Do monkeys have a theory of mind?

The new issue of Smithsonian magazine profiles the work of Yale psychologist Laurie Santos, 32, who hangs out with monkeys on an island off the coast of Puerto Rico to get inside their heads. She draws from cognitive neuroscience and evolutionary psychology to suss out whether these non-human primates have a "theory of mind." The "theory of mind" refers to the ability to recognize and understand others' thoughts, desires, intentions, and feelings--basically to get where someone else if coming from. Santos tries to show that monkeys have this cognitive capacity. The article presents several of her field experiments and the results. From Smithsonian:
"This is what we do," (Santos) says, "hike around looking for monkeys by themselves who are hungry and want to play. It's hard to find social creatures by themselves," she adds as she backs out of the field of view of a primatologist's video camera, "and even harder to find ones that aren't being followed by other researchers..."

Santos' interest here is in what psychologists call "theory of mind," the ability to impute thoughts and intentions to another individual, one of the cornerstones of human cognition. "Sitting here talking with you," Santos explains, "all I can see is your behavior, but I draw inferences about your desires and thoughts. The interesting question is, how far back in evolutionary time does that ability extend? Can it exist without language?" As recently as a decade ago, the conventional wisdom doubted that even chimpanzees, which are more closely related to human beings than are monkeys, possessed theory of mind. This view is changing, in large measure because of the work of Santos and her collaborators. With her students in tow and a small bag of grapes in her pocket, Santos is now out to demonstrate the phenomenon–if a Macaca mulatta can be induced to cooperate.



  1. “The ‘theory of mind’ refers to the ability to recognize and understand others’ thoughts, desires, intentions, and feelings–basically to get where someone else if coming from.”

    So in humans, for example, this would be like where Dubya looks into Putin’s eyes and reads his soul? And discerns where the leaders of Iraq and more recently Iran are coming from?

  2. Theory of Mind, Model of Reality, Game Rules, Empathy. Lower primates obviously think about things, but it’s pretty hard for us to imagine what those thoughts are like. Most of our thoughts are based in our language. Although, most of what passes for human language is just monkey talk (making noise to be heard).

  3. There are a species of monkeys in Japan that rinses off the potatoes they are about to eat in salt water for flavor.
    What frustrates me about this whole debate on teh cognitive skills and brain functions of primates is that skeptics doubt even when a Chimpanzee knows sign language and can communicate their thoughts and feelings and desires. There are chimps that like to paint and they tell you what is pictured in their art work and people among the scientific community doubt their intellect.
    I believe this development in the research of monkeys will yield even less positive acclaim considering the evidence that critics cast doubt upon these same skills and abilities present in the “great apes”.

  4. I’m in favor of “uplifting” lower primates so that they are at least intelligent enough to be toilet-trained, and that means to use and clean a toilet. I want a whole crew of uplifted chimp-slaves to clean my house. How totaly-high-tech-Planet-of-the-Apes-fun would that be? They’d just be working pets, like shepard dogs and guard cats.

  5. I’d disagree that our thoughts are based in our language; if we think about thinking for a minute we’ll quickly “see” how our thoughts occur in pictures/visual form, and how emotions are a blend of visual imagery, biochemistry, and that strange something that distinguishes conscious life from everything else. Language is just the ability to translate direct experience into a transmissible abstraction, but falls far short of being able to communicate the full depth of our thoughts and emotions.

    As we move along the spectrum of consciousness from the smallest brains all the way up to humans, we’re moving along a slope of gradually increasing complexity of all cognitive functions and abilities. At some point emotion, abstract reasoning, and language emerge among the higher species and continue to evolve in complexity all the way up to humans (and ultimately to whales, some would argue…).

    So, it seems to me that every species would possess the characteristics of the Theory of Mind proportional to the degree of brain/cognitive complexity displayed by that species. Consciousness, then, is an evolving continuum more so than a series of arbitrary lines that differentiate abilities (i.e. there’s no precise moment we can point to when empathy emerged within a species of primate).

