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Michael S. Gazzaniga is David T. McLaughlin Distinguished Professor and Director of the Program in Cognitive Neuroscience at Dartmouth College. He is the author of Mind Matters: How Mind and Brain Interact to Create Our Conscious Lives (1989) and Nature's Mind: The Biological Roots of Thinking, Emotions, Sexuality, Language and Intelligence (1994) among many other works.

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The Mind's Past

University of California Press

There is no life that can be recaptured wholly, as it was. Which is to say that all biography is ultimately fiction. What does that tell you about the nature of life, and does one really want to know?
BERNARD MALAMUD, Dubin's Lives

Well, we do know about the fiction of our lives— and we should want to know. That's why I have written this book about how our mind and brain accomplish the amazing feat of constructing our past and, in so doing, create the illusion of self, which in turn motivates us to reach beyond our automatic brain.

Reconstruction of events starts with perception and goes all the way up to human reasoning. The mind is the last to know things. After the brain computes an event, the illusory "we" (that is, the mind) becomes aware of it. The brain, particularly the left hemisphere, is built to interpret data the brain has already processed. Yes, there is a special device in the left brain, which I call the interpreter, that carries out one more activity upon completion of zillions of automatic brain processes. The interpreter,

the last device in the information chain in our brain, reconstructs the brain events and in doing so makes telling errors of perception, memory, and judgment. The clue to how we are built is buried not just in our marvelously robust capacity for these functions, but also in the errors that are frequently made during reconstruction. Biography is fiction. Autobiography is hopelessly inventive.

Over the past thirty years the mind sciences have developed a picture not only of how our brains are built, but also of what they were built to do. The emerging picture is wonderfully clear and pointed. Every newborn is armed with circuits that already compute information enabling the baby to function in the physical universe. The baby does not learn trigonometry, but knows it; does not learn how to distinguish figure from ground, but knows it; does not need to learn, but knows, that when one object with mass hits another, it will move the object.

Even the devices in us that help establish our understanding of social relations may have grown out of perceptual laws delivered to our infant brain. Indeed, the capacity to transmit culture, an act that is only part of the human repertoire of capacities, may grow out of our special capacity to imitate. David and Ann Premack, formerly at the University of Pennsylvania, know a lot about human off-gins. They have spent much of their careers studying the chimpanzee in the laboratory and have found many instances where the chimp's capacities stop and those of a human infant begin. In their view we uniquely possess many automatic perceptual-motor processes that give rise to the complex array of mental capacities, such as belief and culture.

In considering how much complexity is already built into our brains, I ignore the nature-nurture issue in the traditional sense of how much variance in our intellectual lives is due to our genes and how much to our environment. The issue of whether Billy is smarter than Suzy or vice versa is but frosting on a much bigger cake. I am more concerned with why all humans are different from all chimpanzees, and from any other creature for that matter. Why do we have a theory about our dog or cat, but our cat or dog doesn't have a theory about us? Why don't chimps ever imitate actions or develop a history and a culture, but humans do these things reflexively? That difference is huge. The salient task of this book is to understand how human brains carry out these functions and why no other animal comes close. The brain device we humans possess, which I call the interpreter, allows for special human pursuits. It also creates the impression that our brain works according to "our" instructions, not the other way around.

The way our brains get built and the kinds of circuits that get installed have major consequences. Our brains differ from those of animals. Although our brains are founded on the same building block, the neuron, the organization of these billions of units in our brains gives rise to different capacities. The quantitative differences between Billy and Suzy possibly reflect genetic, intrauterine, and environmental factors. Even IQ differences may represent variations in normal birth trauma; new data suggest that cesarean-delivered infants are brighter. But the qualitative difference in the human brain leads to big discrepancies such as in our capacity for reconstructing past events. This

difference deserves our attention. Every normal human, whether a gravedigger or a Nobel laureate, possesses this capacity.

As the Premacks put it, brilliant people like E. O. Wilson at Harvard and Jane Goodall of Tanzania and New Mexico are off-base when it comes to trying to understand the human condition. Wilson claims, "Culture aside from its involvement with language, which is truly unique, differs from animal tradition only in degree." Goodall maintains that, since a chimp cannot talk, it cannot sit down with its peers as humans do and decide what to do tomorrow. The Premacks say, "Animals have neither culture nor history. Furthermore, language is not the only difference between, say, chimpanzees and humans: a human is not a chimpanzee to which language has been added."

