Effects of time of day and signal frequency on vigilance performance

Leary, James Norman (1974) Effects of time of day and signal frequency on vigilance performance. Masters thesis, Memorial University of Newfoundland.

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Abstract

Signal frequency in a visual vigilance task was increased at two different testing times, corresponding to a "low" and a "high point" in the diurnal cycle. Two methods were used to increase signal frequency. An increase solely in signal probability, with total event rate unaffected, improved detection performance mainly at the low point of the cycle. This improvement was accompanied by a decrease in values of the signal detection theory index, β. An increase in total event rate, at a fixed level of signal probability, had no significant effect on detection rates, but decreased false alarm rates at both testing times. The decrease was accompanied by increased values of d; and β. Performance temperature relationships were found only in the high event rate conditions. Morning values of d' exhibited a relationship with degree of introversion. No relationship was found between introversion and daily temperature changes which casts some doubt on the generality of "changeover" theory.

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