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Unformatted text preview: A Brain on the Ceiling of the Sistine Chapel? Between 1508 and 1512, Michelangelo (1475—1564) painted the Sistine Chapel in the Vatican. One panel of the ceiling, his masterpiece The Creation ofAdam (shown on the right), depicts God reaching out to bestow the gift of life upon humanity, through Adam. But the oddly shaped drapery behind God, and the arrangement of his attendants, has prompted speculation that Michelangelo was conveying a hidden message: God and attendants appear to be part of a human brain (Mesh— berger, 1990). Only a little imagination is required to identify the broad outlines of a brain in Michelangelo’s depiction of God (compare it with the midline section of a human brain in Figure 2.1219). During the Renaissance, when this fresco was created, the all-powerful church forbade depiction of the dissected human body, considering it to be a desecration. But there is no doubt that Michelangelo engaged in extensive dissections of cadavers, gaining the detailed knowledge of human anatomy that informs his sculpture and paintings. It is highly likely that he knew perfectly well What a dissected human brain looks like. So, was Michelangelo making a subtle commentary about the origins of behavior, God’s most magnificent creation, or the secrets of nature? We probably will never know. But we can all agree that our uniquely human qualities—language, reason, emotion, and the rest—are products of the brain. The goal of this book is to give you some idea of how this mysterious organ enables humans to paint a masterpiece, sing an aria, or uncover some of the secrets of that very brain itself. 11 this book we explore the many ways in which the structures and actions of the brain produce mind and behavior. But that is only half of our task. We are also interested in the ways in which behavior in turn modifies the structures and actions of the brain. One of the most important lessons we hope to convey is that interactions between brain and behavior are reciprocal. The brain controls behav- ior and, in turn, behavior alters the brain. We hope to give an interesting account of the main ideas and research in bio— logical psychology, which is of great popular as well as scientific interest. Because there are so many pieces to tie together, we try to introduce a given piece of infor— mation when it makes a difference to the understanding of a subject—especially When it forms part of a story. Most important, we seek to communicate our own interest and excitement about the mysteries of mind and body. What Is Biological Psychology? No treaty or trade union agreement ever defined the bOundaries of biological psy- chology. The first peeple‘ to study the relationships between brain and behavior regarded themselves as philosophers, and their findings contributed to the births of biology and psychology. A merging of those disciplines, biological psychology is the field that relates behavior to bodily processes, especially the workings of the 2 CHAPTER 1 5 known as neuroscience (the root neuro— comes from the Greek word neuron, meaning “nerve” or “cord”), biological psychology is also known as behavioral neuroscience. Whichever name is used, the main goal of this field is to understand the biology underlying behavior and experience. is afield that includes many players who come from quite gists, biologists, physiologists, engineers, neurolor biological psychology Also called brain. Because study of the brain i behavioral neuroscience. The study of the biological bases of psychological processes and behavior. euroscience The study of the nenrous Biological psychdogy n different backgrounds: psycholo system. ' ,'_Behavioral.- medicine 3 Developmental neurobiology - 1.1 How Biological Psychology Relates to Other Fields of Study In this graphical representation of the relationships among . biological psychology and other ‘ ; scientific disciplines, fields to— = ‘ ward the center of the map are closest to biological psychology in their history, outlook, aims, and/or methods. BlOLOGlCAL PSYCHOLOGY; SCOPE AND OUTLOOK 3 gists, psychiatrists, and many others. Thus, there are many career opportunities, in both universities and private industry, for people with interests in this field (Hitt, 2007). Figure 1.1 maps the relations of biological psychology to these many other disciplines. Clearly, the biological psychology umbrella is very wide. Five Viewpoints Explore the Biology of Behavior In our pursuit to understand the biological bases of behavior, we use several dif- ferent perspectives. Because each one yields information that complements the others, the combination of perspectives is especially powerful. The five major per- spectives are 1. Describing behavior 2. Studying the evolution of behavior 3. Observing the development of behavior and its biological characteristics over the life span 4. Studying the biological mechanisms of behavior 5. Studying applications of biological psychology—for example, its applications to dysfunctions of human behavior These perspectives are discussed in the sections that follow, and Table 1.1 shows how each perspective can be applied to three kinds of behavior. Behavior can be described according to different criteria Until we describe what we want to study, we cannot accomplish much. Depending on the goals of our investigation, we may describe behavior in terms of detailed acts or processes, or in terms of results or functions. An analytical description of arm movements might record the successive positions of the limb or the cunt-rac- tion of different muscles. A functional behavioral description, by contrast, would state whether the limb was being used in walking, running, hopping,swimming, or texting. To be useful for scientific study, a description must be precise and reveal the essential features of the behavior, using accurately defined terms and units. Kind of behavior Research , perspective Sexual behavior Learning and memory Language and communication DESCRIPTION _ Structural What are the main patterns of In what main ways does behavior How are the sounds of speech reproductive behavior and sex change as a consequence of patterned? ' differences in behavior? experiencewfor example, conditioning? Functional How do specialized patterns of How do certain behaviors lead to What behavior is involved in making behavior contribute to mating rewards or avoidance of statements or asking questions? and to care of young? punishment? _ EVOLUTION How does mating depend on How do. different species compare How did the human speech hormones in different species? in kinds and speed of learning? apparatus evolve? DEVELOPMENT How do reproductive and How do learning and memory How do children learn to speak? secondary sex characteristics change ove:r the life span? develop over the life span? MECHANISMS What neural circuits and hormones What anatomical and chemical What brain regions are particularly are involved in reproductive . changes in the brain hold involved in language? behavior? memories? _ APPLICATIONS Low doses of testosterone Gene therapy and behavioral Speech therapy, in conjunction with ' restore libido in some postmenopausal women. therapy improve memory in some senile patients. amphetamine treatment, speeds language recovery following stroke. 