Signal Detection Theory and Probability Matching Apply to Vigilance

Abstract

Many vigilance tasks require discrimination of infrequent signal events from frequent nonsignals. During performance on these tasks signal detections often decline. But this does not generally signify a loss of vigilance, if one can rely on signal detection analyses showing that signal discriminability remains constant during a vigil and hence that neither attention nor signal processing has waned. This paper confirms that signal detection theory does provide a good fit to vigilance data and that the analyses can therefore be relied on. The paper also shows that probability matching (of signal reports to signal occurrence) occurs. In the main it is the adjustment of report rate toward matching by an alert observer, in control of his or her performance, that produces the vigilance decrement in detections.