,g.?Y?%z(`*^i$f0Professor Paul Bloom: We began the course by talking about one of the foundational ideas of modern psychology. This is what Francis Crick described as "The Astonishing Hypothesis," the idea that our mental life, our consciousness, our morality, our capacity to make decisions and judgments is the product of a material physical brain. What I want to talk about today and introduce it, and it's going to be a theme that we're going to continue throughout the rest of the course, is a second idea which I think is equally shocking, perhaps more shocking. And this has to do with where mental life comes from, not necessary its material nature, but rather its origin. And the notion, this other "astonishing hypothesis," is what the philosopher Daniel Dennett has described as Darwin's dangerous idea. And this is the modern biological account of the origin of biological phenomena including psychological phenomena.
Now, people have long been interested in the evolution of complicated things. And there is an argument that's been repeated throughout history and many people have found it deeply compelling, including Darwin himself. Darwin, as he wroteThe Origin of Species,was deeply persuaded and moved by this argument from--in the form presented by the theologian William Paley. So, Paley has an example here. Paley tells--gives the example of you're walking down the beach and your foot hits a rock. And then you wonder, "Where did that rock come from?" And you don't really expect an interesting answer to that question. Maybe it was always there. Maybe it fell from the sky. Who cares? But suppose you found a watch on the ground and then you asked where the watch had come from. Paley points out that it would not be satisfying to simply say it's always been there or it came there as an accident. And he uses this comparison to make a point, which is a watch is a very complicated and interesting thing.
Paley is--was a medical doctor and Paley goes on to describe a watch and compare a watch to the eye and noticing that a watch and the eye contain multitudes of parts that interact in complicated ways to do interesting things. In fact, to change and to update the analogy a little bit, an eye is very much like a machine known as a camera. And they're similar at a deep way. They both have lenses that bend light and project an image onto a light-sensitive surface. For the eye the light-sensitive surface is the retina. For the camera it's the film. They both have a focusing mechanism. For the eye it's muscles that change the shape of the lens. For a camera it's a diaphragm that governs the amount of incoming light. Even they're both encased in black. The light-sensitive part of the eye and part of the camera are both encased in black. The difference is--So in fact, the eye and a camera look a lot alike and we know the camera is an artifact. The camera has been constructed by an intelligent--by intelligent beings to fulfill a purpose.
6W-u i rK1b g-l0In fact, if there's any difference between things like the eye and things like a camera, the difference is that things like the eye are far more complicated than things like the camera. When I was a kid I had this incredible TV show called "The Six Million Dollar Man." Anybody here ever seen it or heard of it? Oh. Anyway, the idea is there's a test pilot, Steve Austin, and his rocket jet crashes and he loses his--both legs, his arm and his eye, which sounds really bad but they replace them with bionic stuff, with artificial leg, artificial arm and an artificial eye that are really super-powered. And then he fights crime. [laughter] It was [laughs] really the best show on. It was really good, [laughter] but the thing is this was in 1974. It's now over thirty years later and it's true then and it's true now, this is fantasy. It doesn't make it to the level of science fiction. It's fantasy. We are impossibly far away from developing machines that could do this. We are impossibly far away from building a machine that can do what the human eye does. And so somebody like Paley points out, "Look. The complexity of the biological world suggests that these things are complicated artifacts created by a designer far smarter than any human engineer. And the designer, of course, would be God."心理学空间ikH S`O&q%D
I went to Goggle Images. That--I don't mean that to be sacrilegious [laughter] in any sense. You could try this. I went to "Google Images" and typed in "God" and this [a picture of an old-bearded man wearing a crown] is what showed up right in the middle so--And this, Paley argued, and it was--has been convincing throughout most of history, is a perfectly logical explanation for where these complicated things come from. It also has the advantage of being compatible with scripture and compatible with religious beliefs, but Paley made the point this stands on its own. If you find complicated things that--complicated artifacts, you don't assume they emerged by accident. You assume that they were created by an intelligent being.心理学空间i-bk1Y/W-a,b+y
Now, this view has always had problems. This view, you could call it "creationism," which is that biological structures were created by an intelligent being, has always had problems. One problem is it pushes back the question. So you ask, "Where did that intelligent being come from?" And this is a particularly serious problem from the standpoint of the evolution of psychological structures. So, we want to know, "how is it that creatures came across--upon this earth with the ability to reason and plan and do things?" And then the answer is "well, another creature with that ability created us." That doesn't necessarily mean it's wrong, but it means it's unsatisfying. You immediately want to get an explanation for where that other creature comes from.
