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A STUDY OF GALVANOMETRIC DEFLECTIONS DUE TO PSYCHO­PHYSIOLOGICAL PROCESSES; By Boris Sidis, Ph. D., M.D., and H. T. Kalmus, Ph. D., Psych. Rev., November, 1908, December, 1909.

IN our study of galvanometric deflections due to psychophysiological processes we used the following arrangements: In a series with a battery we put a sensitive galvanometer and two electrodes across which the subject placed himself, thus closing the circuit. The battery was a single cell, giving a constant electromotive force of about one volt. The galvanometer was of the suspended coil, D'Arsonval type. The deflections were read by means of a beam of light deflected from a mirror to a telescope with a scale. A deflection of one centimeter on the scale corresponded to less than 10-9 amperes, through the instrument. When the sensitiveness was too great for our experiments a resistance was shunted around the galvanometer. The electrodes were glass vessels of about four litres capacity, nearly filled with a strong electrolyte, such as a concentrated solution of NaCl. Into these vessels copper electrodes of about five hundred centimeters area were placed. The circuit was completed by placing the hands, feet, etc., one into each electrode solution.

        The possible sources of error at this point are twofold: (1) Due to the variation of the liquid level at the wrist, and (2) due to movements of the hand as a whole. To overcome these difficulties the following device was used: The wrist was covered with shellac for a length of several inches, so that the free liquid surface of the electrode was always in contact with shellac. The shellac was covered by a layer of paraffin. The hand was put in splints in such a manner that only a small fraction of the skin was covered and no appreciable muscular contraction of the phalanges could take place. If now a stimulus was given, a stimulus that aroused an emotion, a marked galvanometric deflection was observed.

        As the result of a large series of experiments performed on more than half a dozen subjects we arrived at the conclusion that pure, ideational processes, such as thinking, calculation, solving problems, representing pleasant or painful experiences have no effect, while sudden violent emotions and intense sensory stimulations of a painful and disagreeable character, such as burns, pricks, electric shocks, and fetid smells are followed by marked galvanometric deflections.

        We find in our experiments that muscular activity of those parts the body actually forming the circuit bring about galvanometric deflections, while activity of the more remote parts of the body are ineffective.

        The absolute magnitude of the deflection varies according to the varying condition of the experiment. Different experiments performed with different concentration of electrode-solutions gave different deflections, in fact, the direction and magnitude were varied at will this way. Also substituting lead electrodes for copper electrodes changed the deflections largely. Different parts of the skin gave different original deflections. However, superimposed upon this original steady deflection is a deflection due to various given stimulations, and to the induction of psychophysiological processes to affective and emotional character.

        The shellac and paraffin with which we covered the subject's wrists, as well as the splints put on the hands and forearms, made the skin area washed by the liquid electrodes constant. The galvanometric deflections observed under conditions of stimulation could not therefore be referred to variations in skin contact. If resistance be the factor, then the observed galvanometric deflections may be either due to changes of resistance of the constant area of the skin, or of the body through which the current passes. Skin resistance was eliminated by the following procedure: Hypodermic electrodes were inserted well under the skin until blood flowed. After a few minutes the deflection with the needle electrodes did not differ from those without the needle electrodes. This clearly eliminates the factor of skin resistance.

        That the skin has nothing to do with the phenomena under investigation can be proved by the following procedure: The skin was covered with shellac and paraffin, leaving only the finger nails exposed. Under such conditions definite galvanometric deflections were obtained, deflections induced by emotional states and physiological activities.

        Having excluded skin effects in general and skin resistance in particular, we may consider next the resistance of the body as a possible factor the so-called galvanic phenomenon. Since electrical resistance of a body depends on temperature and concentration of body fluids, we have to consider the two factors. Now electrolytes have a positive temperature-coefficient of about two percent per degree. Our experiments with hot and cold applications gave but slight variations insufficient to account for the galvanometric deflections observed under the influence of emotional states. The variations due to raising the temperature did not differ from those due to lowering the temperature. Furthermore, after a minute or two of continuous cooling or heating of the arms the galvanometric reading was the same as that before the temperature-change. The cold and hot application act, therefore, as do other sensory stimulations. The temperature factor cannot be a cause of the galvanic phenomenon.

        That changes in the concentration of the body fluids or changes of circulation have no effect can be proven by the following simple procedure: The circulation was effectually cut off by Esmarch bandages. The pulse was gone and the hand assumed a cadaverous hue, still the same galvanometric deflections were easily obtained under the same psychophysiological conditions.

        Our experiments go to prove that the causation of the galvanic phenomenon cannot be referred to skin resistance, nor can it be referred to variations of temperature, nor to circulatory change with possible changes in the concentration of the body fluids. Since as we have pointed out the electrical resistance of a given body depend on two factors―temperature and concentration―the elimination of both factors excludes body resistance as the cause of galvanic phenomenon. Resistance being excluded the galvanometric deflection can only be due to variations in the electromotive forces of the body.

        The heart beat should be taken into consideration as one of the possible causes of galvanometric deflections, due to psycho-physiological processes. Experimenting with the capillary electrometer Waller came to the conclusion that "a marked electrical variation is manifested at each pulsation of the heart." We repeated Waller's experiments, but we could not confirm his results with our galvanometer. Vole found, however, that a reversal of the position of the hands―putting the right in place of the left hand―made a difference in the magnitude of the deflection and occasionally in its direction. We find here an additional proof that we deal in the galvanic phenomenon, not with variations of resistance, but with electromotive forces. Our experiments prove that a stimulus causes a deflection superimposed upon the original deflection which is not always in the same direction. The superimposed deflections, due to stimulations, change in direction with the reversal of the hands. We deal here, therefore, with a factor that has direction. Since the factor of resistance has no direction and the only factor that has direction is electromotive force, we come to the conclusion that the galvanic phenomenon is not of the nature of a resistance, but is essentially of the nature of an electromotive force. Our experiments thus clearly show that active physiological processes, sensory, and emotional processes, with the exception purely ideational ones, initiated in a living organism, bring about electromotive forces with consequent galvanometric deflections.

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