Scientists have found the chemical equivalent of the perfect sales pitch: a hormone that makes us more trusting than we normally are.
Volunteers in a study were told they were participating in a decision-making experiment. Those who inhaled the hormone, which occurs naturally in the brain, were more likely to entrust others with large sums of money than were volunteers who inhaled no hormone.
The experiment has profound implications about the nature of human trust. Researchers said their finding might lead to cures for people with disorders that prompt them to hold others at arm's length, but they acknowledged that the chemical, which is widely used in medicine, could be misused.
The experiment, involving 128 participants, was conducted by scientists at the University of Zurich and other academic centers. Researchers had some volunteers inhale oxytocin and then examined how they and those who inhaled a placebo invested money in a mock transaction.
The transaction involved taking a risk: handing over money to a "banker" who had the option of returning the investment with a profit or withholding principal and profit, leaving the investor with nothing. The experiment was a measure of the trust that the investors had in the bankers.
Volunteers who inhaled oxytocin were more likely to trust the banker with money and risk larger sums, the researchers said in an article published yesterday in the journal Nature.
The scientists said they made sure the chemical was not merely enhancing risk-taking behavior by substituting bankers with computers. Without the interaction with a human, the hormone had no effect.
Oxytocin did not alter the behavior of the bankers, which strengthened the researchers' belief that the hormone was influencing trust. Bankers did not need to trust investors, because they were taking no risk. A banker's decision to return money was more a question of fairness, which oxytocin did not affect.
Trust is central to virtually every positive social relationship, from intimate love and friendships to financial transactions and politics, but little had been learned about its biological correlates in the brain, researchers said. Oxytocin is known to be activated in a range of social relationships in many animals, but this is the first time scientists have shown that it can serve as a switch to enhance trust in human relationships.
Ernst Fehr, director of the Institute for Empirical Research in Economics at the University of Zurich and one of the scientists who conducted the experiment, said the peak effect of oxytocin was seen after about 50 minutes and it wore off after two hours.
"Some may worry about the prospect that political operators will generously spray the crowd with oxytocin at rallies of their candidates," said neurologist Antonio R. Damasio of the University of Iowa, who has long studied the neurobiology of human emotions and who wrote a commentary accompanying the study.
At the same time, he added in an interview, politicians and marketers were probably already triggering the natural release of oxytocin in the brains of audiences through their campaigns. "I am more alarmed about the manipulations of marketing than the possibility of oxytocin sprays," he said.
Ethicists and theologians said manipulating the brain at a neurochemical level was different from ordinary kinds of persuasion. David A. Hogue, a theologian and pastoral psychologist at Garrett-Evangelical Theological Seminary in Chicago, said that "anytime we are working directly on the central nervous system, it feels much more intrusive."
Brent Waters, an associate professor of Christian social ethics at the seminary, which is affiliated with Northwestern University, questioned whether trust could be so easily reduced to chemical constructs. "The experiment presupposes a highly diminished and reductionistic understanding of what trust means," he said.
Damasio, the neurologist, said it was inevitable that science was going to learn more about the biological correlates of trust and other human emotions. He said he saw no reason such knowledge should affect notions of human dignity and agency.
"The question is do you want to preclude yourself from understanding, do you want to deny yourself the entire compass of knowledge that can come from science?" he asked.
Fehr and the study's other authors acknowledged the potential for misuse of oxytocin, but he argued that it was no different than any other prescription product. Regulation, he said, could limit abuse.
Hogue, the theologian and pastoral psychologist, said the research held out the possibility of reconciliation between individuals and the potential of healing rifts between political groups, even nations: "While spraying oxytocin on one's political or religious adversaries may be strategically difficult, comprehending the biological correlates of trust could conceivably offer promising avenues for reassessing and reconciling conflict."