Monocular depth perception was compared with binocular depth perception in 5- and 7-month-old infants. Reaching was used as the dependent measure. Two objects, identical except in size, were presented simultaneously to each infant. The smaller object was within reach for the infants while the larger object was just beyond reach. The two objects subtended equal visual angles from the infants' observation point. With binocular presentation, 96% of the 7-month-olds' reaches and 89% of the 5-month-olds' reaches were for the nearer object. With monocular presentation, 58% of the 7-month-olds' reaches and 65% of the 5-month-olds' reaches were for the nearer object. The reaching preferences observed in the monocular condition indicated sensitivity to monocular depth information (motion parallax, accommodation, and relative size information were available). Binocular viewing, however, resulted in a far more consistent tendency to reach for the nearer object. This result suggests that the infants' perception of the objects' distances was more veridical in the binocular condition than in the monocular condition.
Bibliographical noteFunding Information:
This research was supported by National Institute of Child Health and Human Development Grants HD-05027 and HD-01136. Correspondence concerning the article and requests for reprints should be sent to Albert Yonas, Institute of Child Development, University of Minnesota, 51 East River Road, Minneapolis, MN 55455-3045. The authors thank Ann Sorknes for assistance in running subjects, Isabel Smith for editorial assistance, and Kaye O’Geay for typing the manuscript.