The Biology of Emotion

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The Nature of Emotion
3. Emotion can vary in intensity. You can feel pleased, happy, or ecstatic. You can
also feel mildly disappointed, sad, or deeply depressed.
4. Emotional experience is triggered partly by thoughts, especially by a mental assessment of how a situation relates to your goals. The same event can bring on different emotions depending on what it means to you. An exam score of 75 percent may thrill you if your best previous score had been 50 percent, but it may
upset you if you had never before scored below 90 percent.
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5. Emotional experience alters thought processes, often by directing attention toward
some things and away from others. Negative emotions tend to narrow attention,
and positive emotions tend to broaden it. Anxiety about terrorism, for example,
narrows our attention to focus on potential threats in airports and other public
places (Craske, 1999; Yovel & Mineka, 2005).
6. Emotional experience brings on an action tendency, a motivation to behave in certain ways. Grieving parents’ anger, for example, might motivate them to harm
their child’s killer. But for John Walsh, whose son was kidnapped and murdered,
grief led to helping to prevent such crimes by creating America’s Most Wanted, a
TV show dedicated to bringing criminals to justice.
Emotional
experiences depend in part on our interpretation of situations and how those situations relate to our goals. A single
event—the announcement of the results
of a cheerleading contest—triggered
drastically different emotional reactions
in these women, depending on whether
they perceived it as making them winners
or losers.
WINNERS AND LOSERS
7. Emotional experiences are passions that you feel, whether you want to or not. You
do have some control over emotions, though, because they depend partly on how
you interpret situations (Gross, 2001). For example, you can reduce your emotional reaction to a car accident by reminding yourself that no one was hurt and
that you are insured. Still, you can’t just decide what emotions you experience;
instead, you “fall in love” or “explode in anger” or are “overcome by grief.”
In other words, the subjective aspects of emotions are experiences that are both triggered by the thinking self and felt as happening to the self. The extent to which we are
“victims” of our passions versus rational controllers of our emotions is a central
dilemma of human existence.
The objectively measurable aspects of emotion include learned and innate expressive
displays and physiological responses. Expressive displays—such as a smile or a frown—
communicate feelings to others. Physiological responses—changes in heart rate, for
example—provide the biological adjustments needed to perform actions generated by
the emotional experience. If you throw a temper tantrum, for instance, your heart must
deliver additional oxygen and fuel to your muscles.
In summary, an emotion is a temporary experience with positive, negative, or mixed
qualities. People experience emotion with varying intensity as happening to the self,
generated in part by a mental assessment of situations, and accompanied by both
learned and innate physical responses. Through emotion, whether they mean to or not,
people communicate their internal states and intentions to others. Emotion often disrupts thinking and behavior, but it also triggers and guides thinking and organizes,
motivates, and sustains behavior and social relations.
The Biology of Emotion
The biological systems described in the chapter on biology and behavior play a major
role in emotion. In the central nervous system, numerous brain areas are involved in the
generation of emotions, as well as in our experience of those emotions (Barrett &
Wager, 2006). The autonomic nervous system gives rise to many of the physiological
changes associated with emotional arousal.
emotion A temporary positive or negative experience that is felt as happening to the self, that is generated partly
by interpretation of situations, and that
is accompanied by learned and innate
physical responses.
Brain Mechanisms Although many questions remain, researchers have described
three main aspects of how emotion is processed in the brain. First, it appears that
activity in the limbic system, especially in the amygdala, is central to emotion
(Kensinger & Corkin, 2004; Phelps & LeDoux, 2005; see Figure 2.9 in the chapter on
biology and behavior). Normal functioning in the amygdala appears critical to the
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Chapter 8 Motivation and Emotion
ability to learn emotional associations, recognize emotional expressions, and perceive
emotionally charged words (Anderson & Phelps, 2001; Suslow et al., 2006; Whalen
et al., 2004). For example, victims of a disease that destroys only the amygdala are
unable to judge other people’s emotional states by looking at their faces (Adolphs,
Tranel, & Damasio, 1998).
A second aspect of the brain’s involvement in emotion is seen in its control over our
emotional and nonemotional facial expressions (Rinn, 1984). Take a moment
learn to look in a mirror, and put on your best fake smile. The voluntary facial
by
doing movements you just made, like all voluntary movements, are controlled by
the brain’s pyramidal motor system, a system that includes the motor cortex. However,
a smile that expresses genuine happiness is involuntary. That kind of smile, like the
other facial movements associated with emotions, is governed by the extrapyramidal
motor system, which depends on areas beneath the cortex. Brain damage can disrupt
either system (see Figure 8.6). People with pyramidal motor system damage show normal facial expressions during genuine emotion, but they cannot fake a smile. In contrast, people with damage to the extrapyramidal system can pose facial expressions at
will, but they remain straight-faced even when feeling genuine joy or profound sadness
(Hopf, Muller, & Hopf, 1992).
A third aspect of the brain’s role in emotion is revealed by research on the two sides,
or hemispheres, of the cerebral cortex (Davidson, 2000; Davidson, Shackman, &
Maxwell, 2004). For example, after suffering damage to the right, but not the left, hemisphere, people no longer laugh at jokes—even though they can still understand their
words, the logic (or illogic) underlying them, and their punch lines (Critchley, 1991).
