Stereoacuity in young children.

Previous investigations of stereopsis in children have found that stereoacuity improves gradually over time and does not reach adult levels until well into childhood. The unusually protracted period of development implied by these data is at odds with the development of other visual capacities, such as acuity, contrast sensitivity, increment thresholds, and flicker fusion. When tested on those dimensions, children, by the age of five, achieve thresholds that are only moderately higher than those achieved by adults. To determine if the elevated thresholds for stereopsis found in children could be attributable to the methods used to obtain them, the authors assessed stereoacuity of children, 3 to 5 yr of age, using a laboratory test combined with procedures designed to optimize the limited attentional, motivational, and response capabilities of young children. The thresholds obtained (median = 12.6 sec) are much lower than previously reported and are close, but not equal, to the thresholds of adults. These data suggest that the development of stereopsis is not unusually protracted relative to the development of other visual capacities. The elevation of threshold relative to adult values is similar to the shortfall found in studies of other visual capacities and has led investigators to suggest, and the authors concur, that children do not possess the sophisticated cognitive strategies that adults can employ when thresholds are approached and uncertainty is high. Given that interpretation, it is suggested that the maturation of stereoscopic capacity is nearly complete in children 3 to 5 yr of age.