Is the Vigilance Decrement Simply a Response Adjustment Towards Probability Matching?

It is shown that the response behavior in a sample of 30 vigilance studies parallels that found in psychophysical studies of probability matching. By the end of the vigilance session, the mean frequency with which responses are emitted matches the frequency with which signals are presented. When there is an approximate match at the beginning of the session (as with trained subjects in the psychophysical studies), there is little change during the session, but when the initial ratio of responses per signal is high (as it is in most vigilance cases), there is a considerable downward shift towards the probability matching level, paralleling the behavior of naive, untrained subjects in the psychophysical studies. It is suggested that the reduced responding is primarily responsible for the vigilance detection decrement and, therefore, that a major portion of the decrement may simply reflect inadequate training of the subjects.