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Liking and Wanting

Wanting is a motivational state that occurs prior to receiving a reward, while liking is a motivational state that occurs after reward receipt (Berridge & Robinson, 1995). Wanting and liking typically go hand-in-hand, but the two motivational experiences actually have different brain mechanisms (Berridge & Robinson, 1998; Dickinson & Balleine, 2002).

Liking is, essentially, hedonic pleasure, and it motivates behavior by acting as information when people compare competing choices. Wanting can occur without liking, as sometimes people can want what they do not necessarily like. Wanting without liking, however, is only partial reward that occurs without sensory pleasure (e.g., nicotine addiction). For the full experience of reward, wanting and liking need to occur together.

HORMONES IN THE BODY

While many hormones underlie motivation, emotion, and behavior, three are integral to motivation and emotion: cortisol, testosterone, and oxytocin.

Cortisol is the so-called “stress hormone.” When exposed to a stressor, a person’s hypothalamic–pituitary–adrenocortical system reacts, including the release of the hor-mone cortisol from the adrenal gland. Cortisol activation is most likely in the face of social-evaluative threats, such as the presence of an evaluative audience during the per-formance of a task (e.g., public speaking) and almost any effort to negotiate one’s social status when it is in doubt or challenged (Dickerson & Kemeny, 2004). Its rise in response to stress is important because elevated cortisol has been associated with poor intellec-tual functioning, negative affect, and poor health outcomes (Brown & Suppes, 1998;

Kirschbaum, Wolf, May, Wippich, & Hellhammer, 1996).

The steroid hormone testosterone is associated with high sexual motivation (Bancroft, 2002). Testosterone underlies the mating effort— the investment of time and energy into same-sex competition and mate-seeking behavior (Ellison, 2001). As with mate competi-tion, testosterone encourages competition more generally. For instance, high testosterone levels help Wall Street stockbrokers make more money (compete better) during the day’s trading. As a hormone, testosterone is responsive to changing environmental conditions, such that married men have lower testosterone than do unmarried men (Gray, Chapman, Burnham, Lipson, & Ellison, 2004), and men in committed relationships have lower testosterone than men not in relationships (Burnham et al., 2003). From this line of rea-soning, it makes sense that high levels of testosterone are associated with having affairs, while low levels are associated with better parenting (e.g., higher nurturance).

Oxytocin, known as the bonding hormone, is often referred to as the “tend and befriend stress response” that helps explain why people seek counsel and confide in friends during the stressful events in their lives. Oxytocin is a particularly important hormone-based source of motivation for women, as it motivates a third possible —and highly effective —coping response beyond just “fight or flight” —namely, seeking the counsel, support, and nurturance of others during times of stress.

THE WORLD IN WHICH THE BRAIN LIVES

Brain research generally relies on artificial methods of stimulating the brain’s motivational and emotional states (as depicted in Figures 3.4, 3.6, and 3.10). Such research generally

BOX 3 How and Why Antidepressant Drugs Alleviate Depression

Question: Why is this information important?

Answer: To understand how antidepression drugs work to alleviate depression.

Each of us wages a lifelong struggle against depres-sion, and about 1 in 10 suffer from clinical depression.

Aversive, stressful events inevitably come our way, as experiences of loss, rejection, criticism, financial woe, failure, overscheduling, neglect, hassle, and dis-appointment represent the flow of human experience.

These events affect our ongoing bodily biochemistry and, when they deplete our biochemical resources, can leave us vulnerable to depression. Most of us cope well most of the time, but each of us nonetheless remains vulnerable to the feeling that we just might crack under the barrage of stress and disappointment.

Depression is a complex psychological disorder associated with two main types of responsiveness to the environment. On the one hand, exposures to dis-appointment and uncontrollable stress make demands on the limbic system that gradually robs us of brain serotonin. Serotonin deficiency leaves us vulnera-ble to depression (Kramer, 1993; Weiss & Simson, 1985). The popular antidepressant drugs (e.g., Prozac, Zoloft, Paxil, Cymbalta, Lexapro) are SSRIs, or selec-tive serotonin-reuptake inhibitors. These antidepres-sants work on the premise that depression is caused by low serotonin turnover in the serotonin pathways.

