Apes can wield tools, learn sign language, and get hooked on TV. New research credits them with yet another ability once thought to be exclusively human: duplicating the facial expressions of others. The work suggests that this capability, which might help individuals synchronize their emotions, precedes the origin of our species.
Whether we're watching a movie or having coffee with an old friend, often we rapidly and unconsciously mirror the facial expressions of people we are looking at. Smiles, laughs, and grimaces of disgust are contagious. Why we're such copycats isn't clear. Youngsters might be learning the right moves for communication. Facial mimicry may also aid interpretation: To understand an expression, the brain recreates it. Some researchers think that emulating an expression might elicit the same feelings in the viewer, creating empathy.
To determine whether the ability extends to apes, behavioral biologist Marina Davila Ross and colleagues at the University of Veterinary Medicine Hannover in Germany videotaped pairs of young orangutans at play. They analyzed instances in which one of the playmates produced a neutral expression or a so-called open-mouth face (see video), which might be equivalent to the human smile. As the team reports this week in Biology Letters, if an orangutan showed the open-mouth face, its partner was likely to follow suit in less than half a second. When the researchers broke down the interactions by age, they found that mimicry was more common among juveniles and adolescents and when the two playmates were more than 2 years apart in age.
"The study showed for the first time that involuntary mimicry is present in animals, at least for facial displays," says lead author Davila Ross, who's now at the University of Portsmouth in the U.K. However, orangutans didn't always emulate their playmates, and the researchers now want to determine what other factors influence the behavior.
"It's important to demonstrate that facial expression and mimicry have an evolutionary context," says behavioral neuroscientist Stephanie Preston of the University of Michigan, Ann Arbor. That knowledge might help researchers work out how the behavior originated and what role it plays in social situations, she says.