Psychological Reporis, 1999, 84,855-861. O Psychological Reports 1999 DOES COMMUNICATING NONVERBAL DISAGREEMENT DURING AN OPPONENT'S SPEECH AFFECT THE CREDIBILITY OF THE DEBATER IN THE BACKGROUND? ' JOHN S. SEITER Utah Slate University Szrmmary.-Compared to televised debates using a single-screen format, those us- ing a split screen presenting both debaters simultaneously show viewers the nonverbal reactions of a debater's opponent. This study examined the e&ct of such nonverbal reactions on viewers' ratings of the nonverbal communicator's credibility. Students watched one of four versions of a televised debate. One version used a single-screen format, showing only the speaker, while the other three versions used a split-screen format in which rhe speaker's opponent displayed constant, occasional, or no nonver- bal disagreement with the speaker. After watching the videos, students rated the op- ponent's credibility using the Source Credibility Scale of McCroskey, et al. Analysis indicated that nonverbal disagreement by the nonspeahng debater, especially when constant, lowered his ratings of competence, composure, and sociability, while con- stant disagreement decreased his ratings of character while increasing his ratings of extroversion. These results and their implications are discussed. In 1960, the advent of televised debates provided voters new opportu- nities to view political candidates. Since then, such debates have become the subject of considerable research and analysis. Even so, with a few excep- tions, prior research has focused almost exclusively on the effects of the con- tent of a debate while overlooking the importance of nonverbal behaviors and the communication medium (Pfau & Kang, 1991). This is unfortunate when one considers the major role a candidate's nonverbal behavior hkely plays in a debate's outcome. For instance, Pfau (cited by Pfau & Kang, 1991) found that, when the effect of content and relational messages was ex- amined across five different modalities of communication, relational mes- sages, e.g., nonverbal behaviors such as facial expressions or body positions that communicate immedacy or warmth, contributed the most to persua- siveness in television communication. In addition, research has found that candidates are more successful and persuasive when their nonverbal behav- ior communicates involvement, similarity, composure, and relational mes- sages (Oft-Rose, 1989; Pfau & Kang, 1991; Schrott & Lanoue, 1992). Although such research highlights the important role of nonverbal be- havior in televised debates, past studes present an incomplete picture be- 'The author thanks Jeff Abraham, Brent Nakagama, Harold Kinzer, and Gordon Steinhoff for their assistance with this project. Please address requests for reprints to John S. Seiter, Depart- ment of Languages, Philosophy, and Speech Communication, Utah State University, Logan, UT 84322-0720.