Is visually guided reaching in early infancy a myth?
The issue examined was whether infants require sight of their hand when first beginning to reach for, contact, and grasp objects. 7 infants were repeatedly tested between 6 and 25 weeks of age. Each session consisted of 8 trials of objects presented in the light and 8 trials of glowing or sounding objects in complete darkness. Infants first contacted the object in both conditions at comparable ages (mean age for light, 12.3 weeks, and for dark, 11.9 weeks). Infants first grasped the object in the light at 16.0 weeks and in the dark at 14.7 weeks, a nonsignificant difference. Once contact was observed, infants continued to touch and grasp the objects in both light and dark throughout all sessions. Because infants could not see their hand or arm in the dark, their early success in contacting the glowing and sounding objects indicates that proprioceptive cues, not sight of the limb, guided their early reaching. Reaching in the light developed in parallel with reaching in the dark, suggesting that visual guidance of the hand is not necessary to achieve object contact either at the onset of successful reaching or in the succeeding weeks.
Clifton
R K
RK
Department of Psychology, University of Massachusetts, Amherst 01003.
Muir
D W
DW
Ashmead
D H
DH
Clarkson
M G
MG
D001288:Attention; D003623:Dark Adaptation; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009048:Motor Skills; D009119:Muscle Contraction; D009949:Orientation; D011434:Proprioception; D002666:Psychology, Child; D011597:Psychomotor Performance; D012016:Reference Values