Leonardo is a robot, so he does what he is programmed to do, but nothing more. Because he does not have wants and urges—does not crave friendship or desire chocolate or hate homework—he does not initiate his own behaviour. He can learn, but he cannot yearn, and thus he is not motivated to act in the same way that we are. Motivation refers to the purpose for or psychological cause of an action, and it is no coincidence that the words emotion and motivation share a common linguistic root that means “to move.” Unlike robots, human beings act because their emotions move them, and emotions do this in two different ways: First, emotions provide people with information about the world; and second, emotions are the objectives toward which people strive. Let us examine each of these in turn.

In the old science fiction film Invasion of the Body Snatchers, a young couple suspects that most of the people they know have been kidnapped by aliens and replaced with replicas. This sort of bizarre belief is a common story device in bad movies, but it is also the primary symptom of Capgras syndrome (see FIGURE 8.12). People who suffer from this syndrome typically believe that one or more of their family members are imposters. As one Capgras sufferer told her doctor, “He looks exactly like my father, but he really is not. He’s a nice guy, but he is not my father. … Maybe my father employed him to take care of me, paid him some money so he could pay my bills” (Hirstein & Ramachandran, 1997, p. 438).

This woman’s dad had not been body-snatched, of course, nor had he hired his own stunt double. Rather, this woman sustained damage to the neural connections between her temporal lobe (where faces are identified) and her limbic system (where emotions are generated). As a result, when she saw her father’s face, she recognized it, but because this information was not transmitted to her limbic system, she did not feel the warm emotions that her father’s face should have produced. Her father “looked right” but did not “feel right,” so she concluded that the man before her was an imposter (see Figure 8.12).

People with Capgras syndrome use their emotional experience as information about the world and, as it turns out, so do the rest of us. For example, people report having better lives when they are asked about their lives on a sunny day rather than a rainy day. Why? Because people naturally feel happier on sunny days, and they use their happiness as information about the quality of their lives (Schwarz & Clore, 1983). People who are in good moods believe that they have a higher probability of winning a lottery than do people who are in bad moods. Why? Because people use their moods as information about the likelihood of succeeding at a task (Isen & Patrick, 1983). We all know that satisfying lives and bright futures make us feel good—so when we feel good, we conclude that our lives must be satisfying and our futures must be bright. Because the world influences our emotions, our emotions can provide information about the world (Schwarz, Mannheim, & Clore, 1988). Indeed, recent research suggests that people who trust their feelings to provide this kind of information tend to make more accurate predictions and better decisions than people who do not (Mikels et al., 2011; Pham, Lee, & Stephen, 2012).

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The information we get from our emotions is so useful that we can actually be lost without it. When neurologist Antonio Damasio was asked to examine a patient with an unusual form of brain damage, he asked the patient to choose between two dates for an appointment. It sounds like a simple decision, but for the next half hour, the patient enumerated reasons for and against each of the two possible dates, completely unable to decide in favour of one option or the other (Damasio, 1994). The problem was not any impairment of the patient’s ability to think or reason. On the contrary, he could think and reason all too well. What he could not do was feel. The patient’s injury had left him unable to experience emotion, so when he entertained one option (“If I come next Tuesday, I will have to cancel my lunch with Fred”), he did not feel any better or any worse than when he entertained another (“If I come next Wednesday, I will have to get up early to catch the bus”). And because he felt nothing when he thought about his options, he could not decide which one was best. Studies show that when individuals with this particular form of brain damage are given the opportunity to gamble, they make a lot of reckless bets because they do not feel the twinge of anxiety that tells them they are about to do something stupid. On the other hand, under certain conditions, such individuals make excellent investors, precisely because they are willing to take risks that most of us would not (Shiv et al., 2005).

If the first function of emotion is to provide us with information about the world, then the second function is to tell us what to do with that information. The hedonic principle is the claim that people are motivated to experience pleasure and avoid pain, and this claim has a long history. The ancient Greek philosopher Aristotle (350 BCE/1998) argued that the hedonic principle explained everything there was to know about human motivation: “It is for the sake of this that we all do all that we do.” We want many things, from peace and prosperity to health and security, but we want them for just one reason, and that is that they make us feel good. “Are these things good for any other reason except that they end in pleasure, and get rid of and avert pain?” asked Plato (380 BCE/1956). “Are you looking to any other standard but pleasure and pain when you call them good?” Plato and Aristotle were suggesting that pleasure is not just good: It is what good means.

According to the hedonic principle, then, our emotional experience can be thought of as a gauge that ranges from bad to good, and our primary motivation—perhaps even our sole motivation—is to keep the needle on the gauge as close to good as possible. Even when we voluntarily do things that tilt the needle in the opposite direction, such as letting the dentist drill our teeth or waking up early for a boring class, we are doing these things because we believe that they will nudge the needle toward good in the future and keep it there longer.

