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Researchers Find Trust to Be a Hormonal Affair

June 02, 2005|Robert Lee Hotz | Times Staff Writer

The essence of trust -- a catalyst of all friendship, trade and democracy -- is a neurochemical that can be distilled into a nasal spray and used to ease the natural suspicion of strangers, researchers reported Wednesday.

The discovery is the first direct evidence that a hormone called oxytocin, which evolved 100 million years ago to aid mating among fish and breast-feeding among mammals, also promotes trust between human beings, the scientists said.

The research stirred misgivings about the potential for misuse by marketers or political operatives who might use oxytocin to surreptitiously gull a sales prospect or to prime a campaign crowd. The scientists acknowledged the risk but discounted the concern.

In an experiment whose results were published in the current edition of the journal Nature, researchers at the University of Zurich in Switzerland and Claremont Graduate University determined that people who inhaled half a dozen puffs of an oxytocin nasal spray were measurably more likely to risk all their money with a stranger, without consciously knowing why.

"If I increase your level of oxytocin, I can induce you to overcome your anxiety in trusting a stranger," said Paul J. Zak, director of Claremont's Center for Neuroeconomics Studies and an author of the research paper. "It is a [biochemical] signal we induce unknowingly all the time by looking people in the eye or shaking someone by the hand."

Although the researchers set up their experiment to test the effects of oxytocin on financial decisions, they believe the hormone is the keystone of a normal social life.

Trust is as crucial in love and diplomacy as it is in finance. Social phobias, which hinge on the inability to trust other people, are the third most common mental health problem.

"My conjecture is that it applies broadly to all kinds of social interactions where your trust could be abused," said economist Ernst Fehr in Zurich, the senior member of the research team.

The finding is an important advance in understanding the biology of human behavior, experts said.

"The finding has powerful implications for understanding the brain," said University of Iowa neuroscientist Antonio R. Damasio, who was not involved in the research. "Remove trust and you compromise love, friendship, trade and leadership."

Researchers have long known that the hormone was important in the social behavior of animals.

Oxytocin plays a role in human childbirth, when it enhances uterine contractions during labor and may be administered to ease a difficult birth. For nursing mothers, it eases the production of breast milk.

Until now, its role in human social behavior had been a matter of conjecture.

To investigate its effects, researchers set up an experiment in which investors could choose to risk money with strangers in a classic economics investment game. The investors had to decide how much to invest without knowing anything about their trading partners.

"We were trying to understand why people are so trusting with people they have never seen and will never see again," Zak said.

In all, 178 students from universities in Zurich participated.

The students were separated into groups of investors and trustees, who were not allowed to communicate with each other.

Each investor began the experiment with a fund equal to about five Swiss francs that could be invested with a trustee. Any investment would be automatically tripled. The trustee then could decide how much, if any, of the money would be paid to the investor.

Both investor and trustee could take home cash at the conclusion of the experiment, based on how they managed the investments. The more the trustee withheld, the larger his final cash payoff.

By design, the investors were caught in a dilemma.

If they trusted their partners and invested the maximum allowable, they might reap triple their investment. But they could just as easily lose everything if betrayed by a partner who decided to keep all the proceeds.

To heighten the dilemma, the researchers arranged the experiment so that each investor could invest only once with each trustee. An investor could not benefit from his experience with a particular trading partner and a trustee had no incentive to treat the investor fairly because there was no repeat business.

Before launching into four rounds of investment trading, they were given oxytocin or a placebo at random.

The oxytocin used for the experiment was in a hormone supplement once prescribed to women who had difficulty breast-feeding. It is no longer sold in the United States.

The researchers found that the volunteers who took oxytocin were twice as likely to risk all their money with a stranger.

Overall, those who inhaled sprays of oxytocin invested 17% more than investors who received a placebo.

Moreover, the hormone only affected someone's response to another person. Those who engaged in financial trading with a computer partner showed no effect from the hormone, the scientists said.

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