Why Would a Close Friend Affect a Monkey’s Behavior More Than a Relative Would?

Friendships, the existence of strong positive and enduring social bonds, are a crucial feature of animal societies, including our own. Living in groups, and thus having potentially extended networks of social relationships, are highly beneficial; it provides protection against predators, facilitates foraging and access to sexual partners. On the other hand, it also implies some costs: For example, it generally increases the rate of aggression and facilitates disease transmission. Recent developments in the study of animal behavior suggest that friendship evolved to mitigate these costs. These studies also show that the evolutionary precursors of our friendship can be found in a wide range of animals, such as mice, elephants, hyenas, horses, and nonhuman primates.

Most of our knowledge about friendship in other animals comes from primatological studies. Friends can deeply affect individuals’ behavior, communication, and cognition. For example, friendship is associated with increased reconciliation rates as well as increased affiliation between bystanders after conflicts. Both of these social interactions can reduce stress and social instability after fights, and can have long-term benefits to the relationship. Friendship has also been shown to enhance grooming equity and increase offspring survival.

When studying friendship, scientists usually use objective measures, such as the time animals spend in proximity and the frequency of their grooming. Individuals who spend a lot of time together and groom each other often are considered friends. Often, friends are the same age or have similar rank in the group’s hierarchy, and can sometimes belong to the same family. Nevertheless, individuals also have friends who are nonrelatives, and even within the family, the quality of the relationships is not equal. In addition, friendships are sometimes independent of dominance or family ties.

In a recent study, Bridget Waller and I have shown that friendship also influences how monkeys use socio-cognitive skills. In this particular study, we found that the strength of the social bond between two individuals affected the rapidity with which an individual followed the line of sight of another. Other factors, such as social status and family ties, had no effect. This is an important finding because gaze following is thought to be important to obtain valuable information to cope with social and ecological challenges, such as finding food, sexual partners, or locating a predator. Friendship, therefore, seems to facilitate the acquisition of such information. Friends share similar needs and motivations, and therefore, competition among friends is usually reduced and cooperation enhanced.

However, it is important to remember that the findings of this particular study cannot necessarily be generalized across species and context. Crested macaques are characterized by a relaxed social style that provides individuals with an increased opportunity for close individual contacts independently of dominance and kinship. This tolerant social style facilitates information transfer and cooperation and access to valuable resources. This effect might be enhanced among friends as a result of reduced competition and increased cooperation between them. This does not necessarily apply to other species. Rhesus macaques, for example, are less tolerant. Their social relationships are strongly constrained by kinship and dominance, and so we would expect these factors to be more influential.

This raises another question: Why are some species more tolerant than others?

Jerome Micheletta is a doctoral student at the Centre for Comparative and Evolutionary Psychology at the University of Portsmouth.

Category: Q&A

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2 Responses

  1. Social co-operation is what interests scientists for political purposes. If a story of danger exists within a particular social group, it is much more likly that the group protects itself from such danger, whether the story is true or not, as all groups seek to distinguish themselves and survive. Distinguishing oneself and survival is how one’s identity is developed or maintained.

  2. A friend is more likely to affect someone because of shared values, or tolerance of differences. But, if one’s narratives change, then do past experiences affect present cooperative efforts? Is friendship based mostly on past connection or present “realities” or real present realities?

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