Partly Occluded Objects

Newborn infants were familiarized to a three-dimensional display consisting of a rod which moved behind a central occluder, so that , only the top and bottom of the rod were visible. The infants’ eyes were 38 cm from the rod and the occluder was 15 cm in front of the rod, a separation intended to ensure that the gap between the two was detected by the infants. On subsequent test trials the infants looked longer at a complete rod than at two rod pieces, suggesting that the hidden unity, or completeness of the rod had not been perceived. In a study by Johnson and Nhiez (in press), using computer-generated stimuli, 4-month-olds perceived the hidden unity of a similar display presented on a VDU in the complete absence of three-dimensional depth cues. Taken together, these findings suggest that, for these displays, perception of threedimensional depth cues is not necessary for the detection of the unity of partially hidden objects. It is suggested that age changes in early infancy in the perception of occluded objects may result either from the emergence of abilities to perceive objects from kinematic information or from the emergence of sensitivity to that information itself.