Even when highly stressed, brain serotonin remains in these pathways, but it is not readily available for usage. During stressful life events, serotonin is released into the synapse but it also quickly returns (experiences reuptake) back to the sending neuron.

To reverse depression, the antidepressant needs to increase brain–serotonin transmission and turnover, and it does so by preventing reuptake and making greater use of the available serotonin (rather than allowing it to be restored via reuptake). The antide-pressant acts to restore serotonin release and activity back to normal.

The second type of depression is associated with a diminished capacity to experience pleasure and pos-itive feelings. Low dopamine levels can leave the person vulnerable to apathy, boredom, poor concen-tration, and little initiative to embrace the day. In con-trast, dopamine release and activity within the brain’s dopamine pathway generates good feelings, positive affect, and essentially leaves the person primed to a positive mood (Ashby et al., 1999). Some antidepres-sants work by increasing dopamine receptors’ respon-siveness, thereby restoring the person’s capacity to experience pleasure and positive emotions (Willner, Ahlenius, Muscat, & Scheel-Kruger, 1991). Drugs of abuse (e.g., cocaine, amphetamines) also work by enhancing dopamine activity in the brain. Cocaine, for instance, works by inhibiting dopamine reuptake (Di Chiara, Acquas, & Carboni, 1992).

Overall, depression has two faces: serotonin defi-ciency that leaves the person less able to cope with life’s stress and dopamine deficiency that leaves the person less ready to anticipate and experience pleasure.

Knowing this, pharmacological researchers can design drugs to help as each of us wages our lifelong strug-gle against depression. In practice, developing an anti-depressant drug is difficult because serotonin-supplying antidepressant drugs not only supply serotonin, but they also “hijack” dopamine pathways to some degree and inadvertently blunt feelings of love, romance, and attachment to others (Zhou et al., 2005). Few people taking antidepressants, for instance, have the experi-ence of falling in love. Partly for this reason, several antidepressant drugs currently in development work by decreasing cortisol (the stress hormone) rather than by increasing serotonin. What is exciting (and promising) is that both classes of drugs work, in part, by affect-ing neurogenesis—serotonin increases new nerve cell growth whereas cortisol decreases new nerve cell growth. In some sense, sprouting new nerve growth is the key biological event that keeps depression at bay.

applies a mild electrical current or chemical agent (drug, neurotransmitter, hormone) to a particular brain site to investigate the role that brain structure plays in motivation. This research allows us to collect the sort of information summarized in Table 3.1, such that we know that the medial forebrain bundle is a pleasure center, the amygdala is a fear center, and so on for each particular brain structure. What these research studies do not

The World in Which the Brain Lives 69 tell us, however, is how day-to-day events in the social world naturally stimulate these brain structures to generate the motivation and emotion we use to adapt to the world around us.

Motivation Cannot Be Separated from the Social Context in Which It Is Embedded People have needs, such as those for survival, growth, and well-being. And the social world offers an environment full of supports for and threats against these needs. For instance, the weather can be warm and support our well-being, or it can be too cold or too hot and threaten our well-being. A relationship can be warm and nurturing, or it can be cruel and neglecting. The brain is the means by which we generate the motivational and emotional states we need to adapt optimally to the physical and social world around us. So, to answer questions such as “How can I motivate myself?” and “How can I motivate others?”, we can use our knowledge of the brain to create social environments that function as natural stimulants to the motivated and emotional brain.

