The Effect of Signal Rate on Performance in Two Kinds of Vigilance Task 1

Abstract

Signal rates of 180 or 30/hr were presented to 80 subjects in two kinds of vigilance task, the Continuous and the Jump Clocks. In the former, signats were brief pauses in the steady movement of the clock hand, in the latter they were double jumps of the clock hand. The signal rate had little effect on the percentage of signals detected but more false alarms were given at the slow signal rate, so that the detectability (ď) or sensitivity for the signals and the criterial level (beta) tended to be lower. The Continuous Clock with its high required rate of observing showed significant decrements in ď during the session, but the Jump Clock did not. Increases in beta during the session were greater with the fast signal rate. The results are discussed in terms of habituation and observing behavior.