THE INFLUENCE OF NOISE ON TWO DISCRIMINATION TASKS

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Abstract
Recent research has revealed that noise effects on work become apparent in an increasingly irregularity of reaction times instead of in a general decrease in the total number of reactions. This paper is concerned with the measurement of the degree of irregularity in two paper-and-pencil tasks. Both tests were performed twice on different days for half an hour each. The experiment was designed to compare two different noiso conditions : in one the noise changed randomly about an average level of 75 dB., in the other it was steady at 70 da. The number of reactions in every minute was scored. To reach conclusions from the scores about the dogree of regularity of the reaction times, a measure of the variance of the scores waa used. Sinco there appeared a linear trend of score with time, it was decided to calculate the variance of the differences of score betwoen successive minutes rather than of the scores themselves. Two variances wore calculated for each day's work at each task, one over the first fourteen, and one over the last fourteen differences. The ratio of the variances (variance quotient) was taken as an indication of tho change of irregularity as performance proceeded. The results showed that in one task tho variance quotient was singificantly larger under conditions of varying than steady noise. In the other task the same trend appeared in the second day's session but not in tho first. The results favour Broadbent's hypothesis that unpredictable noise affects performance more than does monotonous noise.

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