Introduction to Psychology - Motivation and Emotion (PDF)

CHAPTER 10 Motivation and Emotion Gateway Theme Our behavior is energized and directed by motives and emotions. Camay Sungu/AP/Wide World Photo Gateway Questions What is motivation? Are there different types of motives? What happens during emotion? What causes...

CHAPTER 10 Motivation and Emotion Gateway Theme Our behavior is energized and directed by motives and emotions. Camay Sungu/AP/Wide World Photo Gateway Questions What is motivation? Are there different types of motives? What happens during emotion? What causes hunger? Overeating? Eating disorders? What physiological changes underlie emotion? Can “lie detectors” really detect lies? Is there more than one type of thirst? In what ways are pain avoidance and the sex drive unusual? How accurately are emotions expressed by the face and “body language”? How does arousal relate to motivation? What are learned motives? Social motives? Why are they How do psychologists explain emotions? important? What does it mean to have “emotional intelligence”? Are some motives more basic than others? 319  preview Moved by the Music of Life Robert was in his doctor’s waiting room when he suffered a empathize with the feelings of others. This lack of inner aware- “strange attack.” Robert recalls that the “atmosphere changed, ness can also lead to health problems, such as depression or the walls seemed to close in, and the voices of other patients addictive behaviors (Lumley, 2004). became a buzz.” However, months of therapy were no help In this chapter you will learn how motives provide the drum- because Robert simply couldn’t talk about his feelings. When beat of human behavior and emotions color its rhythms. The asked how he felt, Robert might reply “Fine” or “I don’t know.” Or words “motivation” and “emotion” both derive from the Latin he might describe a bodily sensation by replying, “My stomach word movere (to move). As we will see, both play complex roles hurts” (Lumley, 2004). The scientific name for Robert’s problem in our daily lives. Even “simple” motivated activities, such as is alexithymia (a-LEX-ih-THIGH-me-ah), from the Latin for “can’t eating, are not solely under the control of the body. In many name emotions.” instances, external cues, expectations, learning, cultural values, In a sense, you could say that emotion is the “music” that and other factors influence our motives and emotions (Beck, enriches the rhythms of our lives. Sadly, Robert is not moved by 2004). the music of life as intensely as most of us are. Not only is Robert Let’s begin with basic motives, such as hunger and thirst, unable to name his emotions, he is only vaguely aware of them and end by exploring how emotions affect us. Although emo- in the first place. As you might suspect, people like Robert find tions can be the music of life, they are sometimes the music of it hard to form close relationships because they cannot easily death as well. Read on to find out why. Motivation — Forces motivational state) to develop. The drive was hunger, in Kayleigh’s That Push and Pull case. Drives activate a response (an action or series of actions) Gateway Questions: What is motivation? Are there different types designed to attain a goal (the “target” of motivated behavior). of motives? Reaching a goal that satisfies the need will end the chain of events. What do you plan to do today? What are your goals? Why do Thus, a simple model of motivation can be shown in this way: you pursue them? How vigorously do you try to reach them? When are you satisfied? When do you give up? These are all NEED DRIVE RESPONSE GOAL (NEED REDUCTION) questions about motivation, or why we act as we do. Let’s begin with a basic model of motivation and an overview of types of motives. Motivation refers to the dynamics of behavior — the Aren’t needs and drives the same thing? No, because the strength ways in which our actions are initiated, sustained, directed, and of needs and drives can differ (Franken, 2007). If you begin fasting terminated (Franken, 2007). today, your bodily need for food will increase every day. However, Can you clarify that? Yes. Imagine that Kayleigh is studying you would probably feel less “hungry” on the seventh day of fast- biology in the library. Her stomach begins to growl and she can’t ing than you did on the first. Whereas your need for food steadily concentrate. She grows restless and decides to buy an apple from a increases, the hunger drive comes and goes. vending machine. The machine is empty, so she goes to the cafete- Now let’s observe Kayleigh again. It’s Saturday night: For din- ria. Closed. Kayleigh drives home, where she cooks a meal and eats ner, Kayleigh has soup, salad, a large steak, a baked potato, four it. At last her hunger is satisfied, and she resumes studying. Notice pieces of bread, two pieces of cheesecake, and three cups of coffee. how Kayleigh’s food seeking was initiated by a bodily need. Her After dinner, she complains that she is “too full to move.” Soon search was sustained because her need was not immediately met, after, Kayleigh’s roommate arrives with a strawberry pie. Kayleigh and her actions were directed by possible sources of food. Finally, exclaims that strawberry pie is her favorite dessert and eats three achieving her goal terminated her food seeking. large pieces! Is this hunger? Certainly, Kayleigh’s dinner satisfied her biological needs for food. A Model of Motivation How does that change the model of motivation? Kayleigh’s “pie Many motivated activities begin with a need, or internal defi- lust” illustrates that motivated behavior can be energized by the ciency. The need that initiated Kayleigh’s search was a shortage of “pull” of external stimuli, as well as by the “push” of internal key substances in her body. Needs cause a drive (an energized needs. 320  Motivation and Emotion 321 Incentives Usually, our actions are energized by a mixture of internal The “pull” of a goal is called its incentive value (the goal’s appeal needs and external incentives. That’s why a strong need may beyond its ability to fill a need). Some goals are so desirable change an unpleasant incentive into a desired goal. Perhaps you’ve (strawberry pie, for example) that they can motivate behavior in never eaten a grub worm, but we’ll bet you’ve eaten some pretty the absence of an internal need. Other goals are so low in incentive horrible leftovers when the refrigerator was bare. The incentive value that they may be rejected even if they meet the internal need. value of goals also helps explain motives that don’t seem to come Fresh, live grub worms, for instance, are highly nutritious. How- from internal needs, such as drives for success, status, or approval ever, it is doubtful that you would eat one no matter how hungry ( Figure 10.1). you might be. Types of Motives For our purposes, motives can be divided into three major cate- gories: 1. Biological motives are based on biological needs that must be met for survival. The most important biological motives are hunger, thirst, pain avoidance, and needs for air, sleep, elimination of wastes, and regulation of body temperature. Biological motives are innate. 2. Stimulus motives express our needs for stimulation and Need Drive Response information. Examples include activity, curiosity, explora- tion, manipulation, and physical contact. Although such (a) High-incentive value goal motives also appear to be innate, they are not strictly neces- sary for survival. 