Practice in Clinical & Health Psychology
Electrodermal Biofeedback
Measuring Changes in Skin Electrical Activity



What is Electrodermal Biofeedback?

An electrodermograph (EDG) measures skin electrical activity directly (skin conductance and skin potential) and indirectly (skin resistance) using electrodes placed over the digits or hand and wrist. Orienting responses to unexpected stimuli, arousal and worry, and cognitive activity can increase eccrine   sweat gland activity, increasing the conductivity of the skin for electrical current.

In skin conductance, (SC) an electrodermograph imposes an imperceptible current across the skin and measures how easily it travels through the skin. When anxiety raises the level of sweat in a sweat duct, conductance increases. Skin conductance is measured in microsiemens (millionths of a siemens). In skin potential, a therapist places an active electrode over an active site (e.g., the palmar surface of the hand) and a reference electrode over a relatively inactive site (e.g., forearm). Skin potential is the voltage that develops between eccrine sweat glands and internal tissues and is measured in millivolts (thousandths of a volt). In skin resistance, (SR) also called "galvanic skin response" (GSR), an electrodermograph imposes a current across the skin and measures the amount of opposition it encounters. Skin resistance is measured in kΩ (thousands of ohms).

Biofeedback therapists use one or another of these forms of electrodermal biofeedback when treating such problems as anxiety, hyperhidrosis (excessive sweating), and stress. Electrodermal biofeedback is used as an adjunct to psychotherapy to increase client awareness of their emotions. In addition, electrodermal measures have long served as one of the central tools in polygraphy (lie detection) because they quickly and accurately reflect changes in anxiety or emotional activation.