If our primary motivation is to keep the needle on good, then which things push the needle in that direction and which things push it away? And where do these things get the power to push our needle around, and exactly how do they do the pushing? The answers to such questions lie in two concepts that have played an unusually important role in the history of psychology: instincts and drives.

When a newborn baby is given a drop of sugar water, it smiles, and when it is given a cheque for $10 000, it acts like it could not care less. By the time the baby goes to university, these responses pretty much reverse. It seems clear that nature endows us with certain motivations and that experience endows us with others. William James (1890) called the natural tendency to seek a particular goal an instinct, which he defined as “the faculty of acting in such a way as to produce certain ends, without foresight of the ends, and without previous education in the performance” (p. 383). According to James, nature hardwired penguins, parrots, puppies, and people to want certain things without training and to execute the behaviours that produce these things without thinking. He and other psychologists of his time tried to make a list of what those things were.

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Unfortunately, they were quite successful, and in just a few decades their list of instincts had grown preposterously long and included some rather exotic entries, such as “the instinct to be secretive” and “the instinct to grind one’s teeth.” By 1924, sociologist Luther Bernard counted 5759 instincts and concluded that after three decades of list making, the term seemed to be suffering from “a great variety of usage and the almost universal lack of critical standards” (Bernard, 1924, p. 21). Furthermore, some psychologists began to worry that attributing the tendency for people to befriend each other to an “affiliation instinct” was more of a description than an explanation (Ayres, 1921; Dunlap, 1919; Field, 1921).

By 1930, the concept of instinct had fallen out of fashion. Not only did it fail to explain anything, but it also flew in the face of Western psychology’s hot new trend: behaviourism. Behaviourists rejected the concept of instinct on two grounds. First, they believed that behaviour should be explained by the external stimuli that evoke it and not by the hypothetical internal states on which it presumably depends. John Watson (1913) had written that “the time seems to have come when psychology must discard all reference to consciousness” (p. 163), and behaviourists saw instincts as just the sort of unnecessary “mind blather” that Watson forbade. Second, behaviourists wanted nothing to do with the notion of inherited behaviour because they believed that all complex behaviour was learned. Because instincts were inherited tendencies that resided inside the organism, behaviourists considered them doubly repugnant.

But within a few decades, some of Watson’s younger followers began to realize that the strict prohibition against the mention of internal states made certain phenomena difficult to explain. For example, if all behaviour is a response to an external stimulus, then why does a rat that is sitting still in its cage at 9:00 a.m. start wandering around and looking for food by noon? Nothing in the cage has changed, so why has the rat’s behaviour changed? What visible, measurable, external stimulus is the wandering rat responding to? The obvious answer is that the rat is responding to something inside itself, which meant that Watson’s young followers (the “new behaviourists” as they called themselves) were forced to look inside the rat to explain its wandering. How could they do that without talking about the “thoughts” and “feelings” that Watson had forbidden them to mention?

They began by noting that bodies are a bit like thermostats. When thermostats detect that the room is too cold, they send signals that initiate corrective actions such as turning on a furnace. Similarly, when bodies detect that they are underfed, they send signals that initiate corrective actions such as eating. Homeostasis is the tendency for a system to take action to keep itself in a particular state, and two of the new behaviourists, Clark Hull and Kenneth Spence, suggested that rats, people, and thermostats are all homeostatic mechanisms. To survive, an organism needs to maintain precise levels of nutrition, warmth, and so on, and when these levels depart from an optimal point, the organism receives a signal to take corrective action. That signal is called a drive, which is an internal state caused by physiological needs. According to Hull and Spence, it is not food per se that organisms find rewarding; it is the reduction of the drive for food. Hunger is a drive, a drive is an internal state, and when organisms eat, they are attempting to change their internal state.

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Although the words instinct and drive are no longer widely used in psychology, both concepts have something to teach us. The concept of instinct reminds us that nature endows organisms with a tendency to seek certain things, and the concept of drive reminds us that this seeking is initiated by an internal state. The psychologist William McDougall (1930) called the study of motivation hormic psychology, which is a term derived from the Greek word for “urge,” and people clearly do have urges—some of which they acquire through experience and some of which they do not—that motivate them to take certain actions. What kinds of urges do we have, and what kinds of actions do we take to satisfy them?

Abraham Maslow (1954) attempted to organize the list of human urges (or, as he called them, needs) in a meaningful way (see FIGURE 8.13). He noted that some needs (such as the need to eat) must be satisfied before others (such as the need to have friends), and he built a hierarchy of needs that had the most immediate needs at the bottom and the most deferrable needs at the top. Maslow suggested that, as a rule, people are more likely to experience a need when the needs below it are met. So when people are hungry or thirsty or exhausted, they are less likely to seek intellectual fulfillment or moral clarity (see FIGURE 8.14). According to Maslow, the needs that take precedence are typically those we share with other animals. For example, because all animals must survive and reproduce, all animals need to eat and mate. Human beings have these needs as well, but as you are about to see, they are more powerful and more complicated than most of us imagine (Kenrick et al., 2010).

