Visual feedback and anticipatory hand orientation during infants' reaching.
Infants 5, 7, and 9 mo. of age were videorecorded while reaching for a dowel that either was stationary or changed orientation after initiation of a reach. Visual fixation and hand orientation were monitored throughout each reach, as was the efficiency with which infants contacted the stimulus. In reaching for the stationary stimulus, the 5-mo.-olds showed significantly poorer hand orientation adjustment throughout their reach than 9-mo.-olds. The 7-mo.-olds began a reach with the hand poorly oriented as did 5-mo.-olds, but just before object contact their performance matched that of the 9-mo.-olds. On change-orientation trials, the 5-mo.-olds' reaching was disrupted. They missed, stopped, or withdrew their reach on over half of these trials, and hand orientation on contact was significantly worse than on no-change trials. By contrast, older infants were more skilled in using visual feedback to make corrective adjustments in hand orientation during execution of the reach to secure a smooth contact with the stimulus. These infants showed no difference in hand orientation on contact for change in comparison to no-change trials. The 9-mo.-olds' performance surpassed that of the 7-mo.-olds only in the efficiency with which they contacted the stimulus and the incidence of grasps on first contact.
Morrongiello
B A
BA
Psychology Department, University of Western Ontario, London, Canada.
Rocca
P T
PT
D001288:Attention; D005246:Feedback; D005403:Fixation, Ocular; D006801:Humans; D007223:Infant; D009949:Orientation; D002666:Psychology, Child; D011597:Psychomotor Performance; D012718:Set, Psychology