Testing for executive function in gibbons.

It is a commonly held assumption that we humans have a unique thinking ability that distinguishes us from other animals. However, every time scientists have tested that assumption—whether testing for self-recognition in a mirror, the existence of language, problem-solving ability, knowing what another is thinking (or “theory of mind”), deception, self-awareness—there’s always been at least one nonhuman animal that can do it. “What we’re looking at now is executive function,” says Joanne Altman as she monitors undergraduate students training a Javan gibbon to take the Wisconsin Card Sorting Test (WCST). Commonly used for testing people’s capacity for executive function, the WCST also requires several other cognitive functions, including working memory, visual processing, and attention. Although the gibbons certainly have those other cognitive functions, fruit rewards from the student trainers help keep the gibbons on task and ignoring the people who come to see them at the Greensboro Science Center in North Carolina. The WCST requires an animal (human or otherwise) to sort cards according to a pattern, which they learn through binary (rightwrong) feedback from the tester. Several times during the test, and without warning, the pattern changes. Animals demonstrate executive function when it is clear that they perceive that the old pattern is no longer valid and learn the new pattern. People typically perform well on the WCST unless they have a neurodegenerative disease, certain mental illnesses, or brain injury, especially to the prefrontal cortex. “That part of the brain is the most evolved part of the brain, and even in humans it doesn’t fully develop until we’re about 24 or 25 years old,” says Altman, a psychology professor and the director of undergraduate research at High Point University. “That part is responsible for executive function and decision-making, particularly about risky decisions, which is why young adults tend to get themselves into trouble.” Like most animal behavioral research, just training the gibbons to take the WCST is extremely time intensive. The student researchers have been coming to work with the apes every day for months. Each training session itself only lasts a few minutes, however, after which the animals are rewarded with a handful of fruit all at once—the “jackpot” as the students call it. Whether the gibbons can be trained to take the WCST and, if they can, also demonstrate executive function, Altman still hopes eventually to also test for executive function in orangutans and elephants. Like any scientist, Altman will wait for the experiments to be run, but thinks she has a good idea what the results will be: “Personally, I think we will find that one or more of the higher-order animals— the big-brained animals—have every kind of cognitive capacity that we humans do. So, it’s not a qualitative difference in how we humans differ from other animals, it just might be a matter of degree.” Joanne Altman monitors undergraduate students training a Javan gibbon to take a test for whether the apes have executive function, a cognitive capacity currently considered unique to humans. Image courtesy of Robert Frederick.