THE COUPLING OF HEAD, REACH AND GRASP MOVEMENT IN 9 MONTHS OLD INFANTPREHENSION

In 9-month-old-infants adjustments in the reaching pattern to sudden c hanges in object location were examined. An attractive ball was presen ted to the infants at their midline and on some trials (perturbation t rials) the ball suddenly changed position 15 cm to the right or left d uring the reach. For the perturbed trials the movement times approxima tely doubled compared to the control trials and significantly fewer ba lls were grasped. The results indicate that infants need to finish the first movement before being able to redirect the reach to a new desti nation. The correlation between the latency of the head and hand adjus tment to the perturbation were 0.85 and 0.78 for movements to the left and to the right, respectively, indicating a tight coupling. The time between the start of the perturbation and peak velocity (TPPV) was si gnificantly shorter for the head movement than for the hand movement, indicating that the head is leading the hand.