My tale weaves its way through what we know about brain development and the simple facts of evolutionary theory as they affect our understanding of the human mind and brain. Even though I constantly call on the insights of biology, I also consider devices in the brain that create a different story for our species. That big, beautiful theory of Charles Darwin, one of the most important scientific theories in the history of the world (and not one word of it was generated with a computer's or calculator's help) leads us to inevitable truths. In attempting to understand what the brain is for, any evolutionary biologist begins with the essential question of why any organ or process does what it does. This approach puts us on a new course in considering how the brain enables mind. Instead of looking for unique physical substrates that support specific functions, we might discover how the brain generates ca-

pabilities in informational terms. This is the goal of a serious brain science attempting to understand our psychological selves. Scientists schooled in evolutionary theory keep reminding us of this point. Brain scientists who view the brain as a decision-making device are now gearing their experiments to find answers to the question "What is the brain for?"

The smart-aleck answer to the question is sex. Put more completely, the brain exists to make better decisions about how to enhance reproductive success. Thus, the brain is for helping reproduction and sex. Of course, the body containing it has to survive long enough to have sex. There is little question or disagreement about this. The fun begins with trying to understand how the brain manages this task and where we should look for the answer to the question of the brain's purpose. Most of the scientific observations I report were carried out at the psychological level; this work strongly contributes to the mind sciences, especially when derived from a biological perspective.

All kinds of things immediately get in our way when we try to think about what the brain does. The human brain, with zillions of capacities and devices for helping us make better decisions about how to enhance our reproductive success, can do many other things along the way. While a computer can be used to compute, which is why it was built, it also makes one hell of a paperweight. The finely tuned human brain can engage primal issues of sexual selection, or it can develop the second law of thermo-

dynamics. Understanding how it does the latter may not inform us of what it normally does and how it does it.

The question "What is the brain for?" is quite different from the question "What can the brain do?" Is this distinction important? So what if brains were built to do X but now serve mostly Y functions, one might argue. It is the Y functions in which scientists are interested. Take reading. Brains were not built to read. Reading is a recent invention of human culture. That is why many people have trouble with the process and why modern brain-imaging studies show that the brain areas involved with reading move around a bit. Our brains have no place dedicated to this new invention, but there is a place that manages breathing. Still, many would say, if the brain accomplishes such a function incidentally to what it was constructed for, so be it.

Most scientists, though, concentrate on the incidental mechanisms, which is a pity. If the evolutionary perspective is simply set aside, the data collected by psychologists and neuroscientists are likely to be grossly misinterpreted. The far-reaching implication of the evolutionary view is that models built to explain psychological and behavioral processes examine only the "noise" of the honed neural system devoted to making decisions about survival. Many psychological models of syntax, for example, assume that a child's ability to master this complex skill simply reflects the manner by which all children come to master the problem of communicating with others. B. F. Skinner, America's and Harvard's most outspoken behaviorist, spent his life promoting his view that such human capacities come about through simple reward contingencies experi-

enced by children. While a proponent of this view would never claim a rat could be taught to talk (since it does not have the innate capacity for that skill), a Skinnerian would maintain that simple reinforcement principles teach an animal or a human everything it is capable of doing.

Nowhere has this Skinnerian view been more prevalent than in explorations of human language. For instance, those who suffered the fifties and sixties heyday of behaviorism and rank empiricism remember being instructed that language is acquired through stimulus and response. Not until Noam Chomsky's pioneering work in linguistics did we realize that language reflects a biological event unique to our species. Many topics that wind up being viewed in evolutionary terms were not illuminated by scientists motivated with that agenda. The irony is that Chomksy, who is anything but a student of evolution, cracked the problem from a totally different perspective— that of the formal analysis of language.

