Weak > strong: the ironic effect of argument strength on supportive advocacy.

When people seek support for a cause, they typically present the strongest case they can muster. The present research suggests that under some conditions, the opposite strategy may be superior-in particular, presenting weak rather than strong arguments might stimulate greater advocacy and action. Across four studies, we show that when individuals already agree with a cause (i.e., it is pro-attitudinal), receiving weak arguments in its favor can prompt them into advocating more on its behalf. Perceived argumentation efficacy mediates this effect such that people exposed to weak arguments are more likely to think they have something valuable to contribute. Moreover, consistent with the notion that it is driven by feelings of increased efficacy, the effect is more likely to emerge when initial argumentation efficacy and attitude certainty are moderate or low. Individuals with high argumentation efficacy and high certainty generally advocate more, regardless of the strength of arguments received.