3. Learned motives are based on learned needs, drives, and goals. Learned motives help explain many human Drive activities, such as standing for election, blogging, or Need Response auditioning for American Idol. Many learned motives are related to learned needs for power, affiliation (the need (b) Low-incentive value goal to be with others), approval, status, security, and achieve- ment. Fear and aggression also appear to be greatly affected by learning. Biological Motives and Homeostasis How important is air in your life? Water? Sleep? Food? Tempera- ture regulation? Finding a public restroom? For most of us, satisfy- ing biological needs is so routine that we tend to overlook how David Austen/Woodfin Camp & Associates Motivation Internal processes that initiate, sustain, and direct activities. Need An internal deficiency that may energize behavior. Drive The psychological expression of internal needs or valued goals. For example, hunger, thirst, or a drive for success. Response Any action, glandular activity, or other identifiable behavior. Goal The target or objective of motivated behavior. (a)Figure 10.1 Needs and incentives interact to determine drive strength (top). Moderate need combined with a high-incentive goal produces a strong drive. Incentive value The value of a goal above and beyond its ability to fill a need. (b) Even when a strong need exists, drive strength may be moderate if a goal’s Biological motives Innate motives based on biological needs. incentive value is low. It is important to remember, however, that incentive value Stimulus motives Innate needs for stimulation and information. lies “in the eye of the beholder” (photo). No matter how hungry, few people would be able to eat the pictured grub worms. Learned motives Motives based on learned needs, drives, and goals. 322 CHAPTER 10 much of our behavior they direct. But exaggerate any of these needs 99° through famine, shipwreck, poverty, near drowning, bitter cold, or Core body temperature (°F) drinking 10 cups of coffee, and their powerful grip on behavior becomes evident. We are, after all, still animals in many ways. Biological drives are essential because they maintain homeo- stasis (HOE-me-oh-STAY-sis), or bodily equilibrium (Cannon, 98° 1932). What is homeostasis? The term “homeostasis” means “standing steady,” or “steady state.” Optimal levels exist for body tempera- ture, for chemicals in the blood, for blood pressure, and so forth 97° (Levin, 2006). When the body deviates from these “ideal” levels, 12:00 4:00 8:00 12:00 4:00 8:00 12:00 automatic reactions begin to restore equilibrium (Deckers, 2005). Normal Midnight Noon Midnight Thus, it might help to think of homeostasis as being similar to a Time thermostat set at a particular temperature. Eight 8:00 12:00 4:00 8:00 12:00 4:00 8:00 A (Very) Short Course on Thermostats Time Zones Noon Midnight The thermostat in your house constantly compares the actual room tem- East perature to a set point, or ideal temperature, which you can control. When room temperature falls below the set point, the heat is automatically turned dianFigure 10.2 Core body temperature is a good indicator of a person’s circa- rhythm. Most people reach a low point two to three hours before their normal on to warm the room. When the heat equals or slightly exceeds the set waking time. It’s no wonder that both the Chernobyl and Three Mile Island nuclear point, it is automatically turned off or the air conditioning is turned on. In power plant accidents occurred around 4 AM. Rapid travel to a different time zone, this way room temperature is kept in a state of equilibrium hovering around shift work, depression, and illness can throw sleep and waking patterns out of syn- the set point. chronization with the body’s core rhythm. Mismatches of this kind are very disrup- tive (Hauri & Linde, 1990). The first reactions to disequilibrium in the human body are also automatic. For example, if you become too hot, more blood will flow through your skin and you will begin to perspire, thus lowering body temperature. We are not usually aware of such stand: What could be worse than having someone bounding changes, unless continued disequilibrium drives us to seek shade, around cheerily when you’re half asleep, or the reverse? warmth, food, or water. Shift Work and Jet Lag Circadian Rhythms Circadian rhythms are most noticeable after a major change in Our needs and drives can change from moment to moment. After time schedules. Businesspersons, athletes, and other time zone eating, our motivation to eat more food tends to diminish, and a travelers tend to perform poorly when their body rhythms are few minutes in the hot sun can leave us feeling thirsty. But our disturbed. If you travel great distances east or west, the peaks and motivation can also vary over longer cycles. Scientists have long valleys of your circadian rhythms will be out of phase with the sun known that body activity is guided by internal “biological clocks.” and clocks. For example, you might be wide awake at midnight Every 24 hours, your body undergoes a cycle of changes called and feel like you’re sleepwalking during the day. (Return to Fig- circadian (SUR-kay-dee-AN) rhythms (circa: about; diem: a ure 10.2.) Shift work has the same effect, causing fatigue, irritabil- day) (Beersma & Gordijn, 2007). Throughout the day, activities ity, upset stomach, and depression (Garbarino, 2002; Shen et al., in the liver, kidneys, and endocrine glands undergo large changes. 2006). Body temperature, blood pressure, and amino acid levels also How fast do people adapt to rhythm changes? For major time shift from hour to hour. These activities, and many others, peak zone shifts (5 hours or more) it can take up to 2 weeks to resyn- once a day ( Figure 10.2). People are usually more motivated chronize. The direction of travel also affects adaptation (Herxhei- and alert at the high point of their circadian rhythms (Antle & mer & Waterhouse, 2003). If you fly west, adapting is relatively Mistlberger, 2005). easy; if you fly east, adapting takes much longer ( Figure 10.3). People with early peaks in their circadian rhythms are “day When you fly east, the sun comes up earlier relative to your people,” who wake up alert, are energetic early in the day, and fall “home” time. Let’s say that you live in Seattle and fly to Miami. If asleep early in the evening. People with later peaks are “night you get up at 7 am in Miami, it’s 4 am back in Seattle — and your people,” who wake up groggy, are lively in the afternoon or early body knows it. If you fly west, the sun comes up later. In this case, evening, and stay up late (Duffy, Rimmer, & Czeisler, 2001). Such it is easier for people to “advance” (stay up later and sleep in) than differences are so basic that when a day person rooms with a night it is to shift backward. person, both are more likely to give their relationship a negative Adjusting to jet lag is slowest when you stay indoors, where you rating (Carey, Stanley, & Biggers, 1988). This is easy to under- can sleep and eat on “home time.” Getting outdoors speeds adapta-  Motivation and Emotion 323 To reset the body’s clock in a new time zone, a small amount of Westbound flight 5 melatonin can be taken about an hour before bedtime. This dose Number of individuals is continued for as many days as necessary to ease jet lag. The same 4 treatment can be used for rotating work shifts (Comperatore et al, 1996; Sharkey & Eastman, 2002). 3 2 bridges Changes in melatonin levels are thought to partly explain winter 1 depressions that occur when people endure several months of long, dark days. See Chapter 14, page 479. 2 4 6 8 10 12 14 16 18 20 Days to resynchronize KNOWL E DG E B U I L DE R 5 Overview of Motivation Eastbound flight RECITE Number of individuals 4 Classify the following needs or motives by placing the correct letter in the blank. 3 A. Biological motive B. Stimulus motive C. Learned motive 1. _____ curiosity 4. _____ thirst 2 2. _____ status 5. _____ achievement 3. _____ sleep 6. _____ physical contact 1 7. Motives _________________, sustain, and _______________ activities. 