Two experimental studies investigated the social responsiveness of friends and strangers in an interactive humor situation. Pairs of children 7 and 8 years old were recorded on videotape while watching a comedy film. The intimacy of interactions was examined by analyses of expressive behaviors including laughing, smiling, and looking at the companion. In the first study, friends and strangers were placed in same-sex or mixed-sex pairs Friendship had an overwhelming effect in facilitating responsiveness on all the measures, and the results support Patterson's arousal model of social intimacy: Changes in intimacy behaviors initiated by one person (A) are reciprocated by a second person (B) if those changes produce in B positively valued arousal In the second study, level of intimacy was manipulated to create two situations varying in degree of pleasurable arousal. Results suggest that between friends, a relatively high level of intimacy is found more pleasantly arousing by girls than by boys. Results also indicate that smiling and laughing serve different functions in social interaction: Smiling most directly reflects the congeniality of the social situation, while laughter reflects tension within the individual.Friendship studies have concentrated heavily upon the determinants of friendship patterns, and little is known about the dynamics of friendship in social interaction. A controversial issue in the work on friendship is the contrasting strength and diversity of relationships that boys and girls typically experience. Consistent patterns of behavior within sexes are difficult to detect in view of rapid developmental changes. It has been suggested (cf. Maccoby & Jacklin, 1975) that as they grow older, boys come to interact with relatively more playmates. While preschool boys have more intense relations with fewer others (Clark, Wyon, & Richards, 1969), by 7 and 8 years of age they prefer to play in larger same-sex groups. Girls of 7 and 8, on the other hand, tend to play with one same-sex peer (Waldrop, Note 1). Waldrop and Hal-