Now that you’ve learned about the psychology of emotion and mood, let’s move down a level of analysis to the biology. What systems in the brain enable humans to have a mind filled not only with thoughts, but also feelings? This question has been addressed since the dawn of experimental psychology. We’ll begin by looking back to the late nineteenth century.

JAMES–LANGE THEORY OF EMOTION. In the mid-1880s, a coincidence occurred. Two psychologists working independently, William James and Carl Lange, developed similar, novel ideas about how the brain and body generate emotional experience. The most novel aspect of their ideas concerned the causal relation between emotion and physiological activities in the body.

Intuitively, it seems that emotions cause physiological arousal: You experience an emotion (e.g., fear), which causes your bodily arousal to increase. But James and Lange thought this conception was backwards. The James–Lange theory of emotion proposes that physiological activity causes emotional experience. When something happens—someone insults you; an onrushing car heads your way; your lottery number is chosen (Figure 10.13)—your brain receives information from sensory systems and generates a physiological response in your body. Signals are then sent from your body to your brain, informing the brain that bodily arousal has occurred. Only then, after the brain receives these signals, do you experience an emotion.

The James–Lange theory contends that if you were unaware of the changes in your body, you would not experience an emotion (James, 1884). You would have thoughts—you’d see that you had won the lottery—but they would be cold pieces of information rather than hot feelings.

Years later, two psychologists added a component to the James–Lange formulation. Stanley Schachter and Jerome Singer (1962) suggested that when people experience physiological arousal, they “label” it, that is, they categorize the experience they are having. Social factors influence the labels people use. Different people experiencing the same physiological arousal might use different labels and thus experience different emotions. Schachter and Singer conducted research (detailed in Research Toolkit, Chapter 12) showing that, when in the vicinity of an angry person, people tend to label their own physiological arousal as anger; but if people are with a happy person, they label that same arousal as happiness. Schachter and Singer’s theory attracted much attention in the 1960s and 1970s, but by the 1980s research testing the theory had “yielded disappointing results” (Leventhal & Tomarken, 1986, p. 574) that called into question some of the theory’s assumptions. Other theoretical approaches—such as the appraisal theories discussed earlier in this chapter—became more influential guides to emotion research.

CANNON–BARD THEORY OF EMOTION. In the 1920s, two scientists, Walter Cannon and Philip Bard, developed a major alternative to the James–Lange theory. It is known as—no surprise here—the Cannon–Bard theory of emotion.

According to the Cannon–Bard theory of emotion, information about emotionally arousing events travels from the sensory system to structures in the brain’s limbic system (especially the thalamus; Cannon, 1927). Signals sent from the limbic system, in turn, accomplish two functions simultaneously: (1) They produce the experience of emotion, and (2) they generate the bodily changes (in physiological arousal, facial expression, and body posture) that are distinctive of emotion (see Figure 10.12). Unlike the James–Lange theory, then, in the Cannon–Bard theory bodily arousal does not precede, and is not the cause of, emotion.

Cannon and Bard rejected the James–Lange theory based on evidence unavailable to James and Lange back in the 1880s. By the 1920s, researchers had performed experimental surgeries with animals in which they cut the nervous system connections from the heart, lungs, stomach, and other organs to the brain. After the surgeries, the animals appeared just as emotional as they were previously (Cannon, 1927), a finding inconsistent with the expectations of the James–Lange theory.

CONTEMPORARY STATUS OF THE CLASSIC THEORIES. James, Lange, Cannon, and Bard’s contributions were significant in their days. Those days, however, were long ago. Contemporary advances highlight two main limitations of both the James–Lange and Cannon–Bard approaches.

Both theories tried to identify the way in which emotion is generated. But there may be no one way in which emotion is generated. Some emotions may arise through one type of psychological process, whereas others arise through some other process. Contemporary researchers recognize that multiple processes contribute to emotional experience (LeDoux, 1994; Pessoa & Adolphs, 2010).

A second limitation is that both theories depict a step-by-step sequence of events. One event occurs in the brain, and then another, and then another. Contemporary research on the brain, however, shows that large numbers of brain events occur simultaneously. Networks of neurons provide continuous communication among multiple brain systems that are active simultaneously (Sporns, 2011). Developments in psychological science as a whole have therefore moved the study of emotion beyond the contributions of the James–Lange and Cannon–Bard theories.

One region of brain that is key to emotional life is the limbic system. The limbic system is a set of brain structures residing below the cortex and above the brain stem (see Chapter 3). Limbic system structures are involved in the processing of rewarding, punishing, and threatening stimuli whose presence generates emotional reactions.

