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Development of pattern vision in neonatal mammals requires prolonged exposure to certain contiguities of stimulation according to Riesen (1958) and Hebb (1949). Consistent with this viewpoint are many studies reviewed by these authors demonstrating that certain mammals deprived of patterned visual stimulation early in life show deficiencies in visualspatial performance when compared with normally reared animals. However, Riesen (1958) and Riesen and Aarons (1959) have demonstrated similar deficits in a chimpanzee and in kittens reared with visual stimulation from nearby objects but deprived of the opportunity for gross bodily movement in their presence. Since contiguities of stimulation are not eliminated under this condition of contact with the environment, they are apparently not sufficient for the development of at least some forms of visual-spatial discrimination. The excluded factor, gross bodily •ovement in a stimulus-rich environment,.ppears to be essential for development. This interpretation of Riesens findings threes with that of results obtained in another, j, obviously related, area of research: studies.. the effects of sensory rearrangement 2 in • lan, the type of experiment exemplified by Strattons (1897) classic on inverted vision. Predictable errors in coordination are induced by such rearrangement, but prolonged exposure 10 the environment reduces them. The sugges-on, often implicit in older rearrangement ••udies, that such results may tell us some-1 This research was supported by a grant from the
Held et al. (Wed,) studied this question.