Apes may not build coalitions on the basis of rational calculation

Coalition forming and trading behaviour amongst apes is seen by primatologists as the most important evidence for rational social deliberation and thus social intelligence. However, Charlotte Hemelrijk and Ivan Puga Gonzales of the University of Groningen have used computer models to demonstrate that apes can also form complex coalitions and trade grooming favours without any apparent deliberation (cognition). ‘Accidental proximity’ caused by limited freedom of movement appears to be an important explanatory factor for such behaviour among apes. Their research was published on 30 May in PloS ONE.

Researchers at the Department of Behavioural Ecology and Self-Organization (BESO) of the Centre for Ecological and Evolutionary Studies attempt to understand complex biological patterns by exposing the different organizational levels in a community. The research on self-organization focuses on various communities, such as schools of fish, flocks of birds and groups of primates. One of the lines of research focuses on providing cognitively simple explanations for complex social behaviour.

Not calculating

Charlotte Hemelrijk, Professor of ‘Self-organization of Social Systems’ at the University of Groningen, and her PhD student Ivan Puga Gonzalez conclude from their research that complex coalition-forming and trading for grooming favours among apes may take place without the use of sophisticated cognition. This goes against conventional wisdom, which asserts that coalitions among primates are a sure sign of intelligence and that trading behaviour occurs because individuals keep careful track of how often they have been groomed to be able to return the favour in kind.

Freedom of movement

However, there seems to be another explanation for this behaviour. Individuals in a group have limited freedom of movement due to dominance relations and so repeatedly find themselves in the vicinity of the same group members. It is this proximity that is the reason that they often interact with these group members. They automatically assist the individuals near them during fights and often groom each other. This spatial distribution arises from aggressive interaction; some animals are higher in rank and chase other members of the group away more often. The result is that group members of equivalent dominance are more likely to be found near each other.

Testable hypotheses

Primatologists have always interpreted certain social interaction patterns among group members as trading behaviour. However, these patterns also occur in the computer model developed in Groningen, so without the rational calculating cognitive processes normally associated with them. The model also makes it clear that a more prominent role must be given to the ‘spatial distribution of individuals’ in standard behavioural research, something that has been overlooked thus far. The new model has generated many testable hypotheses for future research.

Note for the press

– An individual-oriented model on the emergence of support in fights, its reciprocation and exchange , PloS ONE, http://dx.plos.org/10.1371/journal.pone.0037271, Hemelrijk, C.K. and Puga-Gonzalez, I., University of Groningen
– More information: Prof. Charlotte K. Hemelrijk, BESO, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, tel. +31(0)50 363 8084 (work), +31(0)50 534 3671 (home),
06-41107818, e-mail c.k.hemelrijk rug.nl