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Watch How You Nod

A nod or shake of a person's head can signal approval or disapproval to others. But those same head movements may be influencing a person's own thoughts as well, according to new research.

Previously, psychologists believed that just as smiling can make a person feel happy, nodding could encourage positive thoughts. It isn't that simple, say psychologists Richard Petty of Ohio State University, Columbus, and Pablo Briñol of the Autonomous University of Madrid in Spain.

Petty and Briñol asked undergraduates to listen to various radio editorials through headphones while either nodding or shaking their heads. As expected, students who nodded during an editorial that made convincing arguments agreed more strongly with what they had heard than those who shook their heads. Surprisingly, students who listened to an editorial that made poorly reasoned arguments had the opposite reaction: Instead of feeling more positive about what they had heard, those who nodded agreed less than those who shook their heads.

The reason for this counterintuitive result, Petty and Briñol suggest in the June issue of the Journal of Personality and Social Psychology, is that rather than simply making a person think more positively, nodding boosts confidence. Just as a speaker facing a nodding audience would feel more confident about the statements, Petty and Briñol argue, a person who nods while listening to something and disagreeing with it would be more certain of that assessment--and disagree even more strongly. A person who shakes his head might lose confidence in his or her own judgement, whether it's positive or negative, like a speaker facing a room full of headshakers.

The study could have implications for a broad range of situations, including political campaigns and advertisements, says psychologist Duane Wegener of Purdue University in West Lafayette, Indiana. Because people tend to subconsciously mimic what they see, a nodding political candidate or salesperson could induce nodding in an audience, causing supporters to agree even more. Nodding could backfire with skeptical listeners by strengthening their disapproval, says Wegener. "It makes it all the more important to target your audience."

Related sites
Richard Petty's home page
Duane Wegener's home page