What do an eight-ball and a cockroach have in common? Social facilitation. What do social facilitation and social inhibition have in common? Robert Zajonc. These riddles may sound bizarre, but there is a themes that connects them. It's the story of social facilitation, a cornerstone of social psychology.

Norman Triplett is reported to have conducted the first social psychology experiment in 1897 on a topic of some concern to social psychologists: What happens to an individual's behavior when other people are watching it transpire? Triplett thought that task performance should be improved (i.e., the presence of others makes us do better at the task), and demonstrated it through his observations of racing cyclists and children reeling in fishing line. Social facilitation, as this effect came to be called, seemed entrenched in social psychology....until Floyd Allport came along. Gordon's older brother, among others, promoted the idea of social inhibition, or that the presence of others should hinder the task performance of an individual. In short, social facilitation and social inhibition were at loggerheads for much of the ensuing history of social psychology....until Robert Zajonc came along. Zajonc proposed that arousal was the mechanism underlying both facilitation and inhibition. The presence of other people is arousing, because of evaluation apprehension, audience effects, and so on. What we do with that heightened arousal, however, is a function of the task at hand. If the task is well-learned, dominant, easy, or something we're good at, the arousal produced by the presence of others should cause us to do better at the task, thus producing a social facilitation effect. However, if the task is novel, difficult, poorly learned, or not high in our repertoire, the arousal produced by the presence of others should cause us to perform the task worse, thus producing a social inhibition effect.

Zajonc was instrumental in synthesizing these competing viewpoints. But what about the 8-ball? In a novel extension of this theory, James Michaels and his colleagues examined social facilitation in the poolroom. Players in a college student union were identified as either above average (making at least two-thirds of their shots) or below average (making no more than one-third of their shots) by a team of raters. The research team of four students then walked to the table to watch the players shoot. In the presence of others the above average players improved their performance, moving from about 70 percent of their shots made (when not observed) to about 80 percent; social facilitation was at work. Those players who were below average suffered the effects of social inhibition. Their accuracy dropped from about 36 percent to 24 percent of shots made when a crowd was watching.

So where do the cockroaches figure in? In probably the most novel extension of all Zajonc demonstrated that facilitation and inhibition were not limited to humans. He placed cockroaches on either runways (a simple task) or in mazes (a complex task) and measured their running speed when either alone or in the presence of a gallery of other roaches. Supporting previous research, the presence of other roaches did indeed facilitate performance on the runway task whereas it hampered performance in the mazes. This same effect has been demonstrated in other species, suggesting that an arousal-based explanation is correct. Now, if only the roaches would get off the pool table...

Michaels, J. W., Blommel, J. M., Brocato, R. M., Linkous, R. A., & Rowe, J. S. (1982). Social facilitation and inhibition in natural setting. Replications in Social Psychology, 2, 21-24.

Zajonc, R. B., Heingartner, A., & Herman, E. M. (1969). Social enhancement and impairment of performance in the cockroach, Journal of Personality and Social Psychology, 13, 82-92.

Zajonc, R. B. (1968). Social facilitation in cockroaches. In E. C. Simmel, R. A. Hoppe, & G. A. Milton (Eds.), Social facilitation and imitative behavior. Boston: Allyn and Bacon.