Do Monkeys Make Faces on Purpose?
NEWS | 09 January 2026
I agree my information will be processed in accordance with the Scientific American and Springer Nature Limited Privacy Policy . We leverage third party services to both verify and deliver email. By providing your email address, you also consent to having the email address shared with third parties for those purposes. Facial expressions are central to social life, yet scientists still don’t fully understand how the brain produces them. For decades, one influential theory has held that what appears on your face is largely an emotional reflex—an honest, automatic readout of what you feel inside. But that view struggles to explain the fact that we often tailor our countenance to the moment: we’ve all smiled politely through a dull date or tried not to smile while holding a royal flush. To find out what’s going on in the brain during facial expressions, researchers turned to rhesus macaques, Old World monkeys with face musculature and neuroanatomy that are similar to that of humans. They recorded neural activity while the animals interacted with one another—as well as with digital avatars and video of other macaques—in the lab. The team’s results, published today in Science, came as a surprise: the monkeys’ expressions, from a threatening face to a friendly “lip-smacking” one, were generated by both the medial cortex and lateral cortex. These brain regions were long thought to operate independently, with the medial dealing with spontaneous emotional expressions and the lateral controlling voluntary actions. “Our study did not show that at all,” says co-lead author Geena Ianni, a neurology resident at the University of Pennsylvania. “It showed that all regions participated in the production of all kinds of facial expressions.” On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. The two regions did, however, run at different speeds. “The way they encode information has a distinct tempo,” says co–lead author Yuriria Vázquez, a neuroscientist at the Rockefeller University. Activity in the lateral cortex shifted quickly, over milliseconds, to coordinate the rapid facial movements that make for smooth social interaction. By contrast, things happen at a more leisurely pace in the medial cortex, perhaps allowing it to track slow-changing contextual factors—such as “Has the alpha male stopped threatening me?”—that influence facial expressions. What’s more, both neural patterns show up before facial movements do, suggesting the brain prepares expressions in advance. This all raises a question: Do macaques intentionally plan the faces they make? That’s the interpretation that Bridget Waller and Jamie Whitehouse, evolutionary psychologists at Nottingham Trent University in England, explore in a commentary on the new study. If facial expressions are partly voluntary, they may be less like emotional mirrors and more like “tools for social influence,” as Waller and Whitehouse put it. At the very least, they seem to arise from complex interactions between emotion and cognition. Alan Fridlund, a social and evolutionary psychologist at the University of California, Santa Barbara, who was not involved in this study, has no trouble believing macaques wield their faces strategically. But he doubts that staged, lab-bound interactions can capture the full reality of primate communications, or the neural activity underlying it; ideally, future research would take place in the monkeys’ natural environment. Still, Fridlund says, the new study “tells us in infinitely more detail how we can investigate the neurology of facial displays.”
Author: Sarah Lewin Frasier. Cody Cottier.
Source