IRRELEVANT STIMULATION AND VIGILANCE UNDER FAST AND SLOW STIMULUS RATES

Abstract : Twenty-four Navy enlisted men served in four onehour watchstanding sessions. Their task was to detect slight increments in the brightness of an intermittent light. These increments (signals) occurred at random intervals at a rate of 24 per hour. Each watch was preceded by a brief warm-up session and a two-minute pretest and was followed by a two-minute posttest. Subjects stood watch under two conditions of stimulus rate: 20/min and 60/min and two conditions of auditory stimulation: variety (music, conversation, etc.) and white noise. Each subject stood one watch under each of the four experimental conditions. There was an interaction between the stimulus rate and the type of irrelevant auditory stimulation. The interaction was not statistically significant in terms of the total percentage of signals detected, but was significant in terms of the decrement in percentage of signals detected. The interaction was in the predicted direction: with the slow stimulus rate there was a greater decrement under the white noise condition than under the variety condition; and with the fast stimulus rate there was a greater decrement under the variety condition than under the white noise condition. (Author)