Animals convert matter into energy by eating, and they are driven to do this by an internal state called hunger. But what is hunger and where does it come from? At every moment, your body is sending signals to your brain about its current energy state. If your body needs energy, it sends a signal to tell your brain to switch hunger on, and if your body has sufficient energy, it sends a different signal to tell your brain to switch hunger off (Gropp et al., 2005). No one knows precisely what these signals are or how they are sent and received, but research has identified a variety of candidates.

For example, ghrelin is a hormone that is produced in the stomach and appears to be a signal that tells the brain to switch hunger on (Inui, 2001; Nakazato et al., 2001). When people are injected with ghrelin, they become intensely hungry and eat about 30 percent more than usual (Wren et al., 2001). Interestingly, ghrelin also binds to neurons in the hippocampus and temporarily improves learning and memory (Diano et al., 2006) so that we become just a little bit better at locating food when our bodies need it most. Leptin is a chemical secreted by fat cells, and it appears to be a signal that tells the brain to switch hunger off. It seems to do this by making food less rewarding (Farooqi et al., 2007). People who are born with a leptin deficiency have trouble controlling their appetites (Montague et al., 1997). For example, in 2002, medical researchers reported on the case of a 9-year-old girl who weighed 90 kg (200 pounds), but after just a few leptin injections, she reduced her food intake by 84 percent and attained normal weight (Farooqi et al., 2002). Some researchers think the idea that chemicals turn hunger on and off is far too simple since animals do not eat indiscriminately; they seem to compensate for macronutrient deficiencies in their diet by selectively consuming food high in that missing nutrient (like protein) (Dibattista & Holder, 1998). This suggests that there may be different hunger signals depending on the nutritional state of the animal (Rozin & Kalat, 1971).

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Whether hunger is one signal or many, the primary receiver of these signals is the hypothalamus. Different parts of the hypothalamus receive different signals (see FIGURE 8.15). The lateral hypothalamus receives orexigenic signals, and when it is destroyed, animals sitting in a cage full of food will starve themselves to death. The ventromedial hypothalamus receives anorexigenic signals, and when it is destroyed, animals will gorge themselves to the point of illness and obesity (Miller, 1960; Steinbaum & Miller, 1965). These two structures were once thought to be the “hunger centre” and “satiety centre” of the brain, but it turns out that this view is far too simple (Woods et al., 1998). Hypothalamic structures play an important role in turning hunger on and off, but the precise way in which they execute these functions is complex and poorly understood (Stellar & Stellar, 1985).

Feelings of hunger tell us when to eat and when to stop. But for the estimated 600 000 Canadians with eating disorders, eating is a much more complicated affair (Government of Canada, 2006). For instance, bulimia nervosa is an eating disorder characterized by binge eating followed by purging. People with bulimia typically ingest large quantities of food in a relatively short period and then take laxatives or induce vomiting to purge the food from their bodies. These people are caught in a cycle: They eat to ease negative emotions such as sadness and anxiety, but then concern about weight gain leads them to experience negative emotions such as guilt and self-loathing, and these emotions then lead them to purge (Sherry & Hall, 2009; cf. Haedt-Matt & Keel, 2011).

Anorexia nervosa is an eating disorder characterized by an intense fear of being fat and severe restriction of food intake. People with anorexia tend to have a distorted body image that leads them to believe they are fat when they are actually emaciated, and they tend to be high-achieving perfectionists who see their severe control of eating as a triumph of will over impulse. Contrary to what you might expect, people with anorexia have extremely high levels of ghrelin in their blood, which suggests that their bodies are trying desperately to switch hunger on but that hunger’s call is being suppressed, ignored, or overridden (Ariyasu et al., 2001). Like most eating disorders, anorexia strikes more women than men, and 40 percent of newly identified cases of anorexia are among women 15 to 19 years old.

Anorexia may have both cultural and biological causes (Klump & Culbert, 2007). For example, women with anorexia typically believe that thinness equals beauty, and it is not hard to understand why. The average woman is 163 cm (5′4″) tall and weighs 69 kg (140 pounds), and so has a Body Mass Index (BMI) of 26.6. The typical fashion model is between 172 cm (5′ 8″) and 180 cm (5′11″), with a BMI of 16.2, which is considered underweight. Indeed, most university-age women report wanting to be thinner than they are (Rozin, Trachtenberg, & Cohen, 2001), and nearly 1 in 5 reports being embarrassed to be seen buying a chocolate bar (Rozin, Bauer, & Catanese, 2003). But anorexia is not just “vanity run amok” (Striegel-Moore & Bulik, 2007). Many researchers believe that there are as-yet-undiscovered biological and/or genetic components to the illness as well. For example, although anorexia primarily affects women, men have a sharply increased risk of becoming anorexic if they have a female twin who has the disorder (Procopio & Marriott, 2007), suggesting that anorexia may have something to do with prenatal exposure to female hormones.

