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This paper is based on part of a dissertation submitted to the faculty of the Department of Psychology of New York University in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The author wishes to express gratitude to Dr. T. C. Schneirla for methodological and theoretical aid from the initial planning stages to the final reports of these experiments. Gratitude is also expressed to the Department of Animal Behavior of the American Museum of Natural History for the use of its experimental facilities.-' Now at the Institute for Research in Human Relations, Philadelphia.