Abstract
In 4โ12 month human infants a briefly applied hand sock frequently resulted in marked prehensile disuse of the socked arm (SA) in excess of the sock's mechanical restriction. Most infants failed to reach with the SA for midline objects on a majority of trials while continuing to use the unsocked arm (UA). The SA grasp and manipulation efforts were also reduced. The onset of disuse was rapid, as was resumption of use after sock removal. The SA disuse was attributed to the effect of excess contactual input from the SA. The character of the disuse differed with age. Whereas younger infants often appeared not to recognize the option to attempt prehension with the SA, older ones were capable at times of deliberate disuse of the arm and could reverse existing patterns of SA disuse. Older infants also displayed: (1) better awareness of the handicapping effects of the sock in the framework of an improved concept of arm structure and function, and (2) better adaptive and compensatory responses including substitute use of the UA. These data were interpreted to suggest a general transition from peripheral to central control of prehensile intention during the 2nd half of the 1st year.