In an initial study, 165 US citizens were presented with either weak or strong arguments made by other voters in favour of Barack Obama's re-election as President. Among the participants who were already supportive of Obama, exposure to the weak rather than strong arguments led them to say they had more intention to persuade other people to vote for Obama. This association was mediated by their feeling more confident about their own persuasive powers. It's as if seeing the poor quality of arguments made by other pro-Obama voters had inspired them to feel they had a valuable contribution to make to the cause. The intentions of anti-Obama participants were unaffected by the strength of the pro-Obama arguments.
Further studies sought to test the limits of this counter-intuitive principle. In one, pro-Obama participants were given false feedback in an earlier writing challenge, either indicating that they were skilled debaters or only average. Exposure to weak pro-Obama arguments subsequently acted as a powerful call to arms, but only for participants who'd earlier been told they were merely average at debating. This reinforces the idea that weak arguments can serve to inspire people they have something to contribute to a cause they believe in, but only if their self-belief was relatively low. If a person is already confident in their debating skills, seeing the weak arguments doesn't seem to have the same inspirational effect.
Another study was based around arguments against a proposal to make a school cafeteria entirely vegetarian. For people who already agreed with the cause (i.e. they too were against the vegetarian proposal), exposure to weak arguments increased their determination to join the campaign, but only if they were initially uncertain about their attitudes toward the issue. Again the implication is that weak arguments can be inspiring for people who are initially less sure of themselves. Seeing the weakness of the existing arguments prompts them to see the valuable contribution they can make.
This same principle was replicated in a fourth study that tested people's actual advocacy behaviour rather than just their intentions. Uncertain participants already against the cafeteria proposal who were shown weak (anti all-vegetarian menu) arguments tended to write longer messages of their own against the plans to create a vegetarian-only cafeteria.
Omair Akhtar and his colleagues emphasised they aren't claiming weak arguments are more persuasive than strong arguments. This isn't about attitude change. Rather, they're saying that weak arguments can more effectively inspire "pro-advocacy" intentions and behaviour in people who are already in agreement with the cause.
"Counter-intuitively it might sometimes behoove advocacy groups to expose their supporters to weak arguments from others - especially if those supporters are initially uncertain about their attitudes or about their ability to make the case for them," the researchers said. "This suggestion might be somewhat radical," they added, "but the current results indicate that it is at least worth considering the potential benefits of weak arguments in advocacy contexts."