Character  &  Context

The Science of Who We Are and How We Relate
Editors: Mark Leary, Shira Gabriel, Brett Pelham
Sep 06, 2019

How Do You Decide Whether to Trust a Stranger?

by Ann-Christin Posten and Thomas Mussweiler
Young female tourist asking for directions and help from man

Imagine the following situation: On a hot summer day, you are at the beach and would like to go into the water, but you aren’t sure what to do with your valuables.  Should you ask the stranger next to you to watch your bag?  How do you judge whether the person is trustworthy or not?

We conducted a series of experiments, in both the United States and in Germany, in which we asked research participants to image scenarios similar to this one.  We asked them how likely a stranger would act trustworthily and, for instance, responsibly watch their bag. In addition, we also asked our participants how likely they would act trustworthily if they were in the shoes of the stranger.

Our results showed that the more likely participants were to act trustworthily themselves (and, for example, watch a stranger’s bag responsibly), the more likely they expected the stranger to also be trustworthy (and watch their bag responsibly). In contrast, participants who thought of themselves as untrustworthy also expected a stranger to be untrustworthy.  

However, when people judge a stranger’s trustworthiness, they do not simply use information about themselves to fill in for the stranger. Rather, they use this information flexibly and adjust how they use this information depending on whether the stranger is similar to or different from them. Only for similar people do they anticipate that the stranger will behave like they would.   

In some of our studies, we encouraged half of the participants to focus on similarity by asking them to look at pairs of pictures (such as pictures of a city) and to identify similarities between the pictures. The other half of the participants saw the same pictures, but we asked them to look for the differences between them. Previous research has shown that searching for similarities versus differences can lead people to focus on how similar (or different) they are from other people in an unrelated follow-up task. In our studies, the follow-up task was the judgment of a stranger’s trustworthiness.

How might this play out when judging trust? Most people see themselves as highly trustworthy: For example, they say that they would responsibly watch the stranger’s bag. Because searching for similarities in the previous picture task would make them focus on similarities between themselves and the stranger (for instance by focusing on the same gender, hairstyle, or that they read the same book), participants would likely perceive the stranger as similar to themselves and expect the stranger to act like they would.  So, knowing that they would watch the bag responsibly would probably lead them to think that the stranger would also watch the bag carefully and be trustworthy. This is just what happened in our studies: people who thought of themselves as trustworthy and were led to focus on similarity (by judging the similarities in the pictures) were more likely to trust the stranger.

However, what happens when people search for differences in the picture task?  Searching for differences led them to focus on differences between themselves and the stranger (for instance by focusing on differences in age, race, or their support for rival sport teams). As a result, they then expected the person to act in ways opposite to themselves.  People who thought of themselves as trustworthy and were led  to focus on differences were less likely to trust the stranger. In some of our studies, the judgment even flipped: people who thought they were untrustworthy perceived the stranger as more trustworthy—simply because they had focused on differences in the picture rating task.

Of course, people don’t only use information about themselves and ignore characteristics of the target person when they decide whether to trust someone.  Along with their own trustworthiness and whether they focused on similarities or differences, the appearance of the other person also affected how much participants trusted him or her. When the other person had a rather trustworthy looking face, participants trusted the person more than when the person had an untrustworthy face.

So, our research found three things that influence how we judge other people’s trustworthiness when we don’t know much about them: how we would behave in that situation, how similar we think the other person is to us, and features of the person’s face.

For Further Reading:  

Posten, A. C., & Mussweiler, T. (2019). Egocentric foundations of trust. Journal of Experimental Social Psychology, 84. doi:10.1016/j.jesp.2019.103820

Posten, A. C., & Mussweiler, T. (2013). When distrust frees your mind: The stereotype-reducing effects of distrust. Journal of Personality and Social Psychology105, 567. doi: 10.1037/a0033170


Ann-Christin Posten is Assistant Professor of Social Psychology at the University of Cologne, Germany.  Thomas Mussweiler is Professor of Organizational Behaviour at the London Business School, United Kingdom.

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Why is this blog called Character & Context?

Everything that people think, feel, and do is affected by some combination of their personal characteristics and features of the social context they are in at the time. Character & Context explores the latest insights about human behavior from research in personality and social psychology, the scientific field that studies the causes of everyday behaviors.  

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