Drugs and Placebos: Drug Guessing by Normal Volunteers

A series of 4 related experiments are described, using male and female student volunteers. Each experiment involved 3 to 5 evening sessions, during which a number of drug treatments were rotated among Ss. After drug ingestion, a series of experimental tasks, differing among the experiments, were used. At the end of each session, S reported on how the drug received had affected him, and classified the drug as a “stimulant,” “depressant,” “tranquilizer,” or as having “no effect.” In one experiment only the first two categories were used. Differences in drugs received accounted for only a small part of the variance in assigned categories. Amphetamines at the dose levels used were better discriminated from placebo than were other drugs. Limited (but recent) prior experience in being an S in drug experiments may facilitate drug recognition, if the experimental situation provides cues to S in relationship to task demands. However, since the over-all accuracy of drug recognition was only slightly better than chance (for both experienced and naive Ss), little error should be expected to arise from application of the usual (inert) placebo controls.