The effects of caffeine on two computerized tests of attention and vigilance

Abstract

AbstractSingle doses of caffeine (250 mg, 500 mg) or placebo were administered double‐blind to healthy volunteer subjects (n = 12), using a fully balanced crossover design (Williams square) with 1‐week washout. Assessments were made predrug, and at 45 min and 165 min post‐drug administration. The test battery comprised physiological measures (blood pressure, heart rate and urinary volume), subjective measures of alertness, a letter cancellation task (one‐target, two‐target and four‐target versions), and two computerized measures of attention and vigilance: a rapid information processing task and a continuous attention task. Physiological variables did not alter following caffeine administration, but subjective and cognitive variables showed significant changes in the predicted direction. Thus, doserelated changes in subjective calmness and interest were observed, together with changes in performance for the letter cancellation task at low and intermediate difficulty levels. A dose‐related performance improvement was observed for the rapid information processing task. The continuous attention task was also sensitive to the effects observed for the rapid information processing task. The continuous attention task was also sensitive to the effects of caffeine. The 250 mg dose offset the decline in attention observed under placebo, and indeed facilitated performance at both post‐drug administration times. The 500 mg dose impaired performance at 45 min and improved it at the 165 min post‐administration time. Sensitivity to vigilance change was also observed within test sessions for this test, indicating that the continuous attention task was more sensitive to caffeine‐induced changes in attention than the rapid information processing task.