And when people are asked to name the emotions shown in slides of facial expressions,
blood flow increases in the right hemisphere more than in the left hemisphere (Gur,
Skolnic, & Gur, 1994). But smiling while experiencing a positive emotion is correlated
with greater activity in the left side of the brain (Davidson et al., 1990). Similarly, when
an area of one patient’s left hemisphere was stimulated, she began to smile, then laugh
(Fried et al., 1998). She attributed her emotional expression to the situation (“You guys
are just so funny . . . standing around”).
The fact that different brain areas appear to be involved in displaying and experiencing positive and negative emotions (Harmon-Jones, 2004; Harmon-Jones & Sigelman,
2001; Heller, 1993) makes it difficult to map the exact roles the two hemispheres play
in emotion (Vingerhoets, Berckmoes, & Stroobant, 2003). Generally, however, most
aspects of emotion—the experiencing of negative emotion, the perception of any emotion exhibited in faces or other stimuli, and the facial expression of any emotion—
depend more on the right hemisphere than on the left (Heller, Nitschke, & Miller, 1998;
Kawasaki et al., 2001).
If the right hemisphere is relatively dominant in emotion, which side of the face
would you expect to be somewhat more involved in expressing emotion? If you said
the left side, you are correct, because, as described in the chapter on biology and
behavior, movements of each side of the body are controlled by the opposite side of
the brain.
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FIGURE
8.6
Control of Voluntary and
Emotional Facial Movements
This man has a tumor in his motor cortex
that prevents him from voluntarily moving
the muscles on the left side of his face. In
the top photograph he is trying to smile in
response to instructions from the examiner. He cannot smile on command, but he
can smile with happiness, as the bottom
photograph shows, because the movements associated with genuine emotion
are controlled by the extrapyramidal motor system, which is beneath the motor
cortex.
The autonomic nervous
system (ANS) triggers many of the physiological changes that accompany emotions
(Vernet, Robin, & Dittmar, 1995; see Figure 8.7). If your hands get cold and clammy
when you are nervous, it is because the ANS has increased perspiration and decreased
the blood flow in your hands.
As described in the chapter on biology and behavior, the ANS carries information
between the brain and most organs of the body—the heart and blood vessels, the digestive system, and so on. Each of these organs is active on its own, but input from the
ANS can increase or decrease that activity. By doing so, the ANS coordinates the functioning of these organs to meet the body’s general needs and to prepare the body for
change (Porges, Doussard, & Maita, 1995). If you are aroused to take action, such as
running to catch a bus, you need more glucose to fuel your muscles. The ANS frees
Mechanisms of the Autonomic Nervous System
325
The Nature of Emotion
Parasympathetic functions
Sympathetic functions
Constricts pupil
Dilates pupil
Stimulates salivation
Inhibits salivation
CNS
Sympathetic
ganglion
Slows respiration
Increases respiration
Slows heartbeat
Accelerates heartbeat
Stimulates
gall bladder
Stimulates
glucose release
Stimulates digestion
Inhibits digestion
Secretes adrenaline
and noradrenaline
Contracts bladder
Relaxes bladder
Stimulates genitals
Inhibits genitals
FIGURE
Norepinephrine
released
Target organ
Acetylcholine
released
Parasympathetic
ganglion
8.7
The Autonomic Nervous System
Emotional responses involve
activation of the autonomic
nervous system, which is organized into sympathetic and parasympathetic subsystems. Which of the bodily
responses shown here do you associate
with emotional experiences?
doing
2
learn
by
parasympathetic nervous system The
subsystem of the autonomic nervous
system that typically influences activity
related to the protection, nourishment,
and growth of the body.
sympathetic nervous system The subsystem of the autonomic nervous system that readies the body for vigorous
activity.
fight-or-flight syndrome Physical reactions triggered by the sympathetic nervous system that prepare the body to
fight or flee a threatening situation.
needed energy by stimulating secretion of glucose-generating hormones and promoting blood flow to the muscles.
Figure 8.7 shows that the autonomic nervous system is organized into two parts: the
sympathetic nervous system and the parasympathetic nervous system. Emotions can
activate either part, both of which send axon fibers to each organ in the body. Generally, the sympathetic and parasympathetic fibers have opposite effects on these target
organs. Axons from the parasympathetic nervous system release the neurotransmitter acetylcholine onto target organs, leading to activity related to the protection,
nourishment, and growth of the body. Axons from the sympathetic nervous system
release a different neurotransmitter, norepinephrine, onto target organs, helping to prepare the body for vigorous activity. When one part of the sympathetic system is stimulated, other parts are activated “in sympathy” with it (Gellhorn & Loofbourrow, 1963).
The result is the fight-or-flight syndrome, a pattern of increased heart rate and blood
pressure, rapid or irregular breathing, dilated pupils, perspiration, dry mouth, increased
blood sugar, “goose bumps,” and other changes that help prepare the body to confront
or run from a threat.
You cannot consciously experience the brain mechanisms that alter the activity of
your autonomic nervous system. This is why most people cannot exert direct, conscious
control over blood pressure or other aspects of ANS activity. However, you can do
things that have indirect effects on the ANS. For example, to create autonomic arousal
of your sex organs, you might imagine an erotic situation. To raise your blood pressure, you might hold your breath or strain your muscles. And to lower your blood pressure, you can lie down, relax, and think calming thoughts.