Brian Hare does a little social learning with chimpanzees at the Tchimpounga Chimpanzee Sanctuary. These orphan chimpanzees can learn from watching others, but not as skillfully as human children.
Brian Hare does a little social learning with chimpanzees at the Tchimpounga Chimpanzee Sanctuary. These orphan chimpanzees can learn from watching others, but not as skillfully as human children. Vanessa Woods
Chimpanzees hang out at the Tchimpounga Chimpanzee Sanctuary, in the Republic of Congo.
Chimpanzees hang out at the Tchimpounga Chimpanzee Sanctuary, in the Republic of Congo. Vanessa Woods
What makes humans different from our closest primate relatives? Scientists have grappled with the question for centuries – even more so since the discovery, in the late 1980s, that humans and apes share pretty much the same genetic code.
Just think about it, says anthropologist Brian Hare: The two species share practically the same DNA, and yet live such different lives.
"We have cars, trains, rocket ships, internets, stuff like this. And we're the only organism on the planet that does all these crazy things," Hare says.
In a new study published in the current issue of the journal Science, Hare and colleagues from the Max Planck Institute in Germany looked at the way humans and other apes learn. Chimps and orangutans are plenty smart in their own way, they found, but human toddlers beat them in tests of "social intelligence."
To investigate what makes human intelligence so different from ape intelligence, the researchers designed over two dozen tests to measure different kinds of intelligence between the two species.
"Our subjects in this study were 2-and-a-half-year-old children," Hare explains. "We looked at 106 children. Then, we had chimps that live in two orphanages in Africa. We had 105 of them." They also studied a group of 30 orangutans in an orphanage in Indonesia.
Each test subject — ape and human — worked with one researcher, who performed dozens of tests over several days. Some scientists have theorized that children would outperform apes on all measures. But in this study, that was not the case.
Children did not perform any better than apes on many tests that measured concrete knowledge.
"They weren't any better than the apes at doing things like adding, counting, remembering where something was hidden," Hare says.
But when it came to solving more social problems, children excelled. Hare defines a "social problem" as the ability to watch somebody else and figure out what they're trying to do — and what they want you to do. In his study, certain tests looked at how adept children and apes were at understanding someone else's intention.
"So, we put food under a cup, and the subject saw where the food was, but an experimenter didn't know the food was there," explains Hare. The goal was to see whether the subject — a child, chimp or orangutan – would point to the correct location, or somehow communicate to the experimenter where the food was hidden, so that the experimenter might give them the food.
Most of the children directed the researcher to where the food was. Most of the apes did not. Results were similar for other tests that measured this more intuitive type of intelligence.
In one test, treats were placed in a tube purposely designed to be difficult to open. After researchers demonstrated how to open it, most of the toddlers were able to imitate and open it. On the other hand, the apes did not follow suit.
"They tried to come up with their own techniques to solve the problem," says Hare. "They didn't learn the actions needed from the researchers' demonstration. They did lots of different things: trying to crack the tube, bang on the cage. But they didn't use the method demonstrated to them."
Being able to learn quickly from others is a social skill that the human children certainly excelled at. Temple University psychology professor Kathryn Hirsch-Pasek says that partly because we humans are so social, we were able to develop sophisticated language, which "has allowed us to record and transmit our history."
"And that means in some sense, we can even speed the course of evolution through language, because we don't have to learn everything with each child born – anew," she says.
So while all primates are social beings, the new study underscores that humans are "ultra-social" — with all its benefits.