Activation of the Autonomic Nervous System
The autonomic nervous system controls all the automatic
functions in the body. See pages 51–52 for more information about the autonomic
nervous system.
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:
- Blood pressure, heart rate, respiration rate, and blood sugar levels
increase and prepare a person for action.
- Pupils dilate to let in more light for vision.
- The digestive processes slow down so that energy can be directed to
the crisis at hand.
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.
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?
