Hanging from the Language Tree

In a famous experiment over 30 years ago, psychology professor Herb Terrace hoped to prove that chimpanzees could acquire speech. Today, as director of the Primate Cognition Laboratory at Columbia, he’s searching for the missing link to cognition.

by Cindy Rodríguez Published Fall 2009
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While the public knows him for his experiment with Nim, Terrace is revered by his peers for his body of work that spans five decades. Robert Hampton, a primate cognition specialist at Emory University, calls him a “leader in the cognitive revolution.” This March, the Comparative Cognition Society, a nonprofit organization of scientists, honored Terrace with a lifetime achievement award for his “Outstanding Contributions to the Study of Cognitive Processes in Animals.”

For the past 30 years, Terrace has been investigating primate intelligence. He’s concerned with these questions: In the absence of language, how do monkeys process information? What is their mental framework? How do they form thoughts? What do they think about?

“I decided to study thinking without language,” Terrace says, “and in particular, how monkeys create sequences in the absence of language.”

Entering the Minds of Monkeys

The hall is long, wide, devoid of color or natural light. White cinder block walls. White ceilings. The cement floors are painted a drab, high-gloss grey. In this sterile environment, in a building on the health science campus, Terrace’s monkeys are helping him make sense of how our minds work.

He works exclusively with rhesus macaques, monkeys that have hairless beige faces that resemble rubber masks. The rest of their bodies, with the exception of their rear ends, are covered with hair. Most of them are brown and tan. Oberon is an exception; his hair is shock white, even though he’s no older than the others. They have long tails, which lie flat when they’re sitting.

Most of them — Macduff, Oberon, Prospero, Horatio, Augustus, Benedict — are named for Shakespearean characters. Terrace also named a couple as homage to two of his favorite composers, Mozart and Coltrane, and two others for pioneering psychologists, Lashley and Ebbinghaus.

The monkeys play and sleep in individual cages so they won’t hurt each other. Vet technicians check on them regularly, feed them Purina Monkey Chow, and give them apples and oranges throughout the day. They place the monkeys in an exercise pen for hours at a time, where they swing and dangle from ropes and branches. But each weekday morning, for about an hour, the monkeys take part in elaborate tests.

Terrace and a team of lab assistants and graduate students are currently conducting four studies with the monkeys. One tests their ability to memorize and recall information. Another shows the monkey’s ability to demonstrate logic and reasoning. Another records their understanding of thematic concepts. A fourth tests metacognition — their ability to think about their thinking.

The trials are conducted in four-foot-square testing chambers, about twice the height of the monkeys, where monkeys tap on touch-screen monitors to record their choices. If they answer correctly, banana pellets pop out of a dispenser. A miniature camera records their actions, which are displayed on a video screen for technicians to observe. The computers also record how fast they answer, when they pause, and for how long.

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