Effects of d -Amphetamine on Task Performance and Social Behavior of Humans in a Residential Laboratory

Six healthy adult male volunteers lived for 11 days in a residential laboratory. Acute effects of d -amphetamine (0, 5, or 10 mg/70 kg) on performance of tasks, social interaction, and self-reports of drug effects were measured. Each day, participants engaged in a 6.5-hr work period and a 6.5-hr recreation period. Beverages containing d -amphetamine or placebo were consumed daily before the work period and before the recreation period. d -Amphetamine increased response rate without affecting accuracy on some tasks. d -Amphetamine increased the proportion of time spent engaging in verbal interaction during the first but not the second week of the study. No changes in self-reported drug effects were observed. Thus, d -amphetamine improved performance in the absence of stimulant-like subjective effects. This differentiation between performance and subjective effects confirms the importance of determining the effects of drugs on a range of behaviors.