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Chimps Nurtured by Humans Have Better Grasp of Tools

  • Adriana Salerno

Everyone is familiar with chimpanzees. We've seen the clever apes at the zoo, in the circus, in the movies, in nature documentaries. DNA analyses have revealed that chimps are humans' closest relatives. But very few people understand how chimps think. Now, researchers at Ohio State University have found that chimpanzees that have been nurtured from birth by humans are more capable than other chimpanzees of using and understanding tools.

Sally Boysen has been studying chimpanzee cognition for over 30 years. A psychologist at Ohio State University, she has focused on chimps' ability to understand numbers and tools, their ability to recognize loved ones, and their seemingly altruistic natures. In the near future, she hopes to teach them to read simple English words. She also really loves her chimps.

Boysen's most recent research compares how three very different groups of chimpanzees performed on two tests. One group was made up of chimpanzees who had been raised under standard laboratory conditions, with no meaningful interactions with humans or each other. Another group contained chimps who had been raised under lab conditions and later taken to a sanctuary were they were able to interact with other chimps.

Finally, there was Boysen's group, which resided at Ohio State and was comprised of so-called "enculturated" chimps. These chimps had had highly social interactions with humans as well as other chimpanzees since they were very young. They had also been immersed in an environment similar to those in which young human children develop, and given a wide range of objects and experiences so as to better understand how the world around them works.

Boysen says the two tasks in her study tested the chimps' ability to use and understand properties of tools to retrieve a food reward.

The first task involved two different rakes: one had a solid, wooden head, and the other one had a flimsy, sponge head. A small cup of yogurt was placed in from of each rake and the chimps had to pull the right one toward them to retrieve their reward. Boysen says, "Even our very youngest chimps, who were first tested at about two years of age, immediately pulled the rake that had the right functional properties, that is, it was rigid and could pull the yogurt towards them." None of the chimps tried to use the rake with sponge strings, the researcher says, "because, after all, that wouldn't work."

The second task was a more complicated version of the first, in which they had two identical tools to work with. These had what were called hybrid heads, that is, one side was rigid and the other side was flimsy. The cup of yogurt would then be placed in front of the wooden side of one rake and in front of the sponge side of the other. "They really had to understand the properties of the tools if they were going to be able to retrieve the yogurt," Boysen says. "And, in fact, our chimpanzees were able to do that, whereas the lab animals that were tested a few years ago failed both tasks."

The group of sanctuary chimps turned out to be the most informative for the researchers, since they performed well on the first task, but failed in the second more complicated one. Boysen believes that trial and error helped them with the easier task. "They likely learned the perceptual characteristics, that is, which rake looked like what, and the one that looks like this functions so we'll keep using that."

The researcher feels that her study shows that chimps need to be raised and cared for in the best environment possible, regardless of whether they live in a zoo, or a lab, or the circus. "They need a very rich and stimulating environment to really maximize their potential, and health, and long life, in captivity," says Boysen.

Even though her primary interest is to study chimpanzees and their abilities to understand the world around them, Boysen believes her research, inevitably, has significant implications for the field of human cognition. This particular study, she says, suggests the importance of early cognitive development in children. If people want to maximize their child's potential, she says, they need to focus more on the early years between birth and age five.

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