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Psychoneuroendocrinology. 2015 Oct;60:114-9. doi: 10.1016/j.psyneuen.2015.06.003. Epub 2015 Jun 17.

Oxytocin enhances implicit social conformity to both in-group and out-group opinions.

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School of Psychology and Center for Studies of Psychological Application, South China Normal University, Guangzhou, China.
Key Laboratory for Neuroinformation, Center for Information in BioMedicine, University of Electronic Science and Technology of China, Chengdu, PR China.
School of Psychology and Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; Department of Psychology, National University of Singapore, Singapore; Singapore Institute for Neurotechnology (SINAPSE), Center for Life Sciences, National University of Singapore, Singapore. Electronic address:


People often alter their own preferences when facing conflicting opinions expressed by others. This is known as the social conformity effect and tends to be stronger in response to opinions expressed by in-group relative to out-group members. The hypothalamic neuropeptide oxytocin promotes in-group favoritism, elicits parochial altruism, and stimulates in-group conformity under explicit social pressure. In a double-blind, placebo-controlled design experiment using a facial attractiveness judgment task, we therefore investigated whether social conformity to either in-group or out-group opinions is influenced by intranasal oxytocin treatment when social pressure is implicit. After oxytocin or placebo treatment, male participants were asked to rate the attractiveness of unfamiliar Chinese female faces, and then they were informed of ratings given by peers from an in-group (Chinese) and out-group (Japanese) simultaneously. They were subsequently asked unexpectedly to re-rate the same faces. Results showed that oxytocin increased conformity to both in- and out-group opinions. Thus oxytocin promotes conformity to opinions of both in- and out-group members when social pressure is implicit, suggesting that it facilitates 'tend and befriend' behaviors by increasing the general level of social conformity.


In-group bias; Oxytocin; Social conformity; Tend and befriend

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