Facially expressive monkeys are more socially successful and lead better connected social groups, according to research by Nottingham Trent University. — AFP
LIKE humans, monkeys are animals that feel and express emotions, notably through postures, vocalisations and facial mimics.
This range of emotions not only helps primates to communicate with their peers, but also to maintain order within their community.
Researchers in Britain investigated the role of facial expressivity in rhesus macaques (Macaca mulatta), known for their vocal and gestural communication. They use these mimics and gestures to reinforce social cohesion within a group.
The social organisation of macaques is governed by a nepotistic, matrilineal hierarchy. The rank of each individual in a group depends on their relationship to one of the leading females.
Indeed, the hierarchical status of females is dictated by that of their mothers.
Males, on the other hand, emigrate from their natal group when they reach puberty to join a new one, where their ability to dominate and unite their fellow males defines their place in the hierarchy.
For their study, the researchers analysed the facial expressions of 66 rhesus macaques living in nine different groups. In particular, they studied their behaviour during friendly grooming behavior, a widespread social interaction among primates.
The scientists noticed that the most expressive males tended to be better integrated into the life of the group.
They participated in more grooming sessions than those with a lower diversity of facial expressions.
What’s more, these males enjoyed stronger social bonds with their peers. They were better integrated into their respective groups and were higher up the hierarchy.
Understanding human social behaviour
While rhesus macaques are reputed to be aggressive and intolerant of others, the researchers found that facially expressive males were more tolerant.
They adopted a leadership style based on sharing and benevolence.
“These findings show that inter-individual differences in facial expressivity are related to differential social outcomes at both an individual and group level. More expressive individuals occupy more beneficial social positions, which could help explain the selection for complex facial communication in primates,” reads the researchers’ paper, published in the Proceedings of the Royal Society B.
The findings of this research contribute to a better understanding not only of rhesus macaques, but also of human beings. Like these primates, we use our facial muscles to express our emotional states – a valuable form of non-verbal communication.
“Humans have evolved incredibly expressive faces with highly complex facial musculature, and these findings helps us understand what advantage this has provided over evolutionary time,” says research project lead, Bridget Waller, professor of evolution and social behaviour at Nottingham Trent University, quoted in a news release. – AFP Relaxnews
