People preaching their point of view seem awfully sure of themselves. But we often try hardest to persuade when our confidence has been shaken, suggests an October study online in Psychological Science. In the experiment, volunteers wrote essays aimed at strangers about their views on animal testing or dietary preference. When the subjects’ confidence was first challenged by recalling experiences that made them feel uncertain or having to write with their nondominant hand, they wrote longer essays. Because we define ourselves largely by our beliefs, the researchers say, we try to shore up our self-confidence by convincing others to see it our way. Supporting this idea was the finding that when the volunteers were given a different opportunity to reaffirm their attitudes before writing their essays, such as making a list of their music and movie preferences, the effect disappeared.