Development of Stereopsis in Infants

Abstract

For developmental psychology visual deficiencies are of great interest, particularly if they are not entirely the result of inherited genetic anomalies, such as color deficiences. Indeed, visual deficiencies after birth, during the critical period of plasticity, can teach us how the proper visual environment performs “fine tuning” of the nervous system for correct performance. Of course, in many cases visual deprivation is caused by genetic defects whose manifestations could be easily corrected by physical means if such deprivation had been noticed before permanent damage occured. Such a typical example is the permanent loss of neural pools tuned to specific orientations caused by severe astigmatism. For instance, Donald Mitchell (1980) reported that one identical twin whose astigmatism was corrected at 5 years of age had no neural deterioration, while his twin brother, whose astigmatism of similar severity was corrected only at the age of 7 years, had considerable neural loss of orientation. If this observation is corroborated, then the critical period for neural orientation tuning is amazingly late, somewhere between 5 and 7 years of age.