4 CHAPTER 1 conserved In the context of Evolution, referring to a trait that is passed on from a common ancestor to two or more descendant species. ontogeny The process by which an indi- vidual changes in the course of its lifetime— that is, grows up and grows old. neuron Also called nerve cell. The basic unit of the nervous system. - We compare species to learn how the brain and behavior have evolved Darwin’s theory of evolution through natural selection is central to all modern biology and psychology: From this perspective emerge two rather different em- phases: (1) the continuity of behavior and biological processes among species be— cause of our common ancestry and (2) the species-specific dzfierences in behavior and biology that have evolved as adaptations to different environments. At some points in this book we will concentrate on continuity—that is, features of behavior and its biological mechanisms that are common to many species. At other points, we will look at behaviors displayed by only a few species. , _ Nature is conservative. Once particular features of the body or behavior evolve, they may be maintained for millions of years and may be seen in animals that oth— erwise appear very different. For example, the electrical messages used by. nerve cells (see Chapter 3) are essentially the same in a jellyfish, a cockroach, and a hu— man being. Some of the chemical compounds that transmit messages through the bloodstream (hormones) are also the same in diverse animals (see Chapter 5). Spe- cies share these conserved characteristics because the features first arose in a shared ancestor (Box I .1). But mere similarity, of a feature between species does not guar— antee that the feature came from a common ancestral species. Similar solutions to a problem may have evolved independently in different classes of animals. The body and behavior develop over the life span Ontogeny is the process by which an individual changes in the course of its life— time—that is, grows up and grows old. Observing the way in which a particular behavior changes during ontogeny may give us clues to its functions and mecha— nisms. For example, we know that learning ability in monkeys increases over sev- eral years of development. Therefore, we can speculate that prolonged maturation of brain circuits is required for complex learning tasks. In rodents, the ability to form long—term memories lags somewhat behind the maturation of learning abil- ity. So, young rodents learn well but forget more quickly than older ones, suggest— ing that learning and memory involve different processes. Studying the develop— ment of reproductive capacity and of differences in behavior between the sexes, along with changes in body structures and processes, enables us to throw light on body mechanisms underlying sex behaviors. Biological mechanisms underlie all behavior The history of a species tells us the evolutionary determinants of its behavior; the history of an individual tells us the developmental determinants. To learn about the mechanisms of an individual’s behavior, we study how his or her present body works. To understand the underlying mechanisms of behavior, we must regard the organism (with all due respect) as a “machine,” made up of billions of nerve cells, or neurons (the Greek word for "nerve" or "cord”). We must ask, How is this thing constructed to be able to do all that? _ Our major aim in biological psychology is to examine body mechanisms that make particular behaviors possible. In the case of learning and memory, for exam- ple, we would like to know the sequence of electrical and biochemical processes that occur when we learn something and retrieve it from memory. What parts ,of the nervous system are involved in that process? In the case of reproductive behavior, we would like to know how the body grows to produce the capacity for sexual behavior. We also want to understand the neuronal and hormonal pro- cesses that underlie reproductive behavior. ,Research can be applied to human problems Like other sciences, biological psychology is also dedicated to improving the human condition. As Albert Einstein once said, concern for humanity and its fate must al~ BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 5 .. Each person has some characteristics shared by... all animals. .. its-DNA, ' ...5.t .essneug firifpsmsfisn: . all vertebrates. .. all other primates (_e.g., hav- ing a hand with an ‘opposég; able thumb and a relatively 3 large, complex brain). I Whether knowledge gained about a process in anotherspecies applies to humans depends on whether we are like that species in regard to that - process. The fundamental research on the _ 5 mechanisms of inheritance in the bac-‘ _ _ ‘ terium Escherichia coli prov'ed‘So widely: '. ‘ f applicable that some molecular biologists E proclai_m_ed,;”What is_true of- E. coli is true-'5 _._ of the elephant.” To a remarkable-extent ' that statement is true, but there" are also - i ' . . someiimportant differences in the genetic‘ mechanisms of E. coliand mammals; ' I I With respectto each biological prop-'_ . erty, researchers must determinehow _ '. animals are identical and howtheyare __ . different. When we seek animal models '--=for studying human behavior or biological ' _ . _ ‘ _ .. ._- _ . .. - . . processes, we must ask-the following ques— .. How'do'similarities and differences ajr'nong'f' tio_n:_Does the proposed animal'modei ' - ' '. people-andanimals fit into biological " - "really-hm somethings _in common with '. psychology? Each person is in some ways I "the process at work in humans? We will ' like _all other people, in some ways like ' seemany cases in which it does) _ ' some other people, and in some ways like " Even within the same species, how- no other person. As the figure shows, We ever, individuals differ from one another: _' can extendthis observation to the much - ;_ cat from cat, bluejay from blue jay, and broader range ofanimai life. insome j 3 ‘ _ person from person. Biological psychology _ ways each person is like all other animals seeks to understand individual differences ' ' (e.g.,needing to ingest complex organic :‘asrwell as similarities. Therefore, the way ‘ nutrients), insome Ways like all other -- in which each person is able to process in- vertebrates (e.g., having a spinal column), __for_mat_ion and store-the memories of these -_ in some ways like all other mammals (e.g.,- "experiences is another part of Our story. nursing our young), and in some ways like ' all mammals... all primates. .. _ . no other person. ways form the chief interest of all scientific endeavors “in order that the creations of our minds shall be a blessing and not a curse.” Numerous human diseases involve malfunctioning of the brain. Many of these are already being alleviated as a result of research in the neurosciences, and the prospects for continuing advances are good. 6 CHAPTER 1 somatic intervention An approach to finding relations between body variables and behavioral variables that involves manipulat- ing body structure or function and looking for resultant changes in behavior. independent variable The factor that is manipulated by an experimenter. dependent variable The factor that an experimenter measures to monitor a change in response to changes in an independent variable. behavioral intervention An approach to finding relations between body variables and behavioral variables that involves intervening in the behavior of an organism and looking for resultant changes in body structure or function. 