Is Visually Guided Reaching in Early Infancy a Myth?

Abstract

The issue examined was whether infants require sight of their hand when first beginning to reach for, contact, and grasp objects. 7 infants were repeatedly tested between 6 and 25 weeks of age. Each session consisted of 8 trials of objects presented in the light and 8 trials of glowing or sounding objects in complete darkness. Infants first contacted the object in both conditions at comparable ages (mean age for light, 12.3 weeks, and for dark, 11.9 weeks). Infants first grasped the object in the light at 16.0 weeks and in the dark at 14.7 weeks, a nonsignificant difference. Once contact was observed, infants continued to touch and grasp the objects in both light and dark throughout all sessions. Because infants could not see their hand or arm in the dark, their early success in contacting the glowing and sounding objects indicates that proprioceptive cues, not sight of the limb, guided their early reaching. Reaching in the light developed in parallel with reaching in the dark, suggesting that visual guidance of the hand is not necessary to achieve object contact either at the onset of successful reaching or in the succeeding weeks.

A biologically inspired learning to grasp system

“…Interestingly for all the three infants the behaviour occurred earlier in the dark. However the findings does not conflict the traditional view of visual guidance for reaching that is reported in the literature as it would be unreasonable to claim that infants do not use vision information when it is available [6]. The infant, when contacted with the object, will occasionally try to grasp the object.…”

“…The advent of voluntary grasping of objects is preceded by several weeks in which infant engages in arm movements and fisted swipes in the presence of visible objects [5]. For many years, it has been accepted that the earliest accurate reaching behaviour is visually guided and appears around 3-5 months [6]. The term visually guided reaching generally refers to the infant's having available continuous vision of the hand and target, whereas visually elicited reaching refers to the vision of the target, followed by a ballistic hand movement.…”

“…The term visually guided reaching generally refers to the infant's having available continuous vision of the hand and target, whereas visually elicited reaching refers to the vision of the target, followed by a ballistic hand movement. Clifton and her co-workers [6] questioned the visually guided reaching hypothesis. They tested seven infants repeatedly between 6 and 25 weeks of age to examine whether infants require vision of their hand when first beginning to reach for, contact and grasp objects.…”

“…The infant, when contacted with the object, will occasionally try to grasp the object. The enclosure reflex will be with the infant until six moths of age and it will take 4 more weeks to stabilise the grasp [6]. However, the fractionated control of finger movements will not be possible since this task requires cortico-motoneuronal system, which has not been developed by the age of reflex grasping and early voluntary grasping [7].…”

“…The advent of voluntary grasping of objects is preceded by several weeks in which infant engages in arm movements and fisted swipes in the presence of visible objects [5]. For many years, it has been accepted that the earliest accurate reaching behaviour is visually guided and appears around 3-5 months [6]. …”