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Bulimia and anorexia are problems for many people. But Canada’s most pervasive eating-related problem is obesity. Currently, 35 percent of adult Canadians are overweight, and 25 percent are obese (Public Health Agency of Canada, 2011a). To give you a sense for what this means, “overweight” for a person who is 170 cm (5´6˝) tall would be 73 kg (161 pounds) or more; and obese would be 87 kg (192 pounds) or more. Rates of obesity across the country vary substantially, but are increasing everywhere (see FIGURE 8.16). Rates of unhealthy weight are increasing among children as well. In 1978, only 15 percent of children were overweight or obese—by 2007, 29 percent of adolescents had unhealthy weights (Statistics Canada, 2010). This is a problem that most adolescents do not outgrow: in fact, many continue to gain excess weight (Public Health Agency of Canada, 2009).

FIGURE 8.17 and TABLE 8.1 allow you to compute your BMI, and the odds are that you will not like what you learn. Although BMI is a better predictor of mortality for some people than for others (Romero-Corral et al., 2006; van Dis et al., 2009), most researchers agree that an extremely high BMI is unhealthy. Every year, obesity-related illnesses cost our nation about $4 billion (Eisenberg et al., 2011; Public Health Agency of Canada, 2009) and affected adults appear to die 3 to 7 years earlier than individuals at a healthy weight (Peeters et al., 2003). In addition to these physical risks, obese people tend to be viewed negatively by others, have lower self-esteem, and have a lower quality of life (Hebl & Heatherton, 1997; Kolotkin, Meter, & Williams, 2001). Obese women earn about 7 percent less than their non-obese counterparts (Lempert, 2007), and the stigma of obesity is so powerful that average-weight people are viewed negatively if they even have a relationship with someone who is obese (Hebl & Mannix, 2003). All of this is terribly unfair, of course. As one scientist noted, we need to declare “a war on obesity, not the obese” (Friedman, 2003).

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Obesity has many causes. For example, obesity is highly heritable (Allison et al., 1996) and may have a genetic component, which may explain why a disproportionate amount of the weight gained by Canadians in the past few decades has been gained by those who were already the heaviest (Public Health Agency of Canada, 2011a). Some studies suggest that “obesogenic” toxins in the environment can disrupt the functioning of the endocrine system and predispose people to obesity (Grün & Blumberg, 2006; Newbold et al., 2005), whereas other studies suggest that obesity can be caused by a dearth of “good bacteria” in the gut (Liou et al., 2013). Whatever the cause, obese people are often leptin-resistant (i.e., their brains do not respond to the chemical message that shuts hunger off) and even leptin injections do not seem to help (Friedman & Halaas, 1998; Heymsfield et al., 1999).

Genes, pollutants, and bacteria have all been implicated in the tendency toward obesity. But in most cases the cause of obesity is not such a mystery: We simply eat too much. We eat when we are hungry, of course, but we also eat when we are sad or anxious, or when we are presented with a visually appealing or delicious food, or when everyone else is eating (Herman, Roth, & Polivy, 2003). Sometimes we eat simply because the clock tells us to, which is why people with amnesia will happily eat a second lunch shortly after finishing an unremembered first one (Rozin et al., 1998) (see The Real World: Jeet Jet?). Although all of these factors influence eating in both normal-weight and obese individuals, work by University of Toronto researchers suggests that obese individuals are particularly sensitive to the sensory qualities of food. In other words, obese individuals overeat more when presented with highly palatable (high fat, high sugar) foods than do normal-weight individuals (Herman & Polivy, 2008). Why does this happen? After all, most of us do not breathe ourselves sick or sleep ourselves sick, so why do we eat ourselves sick?

Blame the design. Hundreds of thousands of years ago, the main food-related problem facing our ancestors was starvation, and humans evolved two strategies to avoid it. First, we developed a strong attraction to foods that provide large amounts of energy per bite (in other words, foods that are calorically rich), which is why most of us prefer hamburgers and milkshakes to celery and water. Second, we developed an ability to store excess food energy in the form of fat, which enabled us to eat more than we needed when food was plentiful and then live off our reserves when food was scarce. We are beautifully engineered for a world in which high calorie foods are scarce, and the problem is that we do not live in that world anymore. Instead, we live in a world in which the fatty miracles of modern technology—from chocolate cupcakes to sausage pizzas—are inexpensive and readily available. As two researchers recently wrote, “We evolved on the savannahs of Africa; we now live in Candyland” (Power & Schulkin, 2009). To make matters worse, many of Candyland’s foods tend to be high in saturated fat, which has the paradoxical effect of making the brain less sensitive to some of the chemical messengers that tell us to stop eating (Benoit et al., 2009).

