Kingdom of the Planet of the Apes Raises the Question: How Intelligent Are Apes?

Kingdom of the Planet of the Apes. King Kong. Curious George. It’s clear humans have a fascination with our closest living relatives in the animal kingdom.

The newest installment of The Planet of the Apes franchise hits movie theaters on Friday. The science fiction storyline puts humans in the forests, and apes as the dominant primate. But in real life, how intelligent are primates? Primatologist Zarin Machanda has dedicated her life to studying this most social order of animals — of which we belong. We share many traits with other primates, such as establishing and maintaining societies and other permanent groups.

Apes, which include orangutans, gorillas, chimpanzees, and bonobos, are incredibly charismatic animals to study. There’s no doubt they tell us something about ourselves, Machanda says. However, when we consider them mirrors, we risk missing out on the true scope of all they really are. Machanda spoke with Inverse about their brilliant minds — and the cognition science still out of reach.

This conversation has been edited and condensed for clarity.

Inverse: Are apes smarter than we thought?

Machanda: Yes and no.

With humans, we can just ask each other. But with apes, or with any of the primates, we have to come up with experiments to figure out what they're thinking. One of the ways that we do that is that we modify experiments done for non-verbal babies.

But one of the problems with that, is that in some way, you have to ask the question: How do we know what we know? Are we actually devising tests that get at something relevant? Are apes smarter than we thought, or are we just better at doing our jobs?

It's just natural to be a human and to watch behavior and ascribe human emotional or cognitive states to that behavior. The classic example of this is mirror self-recognition. When you look in a mirror, you understand that, the thing looking back at you, is you.

Mirror self-recognition has been used to kind of ask whether or not animals have a sense of self-awareness.

In general, we see that chimpanzees and orangutans and bonobos all can recognize themselves in a mirror. But none of the monkeys can, like a baboon. It is actually why most primate researchers who live in habitats with monkeys are missing the side view mirrors off of all of our cars. Baboons see “another” baboon and destroy your side-view mirror.

Gorillas have always failed the mirror self-recognition. But it turns out we were just doing it wrong. Gorillas don't actually like looking anything in the eye, including themselves. That initial look just freaked them out so much that they couldn't acclimate to the mirror.

Researchers eventually rigged up all these video cameras and TV monitors and did a very similar kind of study. And the gorillas passed the test.

In that sense, they're smarter than we knew before, because we're better able to ask the question.

So then, part of the practice of being a primatologist is to recognize our biases in grasping their world?

Yeah, absolutely.

Theory of mind in human psychology asks, do you have a sense that other individuals have a mind? Do you understand that other individuals have thoughts that might be independent of your own thoughts?

Humans actually don't start having a theory of mind until they're about four, which is why if you've ever played hide-and-seek with a two-year-old they'll sometimes stand in the middle of the room and close their eyes and think they're hiding.

It’s very adorable.

Right? But that's the theory of mind that's not yet developed.

For a long time, even into the ‘90s, chimps had not really passed theory of mind tasks. But it turned out it's because we were maybe asking chimps, ‘do you understand what humans are thinking?’ Instead, of, ‘do chimps behave in a way that indicates that they understand what another chimp is thinking?’

Brian Hare, a researcher at Duke, did a study looking at a competitive task, which is much more relevant for a chimp competing for food. They do pass the tests in more ecologically relevant kinds of contexts.

Will you be seeing the new movie?

Yeah, I mean I'll probably take my [research] lab to see it, I suppose. Though I may be partial to King Kong myself, compared to Planet of the Apes. Gorillas display very subtle changes in posture and glances. It does take a while to pick up on some of those things, so good for him [the motion capture actor that played Kong, Andy Serkis].

One pet peeve is that the bad guy in [War for the Planet of the Apes] is a bonobo, which is hilarious. Because bonobos will always make love, not war. They're like the least aggressive of all the primates.

My big pet peeve is that most primates don't have whites around their eyes. Some individuals do, but for the majority of the species, we wouldn't describe it that way.

Also, the whole idea that a chimp could develop language. That they inhale mutating gas and then all of a sudden they can speak is just morphologically not possible.

Why wouldn’t they?

One of the reasons that humans are able to produce the fine-tuned sounds that we make in language is partly because of our larynx. Our voice box is actually much lower in our throats than a chimp.

As we get older, our larynx descends into our throats. It's actually what allows us to make the sounds of language.

What is it that apes generally lack in their brains for language?

The brains of chimps and apes are more similar to the brains of humans than any other primate. We humans clearly have parts of our brain specifically devoted to language. They overlap with parts of the brain of an ape that are devoted to communication.

But, what seems to be the big difference is that apes do not seem to be able to produce grammar.

Apes actually have some comprehension of grammar. Captive chimps can understand sentences in a way that suggests that they understand how a sentence is constructed.

There's a study where they asked a bonobo to put pine needles into the refrigerator. And then they do it. It's a sentence they never would have heard before and they don't just put the pine needles with the refrigerator, or on the refrigerator; they put them inside the refrigerator. They can identify the two words and they understand that the word “into” connects those two words.

Apes have never been able to produce grammar. In all of the sign language studies or lexigram boards (where they have buttons they can push that mean different things), they've never been seen making a grammatical sentence.

So grammar production is the bridge that apes just don't cross?

It certainly seems that way — that it is the production of language that is the bigger kind of stumbling block.

That said, their comprehension is still not sophisticated. An ape wouldn’t follow along if you read a book to them, for instance.

How do primatologists rate ape intelligence?

We're realizing that there is a kind of general intelligence.

I think most primate researchers have had experiences where you see those wheels working inside their brains.

But there are lots of domains of cognition we have to consider on their own.

Grammar is one of them. Another is memory. There are some chips that are phenomenal at memory. They knock humans out of the park.

But are apes as smart as humans? No. Absolutely, humans are the smartest primates. This is why we're on a Zoom call right now, talking about chimps, as opposed to them being on a Zoom call, talking about us.

What about emotional intelligence? For instance, do apes feel empathy?

I don't think you can show that any one action an ape does is empathy. I don't think we have reached a point in our research abilities where an experiment can show that.

Do I think it's possible to have empathy? Absolutely. Do I think it's experimentally provable? No.

Example: You see two male chimps, let’s call them Johnny and Makoku. For 25 years, every time you see one, you see the other. They have always been together. You see them groom each other constantly.

Say over five years the amount of time that Johnny grooms Makoku is equal to the amount of time that Makoku grooms Johnny.

Does that mean these two male chimps like each other, they will sacrifice for each other? Are they really good friends, even keeping track of their mutual grooming over five years?

All they might actually be doing is keeping track of only this 10-minute time frame. The only calculus that they made is you groomed me for five minutes. Now, I'm gonna groom you for five minutes. And has nothing to do with keeping track, or being friends, or anything other than I got groomed for five minutes.

It’s not a sign, necessarily, of equity and devotion to each other.

Humans are great at this because we have language, we can track all of these interactions because we can write. We don't even have to remember.

I'm not saying that chimps don't have friendships. I actually have written lots of papers about these long-term bonds.

But you have to do the due diligence. I do think that it's our responsibility to also understand chimps outside of humans, right? Like chimps are not just studied because of what they say about humans. And because of the similarities to us. On their own, apes are a really interesting species. It behooves us to treat them not just as mirrors of ourselves.