Oxytocin found to drive both love and hate

A new study by researchers at the University of Amsterdam have found that oxytocin, which is usually known for its role in causing feelings of love or affection, also has links with human ethnocentrism. While oxytocin fuels favoritism within a group, it is also associated with derogation between groups.

Ethnocentrism, the view that one’s own group is important and superior to others, often results in prejudice, xenophobia and even violence. However, it can also serve to bind members within a group, given that they have common ground as a basis for cooperation and coordination. For a group to prosper, its members, who are vulnerable to exploitation, need to know who they can trust or mistrust.

A team of researchers in the Department of Psychology at the University of Amsterdam, led by Carsten K. W. De Dreu, conjectured that ethnocentrism may have links with oxytocin, which is known to promote cooperation within groups. Oxytocin is a peptide produced in the hypothalamus of the brain and subsequently released into the bloodstream and brain. As both a hormone and neurotransmitter, it interacts with reward-processing circuits and thereby promotes trust and cooperation.

The researchers had males self-administer oxytocin or a placebo and then perform computer-guided tasks that measured manifestation of ethnocentrism, both in relation to in-group favoritism and out-group derogation.

A variety of tests were used. Some groups were given the Implicit Association Test (IAT), a technique that assesses implicit evaluation by asking participants to categorize positive words and in-group names, as well as negative words and out-group names. Subsequently, they are asked to group positive words and out-group names, and then negative words and in-group names. The results of this test suggested that in-group/positive associations were faster than out-group/positive ones with more oxytocin.

Another test involved infrahumanization, which is the tendency to associate secondary emotions (rather than primary emotions) with in-group members to a greater extent than out-group members. Secondary emotions, such as delight and embarrassment, are seen as uniquely human, while primary emotions, like joy and sadness, are not. This is a manifestation of ethnocentrism. However, these tests showed that while oxytocism promotes in-group favoritism, it does not necessarily promote out-group derogation.

A third test used the Moral Choice Dilemma Task, which presented participants with ethical dilemmas. For example, a trolley is approaching five people, who will be killed upon impact. One may hit a switch that will divert the trolley in such a way that only one person gets killed. In this case, hitting the switch and doing nothing are both defensible choices.

These dilemmas were presented to participants using a variety of different names, some typical to the in-group and some to the out-group. With more oxytocin, males were more likely to sacrifice out-group than in-group targets when presented with these dilemmas.

The experiments suggest that oxytocin may play a role in the occurrence of conflict and violence between social and ethnic groups.