1.2 Three Main Approaches to Study- ing the Neuroscience of Behavior (a) In somatic intervention, investigators change the body structure or chemistry of an animal in some way and observe and measure any resulting behavioral effects. (b) Conversely, in behavioral intervention, researchers change an animal's behavior or its environment and try to ascertain whether the change results in physiological or anatomical changes. (c) Measurements of both kinds of variables allowresearchers to arrive at correlations between somatic - changes and behavioral changes. (d) Each approach enriches and informs the others. (a) Manipulating the body may affect behavior Attempts to apply knowledge also benefit basic research. For example, the study of memory disorders in humans has pushed investigators to extend our knowledge of the brain regions involved in different kinds of memory (see Chapter 17). Three Approaches Relate Brain‘ and Behavior Biological psychologists use three approaches to understand the relationship be- tween brain and behavior: somatic intervention, behavioral intervention, and cor- relation. In the most common approach, somatic intervention (Figure 'l.2u), we alter a structure or function of the brain or body to see how this alteration changes behavior. Here, somatic intervention is the independent variabI/e, and the behavior- al effect is the dependent variable; that is, the resulting behavior depends on how the brain has been altered. For example, in response to mild electrical stimulation of one part of her brain, not only did one patient laugh, but she found-Whatever she happened to be looking at amusing (Fried et al., 1998). I ‘ In later chapters we describe many kinds of somatic mtervention with both humans and other animals, as in the following examples: 0 A hormone is administered to some'animals but not to others; various behaviors of the two groups are later compared. ' ' A part of the brain is stimulated electrically, and behavioral effects are observed. ' A connection between two parts of the nervous system is cut, and changes in behavior are measured. The approach opposite to somatic intervention is psychological or behavioral intervention (Figure 1.21)). In this approach, the scientist intervenes in the behav- ior of an organism and looks for resulting changes in body structure or function. Here, behavior is the independent variable, and change in the body is the depen— dent variable. Among the examples that we will consider in later chapters are the following: ' 0 Putting two adults of opposite sex together may lead to increased secretion of certain hormones. (c) Body and behavioral measures covary Behaviors affected Behavioral variables ((1) Biological psychology seeks to understand all these relationships Somatic intervention I’x/ fl Behavioral intervention BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 0 Exposing a person or animal to a visual stimulus provokes changes in electrical activity and blood flow in parts of the brain. 0 Training of animals in a maze is accompanied by electrical, biochemical, and anatomical changes in parts of their brains. The third approach to brain—behavior relations, correlation (Figure 1.2:), con- sists of finding the extent to which a given body measure varies with a given be- havioral measure. Later we will examine the following questions, among others: 0 Are people with large brains more intelligent than people with smaller brains? 0 Are individual differences in sexual behavior correlated with levels of certain hormones in the individuals? 0 ls the severity of schizophrenia correlated with the magnitude of changes in brain structure? Such correlations shOuld not be taken as proof of causal relationship. For one thing, even if a causal relation exists, the correlation does not reveal its direction— that is, which variable is independent and which is dependent. For another, two factors might be correlated only because a third, unknown factor affects the two factors measured. What a correlation does indicate is that the two variables are linked in some way—directly or indirectly. Such a correlation often stimulates in— vestigators to formulate hypotheses and to test them by somatic or behavioral intervention. Combining these three approaches yields the circle diagram of Figure 1.211. This diagram incorporates the basic approaches to studying relationships between bodily processes and behavior. It also emphasizes the theme that the relations be— tween brain and body are reciprocal: each affects the other in an ongoing cycle of bodily and behavioral interactions. We will see examples of this reciprocal rela— tionship throughOut the book. Neuroplasticity: Behavior Can Change the Brain The idea that there is a reciprocal relationship between brain and behavior has embedded within it a concept that is, for most people, startling. When we say that behavior and experience affect the brain, we mean that they, literally, physically alter the brain. The brain of a child growing up in a French-speaking household assembles itself into a configuration different from that of the brain of a child who hears only English. That’s why the first child, as an adult, understands French effortlessly while the second does not. In this case we cannot tell you what the structural differences are exactly, but we do know one part of the brain that is be- ing altered by these different experiences (see Chapter 19). ' Numerous examples, almost all in animal subjects, show that experience can affect the number or size of neurons, or the number or size of connections between neurons. This ability of the brain, both in development and in adulthood, to be changed by the environment and by experience, is called neuroplasticity (or neural plasticity). Today when we hear the word plastic, we think of the class of materials found in so many modern products. But originally, plastic meant “flexible, malleable” (from the Greek plassein, “to mold or form”), and the modern materials were named plastics because they can be molded into nearly any shape. In 1890, William James (1842—1910) described plasticity as the possession of a structure weak enough to yield to an influence but strong enough not to yield all at once: Nervous tissue seems endowed with a very extraordinary degree of plasticity of this sort; so that we may without hesitation lay down as our first proposition the following, that the phenomena of habit in living beings are due to the plasticity of the organic materials of which their bodies are composed. (p. i 10) correlation “the covariation of two mea- sures. neuropiasticity or neural plasticity The ability of the nervous system to change in response to experience or the environment. 7 8 CHAPTER 1 1.3' The Role of Play in Brain Develoyment A brain region involved in processing odors (the posterodorsal portion of the medial amygdala) was smaller in male rats housed individually compared to males housed 0 together and allowed to play. Other nearby regions were identical in the two groups. (After Cooke et al., 2000.) In the ensuing years, research has shown that the brain is even more plastic than James suspected. For example, parts of neurons known as dendritic spines (see Chapter 2) appear to be in constant motion, changing shape in the course of seconds (H. Fischer et al., 1998). We will see many examples in which experience alters the structure and / or function of the brain. In Chapter 5, hearing a baby cry will cause the mother’s brain to secrete a hormone; in Chapter 7, visual experience in kittens will direct the formation of connections in the brain; in Chapter 12, a mother rat’s grooming of her pups will affect the survival of spinal cord neurons; and in Chapter 17, a sea slug learning a task will strengthen the connections be— tween two particular neurons. Biological and social psychology are related / The plasticity of the human brain has a remarkable consequence: other individuals can affect the physical structure of your brain! Indeed, the whole pointof cOm- ing to a lecture hall is to have the instructor use words and figures to alter your brain, so that you can retrieve that information in the future (in other words, she is teaching you something). Many of these alterations in your brain last only until you take an exam, but every once in a while the instructor may tell you something that you'll remember for the rest of your life. Most aspects of our social behavior are learned—from the language we speak to the clothes we wear and the kinds of food we eat—so our examination of the mechanisms of learning and memory (see Chapter 17) is important for understanding social behavior. ' For an example from an animal