Because of the consistent occurrence of stereopsis at around four months of age, its development was initially attributed simply to the process of maturation. However, scientists who assessed this theory by using drugs to prevent the segregation of pathways at the usual time of the development of stereopsis found that depth perception was undermined. Essentially, maturation in itself does not produce depth perception. Rather, the maturation process combined with experiences in the environment enable infants to develop their capacity for depth perception (Siegler, 1998, p. 121).
The latter theory was further confirmed by studies on cross-eyed children and adults who re
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