Vigilance Effects in Complex Inspection
Two “vigilance” experiments involving complex inspection are described in which the typical item consisted of a disc with a radial spoke inclined at an angle to the horizontal. The size of the disc and the angle of the spoke were both relevant features in the task. In the first experiment the nontarget was a disc of a given size, with a given spoke angle. One target (B) was bigger, while the other (A) had a steeper spoke angle. One group of subjects looked for Target A only, another for Target B, while a third group monitored simultaneously for both. The results show that for each type of target, the overall level of detections and the extent of the within-session decrement were unaffected by the demand to look for the other target as well.
In the second experiment, items varied about a standard value on size and angle. Targets were defined as those items which deviated beyond a critical distance from the standard on either feature dimension, or (in combination) in both. One group of subjects was instructed to give higher priority to detecting size targets; another, that it was more important to spot angle targets; while a third group gave equal priority to both. Performance by the unbiased group was stable throughout the session, whereas within-session declines were observed in the detection of important targets by each of the biased groups. But their performance with respect to the less important target type remained stable throughout. The experimental findings are discussed against a background of concern about the practical relevance of laboratory research on vigilance.
KeywordsFalse Alarm Report Rate Angle Target Important Fault Angle Fault
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