Monkeying Around with Abstract Ideas

Ericson '96 tests the abilities of tamarin monkeys

This story is adapted from one that was published in the Harvard-Radcliffe Undergraduate Research Programs Newsletter.

By John Marchetti

Special to the Gazette

As a psychology concentrator with an interest in nature, Brian Ericson '96 was pretty confident that he'd enjoy Professor Marc Hauser's cross-disciplinary course on the evolution of communication. The class -- listed as Anthropology 170 for those of you following along in Courses of Instruction -- looks at the neurobiology and cognitive psychology of animal communication systems.

What Ericson wasn't counting on was that the course would lead him to a research position in Hauser's lab, an opportunity to conduct his own experiments, and a close friendship with a bunch of monkeys.

"Marc tied a lot of what we talked about in class to ongoing projects in his lab," he says, "and I grew very interested in his work." Toward the end of the semester, Ericson asked Hauser if there were any openings in his lab. Hauser had been impressed with his performance in class and happily signed him on.

Along with the undergraduates, graduate students, and postdocs that populate most research sites, Ericson found himself working alongside a group of nine cotton-top tamarin monkeys. The tamarins are subjects in Hauser's ongoing study of the cognitive mechanisms underlying primate behavior.

They are tiny animals -- "no bigger than a can of Sprite," according to one member of the lab -- that are particularly suited to captivity. They also score high readings on the Cute-O-Meter, which can pose a unique problem for a researcher. "Their faces are so expressive," smiles Ericson, "that it can be pretty tempting at times to read human feelings into their actions."

With support from the Harvard College Research Program (HCRP), Ericson began to explore the monkeys' ability to develop abstract ideas. "Initially, it was assumed that all animals were capable of 'thinking' but only humans were able to formulate abstract concepts and apply them to novel situations," wrote Ericson in his proposal to the HCRP. "Recent research has suggested, however, that this reasoning ability may not be unique to mankind, and that some primates possess similar abilities."

Ericson launched a series of experiments to test the monkeys' understanding of what he termed "natural laws": connectedness, impermeability, inertia, and conservation of energy. In his connectedness experiments, a monkey was presented with two strips of cloth on a long tray. Only one of the strips was continuous, while the other had a gap cut in it. At the end of each strip opposite the monkey, Ericson placed a treat. The monkey was then faced with choosing the strip that, when pulled, would successfully drag the food closer. In subsequent tests, Ericson varied the size, style, and position of the "gapped" and continuous strips.

"It was amazing how well they generalized and abstracted the idea of connectedness over the different tests," Ericson says. "A big test came when I began to use very complicated strips that included wave shapes and gaps bridged by pieces of string. Many of the monkeys mastered these tests immediately, which clearly indicates they'd developed a generic concept rather than simply succeeded at memorization."

Not surprisingly, the monkeys varied a great deal in their abilities. "Some monkeys consistently passed through the tests several days before the others," explains Ericson, "while one exceptional monkey named Locke was at times weeks ahead of the pack." Still, there was enough consistency across subjects to amply support Ericson's hypothesis.

When completed, Ericson's work will contribute to the body of experiments on primate cognition conducted by Hauser's lab over the past few years. "There is an overall scheme to everything that goes on in the lab," explains Ericson. "We are all very aware of each others' experiments.

"The lab is a very cooperative place," he continues. "Marc puts a big emphasis on our weekly lab meetings because he is very interested in hearing a lot of different perspectives."

Hauser is quick to praise Ericson's contributions to his laboratory. "I give our students considerable freedom to be creative, to help design experiments, implement them, and then carry out analyses of the data," he recently reported to the HCRP. "Some students find this freedom intimidating. Ericson took the freedom and ran with it, and many of his experiments have worked beautifully."

Ericson recently had the good fortune to join Hauser and a handful of his undergraduate researchers on a trip to Cayo Santiago. The small island off the coast of Puerto Rico is home to both Hauser's field research site and close to 900 free-ranging rhesus macaque monkeys. Over 10 days on the island, the group performed a number of tests that Hauser expects will lead to a published paper. "People have asked me how the vacation was," says Ericson. "I tell them that the island was beautiful, but we worked hard."

Ericson plans to remain in Hauser's lab through graduation. "It has all been a great experience," he says. "My work in the lab has become a very important part of who I am at Harvard."