Maintenance of Alertness by a Loud Auditory Signal

Abstract

Will a loud auditory signal help maintain a high level of alertness over a long period of visual monitoring? Apparently, yes. When the failure to detect a target is coupled with the occurrence of a loud signal, improved monitoring performance might be reasonably expected because the signal: (1) serves as an “alarm clock” to keep the subject awake; (2) serves to provide information that the target has not been detected; and (3) serves as a “punishment” for having failed to detect the target. Tests were conducted with 15 observers over six 90-min periods. The task of the observer was to detect a momentary change in the predicted course of the needle of a VU meter. The average frequency of targets was 0.8 target per min; the average probability of a target-occurrence was 0.027. After failure of target-detection, a truck horn placed near the ear was blasted. A substantial average gain in monitoring performance, relative to a control condition without the horn, was observed. The largest gain in monitoring performance was provided by the least proficient group of observers. Control tests suggest that the horn is effective primarily because it provides information and/or punishment, and not because it simply serves as an alarm to keep the observers awake.