H5yVi/c)C5IX0More to the point, there's always been evidence for evolution. And what I mean by evolution here isn't necessarily a specific mechanism, but merely the fact that body parts like the eye didn't emerge all of a sudden, but rather have parallels both within other existing animals and across human and biological history. This evidence comes in different forms. There is fossil evidence for different body parts suggesting that they have evolved from more rudimentary form. There is vestigial characteristics. And what this means is there are characteristics that human bodies have that are somewhat inexplicable, like the human tailbone or goose-bumps, unless you view them--the human body in its current form as modifications from a previous form.心理学空间T.`q&VZI
There are parallels with other animals. And this is clear in psychology. So, a human brain is different from the rat, cat, and monkey brain but at the same time you see them following a sort of common plan and common structures. And one rational inference from this is that they're linked through evolutionary descent.心理学空间h'M9~K:d?Hx
OkC%MlC0Finally, there is occasional poor design. So, Paley rhapsodized about the remarkable powers of the human body and the different body parts, but even Paley admitted that there are some things which just don't work very well. Your eye contains a blind spot because of how the nerves are wired up. In the male urinary system the urethra goes through the prostate gland instead of around it, which leads to many physical problems in men later on in life. And so you're forced to either argue that these are really good things or that God is either malicious or incompetent. And those are difficult arguments to make.心理学空间_8]D(CM
iQ4Cmbjz+w4t0So, these are problems with the creationist view. But still, for the longest time in human intellectual history there was no alternative. And in fact, Richard Dawkins, the most prominent evolutionary--one of the most prominent evolutionary biologists alive and one of the most staunchest critics of creationism, has written inThe Blind Watchmakersaying, look, anybody 100 years ago or 150 years ago who didn't believe that God created humans and other animals was a moron because the argument from design is a damn good argument. And in the absence of some other argument you should go--defer to that. You should say, "Well, there are all of these problems but humans and other biological forms must have divine creation because of their incredible rich and intricate structure." What changed all that of course was Darwin. And Darwin--Darwin's profound accomplishment was showing how you get these complicated biological structures, like the eye, emerging through a purely non-intentional, non-created process, a purely physical process. And this could be seen as equal in importance to the claim that the Earth revolves around the Sun and that we're not the center of the universe. And in fact, some scholars have made a suggestion which seems plausible, that the idea of natural selection is the most important idea in the sciences, period.
So, this is not a course in evolution and I expect people to have some background. If you don't have a background in it, you could get your background from external readings but also from--the Gray textbook and the Norton readings will both--will each provide you with enough background to get up to speed. But the general idea is that there are three components to natural selection. There is variation. And this variation gives rise to different degrees of survival and reproduction and gets passed on from generation to generation and gives rise to adaptations, what Darwin described as "that perfection of structure that justly excites our imagination."
/c x+_L5S4[[LE0And the biological world has all sorts of examples. You look at camouflage. Prior to Darwin one might imagine that some intelligent creator crafted animals to hide from their prey. But now we have a different alternative, which is that animals that were better hidden survive better, reproduce more, and over the course of thousands, perhaps millions of years, they've developed elaborate camouflage. There's been a lot of work on Paley's favorite example – the eye. So Darwin himself noted that the human eye did not seem to emerge all at once but rather you could look at other animals and find parallels in other animals that seem to suggest that more rudimentary forms are possible. And more recently computer simulations have developed--have been developed that have crafted eyes under plausible assumptions of selective pressure and what the starting point is.
