Study: Orangutans Show New Ape Talent
Listen to Chris Joyce's report.
'Contemplative' Life May Promote Abstract Thinking
*Listen to a male orangutan's call.
Orangutans and chimps: read about where they live, what they eat, and how they spend their time.
21-year-old Indah on the computer with researcher Robert Shumaker. Photo: Richard Nowitz
Dec. 21, 2001 --
Efforts to measure the intelligence of apes -- our closest living relatives -- have shown them to have remarkable thinking abilities. Gorillas, for example, are able to communicate with sign language. Chimpanzees can count and add numbers.
Relatively few experiments have been done with perhaps the rarest of the apes, the orangutan. A few thousand remain in the wild in Indonesia; the rest are in zoos, such as the National Zoo in Washington, D.C. That's where two orangutans have recently shown some new ape talent. NPR's Christopher Joyce reports for Morning Edition on a new study in the Journal of Comparative Psychology.
Biologist Robert Shumaker studies how apes think. At George Mason University's Krasnow Institute, he has taught two National Zoo orangutans -- Azy and Indah -- to communicate with him by pointing to geometric symbols on a screen.
In Shumaker's system, anything with the name of a food starts with a rectangle. A banana is represented by a rectangle with a slash through it. All objects start with circles, so a cup is a circle with a dot right in the middle.
Bonnie on the National Zoo's o-line, a network of steel cables that lets orangutans swing around like they would in their native habitat.
Photo: Jessie Cohen/National Zoological Park
The ability to point at symbols to communicate different ideas is simple evidence that on their own, orangutans, like other apes and monkeys, are using abstract concepts and understand abstract thought, says Shumaker.
But Shumaker has uncovered in his new research that orangutans are able to do something distinctive among apes.
He gave Indah and Azy a choice between two bowls of grapes. One bowl held more. But there was a trick: The bowl they pointed to first was taken away, and they were left only the grapes in the other bowl to eat. Instinct argued to pick the bigger bowl of grapes first, but the orangutans learned this game wasn't that simple.
They needed to grasp that less would get them more. It's a counterintuitive, complex rule, yet Shumaker says his orangutans quickly understood it -- without coaching. They now choose less to get more almost every time.
What's curious, says Shumaker, is that chimpanzees -- considered the intellectuals of the ape world-- don't get this rule. At least, not with food. When other scientists tried this with chimps, the chimps repeatedly picked the biggest pile of food, even if it meant getting less in the end.
Studying how animals think is tricky work -- it's often hard to tell what's actually being measured. Primatologist Sarah Boysen of Ohio State University says she finds the orangutan experiment a little shaky, and says it certainly doesn't show that orangutans are smarter than chimps.
Boysen argues that chimpanzees can learn the "less-is-more" rule, as long as the rewards don't involve food. Intellectually, she says, they just can't override the instinct to grab-all-the-food-now.
Psychologist Christine Brannon of Duke University, who has experimented with ordinality and monkeys, who show some of the cognitive sophistication of the great apes, says Shumaker's work goes beyond just knowing the difference between less and more.
"It does seem to me that this kind of research has a lot to do with being able to suppress a natural tendency to get more food so it's really about self-control and restraint."
Shumaker notes that orangutans live a more solitary social life than other apes. That may explain the species' more "contemplative" thought process.
"I think that what it is about orangutan social structure that helps them do this task is simply that they don't have to aggressively compete for food with other orangs the way that chimps do, for example."
Shumaker says his experiment, described in this month's Journal of Comparative Psychology, suggests that the kind of social life a species leads -- solitary versus in a group for example -- can shape its mental abilities. And it also suggests that each kind of primate may have added something distinctive to the pot during the evolution of the human brain.
Browse for more NPR stories about orangutans and chimpanzees.
Read about orangutan conservation efforts at www.orangutan.com, a site run by the non-profit Balikpapan Orangutan Society.
Read more about chimpanzees at the Jane Goodall Institute's Web site.
Explore the primate and human evolutionary tree, courtesy of George Mason University.
Read about the orangutan's role in the National Zoo's Think Tank project.
Read more about the Krasnow Institute for Advanced Studies.
*Audio courtesy of Balikpapan Orangutan Society, USA.