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Reported in part before the Eastern Branch of the American Psychological Association, April 2, 1938: "Discrimination learning and delayed response to visual stimuli by chimpanzees," by A. H. Riesen and V. Nowlis; and before the Southern Society for Philosophy and Psychology, April 15, 1938: "Delayed response by chimpanzee to spatial versus non-spatial cues," by H. W. Nissen, A. H. Riesen, and V. Nowlis.

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Infant macaque monkeys (Macaca arctoides) were individually raised to age 6 months in large clear cubes built into one wall of a control colony that allowed them visual access to it but not tactile contact. The two deprivation conditions (Cond 2 and Cond 3) were equal both in physical size and with respect to partial social isolation. They differed in the degree of somatosensory-motor opportunity available during development in that the Cond 2 chamber was empty, whereas Cond 3 contained ladders, a trapeze, and play objects. Four monkeys from each of these conditions were compared with four colony-reared (Cond CR) monkeys. Neuroanatomical changes were evaluated by using light microscopy in Golgi-Cox-stained neocortex. Dendritic spines on the apical shafts of layer IIIB pyramidal cells were counted in primary motor (MI), somatosensory (SI), and visual (area 17, V1) cortical regions. Layer IIIB pyramidal neurons with somas of medium size were selected from each cortical region and the density of apical dendritic spines determined. The basilar dendritic branches of these same neurons were traced, and the dendritic branching complexity was assessed in order to compare the sensitivity of the dendritic spine and branching measures consequent to deprived rearing. The number of apical dendritic spines was significantly reduced in Cond 2 when compared with either Cond 3 or Cond CR (which did not differ from each other). This occurred in both MI and SI cortex, but not in the visual cortex, the region used as a control for a global brain effect. Branching complexity measured on the same pyramidal neurons was reduced only in MI cortex of Cond 2. These results show spine density, a more direct measure of neuronal connectivity, to be the more sensitive measure of early environmental deprivation. Also, the enriched environment provided by Cond 3 relative to Cond 2 offset the effect of partial social isolation such that both morphometric measures had values comparable to Cond CR monkeys.

Animals reared in darkness or in diffused light are slow to utilize spatial cues. The}' learn visual discrimination habits only after more prolonged training than do normally reared animals. A dramatic effect of form deprivation is the lack of interocular equivalence, as revealed in tests for interocular transfer after monocular training. Such findings have been reported for chimpanzees (Chow & Nissen, 1955), cats (Riesen, Kurke, & Mellinger, 1953), and birds (Siegel, 1953). In birds there is less equivalence under normal conditions (Levinc, 1945) and more transfer after deprivation (Siegel, 1953; Tucker, 1957) than appeared for the other two species studied.Common to the previous experiments on visual learning and inlcrocular transfer was the use of stimuli which call upon form vision, e.g., circle versus triangle or horizontal versus vertical stripes. Visual movement and visual intensity discriminations have not been tested in pattern-deprived animals and may depend upon neural processes other than those involved in form vision.Gcstalt psychology first emphasized the unity of the perceptual act in the experience of apparent movement. Wcrtheimcr's (1912) pure phi was perceived motion without object character. Movement perception thus initialed the Gcstalt notion of innate perceptual processes. If the perception of movement is innate, then it may not require form recognition

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