For instance, consider the natural stimulants of motivational brain structures dis-cussed throughout the chapter. Food deprivation explained the rise and fall of ghrelin and leptin hormones. Signals of reward and unexpectedly positive events —a pleasant smell, a gift, a humorous movie —explained dopamine release. Alarm clocks and roller-coaster rides aroused the reticular formation. Threats such as predators, bullies, enemies, and hos-tile opponents stimulated the amygdala. Disappointment, failure, punishing toothaches, novelty, and separation from our loved ones stimulated the “not-okay” mode of the hip-pocampus, just as successfully coping with these aversive events stimulated the release of endorphins and a pleasurable return to the “okay” mode. And drugs such as cocaine and amphetamines stimulated pleasure centers in the limbic system. What all these examples illustrate is that environmental events in the social world act as the natural stimulators of the brain’s basic motivational processes (e.g., pleasure, anxiety, arousal, and mood).

So, while brain researchers conduct studies to artificially stimulate and change ani-mals’ motivational states, researchers in the schools, workplace, clinics, and athletic fields know that the individual’s motivational state cannot be separated from the social context in which it is embedded. Though we know how the brain generates its motivational states, we also know that the motivation experienced by students, athletes, patients, children, and workers is inherently intertwined with the social context provided to them by their teachers, coaches, doctors, parents, and workplace supervisors. This chapter presented the fundamentals of the motivated and emotional brain. The chapters to come present how the social context provides natural stimulations that stir the motivated and emotional brain into action.

We Are Not Always Consciously Aware of the Motivational Basis of Our Behavior

The study of the motivated and emotional brain makes salient one final point about human motivation, namely that we are not always consciously aware of the motivational basis of our behavior. Motives vary in how accessible they are to consciousness and to verbal report. Some motives originate in language structures and the cerebral cortex (e.g., goals) and are thus readily available to our conscious awareness (e.g., “I have a goal to sell three insurance policies today.”). For these motives, if you ask a person why he or she selected

that particular goal, the person more often than not can confidently list the rational and logical reasons for doing so. Despite the fact that people can frequently provide prompt and satisfying motives to explain their behaviors, some motivated acts are impulsive and the reasons we do what we do are not clear, even to us. Some motives have their origins in nonlanguage structures and are thus much less available to conscious awareness and to verbal report. Not many people, for instance, say they feel hungry because of low leptin in the bloodstream. These are the motives that originate in the emotional limbic structures rather than in the language-based cerebral cortex. These motives exist in our awareness only as urges, appetites, and wants.

Many experimental findings can be offered to make the point that motives can and do originate in the unconscious limbic structures rather than in the conscious cerebral cortex. Consider that people who feel good after receiving an unexpected gift are more likely to help a stranger in need than are people in neutral moods (Isen, 1987). People are more sociable on a sunny day than they are on a cloudy day (Kraut & Johnston, 1979).

People commit more acts of violence in the summer months than at other times of the year (Anderson, 1989). Major league baseball pitchers are more likely to intentionally hit batters on the opposing team when the temperature is hot rather than when the temperature is cold or moderate (Reifman, Larrick, & Fein, 1991). In each of these examples, the person is not consciously aware of why he or she committed the social or antisocial act.

Few people, for instance, would say they helped a stranger because they felt good, and few would say they commit murder or throw baseballs at the heads of opponents because of the hot temperature. Still, these are conditions that cause motivations. The brief lesson behind these empirical examples is that the motives, cravings, appetites, desires, moods, needs, and emotions that regulate human behavior are not always immediately obvious or consciously accesible.

CONCLUSION

A half century ago, a young neuroscientist, James Olds, was doing his routine laboratory work by implanting an electrode in the brain stem of a rat. One fateful day, the electrode Olds was implanting accidentally bent and ended up in another part of the brain. Not knowing that the electrode had bent, Olds stimulated the rat and watched with amazement as the rat suddenly repeated its behavior and continued enthusiastically to return to the part of the cage where the earlier electrical brain stimulation occurred. The rat liked the stimulation. In fact, the rat really liked the stimulation. Follow-up studies showed that animals given the opportunity to stimulate themselves would do so (by pressing a lever that would send an electrical current to their own brain; see Figure 3.10). Olds’s research would soon confirm that he had accidentally discovered a pleasure center in the rat’s brain (Olds & Milner, 1954).

