THE EFFECT OF BODY ORIENTATION TO GRAVITY ON EARLY INFANT REACHING

The purpose of the study was to examine the effect of body orientation with respect to gravity on infant's reaching quantity and quality. Tw o groups, 12- to 19-week-old and 20- to 27-week-old infants, were seat ed in three positions: vertical (90-degrees from horizontal), recline (60-degrees), and supine (0-degrees). Nine balls on a black board were presented. Video recordings were used to measure quantity of reaching (number and duration of reaches) and quality of reaching (open or clo sed hand, starting position of the arm, and position of touched and gr asped balls). On the quantity measure there was a significant age x bo dy position interaction that indicated that the 12- to 19-week-olds sh owed reaching behavior in the vertical position equal to that of 20- t o 27-week-old infants in all positions. A similar tendency, although n ot significant, was for the quality measurements. These findings indic ate that the development of reaching does not just reflect maturation of the central nervous system, but a changing interaction between orga nismic and environmental constraints. (C) 1994 Academic Press, Inc.