DEVELOPMENT OF MANIPULATION IN CAPUCHIN MONKEYS DURING THE FIRST 6 MONTHS

This study describes the orderly changes in manipulation over the firs t 6 months in capuchin monkeys (Cebus apella). By 6 months of age, all the basic forms of manipulation seen in adults have appeared. Actions that occur frequently in the first 8 weeks are gentle and involve sus tained visual orientation and aimed reaching. Later actions are more v igorous, and involve grasping. Large increases in the rate of activity are evident over the period of development studied. The increase from the first 8 weeks to the second may be due to (a) an increase in the amount of time spent alert and active, (b) a decrease in the amount of time spent in a ventral position, (c) improvements in postural contro l and stamina and (d) the onset of independent locomotion. Changes in form can be attributed primarily to postural factors and to neuromuscu lar development (precisely aimed and controlled movements appearing in the 5th and 6th months). (C) 1994 John Wiley & Sons, Inc.