There's an ongoing debate in cognitive science about how much of our brain is a product of natural selection and how much of it is a product of social learning. These are not all or nothing claims. So no one thinks that all of the brain is a product of natural selection or that it is all a product of social learning. But what we're going to look at now is a view called evolutionary psychology, which maintains that most of our cognitive capacities are there as a result of natural selection. The four claims of evolutionary psychology are these: first, the human brain is a product of natural selection. Second, the human brain adapted to solve particular problems which our ancestors faced. Third, the cognitive capacities which our ancestors developed that allowed them to solve problems were heritable. They could be transmitted biologically from parent to offspring. Fourth, the brains we have now are the brains which our ancestors evolved all those years ago. Of course, it's possible to endorse the view that the brain is a product of natural selection without being committed to the four claims of evolutionary psychology. Kenny's going to talk you through an alternative later based on social learning. The argument isn't about whether natural selection was involved, the argument is about how we should understand the role of natural selection in shaping the human brain. If there is to be a slogan for the evolutionary psychology movement, it would be that our modern skulls house Stone Age minds. This is a term that was coined by Leda Cosmides and John Tooby, who are commonly acknowledged as the founders of evolutionary psychology. Evolutionary psychologists point out that the vast majority of our species' history was spent living in small hunter gatherer groups in the African savannah. So from about 1.8 million years ago to 10,000 years ago, we were living in these small groups in very hot environmental conditions. This is what evolutionary psychologists refer to as the Environment of Evolutionary Adaptation and they claim that the brains that we have now evolved to solve the problems which this environment of evolutionary adaptation threw up at us. The industrial revolution only happened about 200 years ago and we've been living with, agriculture's been part of our life for about 5000 years and so these are just tiny fractions of the human species' history. For about 99% of our history, we were living in the conditions thrown up by the environment of evolutionary adaptation. One of the effects of this, said evolutionary psychologists, is that some of the cognitive capacities that we have now evolved to suit the conditions in the environment of evolutionary adaptation, but are actually mal-adaptations. That means that they were very beneficial to us when we were hunter gatherers, but they're not so beneficial to us in our modern urban environments. For example, craving salt and sugar is a really good cognitive mechanism to have if you're a hominid and you're trying to get really calorific sources of food to feed yourself and your family. But living in an urban environment where sources of salt and fat and sugar are rife, this becomes a maladaptation. Those cravings cause us to eat far too much of those foods and ends up being unhealthy for us. Stephen Pinker points this out really nicely when he says that we have a really visceral reaction to snakes and spiders, basically things which would have posed a huge threat for us during the environment of evolutionary adaptation but in fact in today's world, snakes and spiders don't really kill very many people per year, in contrast to say, driving without a seat belt. Driving without a seat belt is a much more dangerous thing for humans to be doing in the modern urban environment, but our reaction to this is far less visceral than our reaction to snake bites and spiders. So what were the kind of problems that faced out hominid ancestors? As mentioned before, they lived in small groups of hunter gatherers, so a lot of the problems that faced our ancestors were to do with group living, how to maintain a harmonious group that could live together. So the evolutionary psychologists maintain that our brains evolved to solve the kinds of problems that faced you if you were living in a small group. For example, who should I cooperate with to do my hunting and gathering? If I manage to get some food, who should I be sharing it with? Are there people in my group who are benefiting from my work, but not contributing to it? Am I feeding lazy people who don't do any hunting and gathering themselves? These are precisely the kind of problem that the evolutionary psychologists maintain our brains evolved to solve. They recurred day after day for the 1.8 million years of the environment of evolutionary adaptation. And so it's necessary, say the evolutionary psychologists, that our brains evolved fast and efficient ways of solving these problems. One of the most famous hypotheses from the evolutionary psychologist is that the brain has a part which evolved to solve the cheater detection problem, that is, our brains have got a part which evolved to solve the question of who in my environment is free riding? Who's taking stuff without putting back to the community? Here's how they argue for the hypothesis. There's a logic task devised by the psychologist Peter Wason in the 60s, which is intended to test whether people can follow whether a particular logical rule has been broken. We can kind of work it through like this. Imagine that you have a job as a quality control person in a card manufacturer manufactures cards for games and you've been told that if a card is yellow one one side, then there needs to be a circle on the other side. Now, you've been reassured that every card that you're looking has a color and a shape on each side of it and your job is to check which cards might possibly have broken the rule. So here are the cards, and which ones do you think you need to turn over to ensure that the rule has been kept? So the cards you need to turn over would be the yellow card because we've been told if it's yellow, then it needs to have a circle on the other side. So we turn over the yellow card, and sure enough, there's a circle on the other side. So the rule has been kept. Now we don't need to turn over the circle card because there isn't any rule about if it, if it's a circle then it has to have a particular color on the other side, but