Infants' sensitivity to familiar size as information for distance.

2 experiments tested the effectiveness of familiar size as information for perceived distance. In Experiment 1, under monocular viewing conditions, adults judged the distances to large and small (34.2 cm and 16.9 cm high) photographs of faces and to large and small checkerboard ovals equal to the faces in size. Familiar size influenced subjects' distance estimates. The small faces were judged to be more than twice the distance of the large faces. No significant difference was found between the judged distances to large and small checkerboards. In Experiment 2, the same displays were presented to 5- and 7-month-old infants. Faces were viewed either monocularly or binocularly; checkerboards were viewed monocularly. Duration of reaching was observed as a measure of perceived distance. 7-month-olds gave clear evidence of sensitivity to familiar size. In the monocular-face condition, the difference in duration of reaching to the large and small faces was significantly larger than in either the binocular-face condition or the monocular-checkerboard condition. This indicates that infants were not simply reaching to large faces or large objects without regard to spatial information. Rather, these results indicate that they perceived the large faces to be within reach and the small faces to be beyond reach in the monocular condition. 5-month-olds failed to provide evidence of sensitivity to familiar size.