Do infants see objects or retinal images? Shape constancy revisited

Abstract

Although earlier research by Bower on the spatial constancies indicated that 2-month-olds perceive a veridical three-dimensional world, recent evidence based on distance-appropriate behavior suggests that infants may be responding to differential depth cues per se, devoid of spatial significance. To shed light on this apparent contradiction, a test of the infant's ability to perceive real shape-at-a-slant was conducted using recovery from habituation as an index of discrimination. Groups of 80-day-old babies (total N = 120) were each exposed to one of six treatment conditions. The same figure in the fronto-parallel plane served as the recovery stimulus in all conditions. The to-be-habituated stimulus differed between groups according to whether it deviated from the standard in terms of various combinations of objective shape, projective shape, and slant. While the results were consistent with Bower's conclusion that the momentary retinal projection plays no role in infant perception, they were discrepant from Bower's findings in that subjects appeared to respond exclusively to variation in slant and gave no evidence of perceiving constant shape across changing slant. Whether the ability to perceive real shape was present but masked by salient slant cues or whether infants can detect only the proximal retinal cues specifying slant could not be conclusively determined. A second experiment involving 60-day-olds ( N = 20) and an additional 80-day-old group ( N = 18) indicated that the findings could not be attributed to sampling error, the age differential between Bower's subjects and our own, or tendencies to view the slanted figures projectively.