8. The maintenance of bodily equilibrium is called thermostasis. T or F? 9. Desirable goals are motivating because they are high in 2 4 6 8 10 12 14 16 18 20 a. secondary value Days to resynchronize b. stimulus value timeFigure 10.3 Time required to adjust to air travel across six time zones. The it took individuals to resynchronize was, on average, shorter for westbound c. homeostatic value d. incentive value 10. The term “jet lag” is commonly used to refer to disruptions of travel than for eastbound flights. (Data from Beljan et al., 1972; cited by Moore-Ede, a. the inverted U function Sulzman, & Fuller, 1982.) b. circadian rhythms c. any of the episodic drives d. the body’s set point tion. A few intermittent 5-minute periods of exposure to bright REFLECT light early in the morning are also helpful for resetting your circa- Critical Thinking dian rhythm (Duffy & Wright, Jr., 2005). Bright light affects the 11. Many people mistakenly believe that they suffer from “hypoglyce- mia” (low blood sugar), which is often blamed for fatigue, difficulty timing of body rhythms by reducing the amount of a brain chemi- concentrating, irritability, and other symptoms. Why is it unlikely cal called melatonin produced by the pineal gland. When melato- that many people actually have hypoglycemia? nin levels rise late in the evening, it’s bedtime as far as the brain is Relate concerned. Motives help explain why we do what we do. See if you can think of How does this affect those of us who are not world travelers? There something you do that illustrates the concepts of need, drive, response, and goal. Does the goal in your example vary in incentive value? What are few college students who have not at one time or another effects do high- and low-incentive-value goals have on your behavior? “burned the midnight oil,” especially for final exams. At such Mentally list some biological motives you have satisfied today. Some times it is wise to remember that departing from your regular stimulus motives. Some learned motives. How did each influence your schedule usually costs more than it’s worth. You may be motivated behavior? true hypoglycemia is an infrequent medical problem. to do as much during 1 hour in the morning as you could have row bounds. While blood sugar levels fluctuate enough to affect hunger, done in 3 hours of work after midnight. You might just as well go Because of homeostasis: Blood sugar is normally maintained within nar- to sleep 2 hours earlier. Answers: 1. b 2. c 3. a 4. a 5. c 6. b 7. initiate, direct 8. F 9. d 10. b 11. In general, if you can anticipate an upcoming body rhythm change, it is best to preadapt to your new schedule. Preadaptation refers to gradually matching your sleep–waking cycle to a new time schedule. Before traveling, for instance, you should go to Homeostasis A steady state of bodily equilibrium. sleep 1 hour later (or earlier) each day until your sleep cycle Circadian rhythms Cyclical changes in bodily functions and arousal matches the time at your destination. levels that vary on a schedule approximating a 24-hour day. 324 CHAPTER 10 Hunger — Pardon Me, My from parts of the digestive system, ranging from the tongue and stomach to the intestines and the liver. Hypothalamus Is Growling The liver? Yes, as the levels of blood sugar (glucose) drop, the Gateway Questions: What causes hunger? Overeating? liver responds by sending nerve impulses to the brain. These “mes- Eating disorders? sages” contribute to a desire to eat (Woods et al., 2000). You get hungry, you find food, and you eat: Hunger might seem like a “simple” motive, but we have only recently begun to under- Brain Mechanisms stand it. Hunger provides a good model of how internal and exter- What part of the brain controls hunger? When you are hungry, many nal factors direct our behavior. And, as we will see later, many of parts of the brain are affected, so no single “hunger thermostat” the principles that explain hunger also apply to thirst. Like almost exists. However, a small area called the hypothalamus (HI-po- every other human motive, our hunger levels are affected by both THAL-ah-mus) is especially important because it regulates many internal bodily factors and external environmental and social ones. motives, including hunger, thirst, and the sex drive ( Figure 10.5). To understand how this works, let’s begin with a survey of some of the internal factors controlling our hunger. bridges Internal Factors in Hunger For more information about the role of the hypothalamus in controlling behavior, see Chapter 2, pages 68–69. Don’t feelings of hunger originate in the stomach? To find out, Wal- ter Cannon and A. L. Washburn (1912) decided to see if stomach contractions cause hunger. In an early study, Washburn trained himself to swallow a balloon, which could be inflated through an attached tube. This allowed Cannon to record the movements of Washburn’s stomach ( Figure 10.4). When Washburn’s stomach contracted, he reported that he felt “hunger pangs.” In view of this, the two scientists concluded that hunger is nothing more than the contractions of an empty stomach. (However, this proved to be an © Tribune Media Service, Inc. Reprinted by permission. inflated conclusion.) For many people, hunger produces an overall feeling of weak- ness or shakiness, rather than a “growling” stomach. Of course, eating does slow when the stomach is stretched or distended (full). (Remember last Thanksgiving?) However, we now know that the stomach is not essential for feeling hunger. Even people who have had their stomachs removed for medical reasons continue to feel hungry and eat regularly (Woods et al., 2000). Then what does cause hunger? Many different factors combine to promote and suppress hunger. The brain receives many signals Record of stomach contractions Gastric balloon Time record in minutes Record of hunger pangs Record of breathing Hypothalamus Figure 10.4 In Cannon’s early study of hunger, a simple apparatus was used to simultane- ously record hunger pangs and stomach contractions. (After Cannon, 1934.) Figure 10.5 Location of the hypothalamus in the human brain.  Motivation and Emotion 325 The hypothalamus is sensitive to levels of sugar in the blood area helps keep blood sugar levels steady by both starting and stop- (and other substances described in a moment). It also receives ping eating. The paraventricular nucleus is sensitive to a substance neural messages from the liver and stomach. When combined, called neuropeptide Y (NPY). If NPY is present in large amounts, these signals determine if you are hungry or not (Woods et al., an animal will eat until it cannot hold another bite (Williams et 2000). al., 2004). Incidentally, the hypothalamus also responds to a One part of the hypothalamus acts as a feeding system that initi- chemical in marijuana, which can produce intense hunger (the ates eating. If the lateral hypothalamus is “turned on” with an “munchies”) (Di Marzo et al., 2001). electrified probe, even a well-fed animal will immediately begin How do we know when to stop eating? A chemical called glucagon- eating. (The term “lateral” simply refers to the sides of the hypo- like peptide 1 (GLP-1) causes eating to cease. After you eat a meal, thalamus. ( Figure 10.6). If the same area is destroyed, the animal GLP-1 is released by the intestines. From there, it travels in the may never eat again. bloodstream to the brain. When enough GLP-1 arrives, your desire The lateral hypothalamus is normally activated in a variety of to eat ends (Nori, 1998). As you might imagine, GLP-1 pills show ways. For example, when you are hungry your stomach lining pro- promise in the treatment of obesity (Raun et al., 2007). By the way, duces ghrelin (GREL-in), a hormone that activates your lateral it takes at least 10 minutes for the hypothalamus to respond after hypothalamus (Olszewski et al., 2003). (If your stomach is grow- you begin eating. That’s why you are less likely to overeat if you eat lin’, it’s probably releasing ghrelin.) Ghrelin also activates parts of slowly, which gives your brain time to get the message that you’ve your brain involved in learning. This means you should consider had enough (Liu et al., 2000). studying before you eat, not immediately afterward (Diano et al., In addition to knowing when to start eating and when meals 2006). are over, your brain also controls your weight over longer periods A second area in the hypothalamus is part of a satiety system, or of time. (See “Your Brain’s ‘Fat Point.’ ”) “stop mechanism” for eating. If the ventromedial hypothalamus (VENT-ro-MEE-dee-al) is destroyed, dramatic overeating results. (Ventromedial refers to the bottom middle of the hypothalamus.) Rats with such damage will eat until they balloon up to weights of 1,000 grams or more ( Figure 10.7). A normal rat weighs about 180 grams. To put this weight gain in human terms, picture some- one you know who weighs 180 pounds growing to a weight of 1,000 pounds. The paraventricular (PAIR-uh-ven-TRICK-you-ler) nucleus of the hypothalamus also affects hunger. (See Figure 10.6.) This Corpus Lateral callosum hypothalamus produce Figure 10.7 Damage to the hunger satiety system in the hypothalamus can a very fat rat, a condition called hypothalamic hyperphagia (hi-per-FAGE- yah: overeating). This rat weighs 1,080 grams. (The pointer has gone completely around the dial and beyond.) (Courtesy of Neal E. Miller. Rockefeller University.) Ventromedial Paraventricular hypothalamus nucleus fromFigure 10.6 This is a cross section through the middle of the brain (viewed the front of the brain). Indicated areas of the hypothalamus are associated Hypothalamus A small area at the base of the brain that regulates many aspects of motivation and emotion, especially hunger, thirst, and with hunger and the regulation of body weight. sexual behavior. 326 CHAPTER 10 BR AIN WAVES Your Brain’s “Fat Point” A thermostat set to, say, 72 degrees will con- Can you change your fat set point? Good by resetting your hypothalamus, but psy- stantly turn the heat and/or air conditioning question. Your leptin levels are partly under chologists have studied other approaches on and off to maintain the temperature at genetic control. In rare cases mice (and we to weight loss. We will examine some later that set point. Like a thermostat, your brain humans) inherit a genetic defect that reduces in this section. maintains a set point in order to control your leptin levels in the body, leading to obesity. weight over the long term. It does this by In such cases, the administration of leptin monitoring the amount of fat stored in your can help (Williamson et al., 2005). John Sholtis/The Rockerfeller University body in specialized fat cells (Ahima & Osei, For the rest of us, the news is not so 2004). encouraging because there is currently no Your set point is the weight you main- known way to lower your set point for fat. tain when you are making no effort to gain Since the body replaces fat cells at roughly or lose weight. When your body weight the rate they are lost, the number of fat goes below its set point, you will feel hun- cells remains unchanged throughout adult gry most of the time. On the other hand, fat life (Spalding et al., 2008). To make mat- cells release a substance called leptin when ters worse, radical diets do not help. (But The mouse on the left has a genetic defect that your “spare tire” is well inflated. Leptin is you knew that already, didn’t you?) They prevents its fat cells from producing normal carried in the bloodstream to the hypothal- may even raise the set point for fat, result- amounts of leptin. Without this chemical signal, amus, where it tells us to eat less (Williams ing in diet-induced obesity (Ahima & Osei, the mouse’s body acts as if its set point for fat et al., 2004). 2004). You may not be able to lose weight storage is, shall we say, rather high. The substances we have reviewed are only some of the chemical Obesity in America: A Broad Problem 75 signals that start and stop eating (Geary, 2004). Others continue to be discovered. In time, they may make it possible to artificially Percentage of Americans who are overweight control hunger. If so, better treatments for extreme obesity and 65% 65 self-starvation could follow (Batterham et al., 2003). 56% External Factors in Hunger and Obesity 55 As we have seen, “hunger” is affected by more than just our bio- logical needs for food. In fact, if internal needs alone controlled 48% 48% 45% eating, fewer people would overeat. Nevertheless, roughly 65 per- 45 cent of adults in the United States are overweight ( Figure 10.8). In 2006, more than one-third were obese (Ogden et al., 2007). (See “What’s Your BMI?”) Let’s consider some external influences on 35 hunger and their role in obesity, a major health risk and, for many, a source of social stigma and low self-esteem. As a result, obesity is overtaking smoking as a cause of needless deaths (Murray, 2001). 25 1960 1970 1980 1990 2000 External Eating Cues Figure 10.8 A near epidemic of obesity has occurred in the United States during the last 20 years, with 65 percent of all Americans now classified as over- Most of us are sensitive to external eating cues. These are signs and weight (Ogden et al., 2007). signals linked with food. For example, do you tend to eat more when food is highly visible and easy to get? If so, then external cues affect your food intake. In cultures like ours, where food is plentiful, eating Taste cues add greatly to the risk of overeating (Woods et al., 2000). Many The availability of a variety of tasty foods can also lead to overeating college freshmen gain weight rapidly during their first 3 months on and obesity in societies where such foods are plentiful. Normally, campus (the famous “Frosh 15”). All-you-can-eat dining halls in the tastes for foods vary considerably. For example, if you are well fed, dorms and nighttime snacking appear to be the culprits (Levitsky et leptin dulls the tongue’s sensitivity to sweet tastes (Kawai et al., al., 2003). The presence of others can also affect whether people 2000). If you have noticed that you lose your “sweet tooth” when overeat (or undereat) depending on how much everyone else is eating you are full, you may have observed this effect. Actually, if you eat and how important it is to impress them (Pliner & Mann, 2004). too much of any particular food, it will become less appealing. This  Motivation and Emotion 327 D ISCOVERI N G P S Y CH OL O G Y What’s Your BMI? (We’ve Got Your Number) From the standpoint of fashion, you may (square the number). Then divide the result If your BMI is greater than 25, you should already have an opinion about whether you into your weight in pounds. Multiply the be concerned. If it is greater than 30, your are overweight. But how do you rate from a resulting number by 703 to obtain your weight may be a serious health risk. (There medical perspective? Obesity is directly linked BMI. For example, a person who weighs 220 are two exceptions: The BMI may overesti- to heart disease, high blood pressure, stroke, pounds and is 6 feet 3 inches tall has a BMI mate body fat if you have a muscular build, diabetes, and premature death. But how heavy of 27.5. and it may underestimate body fat in older do you have to be to endanger your health? persons who have lost muscle mass.) Losing (220 pounds) A measure called the body mass index (BMI)  703
27.5 weight and keeping it off can be very chal- (75 inches) (75 inches) can be used to assess where you stand on the lenging. However, if you’re overweight, low- weight scale (so to speak). You can calculate Now, compare your BMI to the following ering your BMI is well worth the effort. In the your BMI by using the following formula: scale: long run, it could save your life. (your weight in pounds) BMI
