Is Trust Uniquely Human?

This post originally appeared here.

One of us (Sara) recently published a book about trust in the healthcare system. While she was spending countless hours studying the nature of this kind of trust, including interviewing over 70 people who self-proclaimed as having lost trust in the healthcare system, she also came across a sizable literature on the question of whether or not trust is uniquely human. As it turns out, it’s not, although the nature of trust in other species might be less sophisticated than the human version of this concept. 

First, though, it’s important to understand what “trust” actually means, as we’ve noticed that many people think they have a good working definition but for most the concept is still quite vague. In an interpersonal setting, which is where trust most frequently manifests, trust is defined as “confidence in the dependability of someone or something.” Trust is also frequently framed in terms of risk, e.g., whether or not you feel comfortable taking the risk of trusting someone, since the stakes can be high if you are wrong and the other person (or people or institution) is not trustworthy. In this sense, trust is inherently future-oriented in that it has to do with making a prediction about whether someone (or a group of people) will act with benevolence, honesty, and fairness. There’s also a distinction between interpersonal trust (trust in another individual) and institutional trust (trust in an institution, such as the government or the police). Despite their technical separation, there’s good reason to believe  that these concepts affect each other. That is, high levels of interpersonal trust often correspond with high levels of institutional trust and vice versa. 

What is going on in the brain when we feel trust? 

There is most likely a release of oxytocin when someone feels trust, which is associated with a reduction in fear, most likely the fear of being wrong in trusting someone. For example, if you loan someone money, this might be based on a feeling of trust that they will pay you back and is associated with an increase in oxytocin, which is associated with a reduction in fear, in this case the fear that you won’t get the money back. Other studies have suggested that decisions to collaborate, which can often be taken as a signal of trust, are associated with increased activity in the ventral striatum and medial prefrontal cortex. The ventral striatum is often associated with positive emotions. 

Is all of this uniquely human? Or do other species experience this phenomenon? 

There is reason to believe that some non-human primates participate in the concept of trust. In one study, for example, chimpanzees in captivity that seemed to be “friends,” e.g., spent a lot of time together and groomed each other frequently, were given two choices: a rope that if pulled would give only them food and leave the other chimp empty-handed or a rope that gave their friend the reward that could also be shared with them. Chimps were more likely to choose the latter option when paired with friends than with non-friends. This suggests that, at least in the context of preexisting relationships, chimps trust their friends in a similar way that humans do. In other words, chimps were making decisions based on predictions of their friends’ future behaviors and trusting that these behaviors would come to life. 

While it’s likely that chimpanzees probably do not experience the full breadth of the concept of trust that humans do (for example, there’s no such thing as institutional trust in the animal kingdom), it’s important to note that trust is not a uniquely human phenomenon. The concept of taking a chance that someone else’s behavior will confer a reward upon oneself is a concept that exists in the human and animal kingdoms alike. In the end, we can see that this all-important concept is in some ways a very basic need and emotion.