Social Affordances and Interaction II: Autism and the Affordances of the Human Environment

The interaction between informational support or task constraints and functional motor performance was explored using kinematic profiles of the arms and hands of 40 participants with and without multiple sclerosis (MS). Three functional tasks were performed under three conditions: impoverished (i.e., participants mimed the tasks), partial (i.e., participants mimed the tasks with a limited array of the objects normally used), and natural (i.e., participants performed the actual tasks). Results indicated that each of the three conditions elicited unique kinematic profiles. Movement time, maximum displacement, and velocity variability were significantly different among each of the three conditions. An ecological interpretation suggested that functional performance emerged from the interaction of the task demands of each condition and of the action capabilities of the participants. Participants with and without MS responded to the three conditions in similar ways, except that those with MS performed the tasks more slowly. We speculated that the slower performance was a function of the reduced and inconsistent action capabilities of the participants with MS.