Evolution of the Brain and Intelligence

"Yes, I did my PhD in London; I had gone to London to do clinical psychology. The course at the Institute of Psychiatry was outstanding, and I did it because I wanted to go on to do criminology—indeed my MSc thesis was on Hans Eysenck’s ‘Theory of Criminal Personality,’ so I was still passionately interested in crime. But on the course seminars were given by various people and one was by a man called George Ettlinger. The year before I did the course, David Milner had done the clinical course and had asked a question in Ettlinger’s seminar, and Ettlinger had asked him if he’d like to come and work with him. So the year I did the course, I asked a question in George Ettlinger’s seminar and he said: ‘Would you like to come and work with me?’! So David and I sat in George Ettlinger’s laboratory, back-to-back because there wasn’t very much room, and we did our theses simultaneously. But now I was not working on crime; we were working on animals… If I ask now how I came to make that huge leap, the reason is that as an undergraduate I was inspired by the lectures given by Marcel Kinsbourne who described various clinical phenomena. The one I really remember is the rare phenomenon when someone with a lesion in the right parietal cortex says, ‘Nurse, somebody is in bed with me.’ It turns out that they think that the left side of their body is somebody else. I’ve never forgotten hearing that. It was very far away from rats and how they find their way down mazes. So I think that when I agreed to work with Ettlinger on animals, I must have had in mind that, yes, there is something really interesting about the brain, but given that at that time we couldn’t look at the human brain during life, the only way of actually looking at the brain is by looking at the brain in an animal. So I worked on animals. And I had a crazy idea, and it comes back to crime. I thought that these kids that I’d worked with were bad at controlling their impulses. And that the prefrontal cortex, or in common parlance, the ‘frontal lobes,’ must be involved in controlling your impulses. Crazy idea. Anyway, I did an experiment in which I had two lights—one on the left and one on the right, and the one on the left came on eight times out of ten, and the one on the right came on two times out of ten. I wanted to know if an animal which had a lesion in its frontal lobes would be tempted to go to the more common light when the less common light came on? In other words, would it be bad at controlling its impulses? And that’s what happened, and I published it. But if you’re going to work on animal brains, the problem is, what if what you learn from animal brains simply doesn’t generalise to people? George Ettlinger was very worried about that. All of us working in the lab met regularly in an internal workshop, and we wrote a paper on whether or not what you find in animals generalises to people. Yes. Harry Jerison was mainly interested in evolution and in particular in the size of the brain. Of course you don’t have the brains of ancestral animals, but if you have skulls or partial skulls, you can work out the size of the brain. You can tell very little from the shape of the inside of the skull, but you can at least measure the size of the brain. So he plotted the size of the brain in ancestral animals and looked at changes over time. And without going into the technicalities of how you compare the size of the brains, it’s obvious that one of the problems is that one of the factors that determines the size of the brain is how big you are. There’s a relation such that an elephant’s got a bigger brain than a mouse. Harry had ideas about how you could get rid of the effect of body size, and look at what he called the ‘extra neurons’ that might contribute to intelligence. I was very interested in that. “He plotted the size of the brain in ancestral animals and looked at changes over time” My problem was the animal experiments that I did when came back to Oxford were very boring to run. Science can often be very dull, collecting the data, and it was. So to keep the mind alive, I started doing some calculations about whether the human brain or different parts of it were bigger than you’d expect, given our size. So, inspired by Harry’s book that came out in 1975, I wrote a series of papers on these issues for the next five years. Then Desmond Morris, the zoologist, produced a book… That’s it. And I thought it was naive. So I thought I should write a professional version. The advantage would be that I could include all these calculations that I’d done about the human brain. So I wrote a book in 1982 called The Human Primate , and I hoped it would make me famous like Richard Dawkins, but it didn’t… Still it was a worthy attempt to try to ask the question as to how people differ from other primates in their brain and behaviour. In other words, what’s special about the human primate? And so I was really influenced by the ideas and questions that George Ettlinger had asked, and by Harry Jerison’s book. It led me to write a book, more