III. The Biological Basis of Emotion
The experience of emotion is accompanied by activation of two major areas of the nervous system: the brain and the autonomic nervous system. Activation of Brain Regions The area of the brain known as the limbic system is highly involved in emotion. One structure in the limbic system, called the amygdala, plays a particularly important role in regulating emotion. Researchers believe that sensory information about emotion-evoking events moves along two pathways in the brain. The information goes first to the thalamus and from there moves simultaneously to the amygdala and the cortex of the brain. The amygdala processes the information quickly and sends signals to the hypothalamus, which in turn activates the autonomic nervous system. The cortex, on the other hand, processes the information more slowly, allowing people to appraise or evaluate the event. Example: When information travels from the sense organs to the thalamus to the amygdala, people respond instantaneously, without thinking, to events in their environment. A parent may snatch her child away from a curb without thinking if she hears the sound of squealing tires coming toward them. The Amygdala Damage to the amygdala results in an inability to appropriately process fear. Animals with damaged amygdalas cannot develop conditioned fear responses. People with damaged amygdalas can’t recognize fear in other people, though they may be able to experience fear themselves. Activation of the Autonomic Nervous System The autonomic nervous system controls all the automatic functions in the body. When an emotion-evoking event happens, the sympathetic branch of the autonomic nervous system, which prepares the body for action, begins to work. It sends signals to the adrenal gland, which secretes the hormones epinephrine and norepinephrine. These hormones in turn prepare a person to face the challenges of the event. The following physical responses are indicative signs in a man or woman:
Autonomic Nervous System The autonomic nervous system is made up of two parts: the sympathetic and parasympathetic nervous systems. Unlike the sympathetic nervous system, which prepares the body for action, the parasympathetic nervous system keeps the body still. The sympathetic nervous system involves expending energy, while the parasympathetic nervous system works to keep energy in the body. Measuring Emotion Researchers often use autonomic responses to measure emotion. One frequently used autonomic response is called the galvanic skin response. The galvanic skin response is an increase in the skin’s rate of electrical conductivity, which occurs when subjects sweat during emotional states. Researchers also use indicators such as blood pressure, muscle tension, heart rate, and respiration rate to measure emotion. The galvanic skin response device is used in polygraph machines, hypnotherapy (to judge if someone has entered a state of hypnosis), and biofeedback in behavior therapy. Polygraph Tests The polygraph, or lie detector, is a device used to detect deception. In reality, the polygraph cannot detect deception. Instead, it measures autonomic indices of emotion. A subject is hooked up to the device and asked a series of neutral questions such as What is your name? Where do you live? and so on. The polygraph records the autonomic responses as the subject answers these questions, establishing the baseline, or normal pattern of autonomic activation. Then the subject answers other questions that can determine guilt or innocence, such as Where were you on the night of the murder? In theory, when lying, the subject feels emotions such as nervousness or anxiety, and the polygraph records accompanying changes in autonomic activation. In practice, the polygraph is not very effective. Polygraph tests have a high error rate for two main reasons:
Differences Among Emotions The release of the hormones epinephrine and norepinephrine accompanies many emotional states, but emotions differ at the biological level:
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Vocabulary to Know
Limbic System Amygdala Autonomic Nervous System Sympathetic Nervous System Parasympathetic Nervous System Galvanic Skin Response Polygraph Quizlet |
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