Comparative Behavioural Neuroscience

What do we mean by “intelligent behaviour”?

We believe that intelligent behaviour has to do with how you create and play with your expectations about the world around you in order to solve problems. We also believe that there is a difference between the kind of intelligence that is relevant for humans in industrialised societies, and the abstract characteristics that define the general idea of intelligence, which should apply no matter the context or who is using it.

This belief is strengthened by the fact that cephalopods, marine animals whose nervous systems are completely different from ours, are able to solve many problems that we once thought only humans could solve. So we want to design experiments that can pose problems to both humans and cuttlefish in more or less the same way, without relying on human language. In this way, we can compare the solutions given by humans versus cuttlefish. If a certain strategy or mental tool for problem-solving is important for both species, it’s likely that such a strategy or tool may be a general principle of intelligence.

A history of “intelligence”: test scores vs. “power” and learning

Often intelligence is used to describe how well we do on tests (sometimes called the “psychometric view”). This assumes that the way we think can be measured by how well we do on tests. Because we believe this, we now have a lot of data on humans solving many different kinds of problems. Many scientists have now analysed over 60 years of test scores, at different times and with different methods. They all realised that people who do well on tests in general also tend to score well on three types of tests:

  1. “Fluid intelligence”, or figuring out solutions to new and unusual problems;
  2. “Crystallised intelligence”, or using what one already know from past experience to solve a problem; and
  3. “Visual-spatial reasoning”, or being able to use visual images and relationships to solve problems.

If intelligence is a single thing that can be measured and improved on (sometimes called “general intelligence”), then anything that changes a person’s score on one type of test should have a similar effect on any of the other two types. But it turns out that this is not true. Take aging, for example. On average, test scores in “fluid intelligence” tend to decrease as a person gets older, while on average, test scores in “crystallised intelligence” tend to stay the same or even increase. So while test scores might tell you who could learn a job faster or more easily, test scores can’t tell you how well a person will perform once they’ve learned the job.

This means that differences in test scores do not capture everything we want to know about the differences in the ways that we think. So scientists came up with another way to think about intelligence, based on more general ideas about the nature of thinking (sometimes called the “cognitive-psychology view”). This point of view assumes that thinking is the process of:

  • creating a mental structure that represents the current problem in your head,
  • remembering information that seems relevant, and
  • playing with the representation in your head, or creating a new representation altogether, in order to find a solution.

If thinking is a process, then intelligence can be described as a combination of several things. One of them is a person’s “power” for thinking, or how well they can use the thinking process described above. The others are learning and experience, which provide knowledge of how to use one’s thinking power and access to useful information. This means that if you are facing a new kind of problem, finding a solution depends on your ability to create new representations in your head. As you learn and gain experience, finding solutions effectively depends on recognising patterns between past solutions and the current problem.

While this viewpoint makes intelligence harder to summarise with numbers, it does a better job of explaining the differences in the ways that humans think.

Why does it matter?

The concept of intelligence is actually quite political, especially when trying to explain its scientific underpinnings.

Even though the scientific community has shown that test scores don’t explain how different ways of thinking affect everyday performance, it’s easy to use standardised tests to place people in schools and in jobs. This means that the education and economic opportunities available to a person are often determined by outdated and biased measures, in large part because the scientific community has not yet validated a new way to understand differences in the ways we think.

And no matter how we measure these differences, it’s clear that the increasingly technological nature of our lives have increased the rewards for those who can exploit technology while at the same time increasing the punishment for those who can’t, meaning that the policies that dictate how to allocate education and economic opportunities have profound effects on people’s lives. This means that progress in our scientific understanding of intelligence and its characterisation is an important part of building a future that welcomes and respects everyone.

Want to learn more?

To learn more, check out the following links!


Controversy of Intelligence: Crash Course Psychology #23
Brains Vs. Bias: Crash Course Psychology #24


Hunt, E. 1995. The Role of Intelligence in Modern Society. American Scientist.

How can we study “intelligence”?

When we want to find out how brains understand the world, how can we study it?

When we encounter familiar objects, like a cup of water, we know what to expect from them. We can imagine picking them up, throwing them around, what they feel like, and what they sound like. One way to study something is to try and build it. As of right now, we do not know how to give this power to imagine to things that we make.

We will try to understand this power by tracking people’s eyes while they watch short movies of surprising or unexpected things happening. In order to be surprised, you have to be able to guess what is going to happen next, and you also have to decide how sure you are about your guess. When your guess is really wrong, but you felt very sure that you would be right, this moment is surprise, and it is in this moment that your understanding of the world breaks. We use our eyes a lot to learn about the world around us, so tracking where people look can help us understand what they expect.

For each person who helps us in this study, we will save a set of movies – one movie of each eye, and a movie showing where those eyes were looking when surprising things were happening. These movies will be anonymised and shared here, so that anyone interested in analysing these movies can do so.

Tracking the movements of the eyes is just one way to study minds non-invasively. There are many aspects of behaviour that can clue us in to a person’s expectations about the world around them, as long as we can recognize the moment of surprise. When surprise goes away, this means that you’ve figured out how to deal with the thing that surprised you, and you’ve changed your understanding of the world. Changing yourself in this way is an important part of learning how to learn, and we believe that learning how to learn is an important part of intelligence.

Why are cuttlefish involved?

The animals we usually study in neuroscience keep their brains hidden deep inside of their bodies, and so it’s very hard to watch the brain while it is working inside of a moving animal. But this is slightly less true about cuttlefish. Instead of packing most (80-90%) of their nervous cells into a brain the way humans do, most (over 60%) of the cuttlefish nervous cells are out in the body.

Cuttlefish neurons control special cells in the skin that can change the cuttlefish’s form, color and feel. One type of special cell is called a “chromatophore” - it’s like a tiny bag full of color, with muscles holding onto it on all sides. Each muscle has 3 or 4 neurons wrapped around it. When the muscles are relaxed, the bag of color is closed tight and can’t be seen; but when the neurons tell the muscles to pull, the bag of color can grow up to five times larger, making the skin in that area change color.

The cuttlefish’s skin has over 20 million chromatophores, each controlled by twenty or more neurons. This means that over a hundred million neurons are working together to control how a cuttlefish appears to other animals. Given that, we believe that looking carefully at cuttlefish skin while it moves through the world could be a way to watch both single neurons and large groups of neurons at the same time without cutting open any part of the animal.

Want to learn more?

To learn more, check out the following links!


Kings of Camouflage: NOVA Documentary about Cuttlefish


Wasserman, E.A. 1993. Comparative Cognition: Beginning the Second Century of the Study of Animal Intelligence. Psychological Bulletin, 113(2), 211.

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