So, this is the theory of natural selection. The good question to ask is, "why am I talking about evolution in Introduction to Psychology class?" And the answer is that there are two ideas which come together. And in fact, they're both of the dangerous ideas. One idea is that Darwin's idea--that biological forms evolve through this purely physical process. The second idea, the rejection of Descartes, is that our minds are the product of physical things and physical events. You bring these together and it forces you to the perspective that what we are--our mental life is no less than the eye, no less than camouflage, the product of this purely physical process of natural selection. More to the point, our cognitive mechanisms were evolved not to please God, not as random accidents, but rather for the purpose of survival and reproduction. More contentiously, you could argue they've been shaped by natural selection to solve certain problems. And so, from an evolutionary point of view, when you look at what the brain is and what the brain does, you look at it in terms of these problems. And this is what psychology is for. This is what our thinking is for. We have evolved mental capacities to solve different problems: perception of the world, communication, getting nutrition and rest, and so on.
(Nj&B}2u!SI+k+O0Now, we're going to talk about how to apply evolutionary theory to psychology. But as we're doing so we have to keep in mind two misconceptions. There are two ways you can go seriously wrong here. The first is to think that, well, if we're taking an evolutionary approach then natural selection will cause animals to want to spread their genes. So, if we're being biological about it, that means everybody must run around thinking "I want to spread my genes." I want to--and this is just really --Oops. I shouldn't do that. This is really wrong. It's [the text on the slides] even in red. And what this fails to do is make a distinction between ultimate causation and proximate causation. And those are technical terms referring to--Ultimate causation is the reason why something is there in the first place, over millions of years of history. Proximate causation is why you're doing it now. And these are different. Obviously, for instance, animals do all sorts of things to help survive and reproduce but a cockroach doesn't think "oh, I'm doing this to help survive and reproduce and spread my genes." A cockroach doesn't know anything about genes. Rather, the mechanisms that make it do what it does are different from its own mental states, if it has any--why it does them.
This is a point nicely made by William James. So, William James is asked, "Why do we eat?" And he writes,
Not one man in a billion when taking his dinner ever thinks of utility. He eats because the food tastes good and makes him want more. If you asked him why you should want to eat more of what tastes like that, instead of revering you as a philosopher, he will probably laugh at you for a fool.
And it's really the common sense answer. "Why are you eating?" Nobody's going to answer, "Because I must sustain my body so as to spread my genes in the future." Rather, you eat because you're hungry.心理学空间rA#p3V T/h(~
?zz%x*cw{3ZX0Those two theories, you eat because you're hungry and you eat to sustain your body so you could spread your genes in the future, are not alternative. Rather, they're different levels of explanation. And you can't confuse them. The ultimate level which does appeal to survival and reproduction does not--is independent from the psychological level. To give another example, people protect their children so you ask, "Why do people protect their children? Why would somebody devote so much effort to protecting and helping and feeding their children?" Well, the evolutionary explanation is animals that don't protect their offspring don't last over evolutionary time. We protect our offspring because they contain fifty percent of our genes, but that's not the psychological explanation. Nobody but a deranged psychologist would ever answer, "Oh, I love my children because they contain fifty percent of my genes." Rather, the psychological explanation is a deeper--is different and has a different texture. And this will be a lot clearer when we talk about the emotions, where you could really see a distinction between the question of why we feel something from an evolutionary point of view and why we feel it from a day-to-day point of view.
The second misconception is that natural selection entails that everything is adaptive, that everything we do, everything we think is adaptive. This is wrong. Natural selection and evolution, more generally, distinguish between adaptations and byproducts and accidents. Many of you are currently, or will as you get older, suffer back pain. If I was to ask you, "So, why do you suffer back pain? How does back pain help you survive and reproduce?" Well, the answer is it's not an adaptation. Back pain is an accidental byproduct of how our backs are shaped. Don't go looking for an adaptive reason for hiccups or self-pity or bloating after you eat. There's all sorts of things a body will do that have no adaptive value, rather just accidents. We have a body that does all sorts of things. Some things it will do by accident and this is certainly true for psychology.
