De Dreu et al (2011)
Uses: Hormones
Aim: To investigate whether oxytocin have an effect on the relationship between ingroup and outgroups.
Method: true double blind, placebo, controlled experiment.
Procedure:
All participants (69 nice) are split up into oxytocin and control group. Oxytocin group is sprayed with nasal spray while control group is sprayed with placebo.
They were then faced with the trolley problem and only the singled outed person's name is revealed to them as either a Dutch, Middle Eastern or German name. They were asked to make the decision of either sacrificing the one person and save the other 5 or they will let the other 5 die while saving the one person.
Results:
Oxytocin groups and control groups are equally likely to sacrifice outgroup targets but oxytocin group are less likely to sacrifice ingroup targets than the control group. Experiment 4 used German names and experiment 5 used middle eastern name and they had similar results. This shows outgroup targets are sacrificed more frequently than ingroup targets in the oxytocin group while in control group they were the same. They are not actively discriminating against outgroup but there is favouritism within the ingroup.
Frequency of sacrificing outgroup targets: Equal in both groups
Frequency of sacrificing ingroup targets: less in oxytocin condition
Are outgroup sacrificed more frequently than ingroup: yes in the oxytocin condition
Conclusion:
Rather than making humans prosocial, oxytocin functions to strengthen an evolutionary evolved and rather a functional tendency to discriminate between in-group and out-group as well as to give members of one’s own group preferential treatment. Such ethnocentrism has adaptive value to individuals and their groups but, unfortunately, also paves the way for intergroup bias, conflict, and violence.
De Dreu, C. K., Greer, L. L., Van Kleef, G. A., Shalvi, S., & Handgraaf, M. J. (2011). Oxytocin promotes human ethnocentrism. Proceedings of the National Academy of Sciences of the United States of America, 108(4), 1262–1266. https://doi.org/10.1073/pnas.1015316108