2 - Brain, Body, And Behavior

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The Brain-Behavior LinkTransforming electricity and chemistry into meanings and feelings The interplay of biological, psychological, and environmental forces

How the Brain Govems BehaviorThe brain's communication How neurons send their messages The links of the nervous system The cerebral cortex and how it makes us human

How Neuroscientists Study the Brain and MindStructural brain imaging Functional brain imaging Electroencephalography

Summary Test Yourself Answers Study GuidePsychology in the Lab and in Life: How the Brain Restores Its Functions Psychology and the Media: Neuroscience in the Future Life Span Perspedive: As the Brain Matures

The Brain's Functions, I: Experiencing the WorldSensing and interpreting the environment Processing and transmitting information Generating body movements Managing coordination and balance sensory

The Brain's Functions, II: Overseeing Emotions and SurvivalThe wellsprings of passions and feelings Staying alive and physiologically in tune The autonomic nervous system: The brain's busy deputy The brain's hemispheres and the regulation of emotion

The Brain's Functions, III: Managing Thought and MemoryThinking and planning How memories are stored and retrieved The growing brain and the developing intellect Left brain, right brain

1. Interview two people you know well, and attempt to construct a case history for each person. Begin by asking what they think are their major personality characteristics-intelligent, outgoing, athletic, and so on. For each characteristic, such as athletic, ask about their first recollections. Why do they think they developed that characteristic, and what factors or events in their past were influential in contributing to it? Concentrate on asking why they did the things they did, what they felt might have happened to them if they had or had not done certain things, and how they felt about themselves and other people. Then try to piece together a cohesive explanation for how the particular characteristic developed in each person. Provide different interpretations of this development from the strict-behaviorist, Gestalt, cognitive, and humanistic perspectives, as well as from the standpoint of the nature-nurture, change-continuity, and individual-context issues. 2. The experimental method is the primary approach psychologists use to determine the causes of behavior. In a simple experiment, participants are randomly assigned to two groups that are treated differently in only one respect-the independent variable. If their behavior then differs by groups, the difference can be attributed to the independent variable. But research is not always this straightforward. Sometimes the difference in behavior can be explained by something other than the independent variable. Below are descriptions of a few hypothetical experiments and conclusions. Write a short discussion of each, pointing out the inadequacies of the experiment for drawing the stated conclusions. Try to suggest factors other than the one mentioned that might have produced the results. Also note any ethical problems that might have arisen. a. Back in the days of "traditional" childbirth, U.S. mothers were allowed only minimal con-

tact with their newborns during the first several hours after birth. To assess whether mothers might be missing something important, researchers arranged for one group to have the traditional minimal contact and another to have several extra hours of contact with their babies. A year later, the "extended contact" mothers were noticeably more emotionally attached to their infants than were mothers in the "traditional" group. The researchers concluded that the first several hours after birth are a highly important period for fostering mother-to-child emotional attachment. b. To test the effects of marijuana on memory, some participants were asked to smoke one marijuana cigarette before memorizing a list of words; other participants instead were asked to smoke one tobacco cigarette. The marijuana group did poorly on the task compared to the tobacco group, and the researcher concluded that marijuana impairs memory. It has been found that children who play violent video and computer games are more aggressive in their play with other children than are children who do not play these games. Therefore, playing violent games makes children more aggressive toward others. An editor of a popular U.S. men's magazine published the results of a readers' survey indicating that by far the majority of men "cheat" on their spouses or partners on more than one occasion, and the longer the two are together, the more likely cheating becomes. The editor concluded that men in general are biologically incapable of being faithful and that the few exceptions in the survey "prove the rule."




For quizzing, activities, exercises, and web links, check out the book-specific website at www.cengage.com/psychology.

It perches on top of your spine, within your skull-3 pounds of pink, soft, strangely wrinkled tissue the size of a grapefruit. In weight, it makes up less than 2% of your body, yet it works so hard that it consumes about 20% of the oxygen that the body uses when at rest. Nature has devised ways to protect it. In addition to being encased in the thick bone of your skull, it is surrounded by a fluid that helps cushion it. And when your body is deprived of food, it is the first to get its share of whatever nutrients are coursing through the blood. "It" is the human brain, which has been described as "the most marvelous structure in the universe" (Miller, 1990). (See Figure 2.1.) All the human capabilities discussed in this textbook-gathering information, learning and remembering, acting intelligently, moving about, developing skills, feeling emotions, coping with stress, relating to others-as well as surviving from moment to moment are managed within the brain. Think of all the things you did in the last 24 hours. Whatever you did-sleep, dream, wake up, dress, eat, study, get angry, make love-your brain was responsible. We function through a network of brain and body systems that is surely one of the great wonders of nature. Knowledge of how these systems work and exactly what they accomplish is essential to an understanding of the entire field of psychology.

FIGURE 2.1 A side view of the human brain. The brainperches on top of vour spine, beneath vour skull-3 pounds of pinkish, soft, strangelv wrinkled tissue the size of a 9 rapefru it.

HOW THE BRAIN GOVERNS BEHAVIORTo appreciate the remarkable powers of the brain, it helps to understand how lower organisms manage to function. A FOCUS QUESTIONS How do neurons work and what do they do? one-celled animal such as a paramecium doesn't need a ner What constitutes the central nervous system? vous system. Its entire single-celled "body" is sensitive to Why do psychologists and other scientists place heat and light and capable of initiating the movements necso much emphasis on understanding the functions essary for life. Larger and more complicated animals, howof the brain's outer surface? ever, must have some kind of nervous system to coordinate their internal functions and movements. This system takes the form of specialized neural fibers that extend throughout the body and are capable of transmitting information back and forth.

Neuron The neural cell; the basic unit of the nervous system. Hormone A biochemical that typically is released into the bloodstream to perform its function at locations distant from the brain, but that can also affect brain functioning itself.

The key to the human brain's mastery is a web of connected pathways running within the brain and to other parts of the body. The brain carries out its many functions through a constant exchange of information, speeding along these trillions of pathways. Indeed, without them, the brain would be helpless to direct and manage our behavior or even to keep us alive.

The Brain's Communication


GliaCells that perform a wide array of functions such as regulating the biochemical environment of the brain, helping sustain neurons, modulating neural transmission, and aiding in the repair of neurons in case of injury. They are also important in early brain development and maturation. Dendrites The primary "receiving" parts of a neuron. Cell body The part of a neuron that converts oxygen, sugars, and other nutrients into energy. Nucleus The core of the ce II body of a neuron or other cell, containing the genes. Receptor sites Spots on the cell body of a neuron that, like the dendrites, can be stimulated by other neurons.

AxonThe fibrous body of a neuron that carries the neural impulse to the terminal branches. Terminal branches The parts of a neuron that send messages to other neurons or to muscles or glands. Myelin sheath A whitish coating of fatty protective tissue that "insulates" the axons of neurons.

The brain contains a staggeringly large number of neurons, or neural cells-eertainly many billions, and perhaps as many as a few trillion (Nicholls, Martin, Wallace, & Fuchs, 2001). Each neuron can receive messages from thousands of other neurons, process these messages in various ways, and then pass its own messages along to thousands more. The total number of possible connections is so great that it defies the imagination. One estimate is 50 trillion (Rosenzweig & Lieman, 1982). Thus, the brain is an intricate tapestry of connections, interconnections, and structures. Little wonder that the brain has been described as "the most complex structure in the known universe" (Fischbach, 1992). Although the diverse neurons of the brain primarily transmit messages, some operate like miniature glands, producing complex biochemicals called hormones (from the Greek word me