Nonetheless, Chomsky's new view of language as a biologically based universal feature of our brain has taken hold. Steven Pinker, a colleague of Chomsky at MIT, has extended it by successfully arguing that language is an instinct—just like any other adaptation. Syntax is not learned by Skinnerian associative systems; rather, we can communicate through language because all members of our species have an innate capacity to manipulate symbols in a temporal code that maps sounds onto meaning. Although we "learn" different sounds for those meanings, the laws of communication are universal. If an evolutionary perspective were not invoked to interpret the work of linguists, more convoluted psychological theories of learning

and development would probably be generated to explain human language, which is in fact an adaptation. Many models have been proposed, but they have little merit or substance.

The debate about the role of evolution and language has produced some strange bedfellows. Stephen Jay Gould sees language as one of his now-famous spandrels, "the tapering triangular spaces formed by intersection of two rounded arches at right angles." Just as these spaces are architectual by-products of mounting a dome onto arches, language, he argues, is simply a by-product of having a big brain. Language came along free with the obvious evolutionary advantage of having a better decision-making device. Oddly, Chomsky seems comfortable with this idea, even though most evolutionary biologists are not.

I think Gould is correct in arguing that there are many spandrels in the mind, but language is not one of them. There are numerous advantages to having language. As the Premacks have pointed out time and again, pedagogy is what our species does best. We are teachers, and we want to teach while sitting by the campfire rather than by being continually present during our offspring's trial-and-error experiences. With language we can communicate both the dangers and the pleasures of the world. Moreover, the advantages of being able to communicate with our nonkin to cooperate in hunting, securing safety, settling disputes, and negotiating a host of daily occurrences are obvious. The appearance of language, slowly but surely gaining in complexity over evolutionary time, can't help but be a huge species event.

Still, I think that many psychological evaluations are su-

perficial. They explain only the noise, or unattended byproducts, of a biological system rather than how the system works and what it is capable of doing. They are indeed spandrels.

In the past decade we have begun to appreciate that the brain is not a big, freewheeling network. It does not make associations based on simple conditional relations and construct from them complex perceptual and cognitive functions. Research in animal psychology, evolutionary psychology, linguistics, and neuroscience has turned to a more fruitful approach to how the brain is structured and how it functions.

This more promising approach is derived from the notion that brains accrue specialized systems (adaptations) through natural selection. These highly specific systems are best understood in relation to their functions. Errors in analysis of their normal function occur when a device proves capable of handling another everyday task and in that capacity appears to have different properties. These proximate properties may be so tangible in our culture that they are accepted as the mechanism involved in the behavior or cognitive function in question.

Modern day illegal drug use, for example, is viewed by some as a deviant behavior produced solely by contemporary social forces. Some discuss at great length reasons for addictions, therapy for addictions, moral implications for drug use, and all the rest. Others simply wonder why we don't use drugs more frequently—if they make us feel

good, why not? None of these proximate reasons reveal the underlying forces at work on drug use.

Randolph Nesse at the University of Michigan nails down the reason why drug use occurs and should be dealt with gently. Several adaptations in our brain modulate our emotional states; fear, anxiety, and sadness all help us in our decision making. They are good devices. To highjack these systems with artificial substances is to impair our ability to use cues from the brain systems that manage these emotions and thus to behave in an adaptive way to new challenges. The seriousness of addiction becomes apparent when viewed from the evolutionary perspective. Our built-in systems for cuing good decisions become broken. We are not hearing our normal brain chemical systems advise us on what is good for us. Debates on the morality of addiction and other factors miss this underlying biological issue.

The ebb and flow of neuronal patterns of firing hold the key to how the brain makes its decisions. The physical substrates allow computations to be carried out; but once they are expressed, it is the pattern of the neuronal code that represents the neural code for a function, like seeing a face or a color. Evolutionary theory has generated the notion that we are a collection of adaptations—brain devices that allow us to do specific things. The brain must deal with new challenges in a complex and probably distributed way. Many systems throughout the brain contribute to a single cognitive function. Here's how it all works.

