP context was found. MTs were slower in the ASD than the TD group (p=0.005). Analysis of Peak Acc and Peak Acc Time revealed a main effect of Group (p<0.001), reflecting lower and more delayed peak acceleration for the ASD than the TD group.

Conclusions:  Our results support the view that motor execution is impaired in ASD. MTs, indeed, were strongly delayed, and peak acceleration was lower and more delayed compared to TD children. ASD children were partially able to modulate their movements according to the context of the action. In the competitive task, however, in which greater predictive abilities were required, their movements did not show the same differences with respect to the cooperative task as in typical children.