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It is all too easy to overeat and become overweight or obese, and it is all too difficult to reverse course. The human body resists weight loss in two ways. First, when we gain weight, we experience an increase in both the size and the number of fat cells in our bodies (usually in our abdomens if we are male and in our thighs and buttocks if we are female). But when we lose weight, we experience a decrease in the size of our fat cells but no decrease in their number. Once our bodies have added a fat cell, that cell is pretty much there to stay. It may become thinner when we diet, but it is unlikely to die.

Second, our bodies respond to dieting by decreasing our metabolism, which is the rate at which energy is used by the body. When our bodies sense that we are living through a famine (which is what they conclude when we refuse to feed them), they find more efficient ways to turn food into fat: a great trick for our ancestors but a real nuisance for us. Indeed, when rats are overfed, then put on diets, then overfed again and put on diets again, they gain weight faster and lose it more slowly the second time around, which suggests that with each round of dieting, their bodies become increasingly efficient at converting food to fat (Brownell et al., 1986). The bottom line is that avoiding obesity is easier than overcoming it (Casazza et al., 2013).

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And avoiding it is not as difficult as you might think. For instance, just by placing hard-boiled eggs approximately 25 cm away from the more healthful ingredients in a salad bar, researchers reduced the number of eggs that customers ate by about 10 percent (Rozin et al., 2011). Replacing the serving spoons with tongs reduced the amount by about 16 percent. In one study, snacking students ate fewer Pringles when every seventh chip was coloured red, presumably because the colour coding allowed them to keep track of how much they were eating (Geier, Wansink, & Rozin, 2012). In another study, people ate 22 percent less pasta with tomato sauce when they used a white plate instead of a red plate, presumably because the white plate provided a stark contrast that allowed them to see what they were eating (van Ittersum & Wansink, 2012). These and dozens of other studies show that small changes in our environments can prevent big changes in our waistlines.

Food motivates us because it is essential to our survival. But sex is also essential to our survival (at least to the survival of our DNA), which is why evolution has ensured that a desire for sex is wired deep into the brain of almost every one of us. In some ways, that wiring scheme is simple: Glands secrete hormones that travel through the blood to the brain and stimulate sexual desire. But which hormones, which parts of the brain, and what triggers the launch in the first place?

The hormone dihydroepiandosterone (DHEA) seems to be involved in the initial onset of sexual desire. Both boys and girls begin producing this slow-acting hormone at about the age of 6, which may help explain why boys and girls both experience their initial sexual interest at about the age of 10, despite the fact that boys reach puberty much later than girls. Two other hormones have more gender-specific effects. Both males and females produce testosterone and estrogen, but males produce more of the former and females produce more of the latter. As you will learn in the Development chapter, these two hormones are largely responsible for the physical and psychological changes that characterize puberty. But are they also responsible for the waxing and waning of sexual desire in adults?

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The answer appears to be yes—as long as those adults are rats. Testosterone increases the sexual desire of male rats by acting on a particular area of the hypothalamus, and estrogen increases the sexual desire of female rats by acting on a different area of the hypothalamus. Lesions to these areas reduce sexual motivation in the respective genders, and when testosterone or estrogen is applied to these areas, sexual motivation increases. In short, testosterone regulates sexual desire in male rats and estrogen regulates both sexual desire and fertility in female rats.

The story for human beings is far more interesting. The females of most mammalian species (e.g., dogs, cats, and rats) have little or no interest in sex except when their estrogen levels are high, which happens when they are ovulating (i.e., when they are “in estrus” or “in heat”). In other words, estrogen regulates both ovulation and sexual interest in these mammals. But female human beings can be interested in sex at any point in their monthly cycles. Although the level of estrogen in a woman’s body changes dramatically over the course of her monthly menstrual cycle, studies suggest that sexual desire changes little, if at all. Somewhere in the course of our evolution, it seems, women’s sexual interest became independent of their ovulation.

Some theorists have speculated that the advantage of this independence was that it made it more difficult for males to know whether a female was in the fertile phase of her monthly cycle. Male mammals often guard their mates jealously when their mates are ovulating, but go off in search of other females when their mates are not. If a male cannot use his mate’s sexual receptivity to tell when she is ovulating, then he has no choice but to stay around and guard her all the time. For females who are trying to keep their mates at home so that they will contribute to the rearing of children, sexual interest that is continuous and independent of fertility may be an excellent strategy.

If estrogen is not the hormonal basis of women’s sex drives, then what is? Two pieces of evidence suggest that the answer is testosterone—the same hormone that drives male sexuality. First, when women are given testosterone, their sex drives increase. Second, men naturally have more testosterone than women do, and they generally have stronger sex drives. Men are more likely than women to think about sex, have sexual fantasies, seek sex and sexual variety (whether positions or partners), masturbate, want sex at an early point in a relationship, sacrifice other things for sex, have permissive attitudes toward sex, and complain about low sex drive in their partners (Baumeister, Cantanese, & Vohs, 2001). All of this suggests that testosterone may be the hormonal basis of sex drive in both men and women.

