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Nod Yourself to Certainty

By Jack LucentiniNovember 10, 2003 6:00 AM


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In 1884 psychologist William James proposed that physical expressions dictate how we feel, not the other way around: Smile and you’ll be happy. The idea slaps common sense in the face, yet new research suggests it is true: Our actions seem to influence not only our emotions but also our beliefs and attitudes.

“We’ve reversed common sense, just like James,” says Richard Petty, a psychologist at Ohio State University. He and his colleagues asked 82 college students either to nod or to shake their heads while listening to a message advocating a new campus ID card system. One version of the message contained reasonable arguments for the system (for instance, it will enhance security). Another version provided more dubious rationales (it will let security guards take longer lunches). Nodders were more likely than shakers to agree with the persuasive message but actually less likely to concur with the weaker one. Contrary to previous studies, head nodding did not simply nudge the subjects toward “yes.” Nodding apparently boosted the subjects’ confidence in whatever assessment they were making, positive or negative, while head shaking undermined it.

In a related study, Petty’s team found that hand use can also influence beliefs. Righties believed more strongly in self-assessments that they wrote using their dominant hand than ones they penned using their left hand. Seeing scraggly handwriting and feeling the shakiness of the left-handed scrawl apparently transmitted a lack of confidence back to the brain. Trying to decide whether to believe these results? Are you nodding?

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