Additivity of Heuristic and Systematic Processing in Persuasion

Effects of Source Credibility, Argument Quality, and Issue Involvement

Abstract

The present study examined the influence of heuristic processing and systematic processing on persuasion (The heuristic-systematic model; Chaiken, 1980). Participants received either a strong or a weak persuasive message attributed to a high-credibility or a low-credibility source. When the participants' issue involvement was high, their attitudes were influenced only by the strength of arguments. When participants' issue involvement was moderate, their attitudes were influenced by the strength of arguments and by the communicator's credibility. When the participants' issue involvement was low, their attitudes were influenced only by the communicator's credibility. These results were in line with the assumption that the two types of processing occur simultaneously, influencing each other.