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1999 LECTURE SERIESHow the Mind WorksDr. Steven Pinker I'm going to be talking about the human mind. And the human mind is a marvelous organ. It's allowed us to walk on the moon, to discover the secrets of life and the physical universe, and to play chess almost as well as a computer. But the human mind presents us with a paradox. On the one hand, the mind is an engineering masterpiece. Despite decades of research and artificial intelligence and computer science, no manmade computer or robot can see, move, speak and understand, or use common sense nearly as well as a person. You can't go to an appliance store and buy a domestic robot like Rosie the Maid and bring it back and expect it to put away the dishes or run simple errands. And the reason is that the mundane mental activity that go into tasks like picking up a glass or recognizing a face or understanding a sentence, turn out to be formidable engineering problems that human engineers have not been able to solve in artificial systems, but that any four-year-old can do effortlessly. On the other hand, for all its engineering excellence, the human mind has a number of apparent quirks. For example, why is the thought of eating worms disgusting? It's a perfectly nutritious form of animal protein. Why does the male of our species do insane deeds, such as challenging each other to duels or murdering their ex-wives? Why do people in all cultures believe in ghosts and spirits? Why do fools fall in love? I'm going to try to make some sense of both these aspects of the paradox, the engineering excellence of the mind and it's apparent quirks, using three key ideas. The first idea is computation, in particular, that the function of the human brain is information processing, or computation. I think this is an idea that solves an ancient problem; namely, what is intelligence and how can a hunk of matter such as a brain accomplish it? Well, there have been many attempts over the decades to define intelligence. I don't think anyone is happy with the traditional psychologists' definition of whatever intelligence tests measure. I think a better definition comes from the philosopher and psychologist, William James, who tried to put his finger on the difference between behavior that we would be willing to credit as intelligent in a human and superficially similar behavior in an inanimate object that we could not call intelligent. And here's how he tries to capture the difference. Romeo wants Juliet as the filings want the magnet, and if no obstacles intervene, he moves her toward, by a straight a line as they. But Romeo and Juliet, if a wall be built between them, do not remain idiotically pressing their faces against the opposite sides like the magnet and the filings with the card. Romeo soon finds a circuitous way, by scaling the wall or otherwise, of touching Juliet's lips directly. With the filings the path is fixed, whether it just be the end depends on accidents. With the lover it is the end which is fixed, the path may be modified indefinitely. This defines intelligence as the pursuit of goals by means of inference, or inference means of knowledge of logic or probability or cause and effect in the world. It means that the goals and knowledge are of a kind of information. They're represented as patterns in bits of matter inside the system. And the patterns are called representations of the goals or knowledge. Moreover, the system is designed so that one representation causes another, just because the way the system is put together following the ordinary laws of physics or chemistry. But it's been rigged up so that the change from representation to representation mirrors laws of logic or statistical inference, with the result that if the initial representation is accurate, the subsequent representations are accurate, and you have the accomplishment of intelligence. Now this idea, sometimes called the computational theory of mind, I think explains this ancient mystery of how a hunk of matter can carry out intelligence. It also solves a major component of what the philosophers call the mind-body problem - how beliefs and desires can cause behavior. We don't just appeal to beliefs and desires to explain Romeo's behavior, but we use it to explain just about any human act. Let's say I ask you why Bill just got on the bus. To answer that question you wouldn't have to put Bill's head in a brain scanner, you wouldn't have to do DNA testing on him. You could just ask him or ask someone who knows him, and they'd be likely to say something like, Well, he wants to visit his grandmother and he knows the bus will take him there. There are no highfalutin scientific theories going to do any better a job at predicting Bill's behavior than that common sense description in terms of what he knows and what he wants. If Bill hated the sight of his grandmother or if he knew that the route had changed, his body would not be on that bus. Well, the mind-body problem is: How do these colorless, odorless, weightless, wispy, little nothing's called beliefs and desires actually cause behavior in the way that one billiard ball can clack into another? Well, the idea that beliefs and desires are a kind of information which can be embodied in states of a fill system, I believe solves that problem. The computational theory of mind has also set the research agenda for experimental psychology and neuroscience for the past several decades. One of the main tasks of psychology is to discover the kinds of representations and information processes that go on in the mind. For example, there's a body of research that shows that if you present people with a prose paragraph, let a person read it and take it away, within seconds they will have lost most of their memory of the verbatim wording of the sentences, but will take an accurate memory of the content or the gist or the meaning of the paragraph. And that suggests that one of the forms of representation in the mind is a kind of propositional database, information about who did what to whom, that's more abstract than literal strings of English words. Another body of research in psychology shows that we have other representations. For example, if I were to ask you, What shape are a German shepherd's ears? or Does the capital letter "N" look like some other letter of the alphabet when it's lying on its side? most people claim to answer that