Trusting a stranger may be a case of déjà vu

All human connections and interactions depend on trust. Every time you board a bus, for example, you trust that the driver will get you to your destination in a reliable and safe manner. In order to have a successful relationship with friends, family and partners, we need to feel we can trust them.

Meeting new people may involve a kind of déjà vu, when trusting them depends on how much they look like an old friend, a new study suggests.

Judging strangers

In a series of experiments, New York University researchers found that study participants were more likely to pick photos of strangers who resembled honest people they had met in an earlier experiment than photos of strangers who reminded them of dishonest people they'd encountered in an earlier game.

"We make decisions about a stranger's reputation without any direct or explicit information about them based on their similarity to others we've encountered, even when we're unaware of this resemblance," said study senior author Elizabeth Phelps. She's a professor in NYU's department of psychology.

"This shows our brains deploy a learning mechanism in which moral information encoded from past experiences guides future choices," she added in a university news release.

Like Pavlov's dog

The research, which was led by Oriel FeldmanHall, as a post-doctoral fellow at NYU, was published in the Proceedings of the National Academy of Sciences.

FeldmanHall is now an assistant professor in Brown University's department of cognitive, linguistic, and psychological sciences.

"Our study reveals that strangers are distrusted even when they only minimally resemble someone previously associated with immoral behaviour," Professor FeldmanHall said.

"Like Pavlov's dog, who, despite being conditioned on a single bell, continues to salivate to bells that have similar tones, we use information about a person's moral character – in this case whether they can be trusted – as a basic Pavlovian learning mechanism in order to make judgments about strangers," she explained.

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