Processing Demands, Effort, and Individual Differences in Four Different Vigilance Tasks

Abstract

In an attempt to specify the limiting conditions of the taxonomy of vigilance tasks, four tasks differing in memory load and in stimuli employed (sensory or cognitive) were compared. Electrodermal activity and subjective measures were used to determine the investment of effort. The data show that vigilance level and vigilance decrement dissociate. The level seems to relate to effort demand and investment; the decrement seems to be task driven, determined mainly by the type of stimuli used. Tasks employing unfamiliar stimuli showed a decline in sensitivity; "cognitive" tasks employing alphanumeric stimuli did not. Principal components analyses suggest that measures of speed and accuracy may reflect relatively independent systems. Subjective data showed that good performers expand more effort in difficult and complex tasks. Effortful processing seems to prevent rather than induce a decline in efficiency.

Stimulant drugs and vigilance performance: a review

“…The way of searching the literature, the ordering of the studies, the inclusion of particular test characteristics purportedly affecting study outcomes, the measures of performance considered etc., are in essence the same as described in an earlier review of the effects of benzodiazepines (Koelega 1989).…”

“…The conclusion that vigilance tasks rank highest in sensitivity to stimulant drug effects was also reached earlier (Koelega 1989) with respect to the effects of (sedative) benzodiazepines, albeit hedged by the finding that in patients, effects were tess often noted than in young volunteers. Lieberman et al (1987b) reported that as little as 32 mg caffeine, typical of the dose found in a single serving of cola beverage, and less than that found in a single cup of coffee, significantly improved auditory vigilance.…”

“…It is striking that many studies reporting no effect (caffeine nos 19, 22, 33; nicotine nos 37, 39, 48) did not use a crossover design. Further, there is a suggestion (studies 21 and 25) that the so-called adaptiverate task is a less sensitive instrument that externally paced tasks (see comments on paced versus unpaced tasks in Koelega 1989). It is not evident that the load imposed by the very high event rate of the RVIP task is a critical determinant, there are also positive effects with lower event rates (studies 25, 26, 27) albeit for caffeine; there are very few nicotine studies employing low event rates.…”

“…Some caveats regarding the sensitivity of vigilance tasks must be entered, however. Different vigilance tasks impose different demands upon perceptual discrimination and working memory (Koelega et al 1989), cf the processing demands of the Mackworth continuous clock (detection of a pause in a moving hand), the Bakan type of task (detection of sequences of odd or even digits), the CPT-X (detection of the letter X) with highly degraded visual stimuli, or the Wilkinson auditory task (detection of a difference in the duration of tones), etc. These tasks contain important differences, and their intercorrelations are often low.…”

“…In an earlier review (Koelega 1989) the position has been defended that we may gain more by exhaustive reviews of specific tasks than by reviewing the effects of drugs on "performance" in general. In vigilance tasks people are required to sustain a high level of attention in order to detect aperiodically occurring, rare, or unusual events.…”