Young Infants’ Perception of Object Unity in Two-Dimensional Displays

Two-dimensional displays were used to investigate the perception of object unity in 48 2-monthold and 48 4-month-old infants. The infants were habituated to a computer-generated display depicting a rod in motion behind a box. Posthabituation test trials consisted of two rod pieces (broken rod) and a complete rod, presented three times each in alternation. The 4-month-olds looked longer at the broken rod than at the complete rod, suggesting that the hidden unity of the rod behind the box was inferred. This finding replicates results with real-object displays and indicates that computer-generated displays may be successfully employed to study questions of object unity in infants. The 2-month-olds looked equally at both test displays. Two months of age may represent a transitional period, from responding to what is directly visible in a visual display to inferring the existence of the occluded portions of objects. Alternatively, infants at this young age may not be sensitive to the visual information that specifies object unity in the displays.