by conjuring up a mental image which feels as if its looking at a picture; and indeed, a large body of research in experimental psychology suggests that the mind is equipped with a kind of a equivalent of a graphic system that manipulates two-dimensional arrays of information. Similarly in neuroscience the key questions in the field of the direct study of the anatomy and physiology of nervous tissue have been directed at figuring out how it processes information, how it performs transformations, how it coats events in the world and so on. One of the cutting-edge topics in modern neuroscience, studied intensively here at UCI Irvine, is the neuro basis of learning in memory. Well, of the thousands of metabolic processes taking place in the brain, how will we know when we have identified those that are necessary for learning in memory? Also, we find some metabolic process that satisfies the requirement of storing and retrieving information. I should add that the computational theory of mind is very different from the computer metaphor of the mind, the idea that the brain literally works like a commercially available digital computer. It most definitely does not. Many differences between brains and computers have been pointed out. Computers are fast. Brains by comparison are very slow. Computers are built out of a components that are extremely reliable. Brains are built out of components, namely neurons, that are statistical and noisy in their operation. Computers are serial, doing one thing at a time; brains are massively parallel. Computers are assembled in a factory and then turned on; brains have to assemble themselves. Computers display screen savers with flying toasters; brains do not. The idea isn't that the computer is a particularly good metaphor, but rather that part of the explanation for what makes a computer do intelligent things overlaps with the explanation of what makes a brain do intelligent things, namely the processing of information. An analogy would be that we invoke the same laws of aerodynamics to explain what keeps birds in the air and what keeps airplanes in the air, but that doesn't commit us to an airplane metaphor for the bird and ask us to look to see whether birds have landing gear and complimentary beverage service and in-flight movies and so on. A final observation is that the computational theory of mind is by no means a banal or obvious statement, and indeed it runs contrary to the most common way of explaining behavior in everyday conversation and in the popular press. Because the essence of this theory is that the mind runs on information that's very different from our common sense notion that the mind runs on energy or pressure. You're apt to hear the following kind of explanation of behavior, especially in the last few weeks. If only Fred had an outlet so he could let off steam, vent his hostility, and channel his rage, rather than bottling it up, he wouldn't have exploded last Tuesday. This is the hydraulic metaphor of the mind, the idea that our thoughts and feelings are driven by an overheated vessel of steam or fluid that has to be properly channeled lest it burst out and do damage. Now there's no doubt that there is something about human behavior that this metaphor captures, but the computational theory of mind turns that into an interesting scientific question; namely, why is the brain going to so much trouble to simulate energy or pressure, given that we know that it doesn't literally work that way? And that's a question I'll return to at the very end of the talk. The second key idea, I think, is evolution. Now how do we understand complex devices? For example, how might you understand this complex device which I bought in an antique store a few years ago? It's got a number of parts and springs and blades and gears and so on. Well, I think the first question that you would ask, the first thing you'd need to know is, what is it for, what was it designed to do? In this case it's an olive pitter. You put the olive over here and it makes a little X-shaped incision at one end, and you put it over on this side and this little plunger pushes out the pit through the incision. Once you know what it's for, then it's no longer a mystery. You know why it has blades in a particular shape, why it's got a spring, why it's got a handle and so on. This is an activity called reverse engineering. In forward engineering you have an idea of what you want a device to do and you go out and build it. In reverse engineering you stumble upon some complex device, and you try to figure out what it was designed to do. So reverse engineering is what I imagine happens at Panasonic when Sony comes up with a new product or vice versa; namely, they go down to Circuit City, buy one, bring it back to the lab, take a screwdriver to it, and try to figure out what all the little gears and belts and widgets are for. Bodies are complex devices. For example, the vertebrate eye is far more complex than an olive pitter. It's got a transparent curved cornea that can focus light. It's got a lens behind the cornea that can change it's shape, and therefore change the focal length of the combined cornea and lens, depending on the distance of the object from the eye. It's got an iris that opens and closes, depending on the ambient illumination. A light-sensitive layer of tissue that happens to lie at the focal plane of the combined cornea and lens. It's impossible to make sense of the eye without saying that in some sense it was designed for forming an image. Now unless you're a creationist, you don't literally believe that the eye was designed by a cosmic engineer, but instead you appeal to Darwin's theory of natural selection which is the only non-miraculous explanation that we have of how signs of design or the illusion of engineering can arise in the natural world. Darwin showed that if you start out with a replicator, a bit of matter with the ability to make a copy of itself including an ability of the copies to make copies, than they will, that the numbers will increase exponentially. They will inevitably compete for the raw materials to make the copies of the energy to power the replication. Since no copying process is perfect, copying errors will inevitably pop up. If any of the errors has the effect of increasing the longevity or replication rate, it will soon come to predominate in the population. As that process is iterated over hundreds