The psycho-galvanic reflex; a comparison of A.C. skin resistance and skin potential changes.

Two closely-related electro-dermal phenomena constitute the so-called " psycho-galvanic reflex ". These are (a) a decrease in the electrical resistance of the skin, and (b) a change in the skin electromotive force in response to a wide variety of stimuli. Fere (1888) connected two electrodes on the forearm of a subject in series with a weak source of electricity and a galvanometer. He observed that various sensory and emotional stimuli were associated with an increased deflection of the meter. Tarchanoff (1890) obtained similar deflections of a galvanometer without the aid of an external electromotive force. Gildemeister (1923) found that the phenomena of Fere and of Tarchanoff possessed similar latent periods. Jeffress (1928) confirmed this, and he also obtained a high positive correlation between the magnitude of the two responses. These workers, like Tarchanoff, used an instrument oflow resistance, which would not fully differentiate potential changes from resistive effects. Forbes (1936) oscillographically recorded the pure potential and impedance changes of a single reacting area of skin. He reported the existence of two distinct components in the potential " waveform ", and he referred to the " slower resistance or impedance response ". Goadby and Goadby (1949) found that the resistance response was abolished by complete exsanguination of a limb, while the potential response remained intact. They concluded that the resistance change was due to vasoconstriction and that the potential variations were probably expressions of activity at sympathetic nerve endings in blood vessels and sweat glands. The object of this paper is to present the results of experiments in which the apparent A.C. resistance and the skin potential of a single reacting area were continuously recorded under a variety of conditions. The mutual independence of the two phenomena was repeatedly confirmed. Methods Material.-The subjects were 17 male and seven female patients who were suffering from various functional mental disorders. Their ages ranged from 16 to 58 years. Several of them were investigated on a number of occasions. Forty-six experiments were performed, during each of which the apparent A.C. skin resistance and the skin electromotive force were recorded for periods ranging from half an hour to more than one and a half hours.