Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls.
Fifty-six heroin addicts and 60 age-matched controls were offered choices between monetary rewards ($11-$80) available immediately and larger rewards ($25-$85) available after delays ranging from 1 week to 6 months. Participants had a 1-in-6 chance of winning a reward that they chose on one randomly selected trial. Delay-discounting rates were estimated from the pattern of participants' choices. The discounting model of impulsiveness (Ainslie, 1975) implies that delay-discounting rates are positively correlated with impulsiveness. On average, heroin addicts' discount rates were twice those of controls (p = .004), and discount rates were positively correlated with impulsivity as measured by self-report questionnaires (p < .05). The results lend external validity to the delay-discounting rate as a measure of impulsiveness, a characteristic associated with substance abuse.
Kirby
K N
KN
Department of Psychology, Bronfman Science Center, Williams College, Williamstown, Massachusetts 01267, USA. kkirby@williams.edu
Petry
N M
NM
Bickel
W K
WK
D000328:Adult; D000704:Analysis of Variance; D002755:Choice Behavior; D006556:Heroin Dependence / Q000523:psychology*; D006801:Humans; D007175:Impulsive Behavior; D008960:Models, Psychological; D012201:Reward