College is all about stepping outside of your comfort zone, embarking on new experiences, and meeting new people—right? Generally, yes. But my college roommate had zero intentions of doing so. She was completely content spending her time with the same old people, doing the same old thing. And she strongly preferred I adapt the same strategy. When I didn’t, she took it upon herself to protect me from the “sketchy” boys and girls I welcomed into my circle.

I never understood why my roommate thought this or that person was untrustworthy—but new research from NYU offers an answer. This study, which will be published in the journal Proceedings of the National Academy of Sciences, according to Neuroscience News, says that our instinct to trust (or distrust) a stranger is rooted in past experiences: we trust strangers who resemble those we know to be trustworthy, and we distrust strangers similar to those who have proven untrustworthy.

Oriel FeldmanHall, the study’s lead author and current assistant professor in Brown University’s Department of Cognitive, Linguistic, and Psychological Sciences, further explains the nature of these findings: “Our study reveals that strangers are distrusted even when they only minimally resemble someone previously associated with immoral behaviors. 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 mechanism in order to make judgments about strangers.”

Senior author and a professor at NYU’S Department of Psychology Elizabeth Phelps goes on to explain that we judge strangers without any real information, only their similarity to another person we’ve encountered. She adds that we do this without even realizing it, which “shows our brains deploy a learning mechanism in which moral information encoded from past experiences guides future choices.”

To reach these findings, the researchers recruited study participants and instructed them to complete a few tasks revolving around a trust game. In this game, subjects had to judge their partner’s trustworthiness and make important decisions based on those judgments. In the first task, they chose one of three players—whom were represented only by facial images—to entrust their money with, keeping in mind that the partner they chose could either share the money or keep it for themselves. They soon learned which player was highly trustworthy, somewhat trustworthy, and not at all trustworthy.

In the next task, the same participants were told to pick new partners for another round. The catch was that, unbeknownst to the subjects, the face of each new partner was morphed in some way with one of the three original partners—so the new partners bore at least a slight resemblance to a previous partner. Now, despite their ignorance to this resemblance, the subjects proved to pick the partners who resembled the trustworthy players from before and consistently avoided working with those who resembled the untrustworthy players.

Looking back at my roommate’s skepticism, she often questioned similar-looking individuals: those who dressed more casually, wore their hair loosely, and displayed a more relaxed demeanor. It’s very possible that she knew someone(s) who shared these physical qualities, found them to be untrustworthy, and now judges others based on this previous experience. This would align with the above findings and explain why she was so quick to write off so many of my new friends.

NYU (2018, January 30). Why Do We Trust, or Distrust Strangers? The Answer is Pavlovian. NeuroscienceNews. Retrieved January 30, 2018 from

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