The neural system of any given animal at any given time is in a specific state, but over time the microarchitecture of the neural system changes. If a randomly mutated change—

one which happens when growth dynamics undergo variations—enhances reproductive success, then future generations are likely to inherit the mutation. For example, a rudimentary eye helps an organism to see a little and therefore helps it to navigate the world. If a mutation improves on the rudimentary eye, the organism will see better, behave more efficiently, and survive longer. The genes for that eye become part of the species' hardware. In fact, as Richard Dawkins of Oxford University has recently pointed out, it would not be surprising if all surviving animals possessed some sort of rudimentary eye. It all may have started with a light-sensitive pigment patch that cued the animal as to whether it was night or day. What is known is that all kinds of eyes have evolved, with many species developing unique ways of seeing.

In no way does an organism construct a solution to a problem de novo. Only by chance is a new network generated and additional characteristics and abilities added. Brain mechanisms evolved by random mutation to meet new challenges and perform tasks that enhance reproductive success. This brilliant idea of Darwin is the only explanation for the apparent engineering or complex organic design in the natural world. Trial and error it is, with the "trial" being the random mutation and the "error" being the evidence that the change in the organism is or is not beneficial. This remarkably simple point is still one of the most misunderstood ideas of our time. No matter how eloquently an evolutionist like Richard Dawkins makes the point, people continue to believe it is wrong. "How," they lament, "can a wonderfully complex entity like a human be the product of chance mutations? We must be

the result of divine design. We couldn't have happened by chance mutation."

Well, the chance factor is embedded in the idea of natural selection, but at the level of the genome. Chance variations in our genes create potentially better mutations, some of which survive. Over millions of years natural selection works on those chance mutations. Chance mutations and natural selection, working together, produced human beings. But it is completely wrongheaded to say that chance variations in our genome produced us suddenly. It was nibble, nibble, nibble for millions of years.

This ad hoc fashion of building the human, and in particular our brain, unfortunately makes it difficult for neuroscientists to tease out which tasks a system has evolved to accomplish. This is surely why finding localized circuits wholly responsible for a perceptual or cognitive capacity is so difficult. A neuropsychologist, the type of scientist who studies the effects of brain lesions on behavior, observes patients with focal lesions—which can result from strokes, tumors, or bullet wounds, or even railroad spikes driven into the skull by explosives. Such a patient may exhibit a specific disorder, such as the inability to detect upright human faces. A neuropsychologist may also study a patient with a large brain lesion that results in an amazingly specific disorder, such as not being able to speak nouns.

In the profoundly fascinating but young study of how the brain represents adaptive changes, not only within but between species, contemporary knowledge is found wanting.

The human brain is generally regarded as a complex web of adaptations built into the nervous system, even though no one knows how. The neural specificity underlying adaptations probably constitutes a network widely distributed throughout the brain. Since evolutionary changes work in ad hoc ways, often by chance commandeering systems to assist in a chore, the prospects for finding a circuit linked to a task may be very poor.

The powerful theory of natural selection determines how we view the evolved brain and its functions; in accepting this approach we reject traditional behaviorist views of psychology, which posit that our minds are built from simple conditioning and associations. Although the behaviorist view is now out of favor among psychologists, the concept of association networks is currently popular among connectionist theorists. The bastion for these ideas is in La Jolla, California. The intellectual leader of this view is the engaging, clever, and always enthusiastic Terry Sejnowski, a professor sponsored by the Howard Hughes Medical Institute at the Salk Institute by the sea.

Sejnowski and his colleagues believe that genetic specification plays little or no role in the development of our mental devices, and they maintain that neurobiology supports this view. Sejnowski refers to his idea as "neural constructivism," which means that "the representational features of cortex are built progressively from the dynamic interaction between neural growth mechanisms and environmentally derived neural activity. This contrasts markedly with popular selectionist models." While some would argue that constructivism need not necessarily conflict with selectionist views, I think he is right to draw the line

at that point. Selectionist models usually refer to how an enviromental stimulus selects out a preexisting capacity that an organism possesses from birth.

Even more boldly, Sejnowski announces that we now know learning guides development; then he quotes a barrage of controversial work. He marries the questionable neurobiology he reviews to the work of Jean Piaget, then suggests children learn domains of knowledge by interacting with the environment. It is not that built-in devices are expressing their capacities.

