Background Behavior in Live Debates: The Effects of the Implicit Ad Hominem Fallacy

This study examined the effects of background nonverbal behavior displayed with the purpose of undermining one\u27s opponent in live debates. Students participated as audience members in one of three versions of a live debate. In one version, the nonspeaking debater remained “stone faced” during her opponent\u27s speech, while in the other two she displayed either occasional or nearly constant nonverbal disagreement. After viewing the debates, students rated the debaters\u27 credibility, appropriateness, and debating skills, in addition to judging who won the debate. Analysis indicated that background nonverbal behavior influenced audience perceptions of some, but not all, dimensions of speaker credibility and only one dimension of debate skill. These results and their implications are discussed