WHO'S THE PRIME PRIMATE?: Can you tell which of these female chimpanzees acts more dominant--more able to displace, threaten or take food from others or more likely to show her high status by decisively intervening in social interactions? Seventy percent of human volunteers in experiments could. (The less dominant chimp is on the left.) Image: James King
What's in a face? A chimpanzee's face, that is. Humans, it seems, apparently remain genetically and culturally close enough to their primate relatives, and are able to accurately guess an individual chimp's personality just by observing it s face. This discovery sheds light on the evolution of our faces, and could yield insights into the nature of autism.
There's an old saying that you can't judge a book by its cover, meaning that one shouldn't judge someone or something based solely on appearances. Recent findings suggest, however, that one actually might be able to correctly guess many aspects of another person's personality just by looking at his or her face if it displays a neutral expression, including traits such as trustworthiness and aggression.
Our faces could be windows into our souls because our ancestors developed them as ways to honestly tell others about ourselves—knowledge that could help social interactions proceed more smoothly. If our brains, faces and ability to analyze them did evolve in this manner, social psychologist Robert Ward at Bangor University in Wales and his colleagues reasoned that we might share part of this system with chimpanzees, humanity's closest living relatives.
In four experiments scientists asked university students to look at chimp faces. First, 43 volunteers viewed photos of chimpanzee faces bearing neutral expressions— for instance, they were not baring their teeth.
The researchers had previously assessed the 37 apes in these pictures according to 15 personality factors, such as "dominant," "active," "sociable" and "sympathetic." Volunteers were shown two photos at a time, each of a different chimpanzee, and asked to guess which one best fit a certain personality trait than the other. People typically accurately identified "dominant" and "active" personalities correctly, and nearly correctly guessed "sympathetic" ones to a significant degree. Intriguingly, volunteers often seemed to judge "sociable" incorrectly, suggesting they misinterpreted what they saw.
In a second experiment Ward and his collaborators had 30 different students rate the chimp faces on a seven-point scale on the four traits identified in the first experiment — dominant, active, sociable and sympathetic. After comparing these results with the personality ratings scientists previously had of the chimpanzees, the researchers found a significant number of the volunteers were able to accurately guess how dominant the apes were.
A third experiment supported these results — 30 more students were shown pairs of chimp faces, each of a different chimpanzee of the same sex, and they typically correctly identified the more dominant ape, proving more accurate with male chimps than females. Dominance, as the scientists described it to volunteers, involved being more able to displace, threaten or take food from others —or more likely to show their high status by decisively intervening in social interactions.
In the last experiment the scientists investigated how well volunteers were able to assess both the dominance of chimps as well as how extroverted a human might be. (In humans psychologists typically consider dominance an extroverted or outgoing personality trait.)
The researchers first had another 36 students complete tests measuring personality, empathy and autism. The volunteers then compared pairs of chimp faces for dominance, and also looked at pairs of black-and-white photos of white women's faces that registered neutral expressions , each of whom scientists had assessed for extroversion.
As before, volunteers typically judged chimpanzee dominance accurately, and also often guessed female extroversion correctly. Interestingly, volunteers whose social skills embodied autisticlike traits were worse at reading the signs of extroversion in the women but did fine when judging chimps. "We are thinking this might reflect additional human-specific social cognition," Ward says. "That is, there would be a set of social skills and traits that we share with our evolutionary relatives, and another set specific to humans and our own adaptive problems."