On the Persuasiveness of Similar Others: The Role of Mentalizing and the Feeling of Certainty

Prior literature has proposed two process explanations for the positive effect of source similarity (i.e., similarity between adviser and advice taker) on persuasion. One explanation is that similar others are perceived to have preferences that are correlated with one's own, and this makes their advice more diagnostic. The other is that similar others are liked more so people follow their advice to maintain connectedness with them. We propose a more general explanation that incorporates the advice taker's processing goals. To process any advice, advice takers activate a mentalizing goal, which is to understand the adviser's mental states. Similarity creates a perception of such an understanding and induces a feeling of certainty (i.e., a feeling of knowing) that validates the advice as a decision input and increases persuasion. A mentalizing explanation accounts for the effect even when similarity cannot lead to perceptions of correlated preferences or to interpersonal liking. Four studies show that the effect attenuates if advice takers are less likely to mentalize, are already primed to feel certain, or misattribute their feeling of certainty to a source other than the advice. Furthermore, the feeling of certainty emanating from similarity even influences decisions unrelated to the advice.