Success Expectancy: A Mediator of the Effects of Source Similarity and Self-Efficacy on Health Behavior Intention

Although many health communication studies have substantiated the role of self-efficacy as one of the most proximal determinants of behavioral intention, a recent body of research has also shown that high self-efficacy does not always translate into intention to perform a recommended health behavior. Recognizing the common ground among three independent lines of research on outcome expectancy, goal attainability, and expectation of success, the present study proposed success expectancy, or perceived likelihood of goal achievement, as a mediator between self-efficacy and health behavior intention, which may explain the inconsistent findings on self-efficacy. An online experiment (N = 336), in which similarity of the source in health messages was manipulated, demonstrated that success expectancy indeed mediated the relationship between self-efficacy and behavioral intention. Success expectancy also mediated the effects of source similarity on behavioral intention, while neither task nor coping self-efficacy showed such effects. These results suggest that health promotion messages focusing specifically on increasing perceptions of success expectancy may be more effective in inducing health behaviors than messages that promote self-efficacy, particularly in health contexts, in which people with high self-efficacy do not tend to successfully enact recommended health behaviors.