model, cousider the fact that rats spend a lot of time investigating the smells around them, including those coming from other rats. Cooke et al. (2000) took young rats, just weaned from their mother, and either raised each male in a cage alone, or raised them with other males to play with. Ex- amination of these animals as adults found only one brain difference between the groups: a region of the brain known to process odors was smaller in the isolated males than in the males raised with playmates (Figure 1.3). Was it the lack of play (Gordon et al., 2003), the lack of odors to investigate, or the stress of isolatiou that made the region smaller? Whatever the mechanism, social experience affects this brain structure. In Chapter 17 we’ll see that social experience also enhances the efH fects of environmental enrichment on brain growth. Here’s an example of how social influences can affect the human brain. When people were asked to put 'a hand into moderately hot water (47°C), part of the brain became active, presumably because of the disc0mfort involved (Rainville et al., 1997). But subjects who were led to believe the water would be very hot had a more activated brain than did subjects led to believe the discomfort would be mini— mal (Figure 1.4), even though the water was the same temperature for all subjects. The socially induced psychological expectation affected the magnitude of the brain 2 "was growth Stunted by the: lest-'9fsppsrtefi .19"th ' m Isolate Volume (mm3 x 104) 0“ Posterodorsal Anterodorsal Anteroventral Posteroventral Quadrants of the medial amygdala BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 9 1.4 Pictures of Pain Subjects told to expect only mild discomfort from putting a hand into 47°C water (left) showed less activation in a particular brain region {the anterior cingulate cortex) than did subjects expecting more discomfort (right) from water of the very same temperature. Areas of high activation are indicated by orange, red, and white. (From Rainville et al., 1997; courtesy of Pierre Rainville.) response, even though the physical stimulus was exactly the same. (By the way, the people with the more activated brains also reported that their hands hurt more.) In most cases, biological and social factors continually interact and affect each other in an ongoing series of events as behavior unfolds. For example, the level of the hormone testosterone in a man’s circulation affects his dominance behav- ior and aggression (see Chapter 15). The dominance may be exhibited in a great variety of social settings, ranging from playing chess to physical aggression. In humans and other primates, the level of testosterone correlates positively with the degree of dominance and with the amount of aggression exhibited. Winning a contest, whether a game of chess or a boxing match, raises the level of testosterone; losing a contest lowers the level. Thus, at any moment the level of testosterone is determined, in part, by recent dominant-submissive social experience; and the level of testosterone determines, in part, the degree of dominance and aggression in the future. Of course,__ social and cultural factors also help determine the fre— quency of aggression; cross—cultural differences in rates of aggression exist that cannot be correlated with hormone levels, and ways of expressing aggression and dominance are influenced by sociocultural factors. Perhaps nothing distinguishes biological psychology from other neurosciences more clearly than this fascination with neuroplasticity and the role of experience. Biological psychologists have a pervasive interest in how experience physically alters the brain and therefore affects future behavior. We will touch on this theme in every chapter of this book and review some of these examples again in the Afterword. Biological Psychologists Use Several Levels of Analysis Scientific explanations usually involve analysis on a simpler or more basic level of organization than that of the structure or function to be explained. This approach is known as reductionism. In principle, it is possible to reduce each explanatory series down to the molecular or atomic level, though for practical reasons this ex- tent of reductionism is rare. For example, most chemists deal with iarge, complex molecules and the laws that govern them; seldom do they seek explanations in terms of atoms. Finding explanations for behavior often requires several levels of biological analysis. The units of each level of analysis are simpler in structure and organiza— reductionism The scientific strategy of breaking a system down into increasingly smaller parts in order to understand it. levels of analysis The scope of experi- mental approaches. A scientist may try to understand behavior by monitoring mol- tion than thoselof the level above. The levels of analyses range-from soc1al interac- ecules, nerve cells] brain regions, or sodai bone to the brain, continuing to success1vely less complex units until we arrive at environments, or some combination of these Single nerve cells and their even simpler, molecular constituents. levels of analysis. 10 CHAPTER 1 Neural systems level: Eyes and visual brain regions Social level: Individuals bEhaving in social interaction Organ level: Brain, spinal cord, peripheral nerves, _ Brain region level: Visual cortex Circuit level: Local neural circuit Cellular level: Single neuron Molecular level 1.5 Levels of Analysis in Biological PSYChOlOQV The scope of biological psychology ranges from the level of the IndIVIdual Interacting with others, to the level of the molecule, Depending on the Naturally, in all fields different problems are carried to different levels of analy— sis, and fruitful work is often being done simultaneously by different workers at question at hand, investigators use differ, several levels (Figure 1.5). Thus, in their research on visual perception, cognitive em leChnlClueS to focus on these many psychologists advance analytical descriptions of behavior. They try to determine levelsrbul always with an eye toward how how the eyes move while looking at a visual pattern, or how the contrast among the” findings apply '03 bEhaVlUF- parts of the pattern determines its visibility. Meanwhile, other biological psycholo— gists study the differences in visual endowments among species and try to deter- mine the adaptive significance of these differences. For example, how is the pres— ence (or absence) of color vision related to the life of a species? At the same time, other investigators trace out brain structures and networks involved in different kinds of visual discrimination. Still other scientists try to ascertain the electrical and chemical events that occur in the brain during vision. A Preview of the Book: Fables and Facts about the Brain Here are some examples of research topics considered in this book: 0 How does the brain grow, maintain, and repair itself over the life span, and how are these capacities related to the growth and development of the mind and behavior from the womb to the tomb? 0 How does the nervous system capture, process, and represent informatiori about the environment? For example, sometimes brain damage causes a . person to lose the ability to identify other people’s faces; what does that tell us about how the brain recognizes faces? ' How does sexual orientation develop? Some brain regions are different in heterosexual versus homosexual men; what do those differences tell us about the development of human sexual orientation? BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK (5) Hearing words Reading words c ‘ What brain sites and activities underlie feelings and emotional expression? Are particular parts of the brain active in romantic love, for example (Figure 1.60)? ' Some people suffer damage to the brain and afterward seem alarmingly unconcerned about dangerous situations and unable to judge the emotions of other people; what parts of the brain are damaged to cause such changes? 