This dissertation used evolutionary theory to explain the persuasive effects of source characteristics on message targets. It was argued that targets are differentially persuaded by sources who possess certain phenotypic characteristics because such responses increased reproductive success over the course of human history and were therefore evolutionarily adaptive. Attitude and attributions toward the source and message were hypothesized to be affected by a three-way interaction between source characteristic, the source's communicated intention of goodwill, and participant dominance. In addition, a structural model was used to test whether source and message attributions mediated the effect of source characteristics on attitude.

Four experiments were conducted to test different phenotypic cues: facial symmetry (Experiment 1, N = 287), facial sexual dimorphism (Experiment 2, N = 278), voice pitch (Experiment 3, N = 286), and facial similarity (Experiment 4, N = 100). These phenotypic manipulations were crossed with message manipulations in which the source framed the advocated action as either benefitting the source or the message targets. Participants were randomly assigned to between-subjects experimental conditions in which they read or listened to a series of persuasive messages attributed to different sources.

Results provided weak support for the hypothesized interaction. Significant two- and three-way interactions were found, but these interactions did not fully support predictions and lacked consistency across experiments. Further, structural equation models demonstrated few and inconsistent effects of source characteristics on attitude or attributions toward the source and message. Despite these findings, the significant results provide some reason to believe that targets' susceptibility to influence may have some evolutionary underpinnings. Implications, limitations, and directions for future research are discussed.