In the intricate social world of rhesus macaques, the ability to convey emotions through facial expressions may be a key to effective leadership, a new study suggests.
Scientists from Nottingham Trent University found that the more expressive a dominant male rhesus macaque is, the more likely he is to have closer social relationships and a more tightly knit group. In the study, the researchers looked at nine social groups of these primates and discovered that males who had more facial expressions were more socially connected and held central positions in their social networks.
The researchers recorded 17 different facial muscle movements on the dominant males in each group using a land Marcel-coded, specialized system called MaqFACS. In addition, the scientists measured social interactions for all 66 monkeys; time spent together and how often they groomed each other.
The findings showed that in male groups with higher levels of facial expressiveness, social integration was higher. That is, this rise in expressiveness seemed to go hand in hand with the more permissive management style, wherein the distribution of social connectedness is more equalized between group members.
This research shows how individual differences in the ability to express emotion can affect social dynamics for primates, including humans,” said Dr. Jamie Whitehouse, Research Fellow in NTU School of Social Sciences and lead author on the study. He added that a wider range of facial expressions might be more useful in fending off complex social relationships than a restricted repertoire is.
According to Professor Bridget Waller, Professor of Evolution and Social Behaviour at NTU and the research project lead, facial expressivity has evolutionary significance: “Humans have evolved incredibly expressive faces with highly complex facial musculature, and these findings help us understand what advantage this has provided over evolutionary time.”.
The work is published in Royal Society journal Proceedings B and is titled “Facial expressivity in dominant macaques is linked to group cohesion.” The study is part of a European Research Council-funded project led by Professor Waller into the evolution of facial expression and its consequences for engaging in social contact.
The findings underline the requirement of facial expressivity to be socially coherent and to become a leader, so the insights gained are not only from primates but extend to human social behavior.