Effects of knowledge of results and signal regularity on vigilance performance

According to Baker (1963), knowledge of results (KR) facilitates vigilance performance by enhancing the generation of accurate expectations regarding the time of appearance of critical signals. The implications of this notion were assessed by comparing effects of true and false (noncontingent) KR within the context of temporally regular and irregular signal schedules. The Ss listened for increments in the duration of recurrent white-noise pulses during a 1-h vigil. Response times (RTs) to signal detections were faster and less variable when signals were presented on a regular as compared to an irregular basis. RTs were also faster and less variable for Ss receiving true or false KR relative to controls who experienced no feedback. However, the facilitative effects of true KR did not exceed those of false KR even when signal presentations were regular in time and apparently predictable. The results are considered as contrary to an expectancy interpretation of the role of KR in the vigilance task.