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The Doppelgänger Bias

A familiar face might influence whether we trust a stranger.


It makes sense that your prior knowledge of a person—whether he has been kind to you or cheated you—determines how you act toward that person in the future. But research suggests that one person’s track record may also influence how you treat people who merely look like him.

In studies led by Brown University neuroscientist Oriel FeldmanHall, participants played a money-sharing game with several male “partners” whose headshots were shown onscreen. (Although players were led to believe they were dealing with real people, the partners were virtual.) As the study participants played, they discovered that these partners were very trustworthy, somewhat trustworthy, or not reliable at all.

Afterward, participants selected from among new faces for another round of play. Unbeknownst to them, the headshots had been digitally morphed to range in their resemblance to those of the original partners. The more a new partner looked like one who had been trustworthy, the more likely he was to be chosen. And the more he resembled an untrustworthy partner, the more he was rejected.

“If somebody elicits a template in your brain that says, ‘This is an X type of person,’” FeldmanHall explains, “that’s an easy way to categorize that individual quickly and efficiently—and sometimes detrimentally.” It’s unclear how far this tendency goes; researchers familiar with the studies speculate that other shared identifiers, such as names or professions, might also steer our judgments.