Exposure to the hormone oxytocin increases the trust that a person places in another. Will disclosure lead to the treatment of social anxiety, or will it be misused by crooks?
Suspicion and trust are two sides of the same coin. During evolution, humans and other animals have carefully walked the line between the need to survive and the benefits and pleasures that come from social cooperation. When a burly man beckons you into a dark alley, the right thing to do would be to walk away quickly, but you might miss an opportunity to discover a great, unknown restaurant.
A study published in the latest issue of the journal "Nature" examined the biological foundations of trust. The researchers - Dr. Ernst Fehr, Dr. Michael Kosfeld and Dr. Markus Heinrichs from the University of Zurich - discovered to their surprise that the trust a person gives to others depends to a large extent on the activity of biological mechanisms: smelling a spray containing a hormone called oxytocin increased the person's level of trust in others.
Oxytocin, a hormone produced in the hypothalamus in the brain, plays many roles. It stimulates contractions during childbirth, and after the baby is born it helps release milk from the mother's breast. In some animal species, especially in rats, it has been proven that the hormone regulates behavior patterns such as motherly love and establishing contact between males and females and affects the ease with which the animal approaches strangers.
Dr. Kosfeld and Dr. Heinrichs therefore had good reason to suspect that oxytocin may regulate trust in humans as well. They also knew, thanks to the work of other researchers, that hormones containing protein particles called peptides could reach the brain if given in spray form. Oxytocin is one of those peptides.
To investigate the role of oxytocin in encouraging trust between people, the researchers invented a game in which the participants of the experiment - 178 college students - participated. The game involved "investors" and "trustees", who did not know each other's identity. Each investor received money, 12 units each worth about 30 US cents. He could keep all the units with him or give four, eight or all 12 units to the trustee - something that would triple their value. The trustee, for his part, could return the units to the investor after tripling the value, or keep them with him.
In previous experiments with this game, it became clear that investors initially behave cautiously and increase the amount they give to trustees only after their partners in the transaction behave fairly and return the money they invested. But the new study did not allow the participants to act in accordance with such a strategy: the interaction between the investors and the trustees was one-time.
Before the start of the experiment, all investors and trustees sprayed a spray into their noses. However, in some cases the spray did not contain oxytocin, but a "neutral" substance. Among investors sprayed with oxytocin, 45% invested all 12 units, while only 21% of those sprayed with a dummy spray did so. On average, the group injected with oxytocin transferred 17% more money to the trustees compared to the amount transferred by the control group. Oxytocin, it turned out, encourages trust between humans.
How can we know that oxytocin increases trust between people, and does not cause a general feeling of cordiality towards the other person or reduces the reluctance to take risks? The researchers showed this in two ways. First, the reaction of the trustees. These people, contrary to the opinion of many, did not take the money and run away. The investors generally received a return for their investment, although less than half the amount tripled. However, the amount returned to investors did not change between the trustees who inhaled oxytocin and the trustees who inhaled a dummy spray. This finding strengthens the hypothesis that oxytocin induces trust specifically, and does not encourage sociable behavior in general.
The hypothesis that oxytocin increases trust between humans was further strengthened when investors were told that a computer, not a human, would be the other party to the transaction and that the amount to be returned would be determined randomly. In such a situation, the group that injected oxytocin and the control group invested equal amounts.
The authors of the study hope that its findings will lead to the treatment of social anxiety and possibly even autism, although neuroscientists who were not involved in the study believe that the road is still very long. "I believe that oxytocin may help people who show a pathologically low level of trust in other people," said Dr. Fehr, "but you cannot make people develop a pathologically high level of trust in others by giving them oxytocin." His office on oxytocin is baseless, Dr. Fehr added.
