PSYCHOGALVANIC REFLEX. The term psychogal vanic reflex (P.G.R.) was first used by Veraguth to describe the change in electrical properties of the human body (or any living animal body) in response to nocuous (emotional) stimuli. The terms galvanic skin reflex, skin constrictor reflex and sweat secretion reflex have been used synonymously. This reflex is usually demonstrated in one of two ways. (a) Electrodes connect the hands directly to a galvanometer. When the subject is stim ulated by a pin prick, threat of injury, etc., the galvanometer, after a latent period of about two seconds, will show a deflection indicating an increased output of electromotive force from the human body. This rises to a maximum within 2 to io seconds and subsides in about the same time. (b) The human subject forms the fourth arm of a balanced Wheatstone bridge electrical cir cuit. On stimulation the galvanometer will deflect as described above. In this case, the deflection indicates a decrease and increase in apparent ohmic resistance of the body.
This phenomenon was first described by Vigouroux (1879). It remained, however, for Veraguth (1909) to draw the attention of a large scientific audience to the psychogalvanic reflex. The physics of the "reflex" is still a matter of dispute. According to Gildemeister it is due to a change in conductivity of the human body which is dependent upon polarization of the membranes of the cells of the skin, so changing the cellular permeability to different ions. The anatomical control of the psychogalvanic reflex has been shown to lie in the sympathetic nervous fibres which lead to the smooth musculature of the walls of sweat glands and capillaries. Any stimulus resulting in activity of the sympa thetic division of the autonomic nervous system will consequently result in changes in tonicity of the involuntary musculature of the skin surfaces of the body which are shown by the secretion of sweat, changes in circulation, local skin temperature, etc.
This combined action leads in turn to variations in electrical con ductivity (psychogalvanic reflex).
Psychologists have, for the past twenty years, been interested in this phenomenon, particularly following the suggestion of Binswanger (1907) that only emotional stimuli elicit the reflex. This view has been held by many subsequent investigators. The work of Radecki 0910 and more recently of Aveling questions the validity of this assumption. It is probable that the psycho galvanic Reflex is elicited most frequently by nocuous stimuli, but that it is not specific to "emotional" situations.
The reflex has found application in many fields of research. Otologists have used it to detect the feigning of deafness in dubious cases. Psychoanalysts have used the phenomenon to gether with word association tests as a means of discovering hidden complexes. , Many investigators have made use of the Psychogalvanic Reflex for the demonstration of individual dif ferences in emotionality. There seems to be fairly good evidence that such differences may be established in this fashion. Psy chiatrists have made use of the reflex in differential diagnosis of organic and functional orders. Attempts toward the practical application of the reflex as an indicator of emotional stability of men who were applying for positions in hazardous occupations have not met any great success.