The La Jolla group draws upon what it calls the "non-stationarity" of the learning device in the brain. Learning transforms the learning device itself, so what has been learned can influence future learning. Sejnowski and his colleagues came to this idea in part because of the difficulties large networks have making guesses about how to organize themselves to solve a problem. They say tiny networks solve small problems and then gradually build up through trial and error.

As David Premack pointed out in his inimitable fashion, the La Jolla group's view of the work amounts to an evolutionist perspective. They want trial and error working ontogenetically, which is to say developmentally; evolutionists have it occurring phylogenetically. The difference is one of time scale, in addition to possible mechanism disparities. But there are deeper problems with connectionist theory. At the level of brain science, the cellular organization of cortical regions can be detected before birth. It is hard to explain to a person who holds a constructivist view that the basic structure of the language cortex is in place

before a baby is born. The baby isn't exactly chatting away about Michael Jackson in utero.

Premack points out another problem with the way the La Jolla group thinks about domain-specific knowledge: the fancy way people have come to talk about the fact that what one needs to know about learning language is different from what one needs to know about learning causality. Each has its own domain. The constructivist view of the brain is that it has a common mechanism that solves the structure of all problems. This is aptly dubbed the problem space. When the common mechanism confronts language issues, it winds up building the brain one way; when it confronts the problem of detecting faces, it builds it another way—and so on. This sort of assertion leaves us breathless because if we know anything, it is that any old part of the brain can't learn any old thing. Yet Sejnowski and his colleagues strongly believe that the environment plays a major role in structuring the brain and that our experience directly reflects reality. As they say, "This interaction . . . is sufficient to determine the mature representational properties of cortex with no need for domain-specific predispositions somehow embedded a priori in the recipient cortex. As a consequence, this makes the relations between environmental changes—whether natural or cultural—and brain structure a direct one." But as Premack says, "When we consider the problems humans are designed to solve, we are struck not by their similarities but by their differences. . .. In the case of language, structure includes phonemes on the one hand, and forms classes, noun vs. verb, on the other. . .. Structure concerns

physical relations such as containment, support, collison, and the like in intuitive physics."

The ethological literature contains many examples to counter Sejnowski's claims concerning how our brains are built. Premack reviews the work of Richard Sayfarh on the vervet monkey:

The vervet's problem domain is predator, the categories of which are: raptor, leopard and snake, to which it produces three different calls. Does the immature vervet figure out the structure of this domain, that is does it learn the categories? No it has the categories: what it learns is how to fine tune the membership of the categories.
For example, a young vervet can mistakenly produce the raptor call to hawks (which resemble the true predator), produce the snake call to inappropriate snakes, and the leopard call to inappropriate ground animals. It corrects these errors, learning to confine the call to the correct member of each category, and to respond more quickly. However, even when the vervet produces its first calls, it does not make between-category errors, e.g., issue the snake call to a bird, etc. Hence, vervets do not "figure out the structure of the problem space." They come with the structure.

Although many people want to believe that things work the way the La Jolla group claims, biology is not so obliging. The evolutionary engine of natural selection builds beautifully crafted devices in weird ways, creating ever more perfect machines from multitudinous random events.

As a result nature tends to use any trick that comes along to make things work. As George Miller at Princeton University put it when explaining why the cognitive revolution in psychology took place, "During the 1950s it became increasingly clear that behavior is simply the evidence, not the subject matter of psychology." Association theory, behavioral theory, and connectionist theory are inadequate. I am sure we'll find principles that describe our mental activity; that's the goal of the mind sciences. But I am also sure that most of them will be instantiated into complex and possibly bizarre neural devices we are born with, just as we are born with antibodies to ward off other challenges from the environment.

When I minored in immunology in graduate school, the conventional wisdom was that the body can make antibodies to any antigen. This was part of a prevalent view that many things in biology can be formed by instruction—that the organism incorporates information from the environment into its function. This is exactly what the neural constructivists are saying today. The idea in immunology was that globulin molecules will form around any antigen and generate an immune response. But by the mid-1960s the revolution in biology had demonstrated that nothing is farther from the truth. It had become clear that organisms, from mice to humans, are born with all the antibodies they will ever have. Instead of the body responding to instruction from the environment, the invading antigen selects a group of antibodies already in the body. These antibodies are amplified and produce the classical immune response. The immune system's complexity is thus built into the body. So is the mind's complexity.

