The Trust Hormone

Oxytocin may make you more trusting, but is that a good thing?
Between emails from Nigeria promising millions of dollars in exchange for your bank account number and advertisements proclaiming the deal of a lifetime, someone is always after your money.

While no one is immune from the occasional bad investment, most of us pride ourselves on being too smart to be duped out of our hard-earned cash.

Recently though, researchers have discovered that the naturally occurring hormone oxytocin might make us more trusting with our money—even after someone betrays us. A Swiss study detailed in the May issue of the journal Neuron showed that volunteers who were given the hormone oxytocin through a nasal spray were more trusting than those given a placebo.

Using functional magnetic resonance imaging, a scanning technology that measures neural activity, the researchers found that the amygdala, the brain’s fear center, was less active in the group that received oxytocin.

Reducing amygdala activity lowers social fear and anxiety, says Markus Heinrichs, author of the study and psychology professor at the University of Zurich. Eventually, he thinks oxytocin could be used to treat disorders characterized by an overactive amygdala, like social phobia.

However, the prospect of inducing trust with a hormone—particularly if administered without consent—raises a few eyebrows. Ethicists worry about the potential for misuse, and one company is already marketing a “trust perfume” made with oxytocin.

“If it turns out that oxytocin makes someone more pliable and receptive, one can think of nefarious uses,” says Paul Root Wolpe, a neuroethicist at the University of Pennsylvania. For instance, he says it would be inappropriate to use oxytocin on prisoners or criminal suspects to elicit a confession because it is unethical to give drugs without consent, not to mention a violation of the Geneva Conventions.

Other researchers assert that oxytocin research is much more likely to lead to useful therapies than abuses, and they say the Neuron study was an important step. They think oxytocin could be used as a treatment for disorders such as social phobia and even autism. Those disorders are characterized by fear, so some think oxytocin could help make people more trusting and less fearful in social situations.

“People are very excited about oxytocin’s use,” says Adam Guastella, a senior clinical research fellow at the Brain and Mind Research Institute at the University of Sydney, Australia, who is not connected with the study. “There are many potential applications.”

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Oxytocin is a mammalian hormone produced in the hypothalamus, an almond-sized area at the base of the brain. The hormone is released by the adjacent pituitary gland, particularly during labor and breastfeeding. It has also been associated with sexual arousal, giving it the nickname the “love hormone.” But oxytocin’s function extends well beyond love, and recent studies have examined its role in trust and social interactions.

A 2005 study in Nature, for example, found that participants who received oxytocin were more likely to trust other people than participants who received a placebo. The recent Neuron study expands on the earlier experiment, showing that not only are people more trusting, but they are more trusting even when they know they are likely to be betrayed. The study also combines brain imaging data with the behavioral data to see which regions of the brain are affected by oxytocin.

“This was the first study where we combined brain imaging, social behavior and substance administration,” says Heinrichs.

Heinrichs and his colleagues performed the experiment on 49 male volunteers. Half of them received a nasal spray of oxytocin and half did not. Then each group played a trust game. The men had to decide whether or not to invest money with another volunteer in hopes of gaining more money. The amount they chose to invest would automatically be doubled. Then the volunteer receiving the money could decide how much, if any, to give back to the investor. The more money the volunteer invested, the more he stood to gain or lose.

The two groups played a round of six games and afterwards were told how often their investments paid off. About half the time, the trustee betrayed the investor. Each group then played another round of trust games with different trustees, and in this round the investors in the placebo group invested less often. But the oxytocin group continued to invest the same amount of money with the trustees.

After learning that their trust had been betrayed, the placebo group’s average investment dropped from about 7.7 to 6.5 out of a possible 12, while the oxytocin group’s average stayed about the same.

All participants were hooked up to a scanner while playing the trust games so their brain activity could be monitored. Researchers found that the amygdala was much more active in the placebo group than in the oxytocin group.

