Perceptions of source efficacy and persuasion: Multiple mechanisms for source effects on attitudes

When communicators are perceived as likely to bring proposed outcomes to fruition, they have source efficacy. Although perceptions of source efficacy are common in persuasion settings, this construct has received little direct research attention. The present research explored how source efficacy may impact persuasion in different ways at different levels of motivation to process messages. Across three experiments, participants encountered message arguments of varying quality from a source manipulated to be relatively efficacious or inefficacious. When motivation to process the message was low, source efficacy served as a peripheral cue (Experiment 1). When motivation was high, efficacy information learned before the message biased processing of ambiguous messages (Experiment 2), but source efficacy learned after the message affected the amount of confidence people had in their message‐related thoughts (Experiment 3). These effects of source efficacy were distinct from effects of perceived source expertise/credibility. Copyright © 2011 John Wiley & Sons, Ltd.