The cognitive trade-off hypothesis

In this post we are going to talk about The cognitive trade off hypothesis. We will explain what it consists of and what are the foundations of this theory.

The cognitive trade off hypothesis

The cognitive trade off hypothesis indicates that humans develop language under pressure from our habitat, and chimpanzees in theirs have been forced to reinforce their memory to recognize where their livelihood is.

The primatologist Tetsuro Matsuzawa has dedicated his life to studying the intelligence of chimpanzees. Thanks to him we know that we are not the smartest beings on the planet, our closest living relative beats us in visual memory.

A three-year-old chimp sits in front of a computer screen, where randomly distributed numbers 1 to 9 appear for a fraction of a second. The primate is able to remember where they were placed in increasing order. He points his finger at them at the empty screen. And he does it at blazing speed! How long has it taken?

He hasn’t even had time to blink. Shouts of admiration in the room for the images that have just been projected. 

Laughs. Nobody is capable. The smartest will have been able to place two or three numbers at most. Awesome, right? I tried it with my college students and the result was 0%. It is not a question of training. They beat us in this cognitive task», says the researcher.

It is a capacity of visual memory that we could have lost as we gave way to the development of language and that our closest cousins​still retain. It is the so-called cognitive exchange hypothesis.

Tetsuro Matsuzawa, director of the Primate Research Institute at the University of Kyoto, has studied the intelligence of chimpanzees for more than four decades to understand how our minds have evolved through them.

“Chimpanzees have their own way of communicating,” he explains during the presentation of his studies at the Biodiversity Foundation, while imitating their calls of ‘hello’.

In his laboratory in Kyoto, he has a ‘partner’, according to himself. It is about Ai, a female chimpanzee that he met when he was one year old and who stars in much of his research at the University of Kyoto. Her name means love: “it’s common in Japan,” she points out.

In 2000 Ai had a calf (Ayumu) ​​that, unlike what was done before in the laboratory, has not been separated from her mother to continue with the research. “We thought it was not the right thing to do. She is present in the studios and thanks to this direct action we can work without protection”.

In fact, the team is able to sit down to do an encephalogram or an ultrasound and thus observe the volume of the brain of a fetus and its evolution in a collaborative way.

In addition to Ai and Ayumu, other chimpanzees live at the Primate Research Institute who freely enter and leave their cages and also participate whenever they want in the different cognitive tests that the researchers prepare. “We do not force them to do these experiments and each receives appropriate tasks.”

They taught them, for example, the alphabet and letters in Japanese that are translated by some colors. “There is no relationship between the symbol of the Japanese letter and the color, and they still identify it. For that you need some imagination, “he says.

This would be the main distinction between humans and chimpanzees. Imagination is a unique force of the human being and is the basis for understanding the minds of others. Chimpanzees live in the present; we also have a past and a future. They live here and now, they have no anxiety. We have hope”.

In the wild, chimpanzees learn the skills of their elders through so-called ‘learning by the teacher’ which, unlike humans, implies that they do not teach their offspring but rather learn by observation. “They show them a model that the calf repeats because it has a very strong motivation. The adult shows a very high tolerance to let them observe and learn”.

They also show other differences such as when they are young. “Only human babies cry at night. Chimp babies don’t do it because the mother is always there. ” Also, mother-to-child collaborative behaviors exist, but not vice versa. “I have seen how a mother extends a hand to her baby, but not the other way around.”

Why can a chimpanzee teach us to understand the human mind?

The chimpanzee study is fairly recent, dating back to about 50 years. But if there were no research on these animals, humans would still be convinced that we are very special specimens. We on the one hand and the animals on the other, in a strict dichotomy.

But when you start to analyze these primates in the wild and in laboratories, you realize that they are very similar and close to humans. Or they even surpass us, as our best-known research has already shown: the visual memory of chimpanzees.

Yes, they are much better at visually memorizing numbers that disappear in a fraction of a second…

It is that this capture of photographic memory does not directly exist in humans. People think that we are the most intelligent creature in the world, that we are not like dogs, turtles or birds, but I say no.

Chimpanzees are better at capturing the numbers 1-9. This is 100% safe. Many have tried to replicate it and no human can compete with young chimpanzees.

Could they surpass us in other facets?

There may be many more things they excel at, but we don’t know yet. If you show them, for example, a photo of someone they know – like Cristiano Ronaldo’s – but turned around, it is not difficult for them to recognize. 

Although they are still somewhat controversial studies and we are waiting for more data.

How do your family relationships compare to ours?

There are not many people who clearly understand family and society in humans. For primatologists who study all species (447 in total, from bonobos, Japanese monkeys, orangutans, gorillas or baboons), humans are just one of them.