Niels Jerne, the brilliant immunologist and Nobel laureate, played a primary role in alerting neuroscientists to the value of biological mechanisms such as selection theory in understanding how the brain enables mind. Jerne pointed out that, despite the long-held belief that biological processes are subject to instruction, every time we figure out a biological process, it is selection, not instruction, that is at work. The finches in the Galapagos Islands, for instance, suffered a drought in 1997. Those with large beaks could make use of a more varied food supply. And so, after a generation or two, smaller-beaked individuals died off, and large beaks became a dominant feature among the finch population. It wasn't that the small-beaked finches had not learned to grow larger beaks to eat the new food supply; rather, the genetic characteristic of large-beakedness was rapidly selected for. The same process occurs in the well-known mutation of microorganisms into resistant strains when antibiotics are used inappropriately. Although instruction may appear to be at work, as if the environment were "telling" organisms to change, selection is in fact calling the shots.

Jerne hypothesized that the nervous system is constructed by a similar process. Perhaps much of what passes for learning (i.e., the body receiving instruction from the environment) is more akin to selection. Jerne suggested that an organism has a cornucopia of genetically determined neural networks for certain kinds of learning. When learning, the system sorts through an array of built-in responses, seeking the appropriate one to use for the environmental challenge.

A more cognitive modification of Jerne's idea would

take into account one of the primary findings of cognitive science over the past forty years. We don't select our ideas preformed, just as we don't select sentences preformed from some inventory, like Tickle-Me Elmo dolls. We form sentences combinatorially, as Chomsky showed the world, with a computational apparatus that recursively combines preexisting elements into bigger and bigger structures. The same is true for our thoughts. The human's devices for meeting new challenges allow for a seemingly endless array of inventive solutions to environmental challenges. But those devices are built in and are brought to bear on new problems.

Jerne's original hypothesis, modified or not, is bold; yet so much of what we now know about the brain, animal behavior, psychological development, evolution, and human neuropsychology is consistent with it. The brain is a collection of systems designed to perform functions that contribute to the primary goal of every brain: to enhance reproductive success. As Paul Rozin, a psychologist from the University of Pennsylvania, noted years ago, just as one can view intelligence as a phenotype and look at the multitude of subprograms that contribute to a skill, one can view human cognition as a phenotype and identify subprograms that make up this feature of brain activity. It is the accumulation of additional circuits that accounts for the unique human experience.

Funnyman Henny Youngman often said, "Timing is everything." With our brains chock full of marvelous devices,

you would think that they do their duties automatically, before we are truly aware of the acts. This is precisely what happens. Not only do automatic mechanisms exist, but the primate brain also prepares cells for decisive action long before we are even thinking about making a decision! These automatic processes sometimes get tricked and create illusions—blatant demonstrations of these automatic devices that operate so efficiently that no one can do anything to stop them. They run their course and we see them in action; as a consequence we have to conclude that they are a big part of us.

Our motor system, which makes operational our brain's decisions about the world, is independent of our conscious perceptions. Too often our perceptions are in error; so it could be disastrous to have our lives depend on them. We would be better off if our brains reacted to real sensory truths, not illusory ones.

If so many processes are automatic, they should function outside of our conscious awareness. But we have come to think that the part of our brain which has grown like Topsy, the cerebral cortex, is reserved for conscious activities. Brain scientists have been wrongheaded about this, too. The cortex is packed with unconscious processes, as are the older parts of our brain.

Imagine that fate has not been good to you, and you suffer a cerebral stroke. It could have been worse, but it does destroy the primary visual system of your brain's right half. You no longer can see anything to the left of your primary visual focus. Reports over the past twenty years indicate that while you may not consciously see in your blind field of vision, your hand or even your mouth might be able to

respond to stimuli presented there. Patients who exhibit this condition, which has been dubbed blindsight, can respond to such stimuli without being consciously aware of them. To explain this odd finding, researchers proposed that the deep, dark, phylogenetically older parts of the midbrain, not the cortex, were carrying out the task. They hoped that the site of unconscious processing had been discovered and could be examined. The promise was great, but this idea has been questioned and is probably wrong. There is no need to look for the unconscious in the mid-brain; it is upstairs in the cortex, right where it belongs.