 703 Underweight less than 18.5 (height in inches) (h height in inches) Normal weight 18.5 to 24.9 To use the formula, take your height in Overweight 25 to 29.9 inches and multiply that number by itself Obesity 30 or greater probably helps us maintain variety in our diets. However, it also If getting sick occurs long after eating, how does it become associ- encourages obesity. If you overdose on fried chicken or French fries, ated with a particular food? A good question. Taste aversions are a moving on to some cookies or chocolate cheesecake certainly won’t type of classical conditioning. As stated in Chapter 7, a long delay do your body much good (Pinel, Assanand, & Lehman, 2000). between the conditioned stimulus (CS) and the unconditioned It is easy to acquire a taste aversion, or active dislike, for a par- stimulus (US) usually prevents conditioning. However, psycholo- ticular food. This can happen if a food causes sickness or if it is gists theorize that we have a biological tendency to associate an merely associated with nausea ( Jacobsen et al., 1993). Not only do upset stomach with foods eaten earlier. Such learning is usually we learn to avoid such foods, but they too can become nauseating. protective. Yet, as we saw previously (in Chapter 7), many cancer A friend of one of your authors once became ill after eating a patients suffer taste aversions long after the nausea of their drug cheese Danish (well, actually, several) and has never again been treatments has passed (Chance, 2006; Stockhorst, Klosterhalfen, able to come face to face with this delightful pastry. & Steingrueber, 1998). If you like animals, you will be interested in an imaginative Taste aversions may also help people avoid severe nutritional approach to an age-old problem. In many rural areas, predators are imbalances. For example, if you go on a fad diet and eat only poisoned, trapped, or shot by ranchers. These practices have grapefruit, you will eventually begin to feel ill. In time, associating nearly wiped out the timber wolf, and in some areas the coyote your discomfort with grapefruit may create an aversion to it and faces a similar end. How might the coyote be saved without a restore some balance to your diet. costly loss of livestock? In a classic experiment, coyotes were given lamb tainted with Emotional Eating lithium chloride. Coyotes who took the bait became nauseated Is it true that people also overeat when they are emotionally upset? and vomited. After one or two such treatments, they developed Yes. People with weight problems are prone to overeat when they bait shyness — a lasting distaste for the tainted food (Gustavson & are anxious, angry, or sad (Geliebter & Aversa, 2003). Further- Garcia, 1974). If applied consistently, taste aversion conditioning more, obese individuals are often unhappy in our fat-conscious might solve many predator–livestock problems. culture. The result is overeating that leads to emotional distress bridges Bait shyness is similar to human aversion conditioning, which Set point The proportion of body fat that tends to be maintained by is used to help people control bad habits, such as smoking, changes in hunger and eating. drinking, or nail biting. See Chapter 15, page 504, to explore Taste aversion An active dislike for a particular food. this connection. Bait shyness An unwillingness or hesitation on the part of animals to eat a particular food. 328 CHAPTER 10 and still more overeating. This makes weight control extremely The Paradox of Yo-Yo Dieting difficult (Rutledge & Linden, 1998). If dieting works, why are hundreds of “new” diets published each year? The answer is that although dieters do lose weight, most Cultural Factors regain it soon after they stop dieting. In fact, many people end up Learning to think of some foods as desirable and others as revolt- weighing even more than before. Why should this be so? Dieting ing has a large impact on what we eat. In North America we would (starving) slows the body’s rate of metabolism (the rate at which never consider eating the eyes out of the steamed head of a mon- energy is used up). In effect, a dieter’s body becomes highly effi- key, but in some parts of the world they are considered a delicacy. cient at conserving calories and storing them as fat (Pinel, Assanand, By the same token, vegans and vegetarians think it is barbaric to & Lehman, 2000). eat any kind of meat. In short, cultural values greatly affect the Apparently, evolution prepared us to save energy when food is incentive value of foods. scarce and to stock up on fat when food is plentiful. Briefly starv- ing yourself, therefore, may have little lasting effect on weight. Dieting “Yo-yo dieting,” or repeatedly losing and gaining weight, is espe- A diet is not just a way to lose weight. Your current diet is defined cially dangerous. Frequent changes in weight can dramatically by the types and amounts of food you regularly eat. Some diets slow the body’s metabolic rate. As noted earlier, this may raise the actually encourage overeating. For instance, placing animals on a body’s set point for fat and makes it harder to lose weight each “supermarket” diet leads to gross obesity. In one classic experi- time a person diets and easier to regain weight when the diet ends. ment, rats were given meals of chocolate chip cookies, salami, Frequent weight changes also increase the risk of heart disease and cheese, bananas, marshmallows, milk chocolate, peanut butter, premature death (Wang & Brownell, 2005). To avoid bouncing and fat. These pampered rodents overate, gaining almost three between feast and famine requires a permanent change in eating times as much weight as rats that ate only laboratory chow (Scla- habits and exercise. fani & Springer, 1976). (Rat chow is a dry mixture of several bland To summarize, eating and overeating are related to internal and grains. If you were a rat, you’d probably eat more cookies than rat external influences, diet, emotions, genetics, exercise, and many chow, too.) other factors. People become obese in different ways and for dif- People are also sensitive to dietary content. In general, sweet- ferent reasons. We live in a culture that provides inexpensive, ness, high fat content, and variety tend to encourage overeating good-tasting food everywhere, and have a brain that evolved to say (Lucas & Sclafani, 1990). Unfortunately, North American culture “Eat whenever food is available.” Clearly, scientists are still a long provides the worst kinds of foods for people who suffer from obe- way from winning the “battle of the bulge.” Nevertheless, many sity. For example, restaurant and fast food tends to be higher in fat people have learned to take control of eating by applying psycho- and calories than meals made at home (Brownell, 2003). “Super- logical principles. (See “Behavioral Dieting.”) sized” meals are another problem. Food portions at restaurants in the United States are 25 percent larger, or more, than they are in Eating Disorders France. Far fewer people are obese in France, most likely because Under the sheets of her hospital bed Krystal looks like a skeleton. they simply eat less. The French also take longer to eat a meal, If her anorexia nervosa (AN-uh-REK-see-yah ner-VOH-sah: self- which discourages overeating (Rozin et al., 2003). starvation) cannot be stopped, Krystal may die of malnutrition. An added problem faced by people who want to control their weight concerns “yo-yo” dieting. “Supersized” portions con- tribute to overeating. A fast-food meal con- sisting of a ham- burger, medium fries, and a Mike Gusastella/Getty Images Jim Spellman/Getty Images medium soda aver- ages 1,200 calories, which is over half the daily caloric need for an adult. Make that a double burger, add cheese, and supersize the fries and the drink Royalty-Free/Corbis and you will consume two thirds of the food you need in a day in just one meal. Notice, too, Actress Valerie Bertinelli has been a lifelong yo-yo dieter who tried many different that people tend to eat all the food they have diets. As a spokeswoman for a national weight-loss program, Valerie lost about paid for, even if it is more than they need. 40 pounds. Will she maintain her weight loss after she reaches her target weight?  Motivation and Emotion 329 D ISCOVERI N G P S Y CH OL O G Y Behavioral Dieting As we have noted, dieting is usually followed you eat, and the feelings and events that your plate, and stop eating before you by rapid weight gain. If you really want to occur just before and after eating. Is a are completely full. Be especially wary lose weight, you must overhaul your eat- roommate, relative, or spouse encourag- of the extra-large servings at fast-food ing habits, an approach called behavioral ing you to overeat? What are your most restaurants. Saying “supersize me” too dieting. Here are some helpful behavioral “dangerous” times and places for over- often can, indeed, leave you super sized techniques: eating? (Murray, 2001). 