Development of cardiac and behavioral responses to a three-dimensional toy stimulation in one- to six-month-old infants.

Concomitance between development of perceptual-motor behavior and cardiac-somatic association was evaluated in 1-6-month-old infants. The behavior was elicited by presenting 3-dimensional objects to 50 infants divided into 5 age groups. Each infant was presented with a sequence of 5 commercial toys on 2 immediately succeeding occasions. Each toy stimulation lasted 30 sec and was divided in 2 phases: distal and proximal to the infant. Cardiac responses during the distal phase (first 15 sec) differed as a function of maturing capability of infants to touch and grasp the toys when they subsequently became proximal (last 15 sec). In younger infants (aged 1-3 months), heart-rate (HR) response was consistently decelerative and indexed orienting and attention to the object. In older infants, HR response shifted to acceleration while they fixated the distal toys, before they could actually reach them. This difference in cardiac reaction was attributed to differing stages of perceptual-motor maturation which permit different transactions with external events: somatic activity (acceleration) or information-getting activity (deceleration).