People often conform to others with whom they associate. Surprisingly, however, little is known about the possible hormonal mechanisms that may underlie in-group conformity. Here, we examined whether conformity toward one's in-group is altered by oxytocin, a neuropeptide often implicated in social behavior. After administration of either oxytocin or a placebo, participants were asked to provide attractiveness ratings of unfamiliar visual stimuli. While viewing each stimulus, participants were shown ratings of that stimulus provided by both in-group and out-group members. Results demonstrated that on trials in which the ratings of the in-group and out-group were incongruent, the ratings of participants given oxytocin conformed to the ratings of their in-group but not of their out-group. Participants given a placebo did not show this in-group bias. These findings indicate that administration of oxytocin can influence subjective preferences, and they support the view that oxytocin's effects on social behavior are context dependent.

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Psychological Science
Erasmus Research Institute of Management

Stallen, M, de Dreu, C.K.W, Shalvi, S, Smidts, A, & Sanfey, A.G. (2012). The Herding Hormone: Oxytocin Stimulates In-Group Conformity. Psychological Science, 23(11), 1288–1292. doi:10.1177/0956797612446026