METAANALYSIS OF THE SENSITIVITY DECREMENT IN VIGILANCE

Observers' perceptual sensitivity to critical target events can deteriorate when they must remain alert for prolonged periods. The dominant characterization of this sensitivity decrement has been the R. Parasuraman and D. R. Davies (1977) taxonomy of vigilance, which attributes the decline in perceptual ability to the type of discrimination (successive-absolute vs. simultaneous-comparative judgment) and the event rate (rate of stimulus presentation) required for task completion. According to the model, sensitivity decrements occur chiefly in tasks that couple successive discrimination with a high event rate. This meta-analysis of 42 vigilance studies attempted to refine the taxonomy by identifying other task characteristics related to the sensitivity decrement. The analysis confirmed that the magnitude of this sensitivity decrement is substantial and that it is a function of the type of discrimination and the event rate, but it also revealed that the current taxonomy should be revised to incorporate a new dimension: the sensory-cognitive distinction.