37.2 Embodied Emotion

Whether you are falling in love or grieving a death, you need little convincing that emotions involve the body. Feeling without a body is like breathing without lungs. Some physical responses are easy to notice. Other emotional responses we experience without awareness.

Emotions and the Autonomic Nervous System

37-3 What is the link between emotional arousal and the autonomic nervous system? How does arousal affect performance?

“Fear lends wings to his feet.”

Virgil, Aeneid, 19 b.c.e.

In a crisis, the sympathetic division of your autonomic nervous system (ANS) mobilizes your body for action (FIGURE 37.3). It directs your adrenal glands to release the stress hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). To provide energy, your liver pours extra sugar into your bloodstream. To help burn the sugar, your respiration increases to supply needed oxygen. Your heart rate and blood pressure increase. Your digestion slows, diverting blood from your internal organs to your muscles. With blood sugar driven into the large muscles, running becomes easier. Your pupils dilate, letting in more light. To cool your stirred-up body, you perspire. If wounded, your blood would clot more quickly.

Figure 37.3
Emotional arousal Like a crisis control center, the autonomic nervous system arouses the body in a crisis and calms it when danger passes.

According to the Yerkes-Dodson law, arousal affects performance in different ways, depending on the task, with moderate arousal leading to optimal performance (Yerkes & Dodson, 1908). When taking an exam, it pays to be somewhat aroused—alert but not trembling with nervousness. Too little arousal (as when sleepy) can be disruptive. And, as we’ll see, prolonged high arousal can tax the body.

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When the crisis passes, the parasympathetic division of your ANS gradually calms your body, as stress hormones slowly leave your bloodstream. After your next crisis, think of this: Without any conscious effort, your body’s response to danger is wonderfully coordinated and adaptive—preparing you to fight or flee. So, do the different emotions have distinct arousal fingerprints?

The Physiology of Emotions

37-4 Do different emotions activate different physiological and brain-pattern responses?

Imagine conducting an experiment measuring the physiological responses of emotion. In each of four rooms, you have someone watching a movie: In the first, the person is viewing a horror show; in the second, an anger-provoking film; in the third, a sexually arousing film; in the fourth, a boring film. From the control center, you monitor each person’s perspiration, breathing, and heart rate. Could you tell who is frightened? Who is angry? Who is sexually aroused? Who is bored?

Emotional arousal Elated excitement and panicky fear involve similar physiological arousal. That allows us to flip rapidly between the two emotions.

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With training, you could probably pick out the bored viewer. But discerning physiological differences among fear, anger, and sexual arousal is much more difficult (Barrett, 2006). Different emotions can share common biological signatures.

A single brain region can also serve as the seat of seemingly different emotions. Consider the broad emotional portfolio of the insula, a neural center deep inside the brain. The insula is activated when we experience various negative social emotions, such as lust, pride, and disgust. In brain scans, it becomes active when people bite into some disgusting food, smell the same disgusting food, think about biting into a disgusting cockroach, or feel moral disgust over a sleazy business exploiting a saintly widow (Sapolsky, 2010). Similar multitasking regions are found in other brains areas.

Yet our emotions—such as sexual arousal, fear, anger, and disgust—feel different to us, and they often look different to others. We may appear “paralyzed with fear” or “ready to explode.” Fear and joy prompt similar increased heart rate, but they stimulate different facial muscles. During fear, your brow muscles tense. During joy, muscles in your cheeks and under your eyes pull into a smile (Witvliet & Vrana, 1995).

“No one ever told me that grief felt so much like fear. I am not afraid, but the sensation is like being afraid. The same fluttering in the stomach, the same restlessness, the yawning. I keep on swallowing.”

C. S. Lewis, A Grief Observed, 1961

Some of our emotions also differ in their brain circuits (Panksepp, 2007). Observers watching fearful faces showed more amygdala activity than did other observers who watched angry faces (Whalen et al., 2001). Brain scans and EEG recordings show that emotions also activate different areas of the brain’s cortex. When you experience negative emotions such as disgust, your right prefrontal cortex tends to be more active than the left. Depression-prone people, and those with generally negative personalities, have also shown more right frontal lobe activity (Harmon-Jones et al., 2002).

Positive moods tend to trigger more left frontal lobe activity. People with positive personalities—exuberant infants and alert, enthusiastic, energized, and persistently goal-directed adults—have also shown more activity in the left frontal lobe than in the right (Davidson, 2000, 2003; Urry et al., 2004). Indeed, the more a person’s baseline frontal lobe activity tilts left—or is made to tilt left by perceptual activity—the more upbeat the person typically is (Drake & Myers, 2006).

