Perception of the manner in which objects may be grasped was examined in a series of experiments with adults and 10-month-old infants; visuomotor adjustment in hand orientation before making contact with objects served as the index throughout. In the first experiment, infants modified their hand orientation to match more closely the long axis of an object. They did so even though the target object could have been grasped by either end with hands oriented orthogonally to the long axis of the object. In two subsequent experiments involving reaching through narrow apertures to grasp the target, anticipatory adjustments in hand posture were evident for adults but not for infants. However, anticipatory adjustments by infants, sometimes appropriate and sometimes inappropriate, were made when the object was of such a size that it could neither be grasped nor retrieved through the aperture. In the final experiment, infants directed their hands first toward a handle, the only graspable part of an object, and oriented their hands so as to be nearly parallel with it prior to contact. This was the only orientation in which a grasp was possible. It was concluded that infants at 10 months respond more appropriately to object properties than to surface apertures that place limitations on how an object may be grasped.
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|Published - Dec 1996