EXCHANGE DELAYS AND IMPULSIVE CHOICE IN ADULT HUMANS

Choice responding by adult humans in a discrete-trial task was examine d as a function of conditions that manipulated either the delay to poi nt delivery or the delay between points and their exchange for money. In point-delay conditions, subjects chose between an ''impulsive'' alt ernative that provided a small amount of points immediately and a ''se lf-control'' alternative that provided a larger amount of points delay ed by 15, 30, or 60 s. Points were exchanged for money immediately fol lowing the session. Subjects preferred the self-control alternative. I n exchange-delay conditions, subjects chose between a small amount of points exchangeable for money immediately following the session and a larger amount of points exchangeable for money after 1 day, 3 weeks, o r 6 weeks. A self-control preference observed for all subjects in the 1-day exchange-delay condition reversed to exclusive impulsive prefere nce for 4 of the 6 subjects when choice conditions involved exchange d elays of 3 or 6 weeks. These results show that human choice is sensiti ve to the manipulation of exchange delays and that impulsive preferenc e can be obtained with exchange delays on the order of weeks.