This chapter explores motivation, including its influences on hunger and weight regulation, sex, affiliation, work and achievement; and motivational conflict. It also explores emotions, the positive or negative affects that often result when our goals are gratified, threatened, or thwarted.

Motivation is a process that influences the direction, persistence, and vigor of goal-directed behavior. Instinct theories of motivation, prominent a century ago, soon gave way to other models. The body's biological systems are balanced to ensure survival. Many behaviors may be motivated by the need to return to homeostasis, the state of internal equilibrium. Drive theory assumed that physiological disruptions to homeostasis produce drives to reduce the tension caused by the disruptions. Incentive theories, in contrast, focus attention on external stimuli as motivators of behavior. According to expectancy x value theory, goal-directed behavior is jointly determined by the person's expectation that a behavior will lead to a goal and the value that the person places on the goal. Many cognitive theorists also distinguish between extrinsic motivation (motivation produced by the desire to obtain rewards and to avoid punishments), and intrinsic motivation (performing an activity for its own sake). Psychodynamic theorists suggest that unconscious motives, thoughts, and inner tensions are an important motivator of behavior. Humanistic theorists such as Maslow stress need hierarchies, particularly the need to fulfill our potential, or self-actualization.

The body monitors its energy supplies, and this information interacts with other signals to regulate food intake. Homeostatic mechanisms are designed to prevent us from running low on energy. Some researchers believe that there is a set point around which body weight is regulated. As we eat, stomach and intestinal distention act as satiety signals, and peptides such as cholecystokinin stimulate brain receptors to decrease eating. Fat cells regulate food intake and weight over the long term by secreting leptin. Many parts of the brain also influence eating. Early studies indicated that the lateral hypothalamus seemed to be a "hunger-on" center. The ventromedial hypothalamus seemed to be a "hunger-off" center. However, modern research indicates that it is not that simple. Various neural circuits within the hypothalamus regulate food intake. Many of these pathways involve the paraventricular nucleus. Eating is also affected by psychological factors. Eating is positively reinforced by good taste and variety, and is negatively reinforced by hunger reduction. Beliefs, attitudes, habits, and psychological needs also affect food intake. Studies of obesity have indicated a strong genetic component. The eating disorders anorexia nervosa, where people severely restrict their food intake, and bulimia nervosa, where people binge and then induce purging, pose serious health problems.

People engage in sex for a variety of reasons, the primary one being pleasure. The typical sexual response cycle consists of four phases: excitement, plateau, orgasm, and resolution. Secretions of gonadotropins from the pituitary glands affect the rate at which the sex organs secrete androgens and estrogens. These sex hormones have both organizational effects that direct the development of sex organs, and activational effects that stimulate sexual desire and behavior. Psychological factors like sexual fantasy can also trigger sexual arousal. The psychological meaning of sex depends strongly on cultural contexts and learning. Cultural norms influence what stimuli are sexually arousing and what sexual behaviors occur. Studies of pornography suggest that violent pornographic films seem to increase, at least temporarily, men's aggression toward women and may promote rape myths. Sexual orientation may have three dimensions: self-identity, sexual attraction, and actual sexual behavior. Many researchers believe in a genetic basis for sexual orientation. Altering prenatal sex hormones can also influence sexual orientation. Studies have also suggested an environmental component. These findings, however, are correlational.

We affiliate with others to gain positive stimulation, emotional support, attention, and opportunities for social comparison. Initial attraction often occurs through mere exposure and matching with others of similar physical attractiveness. Men and women have somewhat different mate preferences. Evolutionary theories such as the sexual strategies theory argue that the difference is due to evolutionary forces, while theories such as social structure theory stress environmental forces. Cross-cultural studies have found that men tend to value younger, attractive women (signifying reproductive potential) while women tend to value men with high earning potential.

The need for achievement is influenced by both motive for success and fear of failure. Individual perceptions, family influences, and cultural influences all influence achievement motivation. Achievement goals can be categorized as mastery goals, performance-approach goals, and performance-avoidance goals. People work for a number of different reasons, including money, personal accomplishment, opportunities for mastery, growth, and satisfying interpersonal relationships. Industrial-organizational (I/O) psychology is concerned with behavior in the workplace. I/O studies have supported the use of job enrichment programs to increase people's intrinsic motivation to work. Employers have also utilized incentive programs and goal-setting programs to increase worker motivation.

Approach-approach, avoidance-avoidance, and approach-avoidance conflicts influence motivation through having to choose between two attractive alternatives, two unattractive alternatives, and attractive and unattractive aspects of the same goal respectively.

Emotions are positive or negative affect states consisting of a pattern of cognitive, physiological, and behavioral reactions to events that have relevance to important goals or motives. Emotions have important adaptive functions. Negative emotions may help us to narrow attention and actions to deal with a threatening situation. Positive emotions may help us to broaden our thinking and behavior so that we explore, consider new ideas, try out new ways to achieve goals, play, and savor what we have. The emotions we have share four common features: they are responses to stimuli, they involve cognitive appraisal, they involve physiological responses, and they include behavioral tendencies. Innate biological factors and learning each play a role in determining the arousal properties of stimuli. Appraisal processes relate to what we think is desirable and undesirable. Culture can also affect appraisal.

Biological factors also play an important role in emotions. Subcortical structures such as the hypothalamus, amygdala, and other limbic system structures are particularly involved. The ability to regulate emotion depends heavily on the prefrontal cortex. Joseph LeDoux has discovered that the thalamus sends messages along two independent neural pathways: to the cortex and to the amygdala. This dual system means that emotional responses can occur both through cortex interpretation and through a more primitive system through the amygdala, which is likely important for survival. Left-hemisphere activation may underlie certain positive emotions, and right-hemisphere activation might influence negative ones. Such activation may also underlie subjective well-being.

Autonomic and hormonal processes may also influence emotions. Some basic emotions, such as anger and fear, show distinctive autonomic processes. The behavioral component of emotions involves expressive behaviors, or emotional displays. Modern evolutionary theorists stress the adaptive value of such displays and suggest that some fundamental emotional patterns may be innate. Studies by Paul Ekman and his coworkers of emotional expressions have shown a wide degree of cross-cultural agreement in evaluations of expressions. The studies also show that different parts of the face provide the best clues for certain emotions and that women are generally more accurate judges of emotional expression. Nevertheless, different cultures have different display rules for emotions.

According to the James-Lange theory, which lives on as the somatic theory of emotion, bodily reactions produce perceptions of emotional states. The Cannon-Bard theory proposed that physiological arousal and the subjective experience of emotion are independent responses to an emotion-arousing stimulus. The facial-feedback hypothesis, consistent with the James-Lange theory, suggests that feedback to the brain from facial muscles produces emotions. In Schachter's two-factor theory, physiological arousal tells us how strongly we feel an emotion, and situational cues provide the information we need to cognitively label the arousal and the emotion.

The positive psychology movement examines factors related to happiness, or subjective well-being (SWB). Research suggests people can be happier if they (1) develop and maintain close relationships, (2) help others, (3) seek meaning and challenge in work, (4) set and work toward meaningful personal goals, (5) make time for enjoyable activities, (6) take care of themselves physically, (7) are open to new experiences, and (8) cultivate optimism and appreciation for what they have.