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In psychology, several of the key findings about trust have been published since 2000, and we are discovering how and why people decide to trust—or distrust—other people. For example, one study showed that people decide within 100 milliseconds whether to trust another person. Another study identified a central network of brain regions involved in the decision to extend trust. It also found that different psychological processes, and different brain networks, are responsible for conditional and unconditional trust. Conditional trust is contingent on the behavior of another person, while unconditional trust is not. Other studies have shown that gossip can help build trust, and that we judge people’s trustworthiness based on two factors: their perceived warmth and their competence, with one taking priority over the other.


A lot of the key articles in psychology on the topic of trust I think have really come out in the 21st century. And one really key article that emerged in 2006 was a study in Psychological Science by Willis and Todorov.

And Willis and Todorov conducted a really elegant study that simply discovered the remarkable finding that trust is something that people tend to judge in another person’s face within 100 milliseconds.

Now, how they conducted this study was they gave participants a variety of different faces — they exposed participants to a variety of different male and female faces.

And the first part of the study just involved an unconstrained session where participants made various judgments about these faces.

So, how attractive is the person in this photograph? How likeable is the person in this photograph? And how trustworthy is the person in this photograph?

In the second portion of the study, participants were presented with the same faces extremely rapidly. So, some were presented at 100 milliseconds; some were presented at 500 milliseconds; and some were presented at 1 second.

And various participants, after this brief exposure to the face, were simply asked the question, “Do you find this person trustworthy, yes or no?”

And what they found was very striking. First of all, there was an extremely high correlation between these snap judgments of, “Do I judge this person as trustworthy, yes or no?” after just a brief exposure to a face — a monumental correlation with those judgments and the judgments made in the absence of time constraints.

So, this suggests that people are making judgments about trustworthiness within 100 milliseconds.

What was also interesting was that, as time increased (so, as participants saw these faces at 500 milliseconds or after a whole second), the correlation didn’t really change that much.

So, what these findings tell us is that trustworthiness is something that people judge very automatically, even before we’ve gotten our wits together to really decide how confident we are in our judgment.

And they really correspond to the same judgments we make about trustworthiness when we have unlimited time to judge people.

BUMPER: Key Research on Trust in Neuroscience

Neuroscientists have also really taken up the topic of trust in their studies as well. One definitive paper on the neural underpinnings of trusting behavior comes from Krueger and colleagues, published in Proceedings of the National Academy of Sciences.

This experiment involved a multi-round trust game. So, this is the game where there is an investor that decides how much money to invest with a trustee, and the trustee then decides how much to pay back.

In these studies, the trust game is administered in a similar fashion to how it’s administered in classic psychological studies, in studies within economics; the only difference, of course, was that in this study, participants brains were scanned while they were making decisions about whether or not to trust and how much to trust people.

The central findings of these studies were that there was a central network of brain regions that was involved in decisions about whether or not to trust, and these brain regions are those that are typically involved in what is called “mentalizing,” or thinking about the mind of another person, thinking about the intentions of another person.

So, this mentalizing network was consistently recruited when people were making decisions about whether or not to trust.

What was also interesting was that this study looked at the differences between conditional trust and unconditional trust.

What’s meant by conditional trust is trust with the assumption that my partner in this game might behave in a self-interested fashion. Conditional trust is, I’m only going to trust you if you’re going to repay me, repay my trust.

Unconditional trust has to do with trusting people indiscriminately, irrespective of what you think their intentions might be.

Another major finding of this study was that separate brain networks were recruited when people engaged in conditional versus unconditional trust, suggesting that these are different psychological processes.

BUMPER: Warmth vs. Competence

A short review paper in Trends in Cognitive Sciences by Susan Fisk, Amy Cuddy and Peter Glick really summarizes a body of research that is essential to understanding how psychologists think about trust and how psychologists study trust in this day and age.

What Fisk and colleagues have found over years and years of studies is that we essentially judge people on two dimensions: How warm is this person? So, how benevolent is this person? And how competent is this person? Does this person have the capability of acting on his or her intentions?

And the most interesting finding that comes out of this research is that people don’t treat warmth and competence the same.

People judge these things relatively rapidly; they base a lot of their judgments about whether to approach or avoid another person on judgments of warmth and competence. But warmth tends to predominate our social judgments.

In other words, warmth is the first thing that we judge when we judge another person (competence comes slightly after), and warmth carries the weight of our judgments when deciding whether or not to trust someone.