we do need to turn over the triangle card. We need to turn it over to make sure that it isn't yellow on the other side, because then it will have broken the rule. Oh, this card is yellow on the other side. So this card is dud. It's broken the rule. Let's try a different puzzle. Imagine now that you're a bouncer at a night club, and you've been told that in this particular club, you can only drink alcohol if you're aged 21 or over. Now imagine that each of these cards represents a patron at the night club, either how old they are, or what they're drinking. Which people do you need to check to make sure that the rule has been kept? Well, you obviously need to check what the 16 year old is drinking to make sure that they're not drinking beer. We should turn that card over. They're drinking orange juice, so that's okay. But you also need to check the age of the beer drinkers. This person is drinking beer, so we need to make that sure they are 21 or over. Oh, that person is 16, so they're going to get thrown out of the night club. How did you fare on these tasks? Most people find the first one significantly more difficult that the second, even people who have taken classes in logic. Cosmides and Tooby take this as evidence for the fact that we have a cognitive adaptation which evolved to allow us to detect cheaters in our environment. We're very good at detecting when a social norm has been violated. But because this part of the brain evolved just to detect the violation of social norms, we can't use it in other situations, even when it would be useful. For example, we can't transfer that ability and use it in an abstract logical setting. So Cosmides and Tooby used this as evidence of the idea that we evolved a particular cognitive ability, the ability to detect cheaters in our environment. The evolutionary psychologist's claim, that the brain evolved to deal with lots of specific different problems, commits them to a very particular view of how the mind is structured. This is the modular view of the mind. It means that the mind is a series of mini-computers, each of which is specialized to do a particular cognitive task. And in the literature, these mini-computers are referred to as modules, or cognitive modules. So, there's a mini-computer that allows us to detect friend from foe. A mini-computer that allows us to do basic mathematical calculations. A mini-computer that can kind of tell us where we are in a, an environment, that deals with spacial cognition. And the evolutionary psychologists say that each mini-computer can only do it's job. So, think about the body more generally. The lungs are very good at extracting oxygen from the air. And the blood is very good, the heart is very good at pumping blood around the body. But if our lungs fail for whatever reason, it's not like the heart can step in and do the work of the lungs and the same goes for the mini computers of the brain. The mini computer that deals with social cognition, that allows you to detect who might be a cheater in your environment, who might be free riding, can't also be used to apply to say, more abstract mathematical logic problem. So in the evolutionary psychology view, the brain is like a Swiss army knife, it's a series of mini computers, each of which is tailored to a specific task. Whereas opponents to evolutionary psychology say the brain is much more like a chef's knife, it has one kind of very good blade which allows it to do a variety of different things and it might not do them as well as a specific tool, but it nevertheless gets the job done. Another reason the evolutionary psychologists endorse the modular view of the brain, that is, the brains consists in a series of mini computers has to do with the complexity of the brain. The brain is an incredibly complex organ and from an evolution perspective, it's unlikely that it just popped into existence as a result of one massive adaptation. Instead, it's likely to evolve over millions and millions of years, changing incrementally in tiny steps. Let's look at the human eye as an analogy. Our very distant ancestors, the ones who lived a really long time ago just in the sea, didn't have eyes as we have them now. They just have light sensors that allow them to detect the difference between light and dark and use that information accordingly. Much, much later, organisms began to evolve retinas and then later, cones and rods which allowed them to have a finer color vision. [SOUND] Now, the human eye evolved very incrementally to the eye that we have now, but we can break it down into the separate parts which evolved separately. The advantage of this is that one part of the eye can break or not work properly without the whole thing going down and that's really important for organisms for whom perception is a really important way of life. This is what happens with color blindness. The parts of the eye which detect color don't work properly, but that doesn't mean that the person is unable to see at all. The rest of the vision functions perfectly normally. It's just that this one component isn't working as it normally does. Now let's return to the human brain. As mentioned before, the brain is probably the most complex organ that we have. And so the evolutionary psychologists say that each module, each mini computer evolved semi-independently of the whole, kind of building on the resources of the brain but without being wholly dependent on it. This is really advantageous because it means that if one computer breaks down, then the whole brain doesn't break down. An organism can't live without a brain, but it can without one part of its brain, one module, not working properly. And so the idea that we have these modules which only take in a limited amount of information, process it and kind of spit out a limited amount of information in turn, these little modules which are kind of blind to the overall workings of the entire brain, isn't so implausible after all, say evolutionary psychologists. Another advantage of thinking of the brain in this way is that natural selection can act on one part of, one module of the brain, for example, improving our spatial cognition without having to tinker or adjust or change the brain as a whole. Can just work on the spatial cognition module. And so the complexity of the brain and trying to explain how such a complex organ could have evolved, is a very strong argument in favor of the modularity of the human mind.
