Known Unknowns: Monkeys May Recognize the Limits of Their Own Knowledge

Media contact: Noelle Lemoine, communications assistant; tele: (413) 597-4277; email: [email protected]

WILLIAMSTOWN, Mass., October 17, 2017—A recent study appearing in Proceedings of the Royal Society B found that non-human primates exhibit a metacognitive process similar to humans. Metacognition is the ability to know what you do or don’t know—and how confident you are in what you think you know. The paper’s title is “A metacognitive illusion in monkeys.”

The researchers, including Williams College Associate Professor of Psychology Nate Kornell, report that monkeys, like humans, can make fairly accurate judgments about their own memories. That’s because monkeys, like people, base their confidence level on fluency, the ease with which something is seen, heard or perceived.

In the study, monkeys were presented with an image on a screen. They were then shown a second screen that contained the original image alongside several “distractors.” The monkeys were asked to identify which of the images they had seen earlier and to make a bet indicating their level of confidence in their selection. If a monkey bet high and chose correctly, it received three tokens. If it bet high but chose incorrectly, the monkey lost three. A low bet was rewarded with a single token, regardless of whether the choice was correct or not.

In further testing, the researchers found that monkeys were more likely to bet heavily on their confidence when presented with high-contrast images—a concept known as “image fluency.” This result echoed findings from studies showing that humans tend to express more confidence in a word or phrase’s correctness, trustworthiness or memorability when it is displayed in a larger type size. The findings from the new study are expected to influence research into metacognition in young children. More broadly, the researchers see their project as part of a larger exploration into whether non-human animals are “conscious” in the human sense.

Previous studies have shown that monkeys can make confidence judgments, but this is the first to investigate how these judgments are made. “The interesting thing is that monkeys and humans appear to make their judgments in the same way,” Kornell says. “We thought monkeys might be less sophisticated than we are, and ironically this would make them less prone to certain mistakes. But it turns out they use the same fluency mechanism as we do, and they are prone to the same illusions.”

Kornell says the work is part of a larger exploration into how, and how much, non-human animals monitor their uncertainty and respond accordingly. “Memory monitoring is far more central to the human experience than we sometimes realize,” he says, adding, as examples, that drivers know when their lost, readers stop when they get to a concept they don’t understand, and people estimate when they aren’t sure of an exact amount. “All of this involves monitoring uncertainty and understanding,” he says.

Kornell conducted the research along with Jessica Cantlon, an associate professor of brain and cognitive sciences at University of Rochester, and Stephen Ferrigno, a Ph.D. candidate at University of Rochester.

Kornell holds a B.A. from Reed College and a Ph.D. from Columbia University. He completed a postdoctoral fellowship at UCLA. An associate professor of cognitive psychology at Williams College, his research focuses on how individuals can increase the efficiency of their learning and how typical learners understand and manage their own learning.


Founded in 1793, Williams College is the second-oldest institution of higher learning in Massachusetts. The college’s 2,000 students are taught by a faculty noted for the quality of their teaching and research, and the achievement of academic goals includes active participation of students with faculty in their research. Students’ educational experience is enriched by the residential campus environment in Williamstown, Mass., which provides a host of opportunities for interaction with one another and with faculty beyond the classroom. Admission decisions on U.S. applicants are made regardless of a student’s financial ability, and the college provides grants and other assistance to meet the demonstrated needs of all who are admitted.