A2n|.YB6R$l+l4Fv0So, a lot of the things, for instance, that occupy our interest or our fascination in day-to-day life are almost certainly evolutionary accidents. The number--The three--Three of the main preoccupations of humans are pornography, television, and chocolate but if I asked you, "Why do you like porn?" and you'd say, "Because my ancestors who liked porn reproduced more than those who didn't," [laughter] it's not true. Rather, you like porn, assuming you do, [laughter] as an accident. You have evolved--For instance, should you be a heterosexual male, you have evolved to be attracted to women. That is most likely to be an evolutionary adaptation because being attracted to women and wanting to have sex with women is one step to the road to having kids, which is very good from an evolutionary perspective.
It so happens, though, in our modern environment that people have created images that substitute. So, instead of actually going out and seeking out women you could just surf the web for hours and hours and watch dirty movies and read dirty books – evolutionary adaptive dead ends. They're accidents. Why do you like chocolate bars, assuming that you do? It is not because your ancestors in the African savanna who enjoyed chocolate bars reproduced more than those who didn't. Rather, it is because we've evolved a taste for sweet things. And we've evolved a taste for sweet things, in part, because the sweet things in our natural environment like fruit were good for us. In the modern world we have created things like chocolate, which are not so good for us but we eat anyway.
A lot of the debates--There's a lot of controversy in psychology over the scope of evolutionary explanations. And a lot of the debate tends to be over what's an adaptation and what isn't. There are some clear cases. We have color vision. Why do we have color vision? Well, I think everybody would agree we have color vision as an adaptation because of the advantages it gives us for seeing and making visual distinctions. We are afraid of snakes. We're going to talk about that in more detail but there's a straightforward adaptive story about that. We are afraid of snakes because, really, our ancestors who weren't afraid of snakes didn't reproduce as much as those that were. We like chocolate bars and we enjoy NASCAR. Those cannot be adaptations because chocolate bars and NASCAR are recent developments that could not have been anticipated by evolution.
+R/pDN,Q_@d:h0Those are easy questions. Here are some hard questions. Music. Everywhere in the world people like music. Is this an adaptation for some selective advantage or is it an accident? Steven Pinker, who wroteThe Language Instinctthat you read before, caused a huge amount of controversy when he argued that music is just an evolutionary accident. He described it as auditory cheesecake, something we like to gorge ourselves on that have no--has no adaptive advantage. Other people argue music does have an adaptive advantage. Sometimes males use violence to coerce sex. Is male sexual violence a biological adaptation or is it an accident? There's more than one language. Is that just an accidental byproduct of the way language works or is there some sort of group or selectionist advantage sketched out in some way of having multiple languages? What about visual art? What about fiction? What about our love for stories? Those are all matters of heated debate.
And so, we have to keep in mind some things plainly are accidents. Some things almost certainly aren't accidents. Where the action is in the study of psychology and the study of evolution of cognition is trying to figure out which is which. So, those are the misconceptions we have to avoid. But still, who cares? Again this is an Introduction to Psych course. Why are we talking about evolution? Why should it matter to a psychologist how the mind has evolved? I'm going to talk about evolution now but for the rest of the course I'm just interested in how our minds are, period. S,o why would evolution matter?
