Sociality effects on the production of laughter.

Certain facial displays (typically the human smile) have been found to vary with a situation's sociality. Because the facial display that accompanies laughter is under less voluntary control, it is a stronger test of sociality effects. Participants (N = 162) were videotaped watching a humorous videoclip in 1 of 3 conditions: alone, in a same-sex dyad with a stranger, or in a same-sex dyad with a friend. The frequency and time spent laughing were significantly greater in one or both dyadic conditions than in the alone condition, although no differences existed for self-reported evaluations of the videoclip's funniness or amusement felt. When the self-report measures were controlled for, the dyads of strangers (compared with the alone condition) were associated with the frequency of laughter. Although the results provide further support for sociality effects, the situational demands faced by participants may be a better predictor of facial displays than level of sociality.