4. Learn to weaken your personal eating 7. Avoid snacks. It is generally better to 1. Get yourself committed to weight cues. When you have learned when and eat more small meals a day than fewer loss. Involve other people in your where you do most of your eating, avoid large ones because more calories are efforts. Programs such as Overeaters these situations. Try to restrict your eat- burned (Assanand, Pinel, & Lehman, Anonymous or Take Off Pounds Sensibly ing to one room, and do not read, watch 1998). However, high-calorie snacks can be a good source of social support. TV, study, or talk on the phone while tend to be eaten in addition to meals. 2. Exercise. No diet can succeed for long eating. Require yourself to interrupt If you have an impulse to snack, set a without an increase in exercise, because what you are doing in order to eat. timer for 20 minutes and see if you are exercise burns calories. To lose weight, 5. Count calories, but don’t starve your- still hungry then. Delay the impulse to you must use more calories than you self. To lose weight, you must eat less, snack several times if possible. Dull your take in. Burning just 200 extra calories and counting calories allows you to appetite by filling up on raw carrots, a day can help prevent rebound weight keep a record of your food intake. If you bouillon, water, coffee, or tea. gains. Add activity to your routine in have trouble eating less every day, try 8. Chart your daily progress. Record your every way you can think of. Stop saving dieting 4 days a week. People who diet weight, the number of calories eaten, steps and riding elevators. Buy a step intensely every other day lose as much and whether you met your daily goal. counter to track the number of steps you as those who diet moderately every day Set realistic goals by cutting down calo- take every day. Walking 10,000 steps per (Viegener et al., 1990). ries gradually. Losing about a pound per day will burn between 2,000 and 3,500 6. Develop techniques to control the act week is realistic, but remember, you are calories a week (depending on your of eating. Whenever you can, check for changing habits, not just dieting. Diets weight). The more frequently and vigor- nutritional information and buy grocer- don’t work! ously you exercise, the more weight you ies and meals lower in calories and fats. 9. Set a “threshold” for weight control. will lose (Jeffery & Wing, 2001). Also begin to take smaller portions. Maintaining weight loss can be even 3. Learn your eating habits by observing Carry to the table only what you plan more challenging than losing weight. It yourself and keeping a “diet diary.” to eat. Put all other food away before is easier to maintain weight loss if you Begin by making a complete, 2-week leaving the kitchen. Eat slowly, sip water set a regain limit of 3 pounds or less. In record of when and where you eat, what between bites of food, leave food on other words, if you gain more than 2 or 3 pounds, you immediately begin to Adam@Home © by Universal Press Syndicate. Reprinted with permission. All rights reserved. make corrections in your eating habits and amount of exercise (Brownell, 2003). Be patient with this program. It takes years to develop eating habits. You can expect it to take at least several months to change them. If you are unsuccessful at losing weight with these techniques, you might find it helpful to seek the aid of a psychologist familiar with behavioral weight-loss techniques. Victims of anorexia, who are mostly adolescent females, suffer devastating weight losses from severe, self-inflicted dieting (Coo- per, 2005). Do anorexics lose their appetite? Although the compulsive Anorexia nervosa Active self-starvation or a sustained loss of appetite attempt to lose weight causes them to not seek or desire food, they that has psychological origins. often still feel physical hunger. Often, anorexia starts with “nor- Behavioral dieting Weight reduction based on changing exercise and mal” dieting that slowly begins to dominate the person’s life. In eating habits, rather than temporary self-starvation. 330 CHAPTER 10 Table 10.1 Recognizing Eating Disorders Anorexia Nervosa Body weight below 85 percent of normal for one’s height and age. Refusal to maintain body weight in normal range. Intense fear of becoming fat or gaining weight, even though under- weight. Disturbance in one’s body image or perceived weight. Self-evaluation is unduly influenced by body weight. Denial of seriousness of abnormally low body weight. Pascal Le Segretain/Getty Images Absence of menstrual periods. Purging behavior (vomiting or misuse of laxatives or diuretics). Bulimia Nervosa Normal or above-normal weight. Recurring binge eating. Eating within an hour or two an amount of food that is much larger than most people would consume. Feeling a lack of control over eating. Anorexia nervosa is far more dangerous than many people realize. This haunt- Purging behavior (vomiting or misuse of laxatives or diuretics). ing Italian anti-anorexia poster shows 68-pound model Isabelle Caro, who has Excessive exercise to prevent weight gain. struggled with anorexia for 15 years. Many celebrities have struggled with eat- Fasting to prevent weight gain. ing disorders, including Karen Carpenter (who died of starvation-induced heart Self-evaluation is unduly influenced by body weight. failure), Paula Abdul, Kirstie Alley, Fiona Apple, Victoria Beckham (Posh Spice), Princess Diana, Tracey Gold, Janet Jackson, and Mary-Kate Olsen. DSM-IV-TR, 2000. time, anorexics suffer debilitating health problems. From 5 to altering what they eat and exercising excessively. Some are going 8 percent (more than 1 in 20) die of malnutrition (Polivy & Her- too far: About 10 percent of anorexics and 25 percent of bulimics man, 2002). Table 10.1 lists the symptoms of anorexia nervosa. are now males (Weltzin et al., 2005). Bulimia nervosa (bue-LIHM-ee-yah) is a second major eating disorder. Bulimic persons gorge on food, then vomit or take laxa- Causes tives to avoid gaining weight. (See Table 10.1.) Like anorexia, What causes anorexia and bulimia? Women and men who suffer most victims of bulimia are girls or women. Approximately 5 per- from eating disorders are extremely dissatisfied with their bod- cent of college women are bulimic, and as many as 60 percent have ies (Crisp et al., 2006). Usually, they have distorted views of milder eating problems. Bingeing and purging can seriously dam- themselves, exaggerated fears of becoming fat, and low self- age health. Typical risks include sore throat, hair loss, muscle esteem. Many overestimate their body size by 25 percent or spasms, kidney damage, dehydration, tooth erosion, swollen sali- more. As a result, they think they are disgustingly “fat” when vary glands, menstrual irregularities, loss of sex drive, and even they are actually wasting away ( Figure 10.9) (Polivy & Her- heart attack. man, 2002). Many of these problems are related to the idealized body Men and Eating Disorders images presented in the media (Levine & Harrison, 2004). Some Eating disorders are on the rise among men. Currently, one third websites even go so far as to endorse anorexia and bulimia of men say they want less body fat and another third want more (referred to by “fans” as “Ana” and “Mia”) (Tierney, 2008). Girls muscles (McCabe & Ricciardelli, 2004). As a result, many men are who spend a lot of time reading fashion magazines or visiting Figure 10.9 Women with abnormal eating habits were asked to rate their body shape on a scale similar to the one you see here. As a group, they chose ideal figures much thinner than what they thought their current weights were. (Most women say they want to be thinner than they currently are, but to a lesser degree than women with eat- ing problems.) Notice that the women with eating problems chose an ideal weight that was even thinner than what they thought men prefer. 