Less stress hormone when teaming up with friends

15 May 2020 | Back to News, Publications and Annual Reports



Working with friends is more fun than with strangers. Scientists from BPRC and the universities of Utrecht and Vienna have now found a scientific explanation for this. The secret lies in the stress hormone cortisol.

Animals work together to defend their territory for example, or to hunt. To enable this, the animals must have complex qualities: they must be able to recognize each other and, for example, to coordinate their actions. This involves certain physiological processes. However, little is known about these (hormonal) processes.

Chewing on a cotton swab

To investigate this, the researchers trained macaques to chew on a cotton swab. Afterwards, the animals received a reward. Using this animal-friendly design, they were able to investigate the levels of cortisol, a stress hormone in the saliva.

Teaming up to collect peanuts

The animals had to cooperate with other animals from their group to perform a task. Only by working together they could complete the task successfully. For example, both animals had to pull one end of a rope in order to be able to collect some bolts. By solving this task, they obtained peanuts as a reward.

Calming effect of friends

It turned out that the level of the stress hormone dropped when monkeys were teaming up with a friend. It did not matter whether the task was successfully completed. Cooperating with a group member with whom the monkey did not have close social bonds had no effect on the cortisol levels, just as when they were just sitting with a friend and not working together. Furthermore, pulling the rope had no effect in itself. Overall, this underlines the importance of close social ties in these animals.

Useful for long-term cooperation

The calming effect of cooperating with friends could be the reason that not only animals, but also humans can engage in long-term partnerships. Other hormones may also play a role in this; further research may provide more insight on this. More information about this research can be found in the scientific article.