Ever since Freud introduced his psychodynamic ideas, people have been fascinated with the unconscious. There, in that mysterious domain of our mental life, ideas are strung together, true relations between facts are seen, plans are made. Although Freud never specified which parts of the brain manage the unconscious, the tacit assumption and sometimes explicit claim is that the older and more primitive regions do this work. Consciousness is rooted in the cerebral cortex—the great big blanket that covers our older midbrain and hindbrain. But, so the theory goes, the mysteries of life—what we do outside of conscious awareness—stir in the Cimmerian depths below.

In the collective enthusiasm for this simplistic thinking, we all missed a fundamental point: Ninety-eight percent of what the brain does is outside of conscious awareness. No one would disagree that virtually all our sensorimotor activities are unconsciously planned and executed. As I sit here and type this sentence, I have no idea how my brain directs my fingers to the correct keys on the keyboard. I have no idea how the bird sitting on the outside deck, a

glimpse of which I must have caught in my peripheral vision, just snagged my attention while I nonetheless continue to type these words. The same goes for intellectual behaviors. As I sit and write, I am not aware of how the neural messages arise from various parts of my brain and are programmed into something resembling a rational argument. It all just happens.

Surely we are not aware of how much of anything gets done in the realm of our so-called "conscious" lives. As we use one word and suddenly a related word comes into our consciousness with a greater probability than another, do we really think we have such processes under conscious control?

Our mind has an absurdly hard time when it tries to control our automatic brain. Remember the night you woke up at 3 A.M., full of worry about this and that? Such concerns always look black in the middle of the night. Remember how you tried to put them aside and get back to sleep? Remember how bad you were at it?

We all have had our interest sparked by an attractive stranger. A struggle ensues as we try to override the deeply wired brain circuitry provided by evolution to maintain our desire to reproduce. Allaying possible embarrassment, the mind gets around the brain's assertion this time and manages to maintain control. Society does have an effect, through yet other brain representations, and thus we are not completely at the mercy of our brain's reproductive systems. Or at least we like to believe so.

Why do some of us like going to work so much? There goes that brain again. It has circuits that need attention, that want to work on problems. Then comes the weekly

lunch, complete with fine wine, delicious food, and stimulating conversation. Mr. Brain, there you go again. I suppose you will want to sleep after lunch, too.

Nowhere is the issue of ourselves and our brain more apparent than when we see how ineffectual the mind is at trying to control the brain. In those terms, the conscious self is like a harried playground monitor, a hapless entity charged with the responsibility of keeping track of multitudinous brain impulses running in all directions at once. And yet the mind is the brain, too. What's going on?

There seems always to be a private narrative taking place inside each of us. It consists partly of the effort to fashion a coherent whole from the thousands of systems we have inherited to cope with challenges. Novelist John Updike muses on this in his book Self Consciousness:

"Consciousness is a disease," Unamuno says. Religion would relieve the symptoms. Religion construed, of course, broadly, not only in the form of the world's barbaric and even atrocious religious orthodoxies but in the form of any private system, be it adoration of Elvis Presley or hatred of nuclear weapons, be it a fetishism of politics or popular culture, that submerges in a transcendent concern the grimly finite facts of our individual human case. How remarkably fertile the religious imagination is, how fervid the appetite for significance; it sets gods to growing on every bush and rock. Astrology, UFOs, resurrections, mental metal-bending, visions in space, and voodoo flourish in the weekly tabloids we buy at the cash register along with our groceries. Falling in love—its mythologization of the beloved and everything that touches her or him is an invented religion, and reli-

gious also is our persistence, against all the powerful post-Copernican, post-Darwinian evidence that we are insignificant accidents within a vast uncaused churning, in feeling that our life is a story, with a pattern and a moral and an inevitability—that as Emerson said, "a thread runs through all things: all worlds are strung on it, as beads: and men, and events, and life come to us, only because of that thread." That our subjectivity, in other words, dominates, through secret channels, outer reality, and the universe has a personal structure.

Indeed. And what in our brains provides for that thread? What system ties the vast output of our thousands upon thousands of automatic systems into our subjectivity to render a personal story for each of us?

A special system carries out this interpretive synthesis. Located only in the brain's left hemisphere, the interpreter seeks explanations for internal and external events. It is tied to our general capacity to see how contiguous events relate to one another. The interpreter, a built-in specialization in its own right, operates on the activities of other adaptations built into our brain. These adaptations are most likely cortically based, but they work largely outside of conscious awareness, as do most of our mental activities.

The left-hemisphere interpreter was revealed during a simultaneous concept test in which split-brain patients were presented with two pictures. One picture was shown exclusively to the left hemisphere and the other exclusively to the right. The patient was asked to choose from an array of pictures ones that were lateralized to the left and right sides of the brain. In one example, a picture of a

chicken claw was flashed to the left hemisphere and a picture of a snow scene to the right hemisphere. Of the array of pictures placed in front of the subject, the obviously correct association was a chicken for the chicken claw and a shovel for the snow scene. One of the patients responded by choosing the shovel with his left hand and the chicken with his right. When asked why he chose these items, his left hemisphere replied, "Oh, that's simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed." In this case the left brain, observing the left hand's response, interpreted that response in a context consistent with its sphere of knowledge—one that does not include information about the snow scene.

What is amazing here is that the left hemisphere is perfectly capable of saying something like, "Look, I have no idea why I picked the shovel—I had my brain split, don't you remember? You probably presented something to the half of my brain that can't talk; this happens to me all the time. You know I can't tell you why I picked the shovel. Quit asking me this stupid question." But it doesn't say this. The left brain weaves its story in order to convince itself and you that it is in full control.

The interpreter influences other mental capacities, such as our ability to accurately recall past events. We are poor at doing that, and it is the interpreter's fault. We know this because of neuropsychologists' research on the problem. My favorite comes from studies of the two half brains of split-brain patients. The memory's accuracy is influenced by which hemisphere is used. Only the left brain has an interpreter, so the left hemisphere has a predilection to interpret events that affect the accuracy of memory. The

interpreterless right hemisphere does not. Consider the following.

When pictures that represent common events—getting up in the morning or making cookies—were shown to a split-brain patient who was later asked to identify whether pictures in another series had appeared in the first, both hemispheres were equally accurate in recognizing the previously viewed pictures and rejecting unseen ones. But when the subject was shown related pictures that had not been shown, only the right brain performed well. The left hemisphere incorrectly recalled more of these pictures, presumably because they fit into the schema it had constructed regarding the event. This finding is consistent with the idea of a left-hemisphere interpreter that constructs theories to assimilate perceived information into a comprehensible whole. In so doing, however, the elaborative processing has a deleterious effect on the accuracy of reconstructing the past.

What is so adaptive about having what amounts to a spin doctor in the left brain? Isn't telling the truth always best? In fact, most of us are lousy liars. We become anxious, guilt ridden, and sweaty. As Lillian Hellman observed, guilt is a good thing; it keeps us on the straight and narrow. Still, the interpreter is working on a different level. It is really trying to keep our personal story together. To do that, we have to learn to lie to ourselves.

Kobert Trivers pointed this out years ago, as I reviewed in my last book, Nature's Mind. In order to convince someone else of the truth of our story we have to convince ourself We need something that expands the actual facts of our experience into an ongoing narrative, the self-image

we have been building in our mind for years. The spin doctoring that goes on keeps us believing we are good people, that we are in control and mean to do good. It is probably the most amazing mechanism the human being possesses.

Come along with me as I weave my way through the mind and the brain. Let me show you why I think our interpreter is reconstructing the automatic activities of our brain. Let me tell you about how our brain is built, how it makes mistakes, how it gets things done for us, and how we put on it a spin that makes it all seem like we are personally in charge. I don't know if I have it all right, but I'm confident I don't have it all wrong!

Excerpted from The Mind's Pastby Michael S. Gazzaniga Copyright © 1998 by Michael S. Gazzaniga. Excerpted by permission.
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