    I guess the question then becomes: How much cognitive complexity does something need to have before we should begin to care about what that something is thinking or feeling?

  6. Every ten years a new set of psychology hotshots approach primatology with the goal of talking to apes or monkeys. It’s easy. Our cousins are intelligent and quick to learn — as much as they can learn, that is. Sure, they can be taught signs and sign language, but what they can’t be taught is the ability that is uniquely human: the ability to symbol.

    Symboling is here defined as the ability to arbitrarily bestow upon a thing or event a quality (or qualities) that cannot be perceived by the five senses, and the likewise ability to appreciate and share such a bestowment from another person. Human language is based on this ability. And Koko, Cheeta, and King Kong ain’t got it.

    Any intelligent species (and there are many) can sign, but only we can symbol. It is, I guess, both our glory and our curse.

  7. The difference is the animal kingdom is “In Minded” We are the only Primates capable of being out of our Minds. Capturing monkey brains in human bodies for study requires something more than grapes. It takes patience, wisdom, compassion, and a deep desire to serve the notion that Humans are capable of accepting responsibility for life on this Planet. When it gets to the point where the majority of Humans are Parasites life will do what life has to do to heal. Dubya can only get a real legacy by looking at his own eyes in a mirror. If He can Grow Up enough to use the power of His position to move the Human Experience toward life sustaining, and away from the Profit in Pain and Suffering that seems to have infested us, His legacy in History will be awesome. The simple notion that life is more fun than most People make it out to be, and We can support each other in that Magical “Pursuit of Happiness ” Keeps hope alive in Me. Happy New Year

  8. Spot on in comment #3, ONEHANDEDBANDIT.

    Also, after many decades of research into just this sort of thing, what ass decides to start from zero with pinheaded monkeys? And why does she think it all starts with spoke language in humans? That is already smelling like hogwash.

    I just hate the idea of primates wasting away their lives in her “lab” back at Yale.

  9. “but what they can’t be taught is the ability that is uniquely human: the ability to symbol”

    There is an argument that the bee dance is a form of symbolism used by non-humans: Communication of distance, quality of food source, and other things; with use of the sun and the horizon as reference points.

  10. Daniel Povinelli, formerly at (I think?) the University of Louisiana, did a whole book’s worth of experiments on things like this called “Folk Physics for Apes.” In it, he argues that a lot of claims about primate Theory of Mind and general intelligence is the result of wishful thinking/observer bias. He then does a whole heap of experiments which seem to indicate that primates are not at all as smart as we think they are. he attributes this to the fact that researchers come to love the little guys, and think of them as “just like little people.”
    For instance, he did one series of experiments in which chimps were unable to understand that researchers with buckets over their heads could not see them.

  11. sorry– for further reading, check out his article at

    In it, he argues that part of the issue is that we still, in some ways, view the human mind/brain as the “best,” rather than just the combination we’ve ended up with. “The overzealous efforts to dismantle arguments of human uniqueness have only served to show that most comparative psychologists working with apes have yet to set aside the antiquated evolutionary “ladder.” Instead, they have only attempted to pull chimpanzees up to the ladder’s highest imaginary rung — or perhaps, to pull humans down to an equally imaginary rung at the height of the apes. A true comparative science of animal minds, however, will recognize the complex diversity of the animal kingdom, and will thus view Homo sapiens as one more species with a unique set of adaptive skills crying out to be identified and understood.”

  12. People need to understand this basic difference.
    Chimps, gorillas, gibbons, bonobos are not monkeys, they are apes, who would be insulted, if pride is an emotion in their repertoire. Not sure about that one.
    PS didn’t you SEE the Planets of the Apes? Not so good for the humans.

  13. #12: Very funny! I loved the disposability of it. I want a red one! In actuality I’d like a robotic version.

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