Vigilance Under Induced Hyperthermia

Abstract

Twelve highly practised subjects were tested in an ambient environment of 103°F (DB), 93°F (WB) on a 1-hour task of visual vigilance, after having performed, in the same environment, physical work which produced an ultimate rise in body-temperature of approximately 0·.4°F for every ten minutes of continuous activity. The vigilance test was not carried out until the subjects had rested for at least thirty minutes after completion of the work; under these circumstances body-temperature remained elevated at a near constant level during the test. Contrary to results reported by earlier workers, no increase in the overall rate at which signals were detected was observed as a result of the raised body-tomperature; however it was found that such an incroase was observable if only those occasions when the subject indicated a high degree of confidence in the accuracy of his report following a signal presentation were scored as detections. Thus there was, in effect, an increase in confidence with raised body-temperature, but no change in detection skill. This increase in confidence was accompanied by an increase in the frequency with which false reports were made; further analysis indicated that this reflected a change in the decision criterion used to determine whether or not a signal had been presented.