Effect of d-amphetamine, secobarbital, and marijuana on choice behavior: social versus nonsocial options

The effects of oral d-amphetamine and secobarbital and smoked marijuana on human social conversation and preference for socializing were studied in three separate experiments. During experimental sessions, active drug or placebo was administered using an acute or divided dosing procedure. Subjects who received drug then engaged in a discrete-trial choice procedure in which they made a series of mutually exclusive choices between a social (talking with their nondrugged partner) and nonsocial (sitting quietly alone) option. Lapel microphones and voice operated relays measured seconds of speech. Subjects engaged in greater amounts of conversation and chose the social option more frequently following acute dosing of d-amphetamine and secobarbital compared with placebo. Acute administration of marijuana did not significantly affect social speech or choice behavior, producing slight decreases in both measures. Acute dosing of all drugs significantly increased subjective drug effect or drug high; however, only secobarbital affected the circular lights task, producing significant performance decrements. The shifts in preference toward the social option observed with d-amphetamine and secobarbital suggest that these drugs increased the reinforcing effects of socializing relative to sitting alone. This may be one mechanism by which psychoactive drugs facilitate social conversation.