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 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.