Skin Conductance Changes Occurring during Mental Fatigue and Anoxemia

Abstract

Listen

Translate article

The concurrent skin conductance changes occurring during the performance of a mental task and the changes concommitant to mental fatigue have been described and reported in the Transactions of the Kansas Academy of Science in 1939 and elsewhere. The purpose of the present paper is to present a report of a study of the effect of anoxemia upon mental performance as reflected in skin-conductance changes. The study is a comparison of skin-conductance changes occurring under breathing of normal air with those occurring during mental work while breathing air of reduced oxygen. The problem as it is here described is part of a larger program of research in which an effort is being made to study several physiological reactions under conditions of mental work. The condition of anoxemia was introduced as a part of the program of research at the suggestion of Bills, who found a relation between the intensity and duration of anoxemia and mental fatigue. The condition of anoxemia was introduced with the hope of exaggerating fatigue and possibly the concurrent physiological reactions-skin conductance in this case. It was understood at the outset that the immediate effect of anoxemia upon the autonomic system, particularly that nervous system mediating the galvanic skin response and skin conductance, would remain in the experiment one of the unknown variables. The present study was not designed to investigate this effect. The mental task was continuous manual responding to serial presentation of colors. Bills' psychergometer was used. Subjects operated a keyboard of five keys corresponding to the five colors which were automatically presented. Each time the subject pressed the correct key the next color was presented. The colors were randomly arranged upon a steel tape. The subjects were first practiced until they reached an average rate of about ninety colors per minute. The subject's color naming responses along with his physiological responses were recorded on a photopolygraph. The skin-conductance changes and the galvanic skin responses were observed and measured by means of a Darrowtype Wheatstone bridge. The skin-conductance changes were continuously recorded throughout the experimental periods. Special equipment was designed to produce the anoxemic condition. Normal air contains 20.9 percent oxygen. In order to reduce the oxygen percentage in the inspired air by a definite amount, it is necessary to dilute normal air by adding nitrogen to it in the proper proportions. If the subject is to breathe air of a certain reduced oxygen content for a considerable period of time, such as an hour, it is necessary to prepare a quantity of such a mixture in an appropriate container beforehand, so that the exact oxygen percentage can be tested by chemical analysis of a sample. The container for the gas mixture was constructed of rubberized cloth with a capacity of 65 cubic feet. Ordinary room air was sucked in and compressed