B"lFt H-cj8]0Well, many people think it doesn't. For instance – and they think it doesn't for different reasons – one claim is a metaphysical one. You might be a dualist. You might reject the idea your mental life is the product of your brain and hence evolution is irrelevant to psychology because the brain and the mind--because the brain, which may have evolved, has nothing interesting to do with the mind. Lisa Simpson got it wrong when she said the Pope--She got it half right when she said the Pope favored evolution. It is true. John Paul II, many years ago, made a statement saying that Darwinian theory is not incompatible. Darwinian theory is a view about the evolution of species that is not motivated by any animus, is a genuine scientific theory, and should it turn out to be true, it is not incompatible to truth about man as taught by the Church. And scientists were thrilled by this and they were--they said he's endorsing evolution. But what a fewer people talk about is the fact that after he said this he drew the line. He allowed for evolution of the body but he would not allow for evolution of the mind. So it was--he wrote:心理学空间'oMrM5M@t
If the human body takes its origin from preexisting living matter, the spiritual soul is immediately created by God. Consequently, theories of evolution which consider the mind as emerging from the forces of living matter or as a mere epiphenomenon of this matter are incompatible to the truth about man.
(F-{/\ V C_h:_0So, you might not want evolution to be true about the mind because you might believe that the mind is not subject to the same physical laws as the rest of the physical world. That's one way you could reject evolutionary psychology. Another way to reject evolutionary psychology is to accept that the mind is a physical thing but then argue that all of these instincts and these hard-wired facets of human nature might exist for other animals but they don't exist for people. So, the anthropologist Ashley Montagu in '73, close to whenThe Six Million Dollar Manwas shown, by the way, said:心理学空间m8nV k:}w#H_'g
With the exception of the reactions of infants to sudden withdrawals of support and to sudden loud noises, the human being is entirely instinctless. Man is man because he has no instincts, because everything he is and has become he has learned from his culture, from the man-made part of the environment, from other human beings.
+U6\-F)uZ(AL lI5^!`0You might say, "Look. He could believe that in '74 but, of course, all of the infant studies that have come out since then suggested that's not true and nobody would believe that nowadays." But in fact, the view is often hold--held--Louis Menand in aNew Yorker article a few years ago wrote, "Every aspect of life has a biological foundation in exactly the same sense, which is that unless it was biologically possible it wouldn't exist. After that it's up for grabs." And this is in the context of an argument that evolution can't tell us anything about what's most interesting about people. Menand is not--is an educated, intelligent scholar. He is presumably well aware of the findings of Spelke and Baillargeon about how people are hard-wired to understand the objects in social life and so on. But his point is just that when it comes to the more interesting aspects of human nature, the stuff we're naturally, intuitively interested in, that's more cultural. And the evolutionary theory and Darwinian theory just doesn't have anything much to say about it, not because the mind is separate from the brain but just because humans are much more cultural organisms, and so biology has little to say about it.
There's a third objection, which is you might think, "Okay, the human mind actually does contain instincts. There is a human nature but we should just study it by studying people. How could evolution, the study of evolution, the consideration of evolution tell us anything interesting?" I actually, in my own work, think evolution can tell us some interesting things. And I want to try to make a case for ways in which evolution can inform and enlighten us about the mind as it is.心理学空间5|` cG ii/xa!{
?,TLf7w0First, I want to make a point, which is although this course is Intro Psych and it is about the mind as it is, still I think by any account the evolution of consciousness, morality and so on, just is intuitively interesting. It's the sort of thing that people are just fascinated by and I think it's a question of interest in and of its own right. But here's how it could tell us about psychology. For one thing, it can tell us what can be innate and what cannot. So, some problems, some evolutionary problems, have been around for a long time and could lead to special biological adaptations. If I told you there is a biological adaptation for talking, mate selection, childcare; maybe it's true, maybe it isn't, but it's not crazy. From an evolutionary point of view, it's a reasonable possibility that it is.
Other problems are recent and our brains could not be specialized to deal with them: written communication, interacting with strangers, driving a car, playing chess. If you were to argue that there's a part of the brain devoted to playing chess, I would say you're utterly wrong. You cannot be right because, from an evolutionary point of view, there could be no such part of the brain evolved because playing chess is a recent innovation. As a result, a focus on evolution could help discipline us to make coherent claims about what is built-in and what isn't built-in.