Men and women may have different levels of sexual drive, but their physiological responses during sex are fairly similar. Prior to the 1960s, data on human sexual behaviour consisted primarily of people’s answers to questions about their sex lives (and you may have noticed that this is a topic about which people do not always tell the truth). William Masters and Virginia Johnson changed all that by conducting groundbreaking studies in which they actually measured the physical responses of hundreds of volunteers as they masturbated or had sex in the laboratory (Masters & Johnson, 1966). Their work led to a deeper understanding of the human sexual response cycle, which refers to the stages of physiological arousal during sexual activity (see FIGURE 8.18). Human sexual response has four phases:

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Although sex is typically a prerequisite for reproduction, the vast majority of sexual acts are not meant to produce babies. University students, for example, are rarely aiming to get pregnant, but they do have sex because of physical attraction (“The person had beautiful eyes”), as a means to an end (“I wanted to be popular”), to increase emotional connection (“I wanted to communicate at a deeper level”), and to alleviate insecurity (“It was the only way my partner would spend time with me”) (Meston & Buss, 2007). Although men are more likely than women to report having sex for purely physical reasons, TABLE 8.2 shows that men and women do not differ dramatically in their most frequent responses about why they have sex. It is worth noting that not all sex is motivated by reasons like these: About half of university-age women and a quarter of university-age men report having unwanted sexual activity in a dating relationship (O’Sullivan & Allegeier, 1998). We will have much more to say about sexual attraction and relationships in the Social Psychology chapter.

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Survival and reproduction are every animal’s first order of business, so it is no surprise that we are strongly motivated by food and sex. But we are motivated by other things too. We crave kisses of both the chocolate and romantic variety, but we also crave friendship and respect, security and certainty, wisdom and meaning, and a whole lot more. Our psychological motivations can be every bit as powerful as our biological motivations, but they differ in two ways.

First, although we share our biological motivations with most other animals, our psychological motivations are relatively unique. Chimps and rabbits and robins and turtles are all motivated to have sex, but only human beings seem motivated to imbue the act with meaning. Second, although our biological motivations are few—food, sex, oxygen, sleep, and a handful of other things—our psychological motivations are virtually limitless. The things we care about feeling and thinking, knowing and believing, having and being are so numerous and varied that no psychologist has ever been able to make a complete list (Hofmann, Vohs, & Baumeister, 2012). Nonetheless, even if you looked at an incomplete list, you would quickly notice that psychological motivations vary on three key dimensions: extrinsic versus intrinsic, conscious versus unconscious, and approach versus avoidance. Let us examine each of these.

Taking a psychology exam and eating a french fry are different in many ways. One makes you tired and the other makes you chubby, one requires that you move your lips and the other requires that you do not, and so on. But the key difference between these activities is that one is a means to an end and one is an end in itself. An intrinsic motivation is a motivation to take actions that are themselves rewarding. When we eat a french fry because it tastes good, exercise because it feels good, or listen to music because it sounds good, we are intrinsically motivated. These activities do not have a payoff: They are a payoff. Conversely, an extrinsic motivation is a motivation to take actions that lead to reward. When we floss our teeth so we can avoid gum disease (and get dates), when we work hard for money so we can pay our rent (and get dates), and when we take an exam so we can get a university degree (and get money to get dates), we are extrinsically motivated. None of these things directly bring pleasure, but all may lead to pleasure in the long run.

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Extrinsic motivation gets a bad rap. Canadians tend to believe that people should “follow their hearts” and “do what they love,” and we feel sorry for students who choose courses just to please their parents and for parents who choose jobs just to earn a pile of money. But the fact is that our ability to engage in behaviours that are unrewarding in the present because we believe they will bring greater rewards in the future is one of our species’ most significant talents, and no other species can do it quite as well as we can (Gilbert, 2006). In research on the ability to delay gratification (Ayduk et al., 2007; Mischel et al., 2004), people are typically faced with a choice between getting something they want right now (e.g., a scoop of ice cream) or waiting and getting more of what they want later (e.g., two scoops of ice cream). Waiting for ice cream is a lot like taking an exam or flossing: It is not much fun, but you do it because you know you will reap greater rewards in the end. Studies show that 4-year-old children who can delay gratification are judged to be more intelligent and socially competent 10 years later and have higher university admissions test scores when they enter university (Mischel, Shoda, & Rodriguez, 1989). In fact, the ability to delay gratification is a better predictor of a child’s grades in school than is the child’s IQ (Duckworth & Seligman, 2005). Apparently there is something to be said for extrinsic motivation.

