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The Monkeys Know What’s Up

Self-awareness isn’t what sets up apart from other animals, even if a lot of early science assumed that to be the case. Monkeys, too, demonstrate metacognition, and they may have other kinds of awareness as well.
A baboon performs the mirror test. (Photo: Moshe Blank/Wikimedia Commons)

A baboon performs the mirror test. (Photo: Moshe Blank/Wikimedia Commons)

Self-awareness, the philosophical “I” that is able to reflect on our place in the world, is what sets us humans apart from other animals. Or does it?

Descartes famously proclaimed “cogito ergo sum,” or, “I think therefore I am,” to capture the existential reality that the only thing in the universe that cannot be doubted is the fact that “I” am thinking. Psychologists would call this a metacognitive thought—thinking about thinking. Through metacognitive monitoring Descartes became certain that he existed and could build the rest of his reality on this fundamental truth. He was thus self-aware, and most of our early science and common sense is based on this being a very important and maybe uniquely human thing. Descartes himself believed animals lacked this “I,” and thus did not have a mind or a soul.

Modern science has shown that there are certainly others in the animal kingdom who, to varying degrees, demonstrate metacognition and self-awareness. Gordon Gallup that chimpanzees, our closest evolutionary relative, could recognize themselves in a mirror. They understood that the object in the mirror was their body, and thus things they saw in a mirror—such as a red splotch on the mirror image’s face—was actually on them. Since then, a few species have passed this test, including all the other great apes (bonobos, gorillas, orangutans, and humans over 18 months old), dolphins, and the Eurasian magpie. Most fail, including monkeys that, while more genetically and neurologically distinct from us than apes, are closer to us than a dolphin or bird.

Although they lack language, psychological tests show that rhesus monkeys have a kind of self-awareness very similar to our own.

But Descartes, the great doubter, might be uncertain about how to interpret these results. Some animals might understand their bodies, but what makes humans special is that we understand our minds. If the mirror test is definitive, why do magpies pass but other cognitively sophisticated avians such as crows and parrots do not? Are human babies born mindless (or soulless)? Why should animals care about a mirror or a mark on their face? Uncertainty surrounding the interpretation of the mirror test led scientists to search for a similar test for the mind.

They found it, of all places, in the study of uncertainty itself. In a coral pool in Florida, J. David Smith and a team of researchers tested whether a dolphin knew when it did not know an answer. The dolphin could answer basic perceptual questions, specifically about the pitch of different tones, using buttons. Questions could be easy or difficult, and getting them correct earned a food reward. It could also make use of an “I don’t know” response that allowed it to avoid answering the question and instead get a guaranteed win. The dolphin answered the easy questions, and escaped the hard ones, suggesting that it was aware of its own uncertainty when faced with a difficult choice. It may or may not have the “I” like Descartes, but it has doubts, it recognizes those doubts, and it can use them to adjust behavior.

Since Smith’s test, several species have passed this uncertainty-monitoring task. Rhesus monkeys in particular have passed perceptual tasks like the one described above (but done visually rather than with tones). They have used the uncertainty response in tasks judging abstract relationships like sameness vs. difference and numerosity, and even in situations where the uncertainty response does not give a guaranteed win but instead only the opportunity to escape the question. In some cases, instead of judging the difficulty of a decision, they judged their own memory strength (dubbed “metamemory”) or made metacognitive responses based on whether they had seen or not seen certain information.

In one interesting case monkeys occasionally had their memory erased using transcranial magnetic stimulation—a non-invasive technique that sends electrical signals into the brain—and they could identify the times when their memory was stolen.

But Descartes still might have a bit of doubt left. The rhesus monkeys in particular are curious because they do not show mirror self-recognition. Why would they monitor their minds but not be aware of the bodily actions their minds presumably direct?

The answer is a bit more practical than philosophical. Rhesus monkeys live in a society built on threat and intimidation. When shown a mirror, their instinct is to attack it. Various techniques are being explored to see if they can calm down enough to eventually recognize themselves, but so far they have not succeeded in fully doing so.

But there is a philosophical problem too. Metacognitive escape behaviors imply mental self-awareness but are not direct reports of it. Touching a dot on your head after seeing it in the mirror is a direct report of bodily, but not necessarily mental, self-awareness. Humans, of course, can directly report their mental states.

In a study recently published in Animal Cognition, I tried to solve both the pragmatic and philosophical problems using a task that both required mental self-monitoring and the identification of actions. In humans it is known, psychologically and neurologically, that the feeling of self-agency—or the sense that some actions are caused by you—comes from monitoring both mental intentions and physical outcomes. We often feel the Cartesian “I” caused something to happen, and we can identify what we caused.

Six rhesus monkeys—housed at the Language Research Center at Georgia State University—and 40 undergraduates were given joysticks, which they used to move cursors on a computer screen while a “distractor” cursor moved more or less independently of their actions. The distractor cursor sometimes partially matched the movement of the subject’s joystick, sometimes it moved exactly opposite their actions, and sometimes it moved at random. After moving for a few seconds, both humans and monkeys were able to identify which cursor was theirs by selecting it from a list of items that included the distractor.

Were they just visually tracking the cursors? Besides human verbal reports indicating they were not, monkeys and humans both had an easier time distinguishing their actions from opposing actions, which had equivalent visual characteristics (moving at the same time, the same distance, etc.) but differed in self-agency. They directly reported their actions, using not only physical observations of their bodies and environment, but also mental awareness of their intentions.

This discovery reveals that rhesus monkeys, like humans, demonstrate both metacognition and self-agency and use it to make decisions. Although they lack language, these psychological tests show that they have a kind of self-awareness very similar to our own.

Consider the simple action of picking up your phone, for example. You plan to pick it up, your brain tells your muscles to move to pick it up, and then your senses actually experience picking it up—the feel of it, the weight of it, the sight of it. You know that you’ve caused the action because your experience matches your expectation and your intention: You wanted to pick up the phone, you acted, and you realize you actually did it. This is the self-agency that rhesus monkeys demonstrate.

Would Descartes have anything left to doubt? Perhaps one thing. Suppose, after picking up your phone, a thief tries to snatch it from you. He holds one end while you hold the other, and you pull in opposite directions. Rhesus monkeys would be able to identify their actions and the opposing actions of the thief, and could make decisions using that information. They might not be able to understand the intentions or motivations of the thief, however.

Monkeys know what they themselves are doing, but there is no evidence—despite many experimental attempts—that they understand anything about the minds of others. Humans have other-awareness that often goes hand-in-hand with our self-awareness. We know rhesus monkeys, and probably all of the animals described above, have some form of self-awareness, but we don’t know how they conceptualize it, or what is it like for them.

Evolutionarily, the discovery of self-agency shows us that humans probably didn’t develop these skills in one drastic leap or receive them as a great metaphysical gift. Self-awareness likely developed gradually and other species probably have reflective minds similar to our own. Indeed, studies by Takaaki Kaneko and Masaki Tomonaga have shown that chimpanzees also have self-agency, and other researchers have observed chimps demonstrating small hints of other-awareness such as competitive perspective-taking or empathy (which, you might notice, is not always the most developed skill in humans).

It’s more than just a philosophical debate. Many humans have deficits in mirror self-recognition, metacognition, or other-awareness. These include individuals with autism, Alzheimer’s disease, and schizophrenia. Researchers are already beginning to apply self-agency tests to these populations in order to identify, and perhaps increase, their self-awareness.