THE AMYGDALA. A structure within the limbic system that is particularly important to emotional response is the amygdala (Gallagher & Chiba, 1996; Hamann, 2011; Figure 10.14). The amygdala plays multiple roles in emotional experience and is particularly active in processing events that have the power to generate negative emotions such as fear.

One function of the amygdala is to detect stimuli that might be threatening to the organism. These stimuli often involve novelty; in general, familiar people and places are less threatening than novel ones. Brain-imaging studies show that the amygdala responds particularly strongly when people see images of other people who are novel, that is, who are strangers to them (Balderston, Schultz, & Helmstetter, 2011).

Research on people with damage to the amygdala provides further evidence of its role in processing emotional information. Such people can recognize the identity of others but have difficulty identifying emotions expressed in others’ faces (Adolphs et al., 1994).

THE CASE OF SM. The amygdala plays a role not only in recognizing threatening stimuli, but also in generating the emotion of fear. Evidence of this comes from a remarkable case—that of SM.

SM is a woman who has experienced bilateral amygdala damage, that is, damage to the amygdala on both the left and right sides of her brain. To learn about her experience of fear, experimenters (Feinstein et al., 2011) exposed her to stimuli that would scare almost anybody: handling a snake and a tarantula in a pet store; going to a haunted house; watching a scary movie. Other people found these stimuli quite scary—but not SM. When exposed to these stimuli, she showed no fear at all! Instead, SM wanted to play with the snakes and tarantulas, even after a store employee said they were dangerous. She smiled and laughed her way through the haunted house, while others screamed with fear. The scary movie—film clips depicting torture, mutilation, and murder—elicited no fear in SM.

SM was not emotionless, however. When she saw the snakes and tarantulas, she showed interest. When she saw funny movies, she laughed. The deficit produced by her amygdala damage was highly specific: It eliminated only one emotion, fear. When researchers asked her to complete surveys of her emotions during daily life, she reported a full range of emotion—sadness, happiness, disgust, anger—except for fear (Feinstein et al., 2011).

Does SM’s case mean that the amygdala, by itself, produces the emotion of fear? No, not at all. Consider this analogy. If the thermostat in your home is damaged, you can’t control your home’s temperature. But the thermostat, by itself, does not produce the hot or cool air that maintains a home’s temperature. It’s just one component in a large system of parts. Analogously, if the amygdala in your brain is damaged, your emotional life is altered. Yet the amygdala is just one component in a large system of brain structures involved in emotional experience.

If you think back to what you learned earlier in this chapter, you can figure out for yourself that emotion must involve brain structures beyond the amygdala. You learned that the psychology of emotion includes the following:

In addition, you saw that these psychological components of emotion are highly coordinated. Your thoughts, feelings, facial expressions, and motives are synchronized. If you think you were insulted, you immediately feel angry; anger is immediately displayed on your face; and you immediately are motivated to act against the person who insulted you.

EMOTION AND INTERCONNECTED BRAIN SYSTEMS. These psychological facts have biological implications. The biological systems of emotion must be capable of explaining the psychological phenomena that you learned about. This means that the biology of emotion must include the following:

EVIDENCE FROM BRAIN-IMAGING METHODS. In recent years, psychologists have employed brain-imaging methods to discover the neural systems involved in emotional experience. Large numbers of studies have visually identified systems within the brain that are most active when people experience emotions. A team of researchers (Kober et al., 2008) has reviewed evidence from more than 150 such studies, in order to obtain an overall depiction of the brain structures involved.

Their results show that a complex network of brain structures contributes to emotion (Figure 10.15). Specifically, six interconnected groups of neural systems are involved. Two of them are in the limbic system, and the others are in the brain’s cortex. The latter include regions of the cortex that play a role in paying attention to stimuli, processing visual information, controlling motor movement, and planning one’s actions.

Furthermore, just as you’d expect from what you learned about the psychology of emotion, these brain systems of emotion were found to be highly interconnected. Activation in one region of the brain tended to co-occur with activation in another and another (Figure 10.15).

Research at a biological level of analysis, then, complements findings at a psychological level of analysis. Psychologically, emotions consist of a number of distinct components. These include both high-level thinking processes through which people determine the meaning of events and low-level, “gut” feelings that add power to emotional experience. Biologically, emotions activate a number of distinct components in the brain systems. These include both low-level mechanisms in the brain’s limbic system and high-level neural networks in the cortex (Pessoa & Adolphs, 2010).