Size constancy in infants: 4-month-olds' responses to physical versus retinal image size.

This study tested whether 4-month-old infants respond primarily to objects' physical or retinal image sizes. In the study's main experiment, infants were habituated to either a 6-cm-diameter disk at a distance of 18 cm or a 10-cm disk at 50 cm. They were then given 2 test trials in which the 6- and 10-cm disks were presented side by side at a distance of 30 cm. For each infant, one test object had a novel physical size but a familiar retinal image size, and the other had a familiar physical size but a novel retinal image size. The infants exhibited a significant looking preference for the object that had a novel physical size. A preliminary experiment found that 4-month-olds' looking preferences are based on novelty, not familiarity, under the conditions of this study. Given this finding, the results suggest that 4-month-old infants attend and respond primarily to physical size, not to retinal image size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binocular vision and spatial perception on 4- and 5-month-old infants.

Conducted 4 experiments investigating the relation between the development of binocular vision and infant spatial perception. Exps I and II compared monocular depth perception in 39 4- and 5-mo-old infants. Results show that Ss in both age groups reached more consistently for the nearer of 2 objects under binocular viewing conditions than under monocular viewing conditions. Exps III and IV investigated whether the superiority of binocular depth perception in 89 4-mo-olds is related to the development of sensitivity to binocular disparity. In Exps I–II, under binocular viewing conditions, Ss who were identified as disparity-sensitive reached more consistently for the nearer object than did Ss who were identified as disparity-insensitive. The 2 group's performances did not differ under monocular viewing conditions. Results suggest that, binocularly, the disparity-sensitive Ss perceived the objects' distances more accurately than did the disparity-insensistive Ss. In Exps II–IV when Ss were habituated to an object, then presented with the same object and a novel object that differed only in size, disparity-sensitive Ss showed size constancy by recovering from habituation when viewing the novel object. Disparity-insensitive Ss did not show clear evidence of size constancy. Findings suggest that the development of sensitivity to binocular disparity is accompanied by a substantial increase in the accuracy of infant spatial perception. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' sensitivity to relative size information for distance.

In Exp I, 40 203–231 day old infants were used to test the hypothesis that sensitivity to pictorial depth information emerges between 5 and 7 mo of age. Pairs of discs and triangles (identical except in size) were presented to Ss to test their reaching preference or lack of it under either monocular or binocular conditions. In Exp II, 20 157–270 day old and 40 140–256 day old infants were tested with the same apparatus and procedures but were moved closer to the objects. Results show that Ss in both experiments were sensitive to relative size. Under monocular viewing conditions, both 203–231 and 157–270 days old Ss showed a preference to reach for the larger object of the pair. Under binocular viewing conditions, no difference in number of reaches for the large and small objects was found in either group. The lack of reaching preference in the binocular condition suggests that the reaching preference observed in the monocular condition was due to the perceived spatial locations of the objects and not to a preference to reach for the larger object without regard to distance. Ss in the youngest age group (140–256 days old) gave no evidence of sensitivity to relative size. Findings support the hypothesis. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)