!@&o1S(Ga0\@*[:H0Third, we're going to talk about human differences in this course. We're going to devote a class to human differences of the sort of what makes you different from her, different from her. Why do we have different intelligences in this class? Why are some of us arrogant and some of us humble? Some of us like--attracted to men, others attracted to women, and so on. But there's also questions of group differences. And evolutionary theory can help us say intelligent things about what sort of group differences you should expect because evolutionary theory predicts that some populations should evolve in different ways than others.
o.jbI:RP(F0The most obvious example is that children should be different from adults. The evolutionary problems faced by a child are very different from the evolutionary problems faced by an adult. And you can make specific and rather interesting predictions about how children's brains should different--differ from adults' brains. Evolutionary theory predicts--does not make any predictions about racial differences or ethnic differences. Some might exist, but there's no adaptive reason why humans who have evolved in different parts of the world should have profound differences in their mental capacities.心理学空间1O Z7f5WQY P6Iv
#]$jiM?R!j,H)Y'N0What does evolutionary theory say about sex differences? Well, it says some interesting things, and we're going to devote a class to discussing them, but what I think is going to be true--proved to be important is that we'll be able to use evolutionary biology to talk sensibly about what sort of distinctions between the sexes, between males and females, one would expect to find and what sort one wouldn't expect to find. We can make educated predictions. I'm going to have--I want to put here a clip of a man. This is a scene from a movie, the movie "Roger Dodger," that begins with a man making quasi-evolutionary claims about the differences between men and women. And I want to put this as an example of what you could call "barroom evolutionary psychology." And I want us to hold this in our minds because we're going to return to these claims and discuss their validity. [clip playing]
R(i#?+^ho0Zi2T0I like this for a few reasons. First, I like the backward reference to William James and utility. Second, it is a gorgeous combination of some things that are actually reasonably rational and total bull crap. And--but what evolutionary biology will give us is the tools to distinguish between the two. On the face of it immediately, the ability to read maps, the claim that that has a biological--that differences in that ability have a biological root is crazy. On the other hand, the claim that one--that males may develop a trait not because it's advantageous but to attract females is less crazy. The telepathic stuff is really crazy but--;So, I'm not at this point--We're going to devote a lecture to sex. I do not, at this point, want to make any claims one way or another. But what I want to suggest is that from a biological point of view we could say sensible and intelligent things about what differences should exist and what shouldn't.
Finally, and most of all, looking at something from the perspective of design, the perspective of what's it for, can often give you interesting insights as to its current nature. And I'll give you two quick examples, one that's not from psychology, one that is. Women suffer--Often women who are pregnant early in their pregnancy suffer from morning sickness, nausea, throwing up and so on. This has traditionally been viewed as just a breakdown in the system--too much hormones, everything's askew; women get nauseous. Margie Profet suggested an alternative and this won her theMacArthur Genius Award.And this was the claim that maybe pregnancy sickness is not an accident; rather, it's designed, it has a biological purpose. In particular, as the baby develops in the uterus, it is vulnerable to various sorts of poisons or teratogens. Profet suggested that pregnancy sickness is a hypersensitive period where women are extremely sensitive, get extremely nauseous towards the sorts of foods that could damage their baby.心理学空间 j%u7RW4on z.]a
Now, if she just ended there it's a story. How do we know it's true? But then she went on to examine it the same way that any scientist examines any claim – by making predictions and testing them. And this makes some interesting predictions. It suggests the timing of onset and offset of pregnancy sickness, of morning sickness, should correspond to the period of maximal vulnerability on the part of the developing embryo or fetus. Suggested the types of foods avoided should correspond to those sorts of foods that were most deadly for the fetus and that were deadly for the fetus during the periods where humans evolved. This last qualification is an important one. Women do not develop an aversion to alcohol during pregnancy even though alcohol is extremely dangerous to the developing child. The answer is an easy one. Alcohol wasn't around during our evolutionary history and we could not have evolved a system to protect ourselves from it.