No abstract

False alarm rates, which affect PPV, determine both the response to alerts (compliance) and the tendency to limit precautions when no alert is issued (reliance).

Responding to alarm systems which usually commit a number of false alarms and/or misses involves decision-making under uncertainty. Four laboratory experiments including a total of 256 participants were conducted to gain comprehensive insight into humans' dealing with this uncertainty. Specifically, it was investigated how responses to alarms/non-alarms are affected by the predictive validities of these events, and to what extent response strategies depend on whether or not the validity of alarms/non-alarms can be cross-checked against other data. Among others, the results suggest that, without cross-check possibility (experiment 1), low levels of predictive validity of alarms ( ≤ 0.5) led most participants to use one of two different strategies which both involved non-responding to a significant number of alarms (cry-wolf effect). Yet, providing access to alarm validity information reduced this effect dramatically (experiment 2). This latter result emerged independent of the effort needed for cross-checkings of alarms (experiment 3), but was affected by the workload imposed by concurrent tasks (experiment 4). Theoretical and practical consequences of these results for decision-making and response selection in interaction with alarm systems, as well as the design of effective alarm systems, are discussed.

Most theories about operators' responses to alarm systems suggest that the operators' behavior is guided by their trust towards the system which in turn results from the subjective perception of system properties, namely the perceived reliability of the alarm system. However, some doubts about that assumption have arisen as recent research has not proven the mediating effect of trust. The purpose of this research was to examine the relationship between alarm system properties, trust, and behavior. The alarm reliability was varied while keeping the other system properties constant. It was found that participants' response-rates to alarms were predicted by their perceived alarm reliabilities. However, no mediation by trust could be established. These results suggest that operators' behavior is not always guided by their trust towards the system. Under specific circumstances their compliance rather depends on rational consideration regarding the most efficient strategy.