of thousands of generations of copying, you will end up with systems that look as if they'd been engineered for efficient survival and replication, whereas in fact, they simply accumulated all of the copying errors that had that as a side effect. The human mind is a complex device, even more complex than an olive pitter, I would submit; and indeed so complex that human engineers have not been able to duplicate it's elementary functions such as recognizing a face, in a computer or robot. And that suggests that psychology is a kind of reverse engineering, a kind of reverse software engineering in this case. And in any kind of reverse engineering, the first question one asks is, what is the function, what is it for? Since the engineering process in the case of the mind was really natural selection, we have an ultimate answer to that question; namely, ultimately the mind is designed to force survival and reproduction in the environment in which the mind evolved, namely, the tribal or hunting and gather environment in which our species spent 99 percent of its evolutionary history until the very recent invention of agriculture and civilizations, only 10,000 years ago. The first idea was computation, the second idea was evolution. And I think a third key idea is specialization. I don't think there's going to be a theory of everything when it comes to the mind. I don't think that the brain is made up of some wonder tissue that miraculously can explain everything we think and feel. I don't think there's going to be one set of mathematical equations that captures the whole system. And that's because the mind has many different kinds of problems to solve - seeing in three dimensions, moving arms and legs, understanding the physical world, finding and keeping mates, securing allies, and many others. These are very different kinds of problems, and the tools for solving them are bound to be different as well. If we know that specific destination is ubiquitous in the rest of biology, the heart looks different from the kidney because the heart is an organ for pumping blood and the kidney is an organ for filtering it; and any organ that's going to be good at one is necessarily going to be bad at the other, and that's why we have one of each. This specialization goes all the way down. Heart tissue is different from kidney tissue, and heart cells are different from kidney cells. Many of the molecules in heart cells are different than the molecules in kidney cells. And it suggests the mind, like the body, is likely to be organized into the mental equivalent of systems, organs, tissues, and so on. So to put the three ideas together. The mind is a system of organs of computation that allowed our ancestors to understand and outsmart objects, animals, plants, and one another. Now I'm going to get concrete, and I'm going to illustrate this idea with four examples. One from seeing, one from thinking, one from the emotions are elicited by the physical world. And the one from the emotions elicited by other people is where the story gets interesting because other people experience emotions in return. Let's begin with seeing. What is seeing? What is the problem of vision? Well, if you go to science fiction movies, the director has the problem of showing what vision is from the point of view of an artificial system like a computer or a robot, and the director's solution is simply to give the audience a video image that's been distorted or decorated in some way to remind the viewer that they're seeing the world through the eyes of a robot or computer. Maybe there will be fish-eye distortion, as in 2001, or coordinates in the upper right-hand corner, as in the Terminator, but it's still a picture. And this is a seriously misleading way to think about what vision is because it only raises the question of who or what is looking at the image, at that picture. A better of way of thinking about vision is that if you could see the world from your brain's-eye view, it wouldn't look like a picture, but rather look like a massive spread sheet with a million numbers, each of which represents the brightness of one patch of the visual field. Collectively that spread sheet is formed when light bounces off objects in the world, is focused by the cornea and lens of the eye on to the retina, giving rise to a two-dimensional projection of the three-dimensional world. The brain's job is to crunch those numbers and to recover an understanding of what objects are out there from that mammoth two-dimensional matrix. The brain has evolved many tricks for recovering 3-D shapes from the 2-D retinal image. And I'll talk about one of them that's sometimes called shape from shading. It relies on a basic law of physics; roughly speaking, the shallower the angle of a surface with respect to a light source, the less light it reflects back to an observer. The mind has evolved a trick to take advantage of that law by, roughly speaking, running it backwards and assuming that the dimmer a patch is on the retina, the shallower the angle of the surface in the world. And in that way the brain can reconstruct a three-dimensional shape from the thousands of surface angles or facets that make up the shape. For example, it's that trick that allows you to see the difference between a ping pong ball and a white poker chip. The ping pong ball reflects a complex pattern of shading which the brain interprets as a spherical shape. There's one problem with this technique, and that is that it makes an assumption about the world. A point that's true of all perceptual systems is pointed out eloquently by your own professor Don Hoffman in his recent book "Visual Intelligence," where he points out that every time we see or recognize something, we make an assumption about how the world is put together. In the case of shape from shading, the assumption is that basically the world is like this, a uniformly, or at least randomly, colored or pigmented surface which is necessary for the brain to get away with assuming that any difference in brightness comes from a difference in angle. If, on the other hand, a difference in brightness came from a difference in the amount of ink or pigment from one spot to the other, it would be fallacious to convert brightness into angle. And the prediction is that a world that violates this assumption should fool the brain into computing incorrect 3-D shapes. This isn't just a theoretical