Orangutans Change Their Laughter Depending on Who They’re With

A smile is more than just a facial expression. It’s a powerful tool of communication, capable of conveying a wide range of emotions. From a hearty laugh to a subtle smirk, our smiles can express joy, affection, submission, or even dismissal. We tailor our smiles to the person we’re interacting with, influenced by age, gender, and relationship status. Even as infants, we learn this social skill. Babies tend to flash broad, open-mouthed grins at their mothers, while choosing a more reserved smile for strangers.

New research reveals that our primate cousins, orangutans and chimpanzees, also change their smiles and laughter based on who they’re interacting with. Just like us, they consider factors like age, sex, and social status to determine how wide or tight-lipped their smiles are. This suggests that the ability to use facial expressions to communicate complex social information is an ancient trait shared by humans and other great apes.

Intriguingly, these apes adjust their laughter in unique ways. Orangutans often flash a “friendly” smile with their upper teeth showing when playing with younger or weaker individuals, possibly to reassure the younger individual. But the opposite was true in chimpanzees, who tend to show more teeth, both upper and lower when playing with older or stronger individuals, signalling submissiveness.

This can be explained by looking at the social structures of these apes. Chimps have a hierarchical social structure, so it’s important to communicate submissiveness and non-hostility. Orangutans, on the other hand, are mostly solitary. Most of the social interactions in the wild occur between mother and offspring. Therefore, communicating reassurance is key.

These findings shed fascinating insight into how smiles and laughter have evolved. This study highlights how important evolutionary history, social and ecological environments, and rearing, are in understanding behaviour in great apes.