Natasha, a chimp at the Ngamba Island Chimpanzee Sanctuary in Uganda, has always seemed different from her peers. She's learned to escape from her enclosure, teases human caretakers, and scores above other chimps in communication tests. Now, Natasha has a new title: genius. In the largest and most in-depth survey of chimpanzee intelligence, researchers found that Natasha was the smartest of the 106 chimps they tested—a finding that suggests that apes have their geniuses, too.
"Natasha was really much better than other chimps," says biologist and first author of the new study Esther Herrmann of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Herrmann and her colleagues had previously tested chimps in a study designed to compare the skills of the animals with those of human children. During the study, they noticed a wide range of skills among the chimps and wondered whether they could measure this variation in ability—and whether there were studies that could predict the chimps’ overall performance in all areas, like an IQ test in humans. So they gave a battery of physical and social tests to 106 chimps at Ngamba Island and the Tchimpounga chimpanzee sanctuary in the Republic of the Congo, and to 23 captive chimpanzees and bonobos in Germany. In one experiment, chimps were asked to find food in a container after it had been shuffled around with empty containers. In another, they had to use a stick to get food placed on a high platform. The researchers analyzed the data to determine if the scores in some tests helped predict performance in others.
"In general, we don’t find any kind of general intelligence factor that can predict intelligence in all areas," Herrmann says. "But we did find a big variation overall, and this one outstanding individual."
The stand-out individual, Natasha, was the chimp that caretakers—who don’t administer tests to the chimps but do feed them, clean their cages, and accompany them on walks—consistently ranked as the smartest based on only the way she interacted with them. But there's nothing about Natasha's life—extra attention or time spent with humans, for example—that explains how she became so astute. "Motivation and temperament probably play a role," Herrmann says. "That's something that we want to look more into."
In general, apes that were good in one area—such as tests requiring creative tool use—were not necessarily good in another—such as copying the actions of a test-giver to get a reward, the team reports this week in the Philosophical Transactions of the Royal Society B. But continuing to add new challenges to the battery of tests still could lead to a standardized intelligence factor, Herrmann says.
Or, it could mean that there are multiple types of intelligence in apes that don’t necessarily relate to each other, suggests primatologist Brian Hare of Duke University in Durham, North Carolina, who wasn't involved in the research.
"This study is top-notch and shows clearly that our traditional ideas about intelligence no longer hold," Hare says. "There are many different types of intelligence that vary independently of one another. This means there are many different types of genius, even in animals."
Herrmann admits that Natasha may have just happened to score highly in each area, and that there are likely other chimps out there that can score as high as Natasha. She has a gut feeling about one in particular that hasn't been tested yet, but who seems highly motivated to solve puzzles and tests to get rewards. Future research on Natasha—and other genius-ranking chimps that the researchers track down—might reveal what social or genetic factors make the apes score higher than others, she says.