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This study examined the effects of caffeine on a protracted visual monitoring task analogous to an aspect of automobile night driving. The task involved monitoring two red lights that moved apart at random intervals. This display simulated the rate-of-closure cue of change in visual angle for a vehicle following 60 yds. behind another vehicle. Twenty measures of response latency were provided for each 5 in each of 4 hrs. of continuous testing. Five groups (n = 20 in each) were given the following treatments: placebo, 200 nig. of caffeine at the beginning of the second hr., 200 mg. at the third hr., 400 mg. at the second, and 400 mg. at the third. The results indicated that caffeine significantly inhibited response blocking (attention lapses). The effects were apparent within 1 hr. following administration and persisted over the remaining hrs. No difference was found between dosage levels or in magnitude of effect at the different administration times.

Studied the effects of prolonged exposure to 2 noise stressors (random and patterned intermittent 0 and 85 db) on the performance of 60 male undergraduates on 3 tasks requiring different abilities (reaction time, rate control, and time-sharing). The sensitivity of alternate metrics of performance degradation was also evaluated within an analysis of covariance design. Ss were randomly assigned to the various treatments, and a series of 2 * 2 * 4 (Noise Intensity * Noise Quality * Trial Blocks) covariance analyses were carried out. The effects of random noise on performance depended on the type of task and performance measure. The reaction-time task was affected, the rate-control task was not, and the time-sharing task was affected only after continued exposure to noise. Patterned noise had insignificant effects. (20 ref)

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