possibility, but it happens all the time. One example is television. If an alien biologist were to visit this planet to study our species, it would no doubt be astonished to find that a typical member of our species spends four to six hours a day staring at a piece of glass in front of a box. Why would we do that? It's because the box has been engineered to display a highly non-uniform, nonrandom pattern of brightness across the surface. Our brain's sticking with its assumption of a uniformly colored world interprets difference in brightness as differences in angle, and so we hallucinate a three-dimensional world behind the pane of glass. Another example is makeup. People who are skilled at applying makeup know that if you put some blush on the sides of the nose, the eye of the beholder will interpret dimmer patches as a more steeper surface, and that will make the sides of the nose look more parallel and make the nose look smaller. Conversely, if you put some white powder on the upper lip, the eye of the beholder will interpret brighter patches as a more perpendicular surface, and that gives rise to that full-lipped, bee-stung pouty look that these supermodels all strive for that the world is randomly pigmented, and the structure of the current world which might be described to defeat those assumptions such as television or makeup. And I think this helps to make sense of some longstanding puzzles in the biology of Homosapiens, such as why do people eat themselves into an early grave with too much junk food? Why do people use contraception? Which, when you think of it, is a kind of Darwinian suicide; you're taking steps to prevent your genes from replicating rather than fostering it. Or gambling and buying state lottery tickets, sometimes known as the stupidity tax, because if the house makes a profit, the players on average must lose. Well, the answer may be that our mental faculties assume a world in which sweet foods are nutritious, which is true of the world we evolved in, in which the only sweet foods were from ripe fruit, not through the world we live in now, where since the industrial revolution, we've had the power to crank out concentrated large quantities of sweet but nonnutritive foods. It assumes a world in which sex leads to babies, which is true of the world we evolved in until the reinvention of reliable contraception. So that by installing sexual desire in animals, the babies took care of themselves. And a world in which statistical patterns have underlying causes, which again is true of just about any world except a world composed of machines that were engineered to display statistical patterns without underlying causes, namely, gambling devices like roulette wheels and slot machines. This brings me to my second example, from thinking. And again I'll begin with a longstanding puzzle which is: what do hunter-gatherers, who represent the kind of lifestyle in which our ancestors evolved, do with their capacity for abstract intelligences? We know that hunter-gatherers have the same brains that we do and are fully capable of learning calculus and chess and physics, but that's not an ability that one can show off in a hunter-gatherer lifestyle, let alone have it translate into more babies. So what do, why are hunter-gatherers so smart in. Well, if a hunter-gatherer were in this room, I think that they would be more justified in posing that question about us modern couch potatoes. Because surviving as a hunter-gatherer is like the world's most challenging I.Q. test. It's like being on a camping trip that lasts a lifetime, but without any of the Swiss army knives or freeze-dried pasta. The reason that it's so challenging is that organisms evolve at one another's expense. Every item of food that we depend on is the body part of some other plant or animal, which being a Darwinian creature has no more of a desire to be eaten than you or I do. And so organisms evolved defenses being eaten. Animals run away, or grow hard shells or spines, or they bite. Plants can't very well defend themselves by their behavior, so they resort to chemical warfare. And most plants have evolved a potent array of toxins and irritants and bitter-tasting substances to deter creatures like us who have designs on their body parts. In evolution, whenever you have a defense, that sets the stage for a more effective offensive to defeat it, which sets the stage for a more effective defensive weapon to repel it, in the biological equivalent of an arm's race. Now when I think what's special about humans is that, whereas most other creatures fight this arm's race in evolutionary time and they have to evolve new defenses, humans, by understanding how the world works, can take part in this race in their own lifetimes. By figuring out how the world works using cause and effect reasoning, we can overtake other animals' fixed defenses faster than they can evolve defenses in return. And indeed, in all human societies, even the so-called technologically primitive ones, there is an impressive array of tools, traps, snares, corrals, poisons, ways of detoxifying plants by cooking or soaking or fermenting, and the use of cooperative action to accomplish collectively what a single person could not accomplish acting alone. And I think it's because of this built-in advantage that whenever humans have entered a habitat, the local species have dropped like flies. Not just in the last century but apparently for tens of thousands of years. I think a way of summing man's place in nature is nicely captured by the entry for our species in Ambrosia Bierce's "Devil's Dictionary." He defines us as follows: "Man, noun. An animal so lost in rapturous contemplation of what he thinks he is as to overlook what he indubitably ought to be. His chief occupation is extermination of other animals and his own species, which, however, multiplies with such insistent rapidity as to infest the whole habitable earth and Canada." Now, as a Canadian, I'm vaguely offended. But on the other hand, I think that's a pretty good characterization of what our intelligence evolved for. The world is a complicated heterogeneous place. And I think there's growing evidence that the mind has evolved a number of different faculties or intelligences or ways of knowing or modules to each of them adapted to understanding one aspect of the world, each of them based on a core intuition of what makes a particular part of the world