VISUALLY-ELICITED FINGER EXTENSION IN INFANTS: REFLEX OR REACHING?

Abstract

Arm and finger movements commonly observed in young infants may be neither responses to internal stimuli, nor attempts to “reach for” objects, but reflex-like responses to stimulation from objects. Schnelria's Approach-Withdrawal Theory proposes that at early stages of development in all animals, low intensities of stimulation evoke approach responses and high intensities evoke withdrawal. This hypothesis was tested in 26 human infants by observing their finger responses to a cone that varied in intensity. It was near or far, large or small, bright or dim, with eight combinations from low (far-small-dim) to high (near-large-bright) intensity. Finger movements (flexion or extension) were recorded and ratios of extensions/flexions + extensions computed. There were significant age. Intensity, and age x intensity effects with younger infants' (10-15 weeks) responses clearly related to intensity, while older infants' (20-25 weeks) responses were not. Younger infants made more extensions (approach) to low intensity stimuli, and more flexions (withdrawal) to high intensity stimuli, their extension ratios following an inverse intensity gradient. Such reflex-like responses in very young infants may contribute to the development of reaching by bringing the hands and other objects into the visual field so that intersensory integration can occur. The development of reaching may thus be facilitated by presenting infants stimuli that effectively elicit approach responses.