In experiment 1, subjects judged time by duration production under no-counting instructions. The productions were made following intravenous injection of atropine sulfate or saline, and after smoking cigarettes with and without (–)-Δ⁹-tetrahydrocannabinol (THC). THC increased the subjective time rate (STR); i.e., the rate at which subjective time passes relative to clock time, whereas atropine had no effect on STR. Thus, reduction in central acetylcholine activity is not a sufficient explanation of THC’s effect on STR. Experiment 2 replicated the THC effect on STR when subjects were counting subjective seconds. This result indicates that THC affects the experience of time as it is passing, and not solely the memory for duration experience after a time period.

The objective of this study was to investigate the interaction between ethanol and dextroamphetamine with regard to psychomotor performance. Twelve healthy, male, paid volunteers, moderate users of ethanol and amphetamines, participated in this study. Ethanol (0.85 g/kg or placebo) was administered over a 30-min interval. Five minutes before the termination of ethanol or placebo ingestion, dextroamphetamine elixir (0.09 mg/kg, 0.18 mg/kg or placebo) diluted in 50 ml of orange juice was administered. Subjects were tested in a single-blind, latin-square, crossover design with each of the following six conditions: placebo ethanol/placebo dextroamphetamine; placebo ethanol/low-dose dextroamphetamine; placebo ethanol/high-dose dextroamphetamine; ethanol/placebo dextroamphetamine; ethanol/low-dose dextroamphetamine; and ethanol/high-dose dextroamphetamine. The variables measured in this study were: subjective rating of ethanol and dextroamphetamine intoxication, accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI task), blood ethanol concentration by breath analyzer, and plasma concentrations of dextroamphetamine by gas chromatography. Results indicate ethanol induced decrements in performance of the skills necessary to drive an automobile were significantly decreased by dextroamphetamine in a dose-response fashion. The administration of dextroamphetamine did not decrease the subjective ratings of ethanol intoxication.