tick. The most basic of these is an intuitive physics, an understanding of how objects fall, roll, and bounce. Where the core intuition is that the world has objects, stable, law-abiding entities that continue to exist even when you don't look at them, and whose behavior could be predicted. Now this isn't an obvious claim. William James famously wrote, "That the world of an infant is a blooming, buzzing confusion, and that the world of an infant is a kaleidoscope of shimmering pixels that it takes a long time for the infant to realize that there are things out there that are causing that sensory flux." Since James's times a number of ingenious methodologies have been invented to empirically determine the world of an infant. And they have shown that babies are not as stoned as William James thought. The experiments basically use cheap tricks of stage magic, hidden compartments, trap doors, wires, mirrors, and so on to rig up a world that violates the laws of physics and to see whether babies are visibly surprised. They've shown that babies really are surprised when one object passes through the space belonging to another object or something goes from A to B without passing through all the locations in between. As one psychologist summed up this research, "It's the world of the parents of an infant that's a blooming, buzzing confusion, not the world of an infant." But there are some objects that seem to defy the laws of physics. The biologist Richard Dawkins wrote, that if you were to throw a dead bird in the air, it would describe a graceful parabola and come to rest on the ground, just like the physics books say it should; but if you were to throw a live bird in the air, it would not describe a parabola and come to rest on the ground, but may not touch land this side of the county boundary. Now these law-defying objects are, of course, living things, and in to culture do people interpret living things as some kind of miracle, but rather they make sense of them through a different kind of law, the laws of an intuitive biology where the core intuition is that plants and animals house a invisible but potent essence that supplies them with the renewable source of energy or oomph that gives them their form, that's passed from a parent to child, and that drives their growth and bodily functions. And I think it's this essence that accounts for why hunter-gatherers are such excellent amateur biologists. Hunter-gatherers invariably have hundreds of words for the local flora and fauna which usually map onto the professional biologist category of the genus or the species. They can make predictions based on the flimsiest of cues; for example, look what to us are a few scratchings in the ground, to deduce what kind of animal left those tracks, where it's likely to be heading, so that they could ambush it there. They could notice a flower in the spring and remember it, and return to it in the fall to dig up the underground tuber that's grown in the interim. And it's the intuition of an essence that leads people to try out the juices and powders from plants and animals as possible medicines, poisons, and food additives. Well, this relates to, I think, a third way of making sense of the world, one that we apply to our own creations, our tools and artifacts. A kind of intuitive engineering that's based on yet another kind of intuition of how the world works. If I were to ask you what all chairs have in common, well, it wouldn't be what they're made of, as it is with plants and animals, because chairs can be made up of metal or wood or plastic; and it wouldn't be their literal physical shape, because chairs can assume a shape of a high-back dining room chair, a bean bag, a severed elephant's foot, and so on. The only thing that chairs have in common is that someone intended them to hold up a human behind. It's the function of an artifact that defines what it is, and this is a different class of objects than the rocks and plants around us. Finally, I think we're equipped with an intuitive version of psychology, that we use to predict other people's behavior. People don't interpret other people as some kind of mechanical wind-up doll, but rather make sense of their behavior by imputing beliefs and desires to them, just as we explained Bill's trajectory ending up on the bus in terms of his desire and his beliefs. Well, what's the evidence that intelligence is divided into these separate ways of knowing? One of them is they, the distinctions appear very early in life while the child is still in the crib. If you show a baby a billiard ball clacking into another, the baby looks for a few seconds and then gets bored. If you show a baby a billiard ball stopping short of another one mysteriously launching, that really grabs their attention. If you now replace the billiard balls with people, you get the opposite reaction from babies. They are not surprised when a person stops short and another ups and leaves. Now what surprises them is a collision. And this suggests that babies distinguish between inanimate objects and human beings quite early in life. These abilities also can fractionate or disassociate in cases of neurological and genetic disorders. There are patients who have lost part of their brain to a stroke or other neurological disease, who may have lost the ability to name living things like fruits and vegetables and animals, but still be able to name manmade things like tools and furniture. There are other patients with different parts of the brain are damaged, where they have the opposite pattern and can name manmade things but not living things, suggesting that manmade things and living things are literally stored in different ways in the cortex. In the condition known as autism, it appears that children are born without the tools of an intuitive psychology. They really do treat other people as mechanical wind-up dolls and have no conception that other people house beliefs and desires the way they do. But I think one of the more interesting ways of seeing the complex structure of mind is to watch what happens when people take a part of the mind that's adapted to one part of the world and misapply it to a different part of the world. An example of that is in slapstick humor, where people laugh if someone slips on a banana peel or gets whacked by a board held by a carpenter. What happens in slapstick humor is that we're suddenly forced to switch from our