There is a lot to be said for intrinsic motivation too (Patall, Cooper, & Robinson, 2008). People work harder when they are intrinsically motivated, they enjoy what they do more, and they do it more creatively. Both kinds of motivation have advantages, which is why many of us try to build lives in which we are both intrinsically and extrinsically motivated by the same activity—lives in which we are paid the big bucks for doing exactly what we like to do best. Who has not fantasized about becoming an artist or an athlete or Kanye West’s personal party planner? Alas, research suggests that it is difficult to get paid for doing what you love and still end up loving what you do because extrinsic rewards can undermine intrinsic interest (Deci, Koestner, & Ryan, 1999; Henderlong & Lepper, 2002). For example, in one study, university students who were intrinsically interested in a puzzle either were paid to complete it or completed it for free, and those who were paid were less likely to play with the puzzle later on (Deci, 1971). In a similar study, children who enjoyed drawing with Magic Markers were either promised or not promised an award for using them, and those who were promised the award were less likely to use the markers later (Lepper, Greene, & Nisbett, 1973). It appears that under some circumstances people take rewards to indicate that an activity is not inherently pleasurable (“If they had to pay me to do that puzzle, it could not have been a very fun one”); thus rewards can cause people to lose their intrinsic motivation.

Just as rewards can undermine intrinsic motivation, punishments can create it. In one study, children who had no intrinsic interest in playing with a toy suddenly gained an interest when the experimenter threatened to punish them if they touched it (Aronson, 1963). University students who had no intrinsic motivation to cheat on a test were more likely to do so if the experimenter explicitly warned against it (Wilson & Lassiter, 1982). Threats can suggest that a forbidden activity is desirable, and they can also have the paradoxical consequence of promoting the very behaviours they are meant to discourage. For example, when a group of daycare centres got fed up with parents who arrived late to pick up their children, some of them instituted a financial penalty for tardiness. As FIGURE 8.19 shows, the financial penalty caused an increase in late arrivals (Gneezy & Rustichini, 2000). Why? Because parents are intrinsically motivated to fetch their kids and they generally do their best to be on time. But when the daycare centres imposed a fine for late arrival, the parents became extrinsically motivated to fetch their children—and because the fine was not particularly large, they decided to pay a small financial penalty in order to leave their children in daycare for an extra hour. When threats and rewards change intrinsic motivation into extrinsic motivation, unexpected consequences can follow.

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When prizewinning artists or scientists are asked to explain their achievements, they typically say things like, “I wanted to liberate colour from form” or “I wanted to cure diabetes.” They almost never say, “I wanted to exceed my father’s accomplishments, thereby proving to my mother that I was worthy of her love.” People clearly have conscious motivations, which are motivations of which people are aware, but they also have unconscious motivations, which are motivations of which people are not aware (Aarts, Custers, & Marien, 2008; Bargh et al., 2001; Hassin, Bargh, & Zimerman, 2009).

For example, psychologists David McClelland and John Atkinson argued that people vary in their need for achievement, which is the motivation to solve worthwhile problems (McClelland et al., 1953). They argued that this basic motivation is unconscious and thus must be measured with special techniques such as the Thematic Apperception Test, which presents people with a series of drawings and asks them to tell stories about them. The amount of “achievement-related imagery” in the person’s story ostensibly reveals the person’s unconscious need for achievement. (You will learn more about these sorts of tests in the Personality chapter.) Although there has been much controversy about the validity and reliability of measures such as these (Lilienfeld, Wood, & Garb, 2000; Tuerlinckx, De Boeck, & Lens, 2002), research shows that a person’s responses on this test reliably predict the person’s behaviour in certain circumstances. For example, they can predict a child’s grades in school (Khalid, 1991). Research also suggests that this motivation can be “primed” in much the same way that thoughts and feelings can be primed. For example, when words such as achievement are presented on a computer screen so rapidly that people cannot consciously perceive them, those people will work especially hard to solve a puzzle (Bargh et al., 2001) and will feel especially unhappy if they fail (Chartrand & Kay, 2006).

What determines whether we are conscious of our motivations? Most actions have more than one motivation, and Robin Vallacher and Daniel Wegner (1985, 1987) have suggested that the ease or difficulty of performing the action determines which of these motivations we will be aware of. When actions are easy (e.g., screwing in a light bulb), we are aware of our most general motivations (e.g., to be helpful), but when actions are difficult (e.g., wrestling with a light bulb that is stuck in its socket), we are aware of our more specific motivations (e.g., to get the threads aligned). Vallacher and Wegner argued that people are usually aware of the general motivations for their behaviour and only become aware of their more specific motivations when they encounter problems. For example, participants in an experiment drank coffee either from a normal mug or from a mug that had a heavy weight attached to the bottom, which made the mug difficult to manipulate. When asked what they were doing, those who were drinking from the normal mug explained that they were “satisfying needs,” whereas those who were drinking from the weighted mug explained that they were “swallowing” (Wegner et al., 1984). The ease with which we can execute an action is one of many factors that determine whether we are or are not conscious of our motivations.

