Source effects in communication and persuasion research: A meta-analysis of effect size

Abstract

The effect of a message source on the persuasion of a target audience has been a topic of interest to scholars in psychology, consumer behavior, and communications for many years. Narrative reviews of this literature are available; the contribution of this study is that we present a quantitative review of studies of source effects on persuasion. One of our research goals is to determine how strong and consistent source manipulations tend to be. We find that, on average, source manipulations account for nine percent of explained variance among studies reporting significant findings. In particular, expertise tends to have the greatest effect on persuasion with an average of 16 percent of the explained variance being due to the expert versus non-expert manipulation. As well as gaining insight into the pattern of results across a body of literature, our findings may be used as benchmarks by researchers, as advocated by Sawyer and Ball (1981), to evaluate results of future persuasion studies employing a source manipulation.