The relationship between grasping and sucking, a possible precursor of hand-mouth coordination, was examined in human newborns of varying gestational ages. Grasping was elicited by rapidly tilting the infant backwards while he rested on a padded board and held a grasp bar. Infants were tilted 4 times under each of 3 conditions: grasping, sucking, and grasping-while-sucking. The dependent variables were strength and duration of grasp and frequency and amplitude of sucks during the 15 sec following the tilt.
The results indicated that grasping did not affect sucking but that sucking increased the strength and the duration of the grasp. Furthermore, either response system was more highly correlated with indices of maturity of the central nervous system when elicited in the presence rather than the absence of the other. We conclude that in human newborns sucking may be dominant over grasping but that both are part of an integrated system which may form the basis for the development of hand-mouth coordination.