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The poet James Thurber (1956) wrote: “All men should strive to learn before they die/What they are running from, and to, and why.” The hedonic principle describes two conceptually distinct motivations: a motivation to “run to” pleasure and a motivation to “run from” pain. The first it what psychologists call an approach motivation, which is a motivation to experience a positive outcome. The second is an avoidance motivation which is a motivation not to experience a negative outcome. Pleasure is not just the lack of pain, and pain is not just the lack of pleasure. They are independent experiences that occur in different parts of the brain (Davidson et al., 1990; Gray, 1990).

Research suggests that, all else being equal, avoidance motivations tend to be more powerful than approach motivations. Most people will turn down a chance to bet on a coin flip that would pay them $10 if it came up heads but would require them to pay $8 if it came up tails, because they believe that the pain of losing $8 will be more intense than the pleasure of winning $10 (Kahneman & Tversky, 1979). Because people expect losses to have more powerful emotional consequences than equal-size gains, they will take more risks to avoid a loss than to achieve a gain. When participants are told that a disease is expected to kill 600 people and are asked to choose between administering Vaccine A, which will save exactly 200 people, or Vaccine B, which has a one-third chance of saving everybody and a two-thirds chance of saving nobody, about three-quarters of them decide to play it safe and select Vaccine A. Yet, when people are given a choice between Vaccine C, which will allow exactly 400 people to die, or Vaccine D which has a one-third chance of allowing no one to die and a two-thirds chance of allowing everyone to die, about three quarters of them decide to take the gamble and select Vaccine D (Tversky & Kahneman, 1981). Now, if you do the math you will quickly see that Vaccine A and Vaccine C are identical, as are Vaccine B and Vaccine D. The descriptions of the identical vaccines are just two ways of saying the same thing. And yet, when vaccines are described in terms of the number of lives lost (as C and D are) instead of the number of lives gained (as A and B are), most people are ready to take a big risk. It is interesting to note that monkeys show the same tendency (Lakshminarayanan, Chen, & Santos, 2011).

On average, avoidance motivation is stronger than approach motivation, but the relative strength of these two tendencies does differ somewhat from person to person. TABLE 8.3 shows a series of questions that have been used to measure the relative strength of a person’s approach and avoidance tendencies (Carver & White, 1994). Research shows that people who are described by the high-approach items are happier when rewarded than those who are not, and that those who are described by the high-avoidance items are more anxious when threatened than those who are not (Carver, 2006). Just as some people seem to be more responsive to rewards than to punishments (and vice versa), some people tend to think about their behaviour as attempts to get reward rather than to avoid punishment (and vice versa). People who have a promotion focus tend to think in terms of achieving gains whereas people who have a prevention focus tend to think in terms of avoiding losses (Higgins, 1997). In one study, participants were given an anagram task. Some were told that they would be paid $4 for the experiment, but they could earn an extra dollar by finding 90 percent or more of all the possible words. Others were told that they would be paid $5 for the experiment, but they could avoid losing a dollar by not missing more than 10 percent of all the possible words. People who had a promotion focus performed better in the first case than in the second, but people who had a prevention focus performed better in the second case than in the first (Shah, Higgins, & Friedman, 1998). Similarly, people with a high need for achievement tend to be somewhat more motivated by their hope for success, whereas people with a low need for achievement tend to be somewhat more motivated by their fear of failure.

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And what is probably the biggest thing that people want to avoid? All animals strive to stay alive, but only human beings realize that this striving is ultimately in vain and that death is life’s inevitable end. Some psychologists have suggested that the motivation to avoid the anxiety associated with death creates a sense of “existential terror” and that much of our behaviour is merely an attempt to manage it. Terror management theory is a theory about how people respond to knowledge of their own mortality, and it suggests that— a shared set of beliefs about what is good and right and true (Greenberg, Solomon, & Arndt, 2008; Solomon et al., 2004). These beliefs allow people to see themselves as more than mortal animals because they inhabit a world of meaning in which they can achieve symbolic immortality (e.g., by leaving a great legacy or having children) and perhaps even literal immortality (e.g., by being pious and earning a spot in the afterlife). According to this theory, our cultural worldview is a shield that buffers us against the anxiety that the knowledge of our own mortality creates.

Terror management theory gives rise to the mortality-salience hypothesis, which is the prediction that people who are reminded of their own mortality will work to reinforce their cultural worldviews. In the last 20 years, this hypothesis has been supported by nearly 400 studies. The results show that when people are reminded of death (often in very subtle ways, such as by flashing the word “death” for just a few milliseconds in a laboratory, or by stopping people on a street corner that happens to be near a graveyard), they are more likely to praise and reward those who share their cultural worldviews, derogate and punish those who do not, value their spouses and defend their countries, feel disgusted by “animalistic” behaviours such as breast-feeding, and so on. All of these responses are presumably ways of shoring up one’s cultural worldview and thereby defending against the anxiety that reminders of one’s own mortality naturally elicit.

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