An international research team led by the University of Konstanz and Oxford Brookes University concludes that gentle touch is not only good for mental health, but also for the evolution of cooperation.

The power of touch and social connections helps people to cope with an increasingly stressful world as indicated by a recent decline in mental health. Gentle, caring touch plays a significant role in strengthening interpersonal bonds and enhancing mental health. It is often referred to as affective or consoling touch, and has been linked to many health benefits including enhanced social connection and trust, stress and pain reduction, and better mental health. As a Konstanz-based researcher and his team observe, caring, gentle social touch can also play a significant role in the lives of animals and may even allow for the evolution of cooperation.

In a recently published study, an international research team, led by Michael Griesser from the University of Konstanz and its Cluster of Excellence "Collective Behaviour" and Miya Warrington from Oxford Brookes University synthesizes evidence from the animal kingdom to highlight the key role of touch in animals for the evolution and persistence of friendships and cooperation.

Griesser and Warrington noticed differences in the level of touch and cooperation between two wild bird species that they both study – Apostlebirds in the Australian outback and Siberian jays in Swedish Lapland. They observed that the high-touch apostlebirds preen each other and cooperated in many contexts, including joint care of young, while Siberian jays do not preen each other and cooperate in few tasks. Teaming up with primatologists, Judith Burkart and Natalie Uomini at the University of Zurich, Switzerland, and African mammal physiologists, Nigel Bennett and Daniel Hart at the University of Pretoria, South Africa, they explored the common features of touch, hormones and cooperation between birds and mammals. Astoundingly, the joint investigation revealed that touch has a key role in forming and maintaining social bonds in general, directly affecting how animals cooperate.

The word “cooperation” is used for many behaviours where the involved individuals benefit, explains Warrington, “but, in fact, not all such behaviours are done out of kindness, or because we are bonded to the other individual. Actually, cooperative behaviours occur along a spectrum”. For example, on one side of the spectrum there are animals, like impalas, that groom each other reciprocally, to remove the parasites off their necks that they can’t reach themselves. Thus, this is a very transactional behaviour. On the other side of the spectrum, animals like marmosets, live in family groups and group members do everything together regardless of immediate direct benefits. Thus, marmosets are very prosocial in most aspects of their lives.

This spectrum of cooperation is not entirely unexpected, reflecting the great diversity in how and why species cooperate. “As we observe in Apostlebirds and Siberian jays, the diversity in cooperation has a link to the level of touching, but also touch sensitivity and the types of bonds in nature” explains Griesser. Indeed, this is seen in mole rats where asocial species have few touch receptors in their skin and are not touch sensitive while the opposite is the case in social mole rat species, for example the eusocial naked mole rat.
In social species, the caring touch offspring receive early on in life sets a dynamic in motion that continues into adulthood. Griesser and Warrington observe that, as a result, animals that grow up with close social bonds engage more likely in social cooperation, not only in the context of their families, but also with other adults, in partnerships and friendships as well as during their own parenthood.