recently, called What is Special about the Human Brain? Well, I have changed my mind. In The Human Primate , I suggested that the trends that you can see if you compare a monkey with a chimpanzee are continued if you look from chimpanzee to human. So what I was stressing was the similarities, that we were following trends. Of course the analyses are based on modern species, not the actual ancestors. But when I came to write my later book I had already done some work using brain imaging. I was beginning to get cold feet because it seemed to me there were some things that might be special, that I should try to investigate. So I went back on some of what I’d said earlier. You’re no good as a scientist if you haven’t ever been wrong. There are some things that you and I can do that other animals can’t do. One of them is what you might call ‘mental trial and error’. We can think: ‘If I do A what would happen? If I do B what would happen?’ and do this before we act. This means that we don’t just rush in. There’s a selective advantage in being able to think before you act. “You’re no good as a scientist if you haven’t ever been wrong” Of course, animals can plan, but the experiments I know of are ones where, let’s say, there’s a maze on a screen and the animal moves a cursor through the maze so as to find a goal in the maze. There are cells in the brain which specify the end location long before the animal has moved the cursor there. The activity of these cells reflects the planning. But of course the maze is visible. Yet I can think about whether I’m going to have cornflakes or cauliflower for breakfast tomorrow, and these are not visible. It’s not clear to me that a chimpanzee can do this. So this idea of mental trial and error seems to me an important way in which people differ, one that confers a major selective advantage. Steve Wise and I wrote a book called The Neurobiology of the Prefrontal Cortex , and we gave it the subtitle: ‘The Origins of Insight’. We were suggesting that the ability to think about the problem before you act depends on the prefrontal cortex. Now wait, Jerison’s book is one of the classics, an example of someone going off and doing something totally new. It’s a very major bit of work involving the analysis of a huge number of fossil skulls. So I don’t think it’s fair to compare the weight of what Harry did with what I did. Yes, work of this sort looks at those respects in which those experiments are valid but also at the limitations of those experiments. The problem is that we don’t just want information about the size of different areas of the human brain: we can get this post-mortem. We need information about the living human brain, that is while we’re doing things. When I did my PhD, the only way of seeing whether somebody had a brain tumour was to pump air into the spinal cord; it went into the fluid filled cavities, the ventricles in the brain, and you could see those in an X-ray. If there was a tumour, the ventricles were distorted. And that was the only way that you could see the brain. It gave the patient a dreadful headache. Since then there have been major advances, first of all CT scans in the early 1970s. You take a series of X-rays from different angles and you can then produce a picture of the brain. Doing this involves computed tomography, so called because a computer is used to reconstruct the whole brain from slices—’tomos’ being Greek for a cut or section. Then later in the 1970 MRI was developed for scanning human tissue. Paul Lauterbur and Peter Mansfield got the Nobel Prize for this development. MRI gives exquisite pictures of the structure of the human brain. “When I did my PhD, the only way of seeing whether somebody had a brain tumour was to pump air into the spinal cord” But in the 1980s, a new method was invented, which enabled you to look at the brain at work: this being positron emission tomography [PET]. The idea is that when an area of the brain is active, it needs oxygen and glucose and these are brought by the arterial blood. So if you can measure the passage of the arterial blood, you will be able to see which areas are active when somebody is in the scanner. And this particular method introduces a radioactive tracer into the blood so that you can detect the blood flow. As it happens, I heard Richard Frackowiak lecture in Oxford in the late 1980s, and I went to see him at the end and asked if I could collaborate. He was working at the MRC Cyclotron Unit at the Hammersmith Hospital, a pure research unit. He said yes, so I started going down to the Hammersmith and doing experiments. Then, yet another method was invented in the early 1990s: it was found that you could measure the ratio of the oxygenated blood and the deoxygenated blood once the oxygen had been removed, and that you could do this using an MRI scanner. The measurement is called the BOLD-contrast and the technique is called fMRI or functional magnetic resonance imaging. However, experiments using PET and later fMRI only took off after the psychologist Posner worked out a way of analysing the data."