Signal Detection Theory Applied to Vigilance

Some 30 articles in the 1960s reported studies of vigilance in which the analytical techniques of signal detection theory were used to obtain separate, presumably independent, measures of sensitivity and the decision criterion. According to three reviews at the end of the decade, most studies showed a change in the decision criterion over time, but no change in sensitivity, and were thus inconsistent with the earlier interpretation of vigilance experiments as exhibiting a decrement in sensitivity. A few experiments did show a sensitivity decrement, however, usually in addition to a criterion change, and some of the later articles provided a preliminary description of the different stimulus conditions producing the different effects.