If you see it from this point of view, we have a very strong bond between a man and a woman. In other primates it also exists, but it does not occur with chimpanzees. 

They can live in a group of fifty individuals or up to a hundred, but the females have relationships with all the males. Their way of living is different.

We are 98.77% chimpanzees according to our genetics. Being our closest ‘cousins’, why are we so different apparently?

One big difference is that his body is covered in black hair. However, if you look at dogs, a chihuahua or a San Bernardo are different breeds but their genetics are the same. It is a unique creature called Canis familiaris.

In humans in one generation the color of hair or eyes can be changed, the external appearance is easy to manipulate. The study of chimpanzees shows us that we cannot get carried away by physical appearances. Humans and chimpanzees are almost the same creature.

You have spent a lifetime studying chimpanzees. What would you like to face in the future?

Now I have started to investigate bonobos, they have dominant females, not like chimpanzees, their sexual behaviors are very different and they do not kill each other either. Gorillas too.

Family is the key

For the primatologist, the key to these differences is that humans form families and chimpanzees do not. «In Africa, in groups of 40, 50 or even 100 individuals there are no families. 

The relationship between mother and baby is very clear, but you don’t know who the father is. To avoid incest, young females leave the groups and the base of the group is the males,” he describes.

“The reason is that we need the help of others to survive, they don’t. The chimpanzee mother is very strong, she doesn’t need a ‘husband’, she can raise her baby by herself, ”she says. And he emphasizes: «Sharing is what makes us human. It’s exciting to see a baby offer food to her mother or a stuffed animal.

At the same time, we can understand the minds of others, fantasize, recreate the past, and imagine the future.

 “We pay for it with anxiety and despair, something that chimpanzees do not have, but that imagination also allows us to have hope,” he points out. And that is worth more than any photographic memory. They, he says, will never do it no matter how much they evolve. There is no Planet of the Apes. It is science fiction.


So, what’s the cognitive trade off hypothesis?

It is clear that animal species have different abilities and talents that are appropriate for their niche in the environment. Each animal has a limited amount of brain size and power, so each skill and talent has an opportunity cost. This is neither controversial nor particularly contested.

The Cognitive tradeoff hypothesis is about apparent tradeoffs between chimpanzees and humans, because it speaks directly to who we are as a species. Evidence suggests that chimpanzees have much superior short-term memory relative to humans. I won’t try to explain the magnitude of the difference, but the video reference shows it well.

The CT hypothesis suggests that losing short-term memory is one of the costs of entering a new environment, the savanna, with different challenges than those faced by chimpanzees who stayed in the forest.

The hypothesis is that our language was developed at the cost of short-term memory, and that language (and the symbolic thinking that accompanies it) was more valuable to us than memory. Dr. Matsuzawa gives excellent reasons why that might be so.

While there is a lot of truth and insight into the hypothesis, there are some problems with it, and I will present them.

We have three times as many neurons as the chimpanzee, so it was not necessarily necessary to lose anything to get our new facilities. That doesn’t preclude an evolutionary bottleneck that did.

What the video evidence shows is short-term memory, which in humans is mediated by the limbic system, not the cortex. Only with consolidation does memory migrate to the cortex. The limited resources there could be the source of the compensation, but again, our larger number of neurons could have mitigated the compensation.

The recent evolution of chimpanzees and humans has been in completely different environments, with different survival needs, so the difference could be adaptive rather than a trade-off.

The last item is what I want to say more about. One of the biggest differences between chimpanzees and humans is their level of socialization. Chimpanzees live in small clans with rigid hierarchical social networks. In such a social environment, small details can be important factors in maintaining the social survival of the individual and even the group.

Humans have a much more open social structure, and we have successfully demonstrated our ability to live in crowded cities of tens and hundreds of thousands. I propose that doing so requires a weaker short-term memory.

Another trade-off that wasn’t discussed is that we dedicate enough memory to the fusiform face area in the right hemisphere to differentiate and remember hundreds of human faces, something a chimpanzee has never needed.

Carefully remembering all the slights and injustices that each of us committed against us would not encourage social cohesion.

I like the cognitive exchange hypothesis, but we don’t have to adopt all the hypotheses that we like. Scientists tend to keep marginal hypotheses in reserve rather than accept/reject them. They may prove useful in the future.

In this post we talked about The cognitive trade off hypothesis. We explained what it consists of and what are the foundations of this theory.

If you have any questions or comments please let us know!


Tetsuro Matsuzawa. (2010, January 14). Cognitive development in chimpanzees: A trade-off between memory and abstraction? Retrieved February 12, 2021, from ResearchGate website: