Conducted an experiment with 102 male undergraduates to test the hypotheses, stemming from S. Schachter's theorizing about emotions and affiliation, that an increase in physiological arousal whose source is not known would (a) increase the desire to affiliate with other persons facing a similar situation, and (b) produce stronger affiliative tendencies than an increase whose source is known. In support of the hypotheses, it was found that the desire to affiliate with others in the same experiment was greater when Ss were given caffeine and told that it was an analgesic than when they were given a placebo and told that it was an analgesic, or when given caffeine and told it was a stimulant. (PsycINFO Database Record (c) 2016 APA, all rights reserved)