People generally believe that more is better in persuasion, for good reason. Past research has shown that providing more arguments can enhance a message’s persuasiveness. In contrast, we demonstrate that increasing the number of arguments in a message can have conflicting effects on perceptions of the message source. Compared to using few arguments, using many arguments makes the source seem more like an expert, increasing persuasion, but it can also make the source appear to have greater persuasive intent, decreasing persuasion. These perceptions suppress each other, resulting in minimal or no overall benefit to persuasion. We document these effects across multiple experiments. We further demonstrate that providing many arguments can have a clear positive or negative effect, depending on whether high expertise or low persuasive intent is more valued. These findings expand our understanding of argument quantity effects in persuasion and contribute to a growing literature on conflicting source perceptions.
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