“The amygdala is very clearly identified with fear and anxiety,” says Ron Stoop of the Center for Psychiatric Neuroscience at the University of Lausanne, Switzerland. “When it is activated you get a fear response; when inactivated, people get very calm.”

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Oxytocin binds to proteins embedded in the cell membrane of the amygdala. This binding activates neurotransmitters that inhibit cells in the amygdala, reducing neural activity. The exact length of oxytocin’s inhibitory effect is unknown, but Stoop says it appears to only be short-lived.

Researchers are now trying to figure out whether oxytocin affects other areas of the brain, says Stoop. Oxytocin could be specific to the amygdala or it could have a general effect on the entire brain, he adds, noting that there are receptors in other parts of the brain like the hippocampus, where memories are formed, and the stria terminalis, which is a band of fibers that connects the amygdala to the hippocampus.

Oxytocin could eventually be used to treat social disorders characterized by excessive fear, such as social phobia, autism and post-traumatic stress disorder. Heinrichs says that the feeling of fear in these disorders is caused by a hyperactive amygdala. He thinks that oxytocin could help reduce that hyperactivity.

But Paul Zak, a neuroeconomist at Claremont University who studies how neural activity influences economic decisions, says it is premature to speculate on clinical uses of oxytocin. The study only evaluated its effects on men, and since oxytocin has a role in breastfeeding and childbirth, it would be important to determine whether the hormone has a different effect on women, he says.

Zak was also critical of the neural imaging used in the Neuron study. One effect of oxytocin is that it lowers a person’s heart rate. Since imaging shows brain activity based on the amount of blood flow, the activity in the amygdala might be lower not because it is being inhibited by oxytocin, but simply because there was less blood flow to the brain in general, according to Zak.

Sydney’s Guastella says it is also important to understand whether or not oxytocin increases pleasure or feelings of reward from social interactions. He says that for oxytocin to effectively treat social disorders, it will have to increase the person’s desire to interact with others, not just increase their likelihood to trust.

So far, giving people extra oxytocin has not produced any harmful side effects, but this needs to be researched better before being used as treatment.

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Still, researchers are taking oxytocin seriously, and not just as a potential clinical treatment. They also acknowledge that its ability to shape behavior raises certain ethical questions. “You can imagine a wide range of scenarios,” Stoop says. He points to politicians potentially using oxytocin to gain voters’ trust or executives who might use it to garner trust in a business deal.

“The danger would be if you could administer oxytocin in a way that someone would not realize it,” Heinrichs says. But, he says, that would be difficult to do since oxytocin has to be administered through a nasal spray to be effective.

However, the Florida-based company Verolabs is already marketing a “liquid trust” perfume. Company officials would not return phone calls, but their website boasts that the perfume will help wearers gain the trust of others in both their professional and romantic lives.

Heinrichs and others dismiss this idea, saying that aerosolized oxytocin would not affect the brain because it quickly degrades. Oxytocin in a perfume spray would diffuse rapidly in the air and it wouldn’t reach the brain in high enough concentrations to have any effect, researchers say. Companies are just looking to make a quick buck, Heinrichs says. Even so, the University of Pennsylvania’s Wolpe still has concerns. “It does raise a number of questions on how it is we form relationships with other people and why some people are more trusting and others are more suspicious and wary,” he says.

But, he also points out that the effects shown in the Swiss study were relatively mild. Oxytocin didn’t cause a dramatic change in behavior, so it would be premature to jump to conclusions on how it could be used, he says. “This isn’t a magic bullet to put something over on someone,” he says.

It is important to figure out the context in which oxytocin could or should be used, says Eric Racine, director of the neuroethics research unit at the Institute of Clinical Research in Montreal. “This study really reflects the exciting advances that have been made in neuroscience, but also the potential ethical implications of knowing how we think, feel and behave,” says Racine. While other fields of science such as genetics and stem cell research have long spurred ethical debates, advances in neuroscience are just starting to raise similar ethical questions, Racine says. Just because we can shape behavior and feelings, he adds, doesn’t mean we should.