A hormone (arginine vasopressin) previously implicated in monogamy and aggression in animals also promotes trust and cooperation in humans in risky situations, California Inatitute of Technology researchers say. The findings, published the week of February 8, 2016 in the online edition of PNAS, could prove useful for helping groups cooperate beneficially. The article is titled “Vasopressin Increases Human Risky Cooperative Behavior.” Research in rodents has shown that the hormone arginine vasopressin (AVP) promotes monogamous pair bonding and parental behavior, but also aggression in males. "Part of the dark side of monogamy is that an AVP-pumped-up male is more likely to behave aggressively toward intruders," says study co-author Colin Camerer, Ph.D., the Robert Kirby Professor of Behavioral Economics at Cal Tech. In the new study, Dr. Camerer and his team tested the hypothesis that AVP might also play a role in social bonding in people and could help explain our species' cooperative tendencies. "One of the reasons humans, rather than apes, rule the world is that we do things that require a great deal of trust. We cooperate in large-scale groups," Dr. Camerer says. "Where does that come from? Is it something like pair bonding, but just scaled up? And if it is, what role does AVP play?" To investigate these questions, Dr. Camerer and his colleagues administered a nasal spray containing AVP or a hormone-free nasal spray (a placebo) to 59 male volunteers, aged 19 to 32 years old. Pairs of subjects then used computers to play a so-called “assurance” game in which they had to choose whether or not to cooperate with another player; "assurance" comes from the fact that subjects will take a risky action if they are sufficiently assured that others will, too.
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