A procedure for studying the within-session onset of human drug discrimination.
The purpose of the present study was to develop a procedure for measuring the within-session onset of human drug discrimination. During daily sessions, under double-blind conditions, caffeine-abstinent adults ingested a letter-coded capsule containing 178 mg caffeine or placebo. Trials were presented at 30-s intervals, beginning immediately after drug ingestion and continuing for 60 min. On each trial, subjects could guess which of their two letter-coded drugs they had received by pressing a left button (for one drug) or right button (for the other drug); subjects could also press a center "no guess" button instead of guessing. Each trial ended after one button press. After each session, subjects were told which drug they had received. Subjects earned one point (worth $0.10 per point) for each correct guess. Subjects lost either 0, 1, or 10 points for each incorrect guess; the point-loss contingencies were varied in random order across sessions. Discrimination earnings accumulated across all sessions. The point-loss contingencies decreased random responding and delayed the discrimination time course. Overall, this procedure provided an orderly and relatively continuous measure of the within-session onset of drug discrimination and should have a range of applications in understanding the human behavioral pharmacology of drugs.
Silverman
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Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224.
Mumford
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GK
Griffiths
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RR
D002110:Caffeine / Q000032:analysis / Q000494:pharmacology*; D004193:Discrimination Learning; D006801:Humans; D010919:Placebos; D011930:Reaction Time; D012463:Saliva / Q000737:chemistry / Q000187:drug effects*
D010919:Placebos; D002110:Caffeine