Trust is important. Without the ability to trust strangers, society would fall apart. You have to trust that people will generally deal with you honestly, and that they will follow through on their commitments. After all, you do not know all the people who grow your food, make your clothes, and take care of your money in the bank. You do not have the time to do all of these things for yourself.
Of course, most of this trust is implicit. You do not often think about the number of strangers you rely on to get through your daily life.
Sometimes, though, you have to place your trust in a stranger more explicitly. Not long ago, I was sitting at an airport by a bank of outlets. A woman walked up, plugged in a cell phone, and asked two of us sitting by the outlets to watch her phone for a few minutes while she went to check her flight. She had to trust that we would not steal her phone, and we had to trust that she was not leaving us sitting next to a dangerous device. And in the end, our mutual trust was rewarded.
An interesting paper that has been accepted for publication in the Journal of Experimental Social Psychology by Sarah Ainsworth, Roy Baumeister, Kathleen Vohs, and Dan Ariely examines whether this kind of trust among strangers requires mental effort.
The measure of trust they used in these studies was a behavioral economics game called the Trust Game. In the Trust Game, participants are given $10. They are told that they can give as much of that money as they want to their partner. The experimenter will then triple the amount of money given to the partner, and the partner can return as much of that money as he or she chooses to the participant. So, if the participant elects to give $3 to the partner, the partner will receive $9 from the experimenter.
This game requires trust. The best joint outcome for the players in this game requires that the participant give all of the money to the partner and requires the partner to split the proceeds. If the participant does not trust the partner, then the participant can choose to keep all of the money.
These researchers suggest that trusting a stranger in this game requires overcoming a natural tendency to avoid risk. To explore this possibility, they overlaid an ego depletion manipulation on this study. The concept behind ego depletion is that when people engage in a period of effortful self-regulation, they have difficulty overcoming their habitual tendencies in the future. So, if trust requires some amount of effort, people who first do a task that requires effort will trust the stranger less than those who do not do this task.
In one study, participants watched a silent video of a woman being interviewed. Periodically, words appeared in the lower right corner of the screen. One group just watched the video, while a second group was told to ignore the words and to return their attention to the woman as soon as they noticed themselves looking at the words. This task has been used in previous research on ego depletion.
After watching the video, participants were given the trust game and were told they were playing with a partner in another room. Participants also filled out a scale that measured the personality characteristic of neuroticism. Neuroticism is the degree to which people tend to focus on negative outcomes and also the degree to which they tend to experience high-arousal emotions like anxiety and anger.
In this study, participants with low levels of neuroticism were not strongly influenced by the ego depletion manipulation. However, those with a high level of neuroticism gave much less money to their partner when they had to avoid looking at the words on the video than when they did not.
The idea here is that people with a high level of neuroticism (and particularly the aspect of neuroticism that focuses on the strength of their negative emotions) have a tendency to fear risk. This group wants to avoid giving money to their partner. Only when they have enough motivational energy will they be able to overcome that tendency.
Two other experiments examined two other factors that also influence people’s likelihood of trusting another person. In one study, some participants were told they would meet their partner after the game. In a second study, participants were given a (fake) EEG measurement at the start of the task. Some participants were told that their partner had a very similar EEG measurement, of the sort you would only expect among siblings, relatives, and close friends.
The ego depletion manipulation did not influence the amount of money people were willing to give to their partner when they believed they would meet their partner or when they believed they were very similar to their partner. It did influence the amount of money that highly neurotic individuals were willing to give in these studies when they did not think they would meet their partner or did not think they were similar to their partner.
Putting all of this together, then, trusting strangers sometimes requires effort. In particular, when you believe you will never meet someone and you have no particular similarity to them, you believe there is a risk to trusting them. The more strongly you react to that kind of risk, the more effort you need to put in to trust a stranger.