The reality is more complex. A nice demonstration of this complexity comes from a study in the December, 2012 issue of Psychological Science by Mirre Stallen, Carsten De Dreu, Shaul Shalvi, Ale Smidts, and Alan Sanfey. These researchers focused on the influence of oxytocin on people’s preferences for new objects.

Groups of six participants were brought to the lab where they were administered oxytocin or a using a nasal spray. Participants were each seated in front of a computer, and they did about 40 minutes of filler tasks to allow the oxytocin to have its effect. Then, participants were informed that the group was divided into two teams. Each participant saw a series of novel icons and were asked to rate how much they liked them. At the bottom of the screen, they could see ratings that they believed were given by other participants. (In fact, the ratings were generated by the experimenters.) They could see whether the ratings came from members of their team or members of the other team.

If oxytocin just increases overall trust, then we would expect that people who are given oxytocin would give preference ratings that are more similar to the other ratings of all of the participants. However, the researchers suggested that oxytocin may have a more specific effect. It might increase people’s tendency to to the ideals of other members of their own social group. In that case, we would expect that people’s ratings would track those of other members of the same team.

To provide a critical test of this possibility, on a certain number of trials, the icons got divergent ratings from the participant’s team members and the other team. Sometimes the team members gave the icon a high preference rating while the other team gave it low ratings and sometimes the opposite occurred.

On these trials, participants who got the placebo were relatively uninfluenced by ratings of their team members. However, the participants who got oxytocin gave significantly higher ratings when their team members also gave the icon a high rating than when they gave it a low rating.

This result suggests that oxytocin increases people’s sense of closeness to their social group (even when that social group is arbitrarily created in the lab). This closeness leads people to generate attitudes that conform to those of their group members. However, it does not increase general trust of all people. The attitudes of people from other groups do not influence their behavior.

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