Motor constraints on the development of perception-action matching in infant reaching

Previous studies on reaching and grasping have suggested that infants need considerable experience at both seeing and touching in order to develop res ponses adapted to the environment. Such an account, however, does not revea l how appropriate perception-action matching emerges from these repeated ex periences at seeing and touching. The present research addresses this issue by investigating the dynamics of perceiving and acting in 5- to 9-month-ol d infants as they saw, reached for, touched, and grasped objects of differe nt sizes and texture. To gain insights into the mechanisms of change that u nderlie pattern formation, we observed infants' responses as a function of time, as infants reached for and manipulated objects successively. We found that the developmental process by which appropriate perception-action matc hing emerges is tied to important changes in the motor system. Before 8 mon ths, infants' reaching responses are constrained by systemic motor tendenci es that conflict with the process of perceptual-motor mapping. When these m otor tendencies disappear, infants are able to use and integrate visual and haptic information to scale their actions to objects. These results are co nsistent with a dynamic systems approach, which views behavioral changes an d their underlying psychological processes as the product of continuous ten sions and interactions between the organism's own constraints and the chara cteristics of the task at hand. (C) 2000 Elsevier Science Inc. All rights r eserved.