2 3 4 5 This is not typical of most women. In this study, only women with eat- ing problems wanted to be thinner than what they thought men find attractive (Zellner, D. A., Harner, D. E., & Adler, R. L. (1989). Effects of eating abnormalities and gender on perceptions of desirable body shape. Journal Perceived ideal weight Actually most attractive to men of Abnormal Psychology, 98(1), 93-96. Copyright © 1989 APA. Reprinted with permission of the publisher.). Perceived as most attractive to men Perceived current weight  Motivation and Emotion 331 these websites are more likely to have distorted body images and Biological Motives Revisited — unrealistic ideas about how they compare with others (Martinez- Gonzalez et al., 2003). Thirst, Sex, and Pain The popularity of fitness, exercise, and sports has also contrib- Gateway Questions: Is there more than one type of thirst? In what uted to eating disorders. Today, more people are changing their diets ways are pain avoidance and the sex drive unusual? in search of a lean, muscular look. People engaged in sports that Most biological motives work in ways that are similar to hunger. require low body fat or extreme weight loss (such as wrestling, gym- For example, thirst is only partially controlled by dryness of the nastics, pole vaulting, high jumping, and even cycling) are particu- mouth. If you were to take a drug that made your mouth con- larly likely to develop eating disorders (Weltzin et al., 2005). stantly wet, or dry, your water intake would remain normal. Like People with eating disorders appear to be trying to gain some hunger, thirst is regulated by separate thirst and thirst satiety sys- measure of control. Anorexic teen girls are usually described as tems in the hypothalamus. Also like hunger, thirst is strongly “perfect” daughters — helpful, considerate, conforming, and obe- affected by learning and cultural values. dient. They seem to be seeking perfect control in their lives by being perfectly slim (Castro et al., 2004). People suffering from bulimia are also concerned with control. Typically they are Thirst obsessed with thoughts of weight, food, eating, and ridding them- You may not have noticed, but there are actually two kinds of selves of food. As a result, they feel guilt, shame, self-contempt, thirst. Extracellular thirst occurs when water is lost from the flu- and anxiety. Vomiting reduces their anxiety, which makes purging ids surrounding the cells of your body. Bleeding, vomiting, diar- highly reinforcing (Powell & Thelen, 1996). rhea, sweating, and drinking alcohol cause this type of thirst (Franken, 2007). When a person loses both water and minerals in Treatment any of these ways — especially by perspiration — a slightly salty Most people suffering from eating disorders will not seek help on liquid may be more satisfying than plain water. their own. This is especially true for men, because eating disorders Why would a thirsty person want to drink salty water? The rea- are still widely perceived to be a female problem (Weltzin et al., son is that before the body can retain water, minerals lost through 2005). Typically, it takes strong urging by family or friends to get perspiration (mainly salt) must be replaced. In lab tests, animals victims into treatment. greatly prefer saltwater after salt levels in their bodies are lowered Treatment for anorexia usually begins with giving drugs to relieve (Strickler & Verbalis, 1988). Similarly, some nomadic peoples of obsessive fears of gaining weight. Then a medical diet is used to the Sahara Desert prize blood as a beverage, probably because of restore weight and health. Next, a counselor may help patients work its saltiness. (Maybe they should try Gatorade?) on the emotional conflicts that led to weight loss. For bulimia, behav- A second type of thirst occurs when you eat a salty meal. In this ioral counseling may include self-monitoring of food intake. A instance your body does not lose fluid. Instead, excess salt causes related cognitive-behavioral approach focuses on changing the think- fluid to be drawn out of cells. As the cells “shrink,” intracellular ing patterns and beliefs about weight and body shape that perpetuate thirst is triggered. Thirst of this type is best quenched by plain eating disorders (Byrne & McLean, 2002; Cooper, 2005). water. The drives for food, water, air, sleep, and elimination are all similar in that they are generated by a combination of activities in Culture, Ethnicity, and Dieting the body and the brain, and they are influenced by various external Women with eating disorders are not alone in having body image factors. However, the drive to avoid pain and the sex drive are problems. In Western cultures, many women learn to see them- more unusual. selves as “objects” that are evaluated by others. As a result, they try to shape their bodies to the cultural ideal of slimness through diet- Pain ing (Fredrickson et al., 1998). How is the drive to avoid pain different? Hunger, thirst, and sleepi- Just looking at a fashion magazine tends to leave women less ness come and go in a fairly regular cycle each day. Pain avoidance, satisfied with their weight and anxious to be thinner (Simpson, by contrast, is an episodic drive (ep-ih-SOD-ik). That is, it occurs 2002). However, women from some cultural backgrounds appear to be less susceptible to the glorification of slimness. For example, Asian-American college students are only half as likely to diet as other college women are (Tsai, Hoerr, & Song, 1998). Within the Bulimia nervosa Excessive eating (gorging) usually followed by self- African-American and Pacific-Islander communities there is a induced vomiting and/or taking laxatives. general preference for a fuller and shapelier figure. In these groups Extracellular thirst Thirst caused by a reduction in the volume of fluids a larger body size is associated with high social status, health, and found between body cells. beauty (Flynn & Fitzgibbon, 1998; Ofosu, Lafreniere, & Senn, Intracellular thirst Thirst triggered when fluid is drawn out of cells due 1998). Clearly, what constitutes an attractive body style is a matter to an increased concentration of salts and minerals outside the cell. of opinion. Episodic drive A drive that occurs in distinct episodes. 332 CHAPTER 10 (Crooks & Baur, 2008). The sex drive in men is related to the amount of androgens (male hormones such as testosterone) pro- vided by the testes. When the supply of androgens dramatically increases at puberty, so does the male sex drive. Likewise, the sex drive in women is related to their estrogen levels (Hyde & DeLama- ter, 2006). However, “male” hormones also affect the female sex drive. In addition to estrogen, a woman’s body produces small amounts of androgens. When their androgen levels increase, many women experience a corresponding increase in sex drive (Van Goozen et al., 1995). Testosterone levels decline with age, and various medical problems can lower sexual desire. In some instances, taking testosterone supplements can restore the sex drive in both men and women (Crooks & Baur, 2008). Alain Evrard/Photo Researchers. Human sexual behavior and attitudes are discussed in detail in Chapter 11. For now it is enough to note that the sex drive is largely non-homeostatic (relatively independent of bodily need states). In humans, the sex drive can be aroused at virtually any time by almost anything. It therefore shows no clear relationship to deprivation (the amount of time since the drive was last satis- Tolerance for pain and the strength of a person’s motivation to avoid discomfort fied). Certainly, an increase in desire may occur as time passes. But are greatly affected by cultural practices and beliefs. recent sexual activity does not prevent sexual desire from occur- ring again. Notice, too, that people may seek to arouse the sex drive as well as to reduce it. This unusual quality makes the sex in distinct episodes when bodily damage takes place or is about to drive capable of motivating a wide range of behaviors. It also