ordinary way of interpreting other people as a mind or a locus of beliefs and desires, to suddenly being reminded that other people are also hunks of matter that ignominiously obey the laws of physics. A belief in souls and ghosts can be seen as intuitive psychology being divorced from intuitive biology. People go overboard and not only impute minds to other people, but impute minds that are free-floating, that are not anchored to bodies. In animistic beliefs, which people impute minds to trees, mountains, and idols, can be seen as an illicit wedding of an intuitive biology to an intuitive biology, physics, or engineering. Well, I'm going to switch now from thought to feeling. And I'm going to discuss an emotion aroused by an aspect of the physical world, an emotion that apparently is present in all human cultures, and that's instantly recognizable, worldwide, by a distinctive facial expression: Disgust. Now like many emotions, disgust has a certain set of stimuli that, in the world, that evoke it or elicit it. My favorite characterization of this eliciting stimulus comes from a fondly remembered piece of music that we used to sing in summer camp, sung to the tune of the "Old Gray Mayer" whose first stanza runs as follows: Great green globs of greasy, grimy gopher guts, mutilated monkey meat, concentrated chicken feet, jars and jars of petrified porpoise pus, and I forgot my spoon. Now this is a pretty effective list of triggers for this emotion. And I'm sure many of you who have gone to summer camp remember it. And indeed, when I've given this lecture at various college campuses, people often come up to me afterwards and they say, well, yeah, I remember that song, but when we went to camp we used to sing it with the following lyrics - and I've accumulated a collection - french fried eyeballs, little birdies dirty feet, chopped up baby parakeet, perforated pony's feet, on and on and on. What's the point of this list, you might be asking yourself, quite legitimately? Well, two things. One of them is that all of these items are parts or products of animals. The other is that it's an open-ended list; you can keep adding verses for as long as your nine-year-old boy's creativity lasts. And what it actually suggests is that it's maybe fruitless to characterize the animal parts and products that elicit disgust. It's basically any animal part or product, and rather it's easy to characterize this tiny number of animal parts and products that don't elicit disgust. In our culture, that very short list comprises the skeletal muscle tissue of cattle, swine, and fish, as well as the mammary secretions of cattle. Any other body part or product from those animals is beyond the pail, mucus, urine, brains, eyeballs, etc. And any body part from an animal not on this list is likely to be unappealing as well. Dog meat, slugs, insects, worms, and so on. Now the precise list varies radically from culture to culture but most, perhaps all, cultures do have a set of animal foods that are considered taboo or beyond the pail, although the precise identity differs. Now it's as if whatever is not permitted is forbidden. Now why would we be hooked up this way? Is this any way to design an intelligent organism? Well, the psychologist Paul Rozen has argued that is. And he's analyzed the psychology of disgust. He's reverse-engineered it in terms of what he calls the omnivores dilemma. There are many organisms that are dietary specialists and have digestive tracts that are optimized for one kind of food, such as pandas who depend on bamboo shoots, or koala bears who depend on eucalyptus leaves. The problem with being a specialist is that if the food you depend on becomes scarce, you have to go hungry. Humans are an example of an omnivore. Our digestive systems can handle a vast array of plant and animal foods. Our problem is that some unknown proportion of them are poison. There are a number of small animals that have evolved potent neurotoxins, and even ordinarily safe foods can become dangerous if they're tainted by spoilage, as we've recently been reminded by all those Draconian warnings from public health officials on how to sterilize your kitchen so you don't contract salmonella poisoning from your next chicken salad sandwich. Now the potentially dangerous animal products vary from location to location, and they concernly couldn't be wired in innately. But it suggests that disgust may be the outcome of the learning process to detect which animal products are safe. The logic is that as kids go grow up, they use their parents and friends the way kings used to use food tasters; namely, if he ate a morsel and didn't keel over dead, that means it's safe. Any other animal product is considered guilty until proven innocent. Now there's another interesting feature of disgust that Paul Rozen calls attention to. I can illustrate it by the following scenario. Imagine I invited you over to my house for a nice cup of cappuccino, and I've made a nice rich cup of dark French roast beans, frothed up the milk, poured it over, put on the cinnamon, the chocolate shavings, put in some raw sugar, and then stirred it for you with my comb. I think you would probably lose your appetite. Now this illustrates a feature of the psychology of disgust called contamination by contact, a kind of modern version of voodoo that we all intuitively engage in. A previously neutral object can instantaneously become contaminated by touching an animal part or product, in turn giving it the power to contaminate anything that it touches, even if nothing looks or tastes or smells any different from before. It's cognitively different. The intuition is that some kind of indescribably vile polluting bits have been left behind and are clinging to the object where they can be deposited on other objects. Now this is a kind of hypothetical construct that children have a name for. They call them cooties, as in, "I don't want to drink your glass of milk, it's got your cooties on it." The thing is, though, that children are right. There are cooties, they're called microorganisms. And microorganisms have an interesting property that distinguishes them from the kind of chemical poisons that are found in plants, namely, germs multiply. What starts out as an undetectable trace can, within a short period of time, become twice, then four times, then eight times, then sixteen times as plentiful, and so can seriously contaminate a