To sum up, we can’t easily see differences in emotions from tracking heart rate, breathing, and perspiration. But facial expressions and brain activity can vary with the emotion. So, do we, like Pinocchio, give off telltale signs when we lie? For more on that question, see Thinking Critically About: Lie Detection.

RETRIEVAL PRACTICE

  • How do the two divisions of the autonomic nervous system affect our emotional responses?

The sympathetic division of the ANS arouses us for more intense experiences of emotion, pumping out the stress hormones epinephrine and norepinephrine to prepare our body for fight or flight. The parasympathetic division of the ANS takes over when a crisis passes, restoring our body to a calm physiological and emotional state.

THINKING  CRITICALLY  ABOUT

THINKING CRITICALLY ABOUT: Lie Detection

37-5 How effective are polygraphs in using body states to detect lies?

Can a lie detector—a polygraph—reveal lies? Polygraphs don’t literally detect lies. Instead, they measure emotion-linked changes in breathing, cardiovascular activity, and perspiration. If you were taking this test, an examiner would monitor these responses as you answered questions. She might ask, “In the last 20 years, have you ever taken something that didn’t belong to you?” This is a control question, aimed at making everyone a little nervous. If you lied and said “No!” (as many people do) the polygraph would detect arousal. This response will establish a baseline, a useful comparison for your responses to critical questions (“Did you ever steal anything from your previous employer?”). If your responses to critical questions are weaker than to control questions, the examiner will infer you are telling the truth.

Critics point out two problems: First, our physiological arousal is much the same from one emotion to another. Anxiety, irritation, and guilt all prompt similar physiological reactivity. Second, many innocent people respond with heightened tension to the accusations implied by the critical questions (FIGURE 37.4). Many rape victims, for example, have “failed” these tests when reacting emotionally but truthfully (Lykken, 1991).

Figure 37.4
How often do lie detection tests lie? In one study, polygraph experts interpreted the polygraph data of 100 people who had been suspects in theft crimes (Klein-muntz & Szucko, 1984). Half the suspects were guilty and had confessed; the other half had been proven innocent. Had the polygraph experts been the judges, more than one-third of the innocent would have been declared guilty, and one-fourth of the guilty would have been declared innocent.

A 2002 U.S. National Academy of Sciences report noted that “no spy has ever been caught [by] using the polygraph.” It is not for lack of trying. The FBI, CIA, and U.S. Departments of Defense and Energy have tested tens of thousands of employees, and polygraph use in Europe has also increased (Meijer & Verschuere, 2010). Yet Aldrich Ames, a Russian spy within the CIA, went undetected. Ames took many “polygraph tests and passed them all,” noted Robert Park (1999). “Nobody thought to investigate the source of his sudden wealth—after all, he was passing the lie detector tests.”

A more effective lie detection approach uses a guilty knowledge test, which assesses a suspect’s physiological responses to crime-scene details known only to the police and the guilty person (Ben-Shakhar & Elaad, 2003). If a camera and computer had been stolen, for example, only a guilty person should react strongly to the brand names of the stolen items. Given enough such specific probes, an innocent person will seldom be wrongly accused.

Research teams are now exploring new ways to nab liars. “Forensic neuroscience” researchers are going straight to the seat of deceit—the brain. fMRI scans have shown liars’ brains activating in places that honest people’s brains do not (Langleben et al., 2002, 2006, 2008; Lui & Rosenfeld, 2009). The Pinocchio-like giveaway signal of lying may be not the length of our nose, but rather the telltale activity in our brain. fMRI scans have shown that brain areas such as the left frontal lobe and anterior cingulate cortex become active when the brain inhibits truth-telling (FIGURE 37.5). A U.S. $10 million Law and Neuroscience Project, led by psychologist Michael Gazzaniga, aims to assess appropriate uses of the new technology in identifying terrorists, convicting criminals, and protecting the innocent. In 2010, a U.S. federal court declared that fMRI lie detection is not yet ready for courtroom use (Miller, 2010). Many neuroscientists concur (Gazzaniga, 2011; Wagner, 2010). Others argue that jurors’ and judges’ seat-of-the-pants judgments “are worse than the science that is excluded” (Schauer, 2010).

Figure 37.5
Liar, liar, brain’s on fire An fMRI scan identified two brain areas that became especially active when a participant lied about holding a five of clubs. (fMRI scan from Langleben et al., 2002.)

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