Does nodding cause contagious agreement? The influence of juror nodding on perceptions of expert witness testimony.

摘要

The act of head nodding is thought to convey a signal of agreement and approval of a message (Helweg-Larson, Cunningham, Carrico, & Pergram, 2004; Stivers, 2008). Head nodding has also been shown to affect attitude change within an individual when the nodding was continuous at the rate of one nod per second (Wells & Petty, 1980; Brinol & Petty, 2003). Nodding may be particularly important in the courtroom environment where jury members can only communicate nonverbally. There are a number of anecdotal accounts of attorneys (Aron, Fast, & Klein, 1996) and expert witnesses looking to the head nodding of jurors as a signal of agreement with their position in a case; and it is often perceived as being an indicator that the juror who nodded will vote in a manner consistent with this position. Although the importance of nodding and the influence that nodding can have on attitude change has been established in the literature, what had not been investigated was the influence of juror nodding on the jurors around them.;The present study examined the influence of varied amounts of head nodding by mock jurors on agreement with expert witness testimony and perceptions of expert credibility. The number of individuals instructed to nod was varied (i.e. 15 or 50 percent of individuals), and the jurors were instructed to only nod while the expert was speaking (N = 303). Results showed there were significant effects of nodding on ratings of expert credibility, and marked effects on ratings of agreement with the testimony of the expert, when the nodding was consistently performed. There was no effect of the number of individuals instructed to nod within a condition on the non-nodding participants, but there was an effect on those who had been instructed to nod that was consistent with correcting for perceived bias (Petty & Wegner, 1993). Need for cognition and locus of control variables were also measured. Implications of the study, including a discussion of the effect of changes to previous nodding paradigms, are included.