New research has found that when it comes to trusting strangers, our brains tend to gravitate toward those who resemble trustworthy people we’ve known in the past.
The new study was conducted by psychologists from New York University and published in the journal Proceedings of the National Academy of Sciences.
If a stranger bears a resemblance to a trustworthy person, then we are inclined to trust them, and if they look like an untrustworthy acquaintance, then we are less likely to trust them.
“Our study reveals that strangers are distrusted even when they only minimally resemble someone previously associated with immoral behavior,” said Oriel FeldmanHall, now an assistant professor in Brown University‘s Department of Cognitive, Linguistic, and Psychological Sciences and the study’s lead author.
FeldmanHall compared the response to Pavlov’s dog, which was a famous experiment in which a dog was trained to salivate at the sound of a bell because it meant feeding time. The dog then salivated whenever he heard a similar bell tone no matter if it meant food or not.
We use the same sort of Pavlovian response when deciding whether or not a stranger is trustworthy.
For the study, the researchers asked participants to play several trust games. Each player had to decide whether or not to entrust their game money to three different players who were represented by a facial image.
In the game, the money could be multiplied four times, as each player was given the opportunity to share the money back with the original player or keep the money for themselves.
The players were categorized as highly trustworthy, somewhat trustworthy, or not at all trustworthy, and the participants associated these categorizations with the facial images of the players they were grouped with.
In a second experiment, the first players were asked to choose new partners, but the new facial images were slightly modified to resemble the original players in their group.
The changes were not noticeable, but the players continued to opt to play with the strangers who had facial images similar to the highly trustworthy individual they played with during the first experiment.
The more a player looked like a highly trustworthy player, the more they were likely to be chosen for the game.
The researchers also examined the brain activity of the participants while they were deciding between players and the same region of the brain was activated during the first and second rounds of the game.
The study shows the unique way in which our brains base trust base decisions on past experiences and facial recognition.
“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 Elizabeth Phelps, the paper’s senior author. “This shows our brains deploy a learning mechanism in which moral information encoded from past experiences guides future choices.”