Responses to alarms are assumed important. Yet failure to respond to alarms is recognized, although is not well understood or quantified. Conditions that might induce a failure to respond include alarm unreliability (i.e., numerous false alarms, the "cry-wolf" effect), high primary task demand, or low criticality of the alarm itself. The goals of this research were to substantiate the existence of the cry-wolf effect, quantifying its effect on operator performance, and to examine the relation between the cry-wolf effect and alarm criticality. One hundred thirty-eight UCF students alternatively performed two primary tasks, chosen from the Automated Performance Test System. Subjects were presented alarms of varying reliabilities (25%, 50%, and 75 % true alarms) and urgencies (low, medium, and high) in three experimental blocks. A series of repeated-measures MANOVAs assessed the effects of increasing alarm reliability, criticality, and performance block on alarm response and primary task performance. A post-experimental questionnaire also provided correlational data to determine relationships between demographic and opinion items and alarm response performance. The results indicate that most subjects (about 90%) do not respond to all alarms but match their response rates to the expected probability of true alarms (probability matching). Further, alarm criticality and primary task difficulty modestly but significantly alter response rates, and the speed and accuracy of responding. About 10% of the subjects responded in the extreme, utilizing an all-or-none strategy. Implications of these results for alarm design instruction and further research are discussed.
Gilson, Richard D.
Doctor of Philosophy (Ph.D.)
College of Arts and Sciences
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Doctoral Dissertation (Open Access)
Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences
Bliss, James P., "The Cry-Wolf Phenomenon and its Effect on Alarm Responses" (1993). Retrospective Theses and Dissertations. 3614.