SOCIAL FACILITATION IN MONKEYS

Abstract

One of the characteristic patterns of social interaction observed in human Ss (Allport, 1924) and in many species of vertebrates (Bayer, 1929; Crawford, 1939) is that of social facilitation. This term, according to Crawford (1939), refers to "any incremenc of individual accivity which results from the presence of another individual, and can be regarded as one of the most basic forms of social interaction" (pp. 410-41 1) . Animal experiments with rats (Harlow, 1932; Bruce, 1937) and with monkeys (Harlow & Yudin, 1933) have shown increased food intake in the presence of other individuals of the same species. Investigations with human Ss have generally been concerned with rates of work output on relatively routine tasks. Although increased work output under social conditions has been obtained both in experimental (Allport, 1924) and in real-life situations (Wyatt, et al., 1934), the effectiveness of the social stimulation was found to be dependent upon several factors. As summarized by Kelley and Thibaut (1954), social facilitation may be dependent upon the difficulty and monocony of the cask, rate of work under solitary conditions, de-gree of activity of others in the group, adaptation to the task, and motivational factors. The present investigation was concerned with social facilitation when pairs of monkeys performed simple tasks for which a food reward was given. The task of pushing a disk against a relatively heavy spring could be readily learned by young monkeys and imposed only few restrictions on the rate of work out-put. The influence of social status on measures of social facilitation was also assessed. METHOD Sz~bjects.-Eight pairs of experimentally naive rhesus monkeys (6 to 7% Ib. body weight) were used. Each pair lived in the same home cage for at least two weeks prior to and then throughout the experimental period. Pairings were arranged so that the two partners were of approximately equal age and body weight; hence, four pairs of Ss consisted of two males each, one pair of two females, and in three pairs a male was with a female. Apparatus.-Each S was tested in a wire mesh testing cage, the front of which consisted of vertical bars spaced 2%" apart. This cage was placed in a soundproof box, arranged so that an illuminated plastic disk (2%" diameter) was in front of the cage and 13" above its bottom. When this disk was pushed 'This investigation was supported in part by Research Grant No. MS45(CS) from the