THE EFFECTS OF DRUGS AND FAMILIARITY ON PERFORMANCE IN CONTINUOUS VISUAL SEARCH

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Abstract
Eighteen students were tested for 1 hr. on a task of visual scanning for frequently recurring signals. The visual display changed continually at a variable fast pace, and signal detection was indicated by pressing a telegraph key. The students performed the task after intravenous administration of 15 mg methamphetamine, or 100 mg pentobarbital/150 lbs body weight, or saline placebo, once with each treatment in the first 3, and once again in the last 3 testing sessions. Performance did not deteriorate with time, and with both active drugs it improved over the hr. Evaluated by correct responses, overall performance was best with methampheta-mine and poorest with pentobarbital. The methamphetamine effect reached statistical significance only in the 2nd testing session, and then only after 15 min. There was no significant gain in accuracy from 1 session to the next or from the 1st 3 to the final 3 tests. Incorrect responses decreased from the 1st to the last 3 sessions, but did not change with drug treatment. Evidence is given for an absolute improvement of sustained attention under methamphetamlne, rather than for a relative effect reflecting a gain from reduced fatigue. Methamphetamlne effects may be contingent on familiarity with the drug experience as well as with the task. Changes in performance, with either active drug tested, are attributed to its effect on central processing operations.

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