Working stress is often easier to endure than being alone – monkeys can also sense this, as an experiment with macaques demonstrates. If these monkeys complete a task on their own, they put them under stress. However, if they cooperated with a friend of their own kind, the level of the stress hormone cortisol dropped significantly. The decisive factor for this relaxing effect was the collaboration – the mere presence of the friend was not enough.
Especially during the weeks of the lockdown to combat the corona pandemic, many professionals had to work in the home office. They sat alone at home instead of being in close contact with their colleagues in the office. This can have advantages when there are conflicts in the team, but working in isolation is often an increased burden. Because just asking something or devoting yourself to a task together is difficult under these circumstances despite video conferences. Social isolation and the limited possibilities of cooperation lead to stress.
Cooperation, social closeness and stress
So we humans are obviously not an isolated case, as Martina Stocker from the University of Vienna and her colleagues have now found out in an experiment with great macaques (Macaca fascicularis). They wanted to know what influence the cooperation and the social relationship have on the stress level of these monkeys. It has long been known that the presence of friends has a positive, relaxing influence on most primates. Physical closeness, mutual grooming or simply the presence reduce the stress level. At the same time, many animal species are more cooperative when they are supposed to work with a friend of their own.
“We therefore wanted to investigate the relationship between cooperation, social relationships and the level of the stress hormone cortisol in great monkeys,” said the researchers. For their experiment, they first taught the monkeys how to reward themselves by pulling a rope. In control experiments, they should either master this task alone or while a comrade was sitting in the cage next door. In the cooperation test, however, this changed: Now the reward only came within reach if two monkeys worked together by both pulling their end of the rope towards them at the same time. Before and after each run, the researchers took saliva samples and determined the content of the stress hormone cortisol.
Cooperation reduces stress, closeness alone does not
The experiments showed something surprising. Because contrary to expectations, the passive presence of a friend of a friend was not enough to reduce the stress level of the monkeys. If the friend just sat next to him while the test person was pulling the rope, the friend did not relax – even if he received his reward. It was different, however, when both monkeys actively cooperated and solved the rope task together: Then their cortisol levels dropped significantly, as Stocker and her team found. “This suggests that it is the cooperative dealings with a friend of his own kind and not just his mere presence that is crucial for the reduction of cortisol,” said the researchers.
It was also unexpected to observe that the tightness of the bond between the two partners had no effect on whether they cooperated at all or not. “This contradicts studies with chimpanzees or barbary macaques that have found a positive effect of social proximity on cooperation,” the scientists explain. However, when the Javanese monkeys worked together, pairs of friends relaxed more than just loose acquaintances, as the cortisol values showed. Stocker and her team suspect that the “cuddly hormone” oxytocin could play an important role in this effect. It may be distributed more during the cooperation and then helps to reduce stress. However, further studies have to show whether this is the case.
Overall, however, the experiment demonstrates that cooperation also helps reduce stress in monkeys. Conversely, this effect could even be one of the driving forces of the cooperation: “This relaxing effect of cooperative interactions with friends who are friends could be the reason for the maintenance of long-term cooperation, as it does with these macaques, but possibly also with other species and / or humans is to find, ”says Stocker.
Source: University of Vienna; Technical article: Royal Society Open Science, doi: 10.1098 / rsos.191056