Researchers from the University of Zurich, including Charlotte Debras and Adrian Jaeggi from the Institute of Evolutionary Medicine, ran soccer tournaments with the Indigenous Tsimane in the Bolivian Amazon to study natural changes in oxytocin during competition. The Tsimane were selected because their lifestyle can influence hormones and because social bonds are central in highly interdependent communities. The team measured oxytocin by collecting urine samples from players before and after matches.
Findings showed the largest oxytocin increases after matches versus familiar rivals. The rise was smaller when opposing teams came from different communities, but oxytocin also rose when the Tsimane played non-Tsimane opponents. This pattern indicates oxytocin reacts to the salience of the opposition, with heightened reactivity toward both known rivals and a clearly defined out-group.
Researchers reported a sex difference: men showed oxytocin changes around games, while women’s levels did not differ before and after matches. They suggested several possible explanations: some women began with higher baseline levels because they were breastfeeding, women played less often and soccer may carry different social significance for them, and the "male warrior hypothesis" proposes that men evolved to invest more in intergroup competition. The team also noted a key limitation: the study cannot determine whether higher oxytocin mainly promotes within-team cohesion or fuels competition with opponents. Similar links between oxytocin and group conflict have been observed across species, and the research appears in the Proceedings of the Royal Society B.
Difficult words
- oxytocin — hormone associated with social bonding and trust
- interdependent — relying on each other; mutually dependent
- salience — how noticeable or important something seems
- out-group — a social group seen as different or outside
- baseline — typical starting amount or level before change
- breastfeeding — feeding an infant with milk from the mother
- cohesion — the quality of staying together as a group
- intergroup — between different groups competing or interacting
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How might oxytocin increases affect relationships within a team and toward opponents in competitive games? Give reasons based on the article.
- What additional evidence or research methods would help determine whether oxytocin mainly promotes team cohesion or fuels competition?
- How could cultural differences in how communities value soccer affect the study's results? Give examples.
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