Infant perception of object unity in static displays

The present study examined infants' capability of extracting object unity in a stationary two-dimensional rod-and-box display. The infants were habituated to a centre-occluded rod and were afterwards tested with both a broken rod and a complete rod. The looking pattern of both female and male participants aged 8 months did not reveal the ability to amodally complete the partly hidden rod. Nine-month-old females, however, looked reliably longer at the broken test stimulus than at the solid test display, implying that they had perceived the partially occluded rod presented in the habituation period as a connected whole. Their male counterparts, on the other hand, did not differentiate between the test patterns. These findings suggest that the capability of perceiving object unity in displays in which the relative depth ordering of surfaces is specified solely by the pictorial depth cue of interposition emerges after about 8 months of age. Furthermore, the results argue for a differential perspective including sex as a moderator variable.