Childbirth Hormone Increases Trusting Nature

It sounds like something straight out of a fairy tale -- a potion that makes people trust others more than they normally would.

But the news comes from scientists, not the Brothers Grimm. Their report can be found in the scientific journal Nature, not on a shelf with children’s books such as Jack and the Beanstalk or Cinderella (or, for that matter, political conspiracy thrillers like The Manchurian Candidate.)

The experiment had nothing to do with elves, wizards, or bubbling cauldrons of mysterious brews. Instead, it centered on a chemical called oxytocin. Oxytocin appears to enhance trust, write the researchers, who included Michael Kosfeld, PhD, of Switzerland’s University of Zurich.

Click here to read Web MD's "What Your Brain Knows About Trust."

What’s Oxytocin?

Oxytocin is a hormone found in many mammals, including humans.

In nonhuman mammals, oxytocin is important in social attachments and affiliations -- who the animals hang out with. In people, oxytocin plays a role in milk secretion and in inducing labor. The hormone also functions in areas of the brain that affect emotional and social behavior. It plays a role in bonding after mating, bonding after childbirth, sexual behavior, and the ability to form normal social attachments, says the study.

A Recipe for Trust

Kosfeld and colleagues tested two nasal sprays -- one with oxytocin and one without it. Otherwise, the sprays were identical.

The study included 194 healthy male students who were about 22 years old. They were told not to eat or drink two hours before the experiment and to skip cigarettes, alcohol, and caffeine for 24 hours prior to the test.

The men got a single dose of one of the nasal sprays without knowing what the sprays contained. Fifty minutes later, the test began.

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Trust Test

First, a group of men were randomly and anonymously paired up into one-on-one sets of “investors” and “trustees.” The investors had a certain amount of money, and they could give any portion of it to their trustee to make the money grow.

But the trustees weren’t always trustworthy. They could break the rules and pocket some of the investor’s cash. The investors had no way to know in advance what kind of trustee they were dealing with.

Oxytocin appeared to increase trust. Investors who inhaled oxytocin were more trusting than those who got the placebo.

The trustee’s behavior wasn’t affected by either nasal spray. The trustee’s job didn’t require trust; they didn’t have any of their own money on the line.

Next, the other participants took the same test, but their “partner” was a computer, not a person. Oxytocin didn’t make any difference under those circumstances. That suggests that oxytocin affects interpersonal trust, not willingness to take a risk, say the researchers.

Blind Trust?

The researchers say oxytocin may influence “prosocial approach behavior.” In other words, it could make people more willing to approach others.

That’s what happened in the trust test. The trustees couldn’t contact the investors first; the investors had to start the process.

Oxytocin didn’t take away free choice. But it may have inclined people to be more trusting. The results weren’t due to mood or calmness, say the researchers.

Click here to read Web MD's "Brain Knows Imagined Pain."

Villain’s Brew or Therapeutic Resource?

Kosfeld and colleagues say their findings could be exploited, but they also hope that the results could help treat conditions including social phobias and autism, where trust and social approach skills are flawed.

Here’s how a journal editorial puts it:

“Some may worry about the prospect that political operators will generously spray the crowd with oxytocin at rallies of their candidates,” writes Antonio Damasio, MD, a neurology professor and head of the University of Iowa’s neurology department.

“The scenario may be rather too close to reality for comfort, but those with such fears should note that current marketing techniques -- for political and other products -- may well exert their effects through the natural release of molecules such as oxytocin in response to well-crafted stimuli. Civic alarm at the prospect of such abuses should have started long before this study, and the authors cannot be blamed for raising it.”

“Whatever the beneficial biomedical applications, or the abuses, may turn out to be, Kosfeld et al. have made a valuable contribution to our understanding of the role of neuromodulators in human behavior that involves choice,” says Damasio.

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By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Kosfeld, M. Nature, June 2005; vol 435: pp 673-676. Damasio, A. Nature, June 2005; vol 435: pp 571-572. News release, Nature.