large object even if it begins with an undetectable amount. And so it suggests that there's some degree of warrant in world for the intuition of contamination by contact, and that the emotion of disgust play be kind of intuitive microbiology. Well, my final example is going to come from our emotions elicited not by greasy, grimy gopher guts, but by other people. And again I'll begin with a puzzle; namely, why are our emotions about other people so often passionate and seemingly irrational? Examples are pursuing vengeance until you draw your last breath, vowing not to rest until you slay the guy whose great grandfather slew your great grandfather, defending your honor at all costs, challenging someone to a duel if he besmirches your reputation with an unkind remark, stabbing the guy who disses your brand of sneakers, falling head over heels in love, and so on. The most common explanation for passion is the romantic theory, coming out of the romantic movement from Germany and France and England a couple of hundred years ago. And that is that we all house a primal force which is part of our heritage from nature, that it's fundamentally irrational and maladaptive unless it's channeled into art and creativity. And this, of course, alludes back to hydraulic theory of the mind, and it's one of the key ideas behind Freud's theory of psychoanalysis. Now I'm going to argue for a very different theory, called the strategic theory, based on the notion of paradoxical tactics from the mathematical theory of games, which states that there are circumstances in which a sacrifice of freedom and rationality can actually give an agent an advantage, in particular, in any situation of promises, threats, and bargains. And just to show you how unromantic this theory is, I'm going to use it to reverse-engineer romantic love, yes. Now, romantic love actually has been studied for many decades by social scientists. And there's one conclusion they've drawn that I'm sure that will be recognizable to any of you who have recently been on the dating scene; and that is that love is a kind of marketplace and that there is a rational component of, namely, smart shopping. All of us at some point in our lives are in search of the best looking, richest, nicest, smartest, funniest person who will settle for us. But there's a problem with smart shopping; namely, your perfect match is a needle in a haystack, and you might die single if you wait indefinitely for him or her to show up. So all of us have to trade off value against time, and at some point set up house with the best person we've found so far. And this can explain probably the most powerful empirical effect in mating; namely, the tendency for people of similar desirability to end up together a sort of mating by mate value. Generally, if you look at a sample of couples, the husband and wife or boyfriend and girlfriend are pretty closely matched in terms of desirability to third parties. The tens marry the tens, and the nines marry the nines, and the eights marry the eights, and so on. On the other hand, I think you'd agree that there is something about the experience of love in this coldhearted social science, analysis leaves out; namely, the irrational part of love, the involuntariness and caprice. You can't will yourself to fall in love with someone, and you can't predict down to the last match who will end up with whom. I'm sure all of us know people, I'm sure many of us are people, who at some point have been fixed up with the perfect mate on paper. They're nice, they're good looking, they're funny, etc. But somehow when the two people meet you just don't hit it off. Sparks don't fly, cupid didn't strike. The earth didn't move. Why? Well, the economist Robert Frank at Cornell University has analyzed this paradox in terms of what economists call the commitment problem. Now romance is a kind of promise. You're promising to spend the rest of your life with someone, bring up children together, forego opportunities to be with other people. And as with any promise, a rational agent might find it in his or her interests to break the promise, especially in the case of love, where, if by necessity, you've had to trade off value against time and set up house with the best person you've found so far. Well, by the law of averages someone even better is bound to show up in the future, it's just a question of when. Perhaps, Tom Cruise or Cindy Crawford moved into the apartment next door and will be momentarily available. Well, at that point someone following the smart shopping strategy would drop his or her mate like a hot potato. But in this hypothetical world of rational agents, the partner could predict that that day would come and they would have been crazy to have entered the relationship to begin with because relationships have certain irrecoverable costs, opportunity costs of being with some other person, sacrifices such as getting rid of your apartment and selling your stereo and so on. And so we have the paradoxical situation that what ought to be in the interests of both parties neither party can agree to because neither of them has grounds for trusting the other. The problem is how do you make a promise credible? Well, Frank suggests that perhaps the solution is that if we're constitutionally put together so that we don't decide to fall in love for rational reasons, perhaps that means we're a little less likely to decide to fall out of love for rational reasons; and the very involuntariness of romantic love serves as a guarantor of the promise in the eyes of the person that we're extending the promise to. It's one of many cases in which a lack of freedom and rationality can paradoxically be an advantage. There are many analogies from the world of laws and contracts that Frank, and before him Thomas Shelling, have pointed out. For example, the law that allows the bank to foreclose on your mortgage and repossess your house constrains your freedom, your freedom to live in the house without making your mortgage payments. But on the other hand, it's only that law that made it worth the bank's while to lend you the money to begin with, and so paradoxically that law works to the advantage of borrowers as well as lenders. Another example is that the law that defines the rights of corporations says that a corporation has the right to sue and the right to be sued. The right to be sued? What kind of right is that? Well, it's the