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In Oxytocin We Trust

Controversial uses of a reproductive hormone

Michelle Shum

Fall 2005

oxytocin reproductive hormone    A candidate surreptitiously mists the air, brainwashing a crowd at a political rally. A government interrogator pries classified material from a terrorist with a trust-inducing chemical. Unscrupulous marketers successfully snare consumers into a department store pumped with a mind-altering hormone. Rest assured, these bizarre conspiracies will most likely never occur. However, recent scientific advances have yielded a hormone-based drug that may promote trusting behavior in humans, and further research of this substance may uncover new treatments for patients with social phobias and other clinical disorders.

    A Swiss research team has discovered “trust in a bottle,” an experimental nasal spray containing the hormone oxytocin, which may inhibit anxiety and promote feelings of trust among its users. Ernst Fehr, PhD, Director of the Institute for Empirical Research in Economics at the University of Zurich, led the study and recently published his findings in Nature and the American Economic Review.

    Oxytocin has long been considered a strictly reproductive hormone that is present in both sexes.    It works by “promoting monogamy, devotion, and selfless behavior required to raise offspring,” says Dacher Keltner, PhD, of the University of California, Berkeley (UC Berkeley).

    The secretion of oxytocin by the neuroendocrine cells of the posterior pituitary gland is controlled by the hypothalamus, which regulates basic bodily functions such as hunger, thirst, and body temperature. It is primarily secreted in females to stimulate uterine contractions during childbirth and to induce lactation. Oxytocin is also released in both men and women during sex to facilitate mate-bonding, a mechanism Dr. Fehr describes as enabling individuals to “overcome their natural avoidance of proximity and to inhibit defensive behavior.”

    Markus Heinrichs, PhD, and Michael Kosfeld, PhD, at the University of Zurich, worked with Dr. Fehr to examine the hypothesis that oxytocin does indeed facilitate trust. According to their analysis, comparing behavior in a group of subjects that received oxytocin with a control group that received a placebo indicated that oxytocin may provide a biological basis for trusting behavior in humans. The study included 178 male student participants who received either a single intranasal dose of 24 international units of oxytocin or a placebo. In the first portion of the experiment, which specifically tested oxytocin’s effect on trusting behavior, each subject played the role of an investor who could lend a “trustee” up to 12 units of money equivalent to approximately 32 cents. The trustee tripled the investor’s money but was not obligated to return any amount of the investment.

    Of the 29 participants who received oxytocin, 45 percent invested the maximum amount of 12 monetary units, thereby demonstrating what Dr. Fehr termed “maximal trust.” Only 21 percent were stingy enough to invest fewer than eight monetary units, whereas the placebo group exhibited the antithesis of trusting behavior. Only 21 percent of the placebo participants invested all 12 units, whereas 45 percent invested at much lower levels. Overall, investors who inhaled oxytocin invested 17 percent more than investors on the placebo.

    The second portion of the study examined subjects’ willingness to take risks—whether oxytocin allowed users to overcome a general aversion to risk or if it specifically facilitated trusting behavior in social interactions. When investors were asked to entrust money to a computer program, no significant difference was seen between the average amounts invested by the oxytocin and placebo groups. As a result, Dr. Fehr and his colleagues concluded that oxytocin “specifically affects trust in interpersonal interactions.”

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