occur. Most drives prompt us to actively seek a desired goal (food, explains why sex is used to sell almost everything imaginable. drink, warmth, and so forth). Pain prompts us to avoid or elimi- The non-homeostatic quality of the sex drive can be shown in nate sources of discomfort. this way: A male animal is allowed to copulate until it seems to Some people feel they must be “tough” and not show any dis- have no further interest in sexual behavior. Then a new sexual tress. Others complain loudly at the smallest ache or pain. The partner is provided. Immediately the animal resumes sexual activ- first attitude raises pain tolerance, and the second lowers it. As this ity. This pattern is called the Coolidge effect after former U.S. suggests, the drive to avoid pain is partly learned. That’s why mem- president Calvin Coolidge. What, you might ask, does Calvin bers of some societies endure cutting, burning, whipping, tattoo- Coolidge have to do with the sex drive? The answer is found in the ing, and piercing of the skin that would agonize most people (but following story. apparently not devotees of piercing and “body art”). In general, we While touring an experimental farm, Coolidge’s wife report- learn how to react to pain by observing family members, friends, edly asked if a rooster mated just once a day. “No ma’am,” she was and other role models (McMahon & Koltzenburg, 2005). told, “he mates dozens of times each day.” “Tell that to the presi- dent,” she said, with a faraway look in her eyes. When President The Sex Drive Coolidge reached the same part of the tour, his wife’s message was Sex is unlike other biological motives because sex (contrary to any- given to him. His reaction was to ask if the dozens of matings were thing your personal experience might suggest) is not necessary for with the same hen. No, he was told, different hens were involved. individual survival. It is necessary, of course, for group survival. “Tell that to Mrs. Coolidge,” the president is said to have replied. The term sex drive refers to the strength of one’s motivation to engage in sexual behavior. In lower animals the sex drive is directly related to hormones. Female mammals (other than humans) are KNOWL E DG E B U I L DE R interested in mating only when their fertility cycles are in the stage Hunger, Thirst, Pain, and Sex of estrus, or “heat.” Estrus is caused by a release of estrogen (a RECITE female sex hormone) into the bloodstream. Hormones are impor- 1. The hunger satiety system in the hypothalamus signals the body tant in males as well. In most animals, castration will abolish the to start eating when it receives signals from the liver or detects changes in blood sugar. T or F? sex drive. But in contrast to females, the normal male animal is 2. Maintaining your body’s set point for fat is closely linked with the almost always ready to mate. His sex drive is primarily aroused by amount of __________ in the bloodstream. the behavior and scent of a receptive female. Therefore, in many a. hypothalamic factor-1 species mating is closely tied to female fertility cycles. b. ventromedial peptide-1 c. NPY How much do hormones affect human sex drives? Hormones d. leptin affect the human sex drive, but not as directly as in animals Continued  Motivation and Emotion 333 3. People who frequently diet tend to benefit from practice: They lose weight more quickly each time they diet. T or F? 4. Bingeing and purging are most characteristic of people who have a. taste aversions b. anorexia c. bulimia d. strong sensitivity to external eating cues 5. In addition to changing eating habits, a key element of behavioral dieting is a. exercise b. well-timed snacking c. better eating cues d. commitment to “starving” every day 6. A cancer patient has little appetite for food several weeks after the nausea caused by chemotherapy has ended. Her loss of appetite is probably best explained by a. increased NPY in the brain b. a conditioned taste aversion Figure 10.10 Monkeys happily open locks that are placed in their cage. Because no reward is given for this activity, it provides evidence for the existence of c. the aftereffects of yo-yo dieting d. a loss of extracellular hunger stimulus needs. (Courtesy of Harry F. Harlow.) 7. Thirst may be either intracellular or ___________________________. 8. Pain avoidance is an _________________________ drive. 9. Sexual behavior in animals is largely controlled by estrogen levels in the female and the occurrence of estrus in the male. T or F? details. The drive for stimulation is already present during infancy. By the time a child can walk, there are few things in the home that REFLECT have not been tasted, touched, viewed, handled, or, in the case of Critical Thinking toys, destroyed! 10. Kim, who is overweight, is highly sensitive to external eating cues. How might her wristwatch contribute to her overeating? Stimulus drives are readily apparent in animals as well as Relate humans. For example, monkeys will quickly learn to solve a Think of the last meal you ate. What caused you to feel hungry? What mechanical puzzle made up of interlocking metal pins, hooks, and internal signals told your body to stop eating? How sensitive are you to external eating cues? How were you influenced by portion size? Have you latches (Butler, 1954) ( Figure 10.10). No food treats or other external rewards are needed to get them to explore and manipulate developed any taste aversions? A friend of yours seems to be engaging in yo-yo dieting. Can you their surroundings. The monkeys seem to work for the sheer fun explain to her or him why such dieting is ineffective? Can you summarize of it. how behavioral dieting is done? If you wanted to provoke extracellular thirst in yourself, what would you do? How could you make intracellular thirst occur? Arousal Theory Are stimulus drives homeostatic? Yes. According to arousal theory needs for food. we try to keep arousal at an optimal level (Franken, 2007; Han- eaters, who tend to get hungry at mealtimes, irrespective of their internal 10. The time of day can influence eating, especially for externally cued cock & Ganey, 2003). In other words, when your level of arousal Answers: 1. F 2. d 3. F 4. c 5. a 6. b 7. extracellular 8. episodic 9. F is too low or too high, you will seek ways to raise or lower it. What do you mean by arousal? Arousal refers to activation of the body and the nervous system. Arousal is zero at death; it is low Stimulus Drives — Skydiving, Sex drive The strength of one’s motivation to engage in sexual Horror Movies, and the Fun Zone behavior. Gateway Question: How does arousal relate to motivation? Estrus Changes in the sexual drives of animals that create a desire for Are you full of energy right now? Are you feeling tired? Clearly, mating; particularly used to refer to females in heat. the level of arousal you are experiencing is closely linked with your Estrogen Any of a number of female sex hormones. motivation. Are there ideal levels of arousal for different people Androgen Any of a number of male sex hormones, especially and different activities? Let’s find out. testosterone. Most people enjoy a steady “diet” of new movies, novels, tunes, Non-homeostatic drive A drive that is relatively independent of fashions, games, news, websites, and adventures. Yet stimulus physical deprivation cycles or bodily need states. drives, which reflect needs for information, exploration, manipu- Stimulus drives Drives based on needs for exploration, manipulation, lation, and sensory input, go beyond mere entertainment. Stimu- curiosity, and stimulation. lus drives also help us survive. As we scan our surroundings, we Arousal theory Assumes that people prefer to maintain ideal, or constantly identify sources of food, danger, shelter, and other key comfortable, levels of arousal. 334 CHAPTER 10 HUM AN D IVERS I T Y Xtreme! Where would you prefer to go on your next ties like bungee jumping, scuba diving, ski- Boredom susceptibility summer vacation? How about a week with ing, surfing, skydiving, or whitewater rafting I can?