0 How does the brain manage to change during learning, and how are memories retrieved? _ ' Why are different brain regions active during different language tasks (Figure 1.615)? The relationship between the brain and behavior is, on the one hand, very mys— terious because it is difficult to understand how a physical device, the brain, could be responsible for our subjective experiences of fear, love, and awe. Yet despite this mystery, we all use our brains every day. Perhaps it is the "everyday miracle” aspect of the topic that has generated so much folk wisdom about the brain. Think of it as "neuromythology." ' Sometimes these popular ideas about the brain are in line with our current knowledge, but in many cases we know they are false. For example, the notion that we normally use only a tenth ,(or a third, or a half, or some other fraction) of our brain is commonplace, but patent nonsense. Brain scans make it clear that the entire brain is activated by even fairly mundane tasks. Indeed, although the areas of activation shown in Figure 1.6 appear rather small and discrete, we will show in Box 2.3 that experimenters must work very hard to create images that separate activation related to a particular task from the background of widespread, ongo— ing brain activity. In fact, it’s fairly easy to reel off a host of commonly held beliefs about the rela- tionships between the brain and behavior. Table 1.2 presents a list of such beliefs that you may have heard, interspersed with some claims that are true but may sound improbable. ' Neuroscience Contributes to Our Understanding of Psychiatric Disorders One of the great promises of biological psychology is that it can help us understand brain disorders and devise treatment strategies. Like any other complex mecha— nism, the brain is subject to a variety of malfunctions and breakdowns. People H Seeing words Generating words 1.6 "Tell Me Where Is Fancy Bred?" (a) The parts of the brain high- lighted here become especially active when a person thinks about his or her romantic partner. (b) Different brain regions are activated when people perform four differ- ent language tasks. The techniques used to generate such images are described in Chapter 2. (Part a from Bartels and Zeki, 2000; part b courtesy of Marcus Raichle.) 12 CHAPTER 1 TABLE 1.2 -Nasrsmyihslsgy:-_racrsj_sr Fablesgz-t .. _ _ __ ._ _ __. _ . . Chapter statement 7 _ True? where dismissed Some human nerve cells are more than 3 feet long. ' I . . True 2 ' Nerve impulses travel at the speed of light. _ I - False 3 More people die each year from the use oflegal drugs than illegal drugs. True 4 Only humans seek mind-altering substances. ' A = False 4 Our bodies make chemicals that are similar in structure to heroin and marijuana True - 4 Testosterone is made only by males, and estrogen is made only by females. ~ 'False /. 5 Only humans have created cultures. ' ' _ False Once our'brains are developed, we can never grow new nerve cells. - False ‘ Some people are incapable of feeling pain: ' _ True 1 "81 Different parts of the tongue are specialized to recognize certain tastes. ' False 9 Dogs are color-biind. I ' 7 False 10 Each side of the brain controls the muscles on the opposite side of the body. . ' True 11 There are no anatomical differences between men's and women's brains. ' _ False 12 In some animal species every individuai is female. I True 12 Some people are "born gay. " ' Uncertain ‘ 12 Most of our energy is expended just maintaining our body temperature. True 13 We can lose weight permanently by surgically removing fat from our bodies. False 13 The peaks in cases of depression and suicide occur around Christmas holidays. False 14 During sleep the brain is relatively inactive. Not always 14 Sleepwalkers are acting out dreams. False 14 Prolonged sleep deprivation will make you temporarily crazy. False 14 Some animals can havehalf their brain asleep and the other half awake. True 14 The left side of the face isrnore emotionally expressive than the right side. I True 15 Prolonged stress can cause heart disease. _ True “£5 Ali cultural groups recognize the same facial expressions for various emotions. I Uncertain 15 ' It is'possible to determine scientifically whether someone is lying. . False (for now) 15 Scientists are not sure ‘why antidepressant drugs work. - . True 16 People in northern countries are more susceptible to seasonal depression. Uncertain 16 Some people are incapable of producing any new memories. True 17 We never really forget anything that we have experienced. - Uncertain 17 Each memory is stored in its own brain cells. - False (probably) 17 A stimulating environment can change the structure of an animai's brain. True ‘ 17 We can take in awhole visual scene in just a single glance. ' False 18 My brain decides what I will do next, before my conscious seif is aware of the decision. Uncertain 18 People are “right—brained" or "left—brained." False 19 A child can have half of the brain removed and still develop normal intelligence. True 19 Chimpanzees can use symbols to communicate. _ . True 19 afflicted by disorders of the brain are not an exotic few. At least one person in five around the world currently suffers from neurological and / or psychiatric disorders that vary in severity from complete disability to significant changes in quality of life. Figure 1.7:: shows the estimated numbers of US. residents afflicted by some of the main neurological disorders. Figure 1.7!: gives estimates of the numbers of U.S. adults who Suffer from certain major psychiatric disorders. The percentage of US. adults suffering from mental illness may be increasing (Torrey, 2002). The toll of these diSorders is enormous, in terms of both individual suffering and social costs (Demyttenaere et ai., 2004). The National Advisory Mental Health BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK (6!) Prevalence of neurological disorders Parkinson’s disease Eigla‘cgfid and Huntington's Early developmental tguma disease disorders (mental 1 000 000 500,000 retardation, cerebral ' ’ palsy, perinatal injuries) 750,000 1.7 The Toll of Brain Disorders As these pie charts show, neurological (a) and psychiat- ric (b) disorders are quite common in the United States. As brain research progresses, the dis- tinction between psychiatric and neurologicai disorders begins to seem artificial or arbitrary. Council estimated that direct and indirect costs of behavioral and brain disorders amount to $400 billion a year in the United States. For example, the cost for treat- ment of dementia (severely disordered thinking) exceeds the costs of treating can— cer and heart disease combined. The World Health OrganizatiOn (2004) estimates that over 15% of all disease burden, in terms of lost productivity, is due to mental disorders. The high cost in Suffering and expense has compelled researchers to try to understand the mechanisms involved in these disorders and to try to alleviate or even prevent them. In this quest, the distinction between clinical and laboratory approaches begins to fade away. For example, when clinicians enc0unter a pair of twins, one of Whom has schizophrenia While the other seems healthy, the discovery of structural dif- ferences in their brains (Figure 1.8) immediately raises questions for laboratory scientists: Did the structural differences arise before the symptoms of schizophre- nia, or the other way around? Were the brain differences present at birth or did they arise during puberty? Does medication that reduces symptoms affect brain structure? We’ll consider these questions at length in Chapter 16. (:1) Person with (:5) Normal schizophrenia tesy of E. Fuller Torrey.) (0) Incidence of psychiatric disorders Schizophrenia 