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 b etween monetary rewards ($11-$80) available immediately and larger rewards ($25-$85) available after delays ranging from 1 week to 6 months. Participa nts 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, 19 75) implies that delay-discounting rates are positively correlated with imp ulsiveness. On average, heroin addicts' discount rates were twice those of controls (p = .004), and discount rates were positively correlated with imp ulsivity