right to enter into a contract or to make a promise with a party that has the potential to be harmed if you back out; therefore, by making the promise more credible, it expands the range of options in life. Well, are there any additional kinds of evidence for this ingenious theory in terms of the details of the psychology of romance? Well, I think there are. One of them is the mere fact that romantic love appears to be a universal human emotion. In a recent ethnographic survey, Yonie Harris has shown that something that we would call romantic love has been described in all of the world's cultures. This comes as a shock to many contemporary intellectuals, for whom it's the conventional wisdom that romantic love is a recent invention of Hollywood script writers or romance novelists; that it's a social construction of the last few centuries. I think what's happened is that the intellectuals have basically bought into society's party line, coming from the fact that romantic love is a nuisance to parents. Parents would just as soon sell or trade their children in arranged marriages, and so inevitably spread the disinformation that romantic love doesn't exist, which often becomes the culture's party line, but apparently romantic love does exist. Another kind of evidence for this is the whole psychology of courtship. What people do to try to get other people to fall in love with them. If you were to whisper into your lover's ear, "You're the nicest, best looking, smartest, richest person I've found so far," you would probably kill the romantic mood. Even though I think the research suggests that there's a lot of truth to it. Instead the way to a person's heart is to declare the exact opposite, that it's your irreplaceable, idiosyncratic, unique personality traits, rather than your overall desirable characteristics that attract me to you, and that moreover it was not a conscious decision on my part, but rather somethingÉwhen we're in the throws of passion, we broadcast it, we show it. We tremble, we blush, we blanch, our voice croaks, we get goofy expressions on our face and so on. And one way to analyze it is that we are broadcasting the fact that our current course of action is under the control of involuntary division, the central nervous system; the limbic system which is the part responsible for housekeeping and physical plant function such as heart rate and blood circulation. It's not a course of action that's under the control of the rational voluntary division, the central nervous system. The cortex is not a decision that we talked ourselves into, and is therefore not a decision that we're likely to talk ourselves out of. Now if passionate love and loyalty and friendship are guarantors that our promises are not double crosses, by symmetrical logic one can show that passion and vengeance and a desire to defend one's honor can serve as a guarantor that our threats are not bluffs. Now all people survive with some of the implicit threats that they carry around with them. If you harm me, there will be some kind of retribution that will make it not worth your while. The problem with any kind of threat is that when it's time to carry it out, there is nothing in it for the threatener. You could get hurt beating someone up in retaliation. Since the target of your threat knows that, they can threaten you right back by refusing to comply with the threat. They can, as we say "call your bluff," knowing that the only value of a threat is as a deterrent. Once it comes times to carry out the threat, all of the economic analysis says that there's nothing to be gained and everything to be lost. Well, one way around this paradox is to be so constituted that it would be an intolerable insult to let the offense go unpunished, and to be a hot head who can't help but exacting revenge, even if in the short-term it does you more harm than good. And this is a kind of logic that is spelled out in many plots in the world's fiction, of which my favorite example is a scene from the "Maltese Falcon" by Dashel Hammet, where, for those of you who have seen the film may remember, that there is a stand off between Sam Spade, played by Humphrey Bogart, and Casper Guttman, played by Sidney Greenstreet, in which Bogart defies Greenstreet to kill him, knowing that he needs Bogart alive to retrieve the precious falcon; Bogart is the only one who knows where it is. And the Casper Guttman replies, "That's an attitude, sir, that calls for the most delicate judgment on both sides. Because as you know, sir, in the heat of action men are likely to forget where their best interests lie and let their emotions carry them away." And a very effective retort and a beautiful illustration of the paradoxical strategic role of the passionate emotions. Well, let me conclude. Is this a cynical view? I will certainly acknowledge that most people don't like to think of themselves as a system of computers designed by natural selection to promote survival and reproduction. On the other hand, I think this line of thinking is unavoidable for anyone, any scientifically literate person who has been following recent developments in the interface of mind and brain. I think it's no longer deniable that the mind is a product of the activity of the brain, that the brain is a product of evolution like other organs, and that evolution is not guaranteed to produce niceness. On the other hand, I don't think of it as a cynical view; and in fact, I think it holds out more hope for cautious optimism than some of the traditional ways of thinking about our specie's place in nature. Of the three ideas that I mentioned, the idea of computation suggests that the human mind is not just a bundle of crude drives and reflexes, but is composed of intricate, ingenious, and powerful software. The idea of evolution suggests that our legacy from the natural world is not just the nasty brutish emotions like greed, aggression, lust, a thirst for blood, a territorial imperative, and so on, but that by the same token the kinder, gentler emotions such as love, friendship, and a sense of justice are every bit as much part of our inheritance from the process of natural selection. Finally, the idea of specialization that the mind is composed of many interacting parts, holds out the hope that some parts of the mind, those with the longest view of the future, can figure out ways of outsmarting the other parts. |
Irvine Health Foundation |