Electrodermal Activity (EDA) and Behavior
The idea of studying electrical activity of the skin probably does not cause much excitement in the average person. However, as an important measure in psychophysiology, it has had a long and interesting history; and it has been a very ively topic of research. Sample issues involving electrodermal activity (EDA) are whether it can distinguish between positive and negative emotions and whether persons who show large numbers of spontaneous changes in activity are more efficient at processing information. In addition, psychophysiologists have asked questions regarding relationships between EDA and response speed, and whether it varies with learning efficiency. Researchers have investigated whether EDA can tell us anything about motivational level, and have explored it extensively in studies of the orienting response. The extent to which EDA can be classically or instrumentally conditioned has also been an important issue. Another, albeit controversial, issue regards the use of skin activity changes to indicate whether a person is lying. The topic of lie detection is discussed more fully in chapter 15 on applications of physiological measures to practical problems.
The observation that changes in electrical activity of the skin can be produced by various physical and emotional stimuli was reported by Charles Fere, a French neurologist, in 1888. Almost simultaneously, a Russian physiologist ( Tarchanoff in 1890) observed similar changes in skin activity (see Woodworth & Schlosberg, 1954). The techniques of the two scientists differed. Fere's procedure involved the passing of a small current between two electrodes on the skin surface, and changes in electrodermal activity (EDA) were observed when a person was presented with various stimuli ( Neumann & Blanton, 1970; Woodworth & Schlosberg, 1954). A galvanometer was used to measure the increases in skin conductance that occurred when visual, auditory, or emotion-provoking stimuli were introduced. This phenomenon was soon labeled the psychogalvanic reflex (PGR) and later, the galvanic skin response (GSR) by early investigators. Fete felt that his results with sensory and emotional stimuli showed that the responses were indicators of nervous system excitation, or arousal, to put it in more modem terms. Measures of EDA were used in the early 1900s by Carl Jung, the noted Swiss psychiatrist, to study emotional reactions of his patients to word associations.
Tarchanoff's procedure obtained similar galvanometer deflections without the use of externally applied current; that is, there were natural differences in electrical potential between two skin areas, and this potential changed when the subject was stimulated. Fere and Tarchanoff contributed what were to become two basic methods for the measurement of EDA: the recording of skin conductance (SC) and skin potential (SP). Boucsein ( 1992) relates that although the discovery of EDA phenomena is attributed to Fere and Tarchanoff, the history of this physiological measure dates back to 1849. The German scientist, DuBoisReymond, noted in 1849 that electric current flowed between the two hands when they were immersed in a zinc sulphate solution. Although he observed electrodermal activity, DuBois