Researchers soon began to intentionally bend their electric probes as they started the field of neuroscience down its path toward understanding the neural basis of plea-sure and aversion (Hoebel, 1976; Olds & Fobes, 1981; Wise & Bozarth, 1984). First, specific brain structures such as the septal area, hypothalamus, mammillary bodies, and medial forebrain bundle were identified as important to the motivational process (Olds

& Olds, 1963). Then, the consensus converged on the idea that motivational experiences (e.g., pleasure, aversion) were not localized in any one specific brain structure but were

Summary 71 instead coordinated among many brain areas known as neural circuits, such as those found in the limbic system (Isaacson, 1982). Later research extended the study of brain circuits to include the study of chemical circuits or pathways in which various brain sites communicated through one specific neurotransmitter, such as dopamine. These efforts to map out the motivational significance of specific brain structures, neural circuits, and chemical pathways allowed researchers to understand how the brain creates, maintains, and regulates motivation, emotion, and mood. In the chapters to come, the emphasis will switch to the motivational significance of external events, relationships, and com-plex environments such as classrooms. Hence, the contents of this chapter allow us to understand the biology and the neuroscience underlying and supporting the motivational states yet to be discussed.

SUMMARY

When thinking about the brain, most people focus their attention on its cognitive and intellectual functions, including thinking, learning, and decision making. But the brain is not only an agent of thought, it is further an agent of motivation and emotion. It is the brain that generates cravings, appetites, needs, desires, pleasure, and the full range of the emotions. To illustrate how the brain creates, maintains, and regulates motivational and emotional states, consider the following three principles that organize how motivational researchers study the brain. First, specific brain structures (e.g., hypothalamus, amygdala) generate specific motivational states. Second, biochemical agents (e.g., neurotransmitters, hormones) stimulate these brain structures. Third, day-to-day events (e.g., a letter from a friend, dense traffic) are the events in our lives that stir brain-stimulating biochemical agents into action.

Looking inside the brain with techniques like surgery and fMRI (functional magnetic reso-nance imaging) yields a map of the anatomical location of several key brain structures related to motivation and emotion. The brain structures associated with positive feelings and approach motivation include the hypothalamus, medial forebrain bundle, septal area, orbitofrontal cortex, nucleus accumbens, medial prefrontal cortex, and left prefrontal cortex. The brain structures asso-ciated with negative feelings and avoidance motivation include the amygdala, hippocampus, and right prefrontal cortex. For instance, stimulation of the medial forebrain bundle leads people to report positive feelings and animals to behave in ways as if they had just received positive rein-forcement. Stimulation of the amygdala leads people to report negative feelings and to show the behavioral activation associated with a coordinated fear response.

Neurotransmitters act as chemical messengers within the brain, and a “neurotransmitter path-way” refers to a cluster of neurons that communicate with one another by using one particular neurotransmitter. The four motivationally relevant neurotransmitter pathways are dopamine, sero-tonin, norepinephrine, and endorphin. The dopamine pathway is particularly important as its primary motivational function is to generate positive feelings and it explains the biology of incentives, reward, motivated action, addictions, and liking versus wanting. Upon encountering motivationally significant events, the brain detects some events as “biologically significant” and releases dopamine that generates good feelings and stimulates goal-directed approach behavior.

Furthermore, the pleasurable experience of dopamine allows the person to learn which environ-mental events are associated with pleasure and approach and which other environenviron-mental events are associated with stress and withdrawal. Dopamine release is therefore a neural mechanism by which motivation is translated into action. Like neurotransmitters, hormones underlie motivation and action, including cortisol (the stress hormone), testosterone (the mating hormone), and oxytocin (the tend-and-befriend stress hormone).

The purpose of this chapter was not to overwhelm the reader with neurophysiological ter-minology. Instead, it was to lift the veil of mystery of just what the brain does to generate and maintain motivational and emotional states. The final two points of emphasis were that (1) moti-vation cannot be separated from the social context in which it is embedded and (2) we are not always consciously aware of the motivational basis of our behavior. In the remaining chapters the emphasis switches to understanding how external events, relationships, and complex environments such as classrooms stir the brain to experience motivation and emotion.