Abstract

A SUMMARY OF EXPERIMENTAL RESEARCH ON THE EFFECTS OF EVIDENCE IN PERSUASIVE COMMUNICATION James C. McCroskey r-pRADITIONA L theories of rhet- writer that underlie this paper are _|_ oric, person-to-group persuasive reported in detail elsewhere.2 communication, stress the value of docu- mented supporting materials, commonly STUDIES REPORTED BY OTHER called evidence, in the production of RESEARCHERS attitude change. Contemporary theorists Nine studies have been reported by for the most part concur with traditional other investigators that involved research theorists in this regard. However, be- on the effect of evidence on attitude cause of the conflicting findings of the change in persuasive communication. few reported experimental studies of the Two of these found that inclusion of effect of evidence on attitude change, evidence increased the amount of atti- some writers have questioned whether tude change produced by the message; evidence actually has much, if any, im- two found a trend in this direction; and pact in persuasion. After reviewing some five observed no significant effect on of these studies, for example, Gregg con- attitude change attributable to evidence. cluded that "the audience reaction to an argument may have little or nothing to The two earliest reported studies, do with whether