Mental leap: what apes can teach us about the human mind

Science News,  Sept 2, 2006  by Eric Jaffe

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At the opening of Stanley Kubrick's 1968 film 2001:A Space Odyssey, a group of apes hovers around an object that has suddenly appeared in the desert. The sleek, black, rectangular object is five times as tall as the apes and clearly crafted by intelligent beings. The apes approach it with caution, and one animal runs a timid hand along the clean edges that glimmer in the sunlight.

Suddenly, something clicks in the ape's mind. The sight of a sophisticated innovation has launched dormant aptitudes, and the ape has realized that a large bone can be used as a weapon to advance its kind. Standing more erect than before and brandishing the weapon, the ape attacks another group.

The film then fast-forwards through the remainder of cognitive evolution in a flash: The bone, tossed into the air, becomes a space station floating through the cosmos.

Too bad the camera didn't cut instead to a laboratory at the Max Planck Institute in Leipzig, Germany, where scientists are discovering details about apes' brains that could fill in some of the movie's multimillion-year gap. Researchers at the institute, Josep Call and Nicholas Mulcahy, recently demonstrated that apes possess a surprising understanding of tools and even make plans to use them. In fact, the study suggests that planning skills go back 14 million years to ancestors of apes and people.

Two other knacks once considered unique to humans have recently turned up in apes. A team of scientists watching apes at the Yerkes Primate Center at Emory University in Atlanta reports that the animals conform to cultural norms--that is, they do a task the same way that others in a group do it, even if an alternative method exists.

Another team studying apes raised at the Language Research Center at Georgia State University, also in Atlanta, concludes that young animals play make-believe, an activity considered an early sign of linguistic abilities.

These studies represent an effort to understand some of the human mind's fundamental mechanisms. While recognizing a difference in the degree of human and ape capabilities, "I don't think there's a difference in kind," says Call.

Investigating these differences could reveal "the processes that led to our position," says Carel van Schaik, director of the Anthropological Institute and Museum at the University of Zurich in Switzerland. "We can build a bridge across the [ape-human] gap without denying that there are some really big differences."

PLANNING OF THE APES For Call and Mulcahy, the most fitting metaphor for ape cognition isn't A Space Odyssey but an Estonian folktale. In that story, a young girl dreams of attending a party where she can't eat dessert because she has no spoon. The next night, the girl takes a spoon to bed, in case the dream recurs.

The scientists placed bonobos and orangutans in a similar scenario. Previous studies had clearly shown that apes use tools to satisfy an immediate need. In the wild, for example, they frequently transport rocks to smash open nuts. But the researchers wanted to know whether apes would hold on to a tool that they wouldn't need until much later.

Before the test, the apes had learned how to retrieve a bunch of grapes locked inside a container. The apes had to insert a thin plastic pipe into a slot, as though the pipe were a key. In the test, Call and Mulcahy led the apes, one at a time, into a test room where each animal saw the grape-holding container and four objects: a dowel, a plastic dish, a bowl, and the slot-fitting pipe.

Here, the experiment went beyond observations of tool use. A Plexiglas panel blocked the container, so the ape couldn't retrieve the grapes, even with the right tool. Each animal was free to take away an object when it left the room and wasn't permitted to return for an hour.

By then, the researchers had removed the Plexiglas and all the tools. An ape that had selected the right tool, removed it from the test room, and brought it back after the delay could then help itself to grapes. In other words, the successful animals planned ahead.

The test was performed 16 times for each of three bonobos and three orangutans. On average, each ape solved the task 7 times, with one ape solving it 15 times and another only twice. The animals improved slightly as they repeated the test.

The best-performing bonobo and orangutan were brought back for a more difficult test. In 16 additional trials, each of these two apes visited the test room and then was kept out of it overnight, yet about half the time they carried the appropriate tool into the room the next morning.

But, the most impressive display of sophisticated thinking, Mulcahy says, came from an unexpected incident. An orangutan brought back the wrong tool and then shaped it into a usable key.

To learn whether the apes were carrying the tools simply by force of habit or because they enjoyed doing so, Call and Mulcahy performed another test, in which they repeatedly removed the grapes after a first showing behind the Plexiglas. That way, the apes could learn that there was no reason to haul the tool around-after all, why bring a spoon to a party without desserts?