1,500,000 1.8 Identical “wins but Nonidentical Brains and Behavior images of the brains of identical twins, the fluid-filled cerebral ventricles are prominent as dark "butterfly" shapes. The twin whose brain is imaged in (a) suffers from schizophrenia and has the enlarged cerebral ventricles that some researchers believe are Characteristic of this disorder. The other twin does not suffer from schizophrenia; his brain (b) clearly has smaller ventricles. (Cour- 13 In these 14 CHAPTER 1 Animal Research Makes Vital Contributions Because we will draw on animal research throughout this book, we should com— ment on some of the ethical issues of experimentation on animals. Human be- ings’ involvement and concern with other species predates recorded history. Early humans had to study animal behavior and physiology in order to escape some species and hunt others. To study biological bases of behavior inevitably requires research on animals of other species as well as on human beings. Psychology stu— dents usually underestimate the contributions of animal research to psychology because the most widely used introductory psychology textbooks often present major findings from animal research as if they were obtained with human subjects (Domjan and Purdy, 1995). . - Because of the importance of carefully regulated animal research for'both human and animal health and well-being, the National Research Council (NRC Commit- tee on Animals as Monitors of Environmental Hazards, 1991) undertook astudy on the many uses of animals in research. The study notes that 93% of the mammals used in research are laboratory—reared rodents. It also reports that most Americans believe that animal research should continue. Of course, researchers have an obli— gation to minimize the discomfort of their animal subjects, and ironically enOugh, animal research has provided us with the drugs and techniques to make most research painless for the animal subjects (Sunstein and Nussbaum, 2004). Nevertheless, a very active minority of people believe that research with ani- mals, even if it does lead to lasting benefits, is unethical. For example, in his 1975 book Animal Liberation, Peter Singer asserts that research with animals can be jus- tified only if it actually produces benefits. The trick, of course, is how to predict which experiment will lead to a breakthrough. Singer has repeatedly refused to say that animal experimentation is never justified (Neale, 2006). in the meantime, animal rights groups have vandalized labs, burned down buildings, and exploded bombs in laboratories (Conn and Parker, 2008). in 2008, animal rights extremists set off firebombs at the homes of two scientists in Santa Cruz, California. One scientist’s family, including two young children, had to flee their home through a second-story window (Paddock and La Ganga, 2008). The History of Research on the Brain and Behavior Begins in Antiquity Only recently have scientists recognized the central role of the brain in control” ling behavior. When Egyptian pharaoh Tutankhamen was mummified (about 1300 BCE), four important organs were preserved in alabaster jars in his tomb: liver, lungs, stomach, and intestines. The heart was preserved in its place within the body. All these organs were considered necessary to ensure the pharaoh’s contin- ued existence in the afterlife. The brain, however, was thrown away. Although the Egyptian version of the afterlife entailed considerable struggle, the brain was not considered an asset. Neither the Hebrew Bible (written from the twelfth to the second century BCE) nor the New Testament ever mentions the brain. However, the Bible mentions the heart hundreds of times and makes several references each to the liver, the stom— ach, and the bowels as the seats of passion, courage, and pity, respectively. “Get thee a heart of wisdom,” said the prophet. The heart is also where Aristotle (about 350 BCE), the most prominent scien~ fist of ancient Greece, located mental capacities. We still reflect this ancient notion when we call people kindhearted, openhearted, fainthearted, hardhearted, or heartless, and when we speak of learning by heart. Aristotle considered the brain to be only a cooling unit to lower the temperature of the hot blood from the heart. ArOund 400 BCE the great Greek physician Hippocrates was expressing the minority view when he wrote, BIOLOGECAL PSYCHOLOGY: SCOPE AND OUTLOOK Not only our pleasure, our joy and our laughter but also our sorrow, pain, grief, and tears rise from the brain, and the brain alone. With it we think and understand, see and hear, and we discriminate between the ugly and the beautiful, between what is pleasant and what is unpleasant and between good and evil. Around 350 BCE, the Greek physician Herophilus (called the "Father of Anato— my”) advanced our knowledge of the nervous system by dissecting bodies of both people and animals. He traced nerves from muscles and skin into the spinal cord and noted that each region of the body is connected to separate nerves. A second-century Greco-Roman physician, Galen (the "Father of Medicine”), treated the injuries of gladiators. His reports of behavioral changes caused by in- juries to the heads of gladiators drew attention to the brain as the controller of be— havior. Galen advanced the idea that animal spirits—a mysterious fluid—passed along nerves to all regions of the body. But Galen’s ideas abOut the anatomy of the human brain were very inaccurate because he refused to dissect humans. Renaissance scientists began to understand brain anatomy The eminent Renaissance painter and scientist Leonardo da Vinci (1452—1519) stud- ied the workings of the human body and laid the foundations of anatomical draw- ing. He especially pioneered in providing views from different angles and cross— SectiOnal representations. His artistic renditions of the body included portraits of the nerves in the arm and the fluid—tilled ventricles of the brain (Figure 1.9). Renaissance anatomists emphasized the shape and appearance of the exter— nal surfaces of the brain because these were the parts that were easiest to see when the skull was removed. It was immediately apparent to anyone who looked that the brain has an extraordinarily complex shape. To Renaissance artists, this marvelous structure was God’s greatest gift to humankind. So, in lvfichelangelo’s painting on the ceiling of the Sistine Chapel, part of which is pictured at the be— ginning of this chapter, God seems to ride the form of the human brain when bestowing life to Adam. In 1633, Rene Descartes (1596-4650) wrote an influential book (De Homine [On MnnD in which he tried to explain how the behavior of animals, and to some ex- tent the behavior of humans, could be like the workings of a machine. In addition to tackling other topics, Descartes proposed the concept of spinal reflexes and a (.91) Early drawing 15 1.9 Leonardo da Vinci's Chang- ' ing View of the Brain (a) In an early representation, Leonardo simply copied old schematic drawings that represented the cerebral ventricles as a linear series of chambers. (b) Later he made a drawing based on direct observation: after making a cast of the ventricles of an ox brain by pouring melted wax into the brain and let— ting it set, he cut away the tissue to reveal the true shape of the ventricles. 16 CHAPTER 1 1.10 An Early Account of Reflexes In this depiction of an explanation by Des- cartes, when a person’s toe touches fire, the heat causes nervous activity to onw up the nerve to the brain. From there the nervous activity is "reflected" back down to the leg muscles, which contract, pulling the foot away from the fire; the idea of activity being reflected back is what gave rise to the word reflex. In Descartes's time, the difference between sensory and motor nerves had not yet been discovered, nor was it known that nerve fibers normally conduct in only one direction. Nevertheless, Descartes promoted thinking about bodily processes in scientific terms, and this focus led to steadily more accurate knowledge and concepts. dualism The notion, promoted by Rene Descartes, that the mind is subject only to spiritual interactions, while .the body is subject only to material interactions. phrenology The belief that bumps on the skull reflect enlargements of brain regions responsible for certain behavioral faculties. neural pathway for them (Figure 1.10). Attempting to relate the mind to the body, Descartes suggested that the two come into contact in the pineal gland, located within the brain. He suggested the pineal gland for this role because (1) whereas most brain structures are double, located Symmetrically in the two hemispheres, the pineal gland is single, like consciousness; and (2) Descartes believed, errone— ously, that the pineal gland exists only in humans and not in animals. As Descartes was preparing to publish his book, he learned that the Pope had forced Galileo to renounce his teaching that Earth revolves around the sun, threat— ening to execute him if he did not recant. Fearful that his own speculations about mind and body could also incur the wrath of the church, Descartes withheld his book from publication. It did not appear in print until 1662, after his death. Des- cartes believed that, if people were nothing more than intricate, machines, they could have about as much free will as a pocket watch, and no opportunity to make the moral choices that were so important to the church. He asserted'that‘ humans, at least, had a nonmaterial soul as well as a material body. This notion of dualism spread widely and left other philosophers with the task of determining how a nonmaterial soul could exert influence over a material body and brain. Biological psychologists reject dualism and insist that all the workings of the mind can also, in theory, be understood as purely physical processes in the material world, speu cificaily in the brain. The concept of localization of function arose in the nineteenth century By the end of the 1600s, the English physician Thomas Willis (1621—1675), with his detailed descriptions of the structure of the human brain and his systematic study of brain disorders, convinced educated people in the Western world that the brain is the organ that coordinates and controls behavior (Zimmer, 2004). A popular notion of the nineteenth century, called phrenology, elaborated on this idea by asserting that the cerebral cortex consisted of separate functional areas, and that each area was responsible for a behavioral faculty such as love of family, perception of color, or curiosity. Investigators assigned functions to brain regions anecdotally, by observing the behavior of individuals and noting, from the shape of the skull, which underlying regions of the brain were more or less developed (Figure 1.! I 11). Opponents rejected the entire concept of localization of brain function, insist— ' ing that the brain, like the mind, functions as a whole. Today we know that the whole brain is indeed active when we are doing almost any task. When we are performing particular tasks, however (as we saw earlier in this chapter), certain brain regions become even more activated. Different tasks activate different brain regions. Modern brain maps of these places where peaks of activation occur (Figure I .'l 'l b) bear a passing resemblance to their phrenological predecessors, differing only in the specific locations of functions. But unlike the phrenologists, we con— firm these modern maps by other methods, such as examining what happens after brain damage. Even as far back as the 1860s, the French surgeon Paul Broca (1824—1880) argued that language ability was not a property of the entire brain but rather was localized in a restricted brain region. Broca presented a postmortem analysis of a patient who had been unable to talk for several years. The only portion of the patient’s brain that appeared damaged was a small region within the frontal portions of the brain on the left side—a region now known as Bruce’s area (labeled “Speech production” in Figure 1.11b). The study of additional patients further convinced Broca that language expression is mediated by this specific brain region rather than reflecting activities of the entire brain. These nineteenth—century observations form the background for a continuing theme of research in biological psychology—notably, the search for distinguishing differences among brain regions on the basis of their structure, and the effort to relate different kinds of behavior to different brain regions (M. Kemp, 2001). An BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 'I7 reasoning Spatial working memory Mathematical approximations Anticipation of pain Object working memory Exact mathematical calculations Olfaction Pleasant touch Speech production of paJ-n additional theme emerging from these studies is the relation of brain size to ability (Box 1.2). ' - in 1890, William Iames’s book Principles of Psychology signaled the beginnings of a modern approach to biological psychology: The strength of the ideas described in this book is evident by the continuing frequent citation of the work, especially by contemporary cognitive neuroscientists. In James’s work, psychological ideas such as consciousness and other aspects of human experience came to be seen as properties of the nervous system. A true biological psychology began to emerge from this approach. Modern biological psychology arose in the twentieth century The end of the nineteenth century brought many important developments for bio- logical psychology. German psychologist Hermann Ebbinghaus showed in 1885 how to measure learning and memory in humans. In 1898, American psycholo— gist Edward L. Thorndike demonstrated how to measure learning and memory in animals. Early in the twentieth century, Russian physiologist Ivan P. Pavlov announced research in his laboratory on conditioning in animals. American psychologist Shepard i. Franz (1902) sought the site of learning and memory in the brain by removing different brain regions in animal Subjects. This work started a search for the traces of experience in the brain—a quest that Karl S. Lashley (1890—1958) referred to as the “search for the engram.” Lashley studied with Franz and took over the problem of investigating the locations and mecha- nisms of memory functions in the brain. in a long career, Lashley contributed many important findings and trained many students to study the biological mechanisms not only of learning and memory, but also of perception and motivation. Biological psychology bears the strong imprint of Canadian psychologist Don- ald O. Hebb (1904—1985), a student of Lashley (P. M. Milner, 1993). In his book The Organization of Behavior (1949), Hebb showed, in principle, how complex cogni— tive behavior could be accomplished by networks of active neurons. He suggested Olfaction Voluntary eye F CE Motor Visual spatial movements aHand execution attention Momr Foor Somatosensory Analyfic Anticipation preparation Face d cortex and figural Halli)DIE reasoning Mathematical approximations Visual spatiai attention - Monon perception [-A k fbspeaa perception \IPrima-ry visual cortex " Color perception Face recognition Auditory cortex Anticipation Semantic priming Spoken language of visual words comprehension 1.11 Old and New Phrenology (a) In' the early nineteenth century, certain "facul- ties," such as skill at mathematics or a tendency toward aggression, were believed to be directly associated with particular brain regions. Phrenologists used diagrams like this one to measure bumps on the Skull, which they took as an indication'of how fully developed each brain region was in an individual, and hence how fully that person should display particular qualities. - (b) Today, technology enables us to roughly gauge how active different parts of the brain are when a person is performing vari— ous tasks (see Chapter 2). But virtually the entire brain is active during any task, so the localization of function that such studies provide is really a measure of where peak activity occurs, rather than a suggestion of a single region involved in a particular task. (Part b after Nichols and Newsome, 1999.) 18 CHAPTER i Does a bigger brain indicate greater intel- _ ligence? Brain size does seem to explain many species differences in complex _ behavior, as well as the remarkable expan— sion of the human brain over the past few million years (see Chapter 6). But do variations in brain size within our species correlate with intelligence? This question - has been the subject of lively controversy _ for at least two centuries. Sir Francis Galton (1822—191 1), who invented the correlation coefficient, stated that thegreatest disap—_ ' pointment in his life was his failure to find a significant relationship between head size and intelligence. But Galton had to use head size, when he really wanted to mea-‘ ‘ sure brain size. in addition, he had to rely . on teachers’ estimates of their students’ ' intelligence, and every student knows _ that teachers can be quite wrong. Other investigators in the nineteenth__century' ' _ mea‘suredthevolumes of skulls (Figure A) 'of various groLIpsand estimated 'intelli—QE ' 7. gence on the basis of people‘s-occupations ' .or other doubtful criteria. _ The development and standardization of intelligence quotient (IQ) tests in the' twentieth century provided invaluable __ help for One side of the ques— ' ' , “tion, and these scores indeed. I _ ‘ correlate, with ranges from' _ +0.08 to +0.22, with estimates. _. of brain size from-head size - ' - - (Van Valen, 1974). _ Newer, noninvasive tech- niques (discussed in detail in Chapter 2) to visualize the brains of living subjects now make it possible to directly measure brain size. One study found a significant correlation coefficient of about 0.26 be- tween brain size and IQ (Post- huma et al., 2002). in another ‘ study, brain scans such as ‘ those shown in Figure B were used for measuring the sizes of different brain regions. After correction for body size, the correlation between brain size and IQ scores was 0.38 (An- dreasen et al.,1993).lQ seems Case of the Brain and L f " " (A) A nineteenth-century apparatus for measuring the volume of the braincase to correlate better with the volume of the front of the brain than the back (Colom et al., 2009). When the brains of children were measured at age 6 and again at 1 1, those with the highest lQ displayed the greatest thickening of the outer layer of the brain, especially in the front (P. Shaw et al., 2006). (B) Images from a modern brain measurement study Anotherbrain—imaging .technique revealed _I correlations between IQ scores and the ex.- ' tent of connectivity between brain regions - (Chiang et al., 2009), . Thus, on the basis of modern tech- niques, the long-standing controversy appears to have been settled in favor of a significant correlation between _ brain size and intelligence. Note,. however, that the modest size of. ._ the correlations, while statisti— _ . _ _ cally significant, indicates that. _ . only about 10% of variability in _ _ - 'IQ is accounted for by brain size; '-1 Thus, there is plenty of room for other factors to contribute to overall IQ. in addition, many people dispute whether IQ tests really measure a general prop— _ .._ erty of intelligence (Stanovichr ._ 2008) _ Historically, scientists have misused information about - brain size in racially or ethnically. -. prejudicial ways (5. J. Gould, 1981). in fact, however, all racial groups show overlapping and widely varying intelligence and brain size. (Figure A from the Bettmann Archive; Figure B courtesy of Nancy Andreasen.) M BlOLOGlCAL PSYCHOLOGY: SCOPE AND OUTLOOK 19 how brain cell connections that are initially more or less random could become organized by sensory input and stimulation into strongly interconnected groups that he called cell assemblies. His hypothesis about how neurons strengthen their connections through use gave rise to the concept of the Hebbian synapse, a topic much studied by current neuroscientists (see Chapters 7 and 17). Consciousness is a thorny problem Almost anyone using this book has at some time wondered about consciousness: the personal, private awareness of our emotions, intentions, thoughts, and move— ments, and of the sensations that impinge upon us. How is it possible that you are aware of the words on this page, the room you are occupying, the goals you have in life? ' In his review of theories of consciousness, Adam Zeman (2002) notes that al- most all scientists agree on some aspects of consciousness: ' Consciousness matters; it permits us to do certain important things, like planning and mentally “simulating” what might happen in the future. 0 Consciousness is bound up somehow with the activity of the brain. 0 We are not aware-of all of our brain’s activities. Some brain activity, and therefore some of our behavior, is unconscious. 0 The deepest parts of our brain are important for arousal. 0 The topmost parts of the brain are responsible for whatever we experience from moment to moment. In the chapters to come, we will see many examples of experiments that demon- strate these properties of consciousness. However consciousness is brought about, any satisfying understanding would be able, for example, to explain why a certain pattern of activity in your brain causes you to experience the sensation of blue when looking at the sky (Figure 1.12), or the smell of cinnamon when entering a bakery A good theory would let us predict that, by messing about with your brain, changing particular connections or activating particular neurons, you would now experience yellow when seeing the sky (and it’s not fair to put colored goggles in front of your eyes; that’s easy to understand). Unfortunately, we are nowhere near understanding consciousness this clearly. We describe some intriguing (and disturbing) experiments explicitly directed at human consciousness in our new Chapter 18. In the rest of the book we rarely use the words conscious or consciousness. Normally we cannot say anything about the particulars of what human or animal subjects are experiencing, but only whether their behavior suggests that the brain detected a signal or event. Thus, we are in no position to know whether complicated machines like computers are, or might one day be, conscious. Some people even doubt whether our "merely human” brains will ever be able to understand something as complicated as consciousness. Nevertheless, any gains we make in understanding how the brain works, which is the subject of this book, will bring us closer to that goal. ' Recommended Reading Blackmore, S. (2004:). Consciousness: An introduction. New York: Oxford University Press. Carter, R. (2009). The human brain book. London: Dorling Kindersley. Doidge, N. (2007). The brain that changes itself. New York: Penguin. Finger, 5. (1994). Origins of neuroscience. New York: Oxford University Press. Gallagher, 5. (2006). How the body shapes the mind. New York: Oxford University Press. Zirnrner, C. (2004). The soul made flesh: The discovery of the brain—and how it changed the world. New York: Basic Books. 1.12 How Blue the Sky? We would ail agree that this sky is the color everyone calls "blue." But in Chapter 18 we will ask whether everyone who sees that sky has the same experience of color. consciousness The state of awareness of one’s own existence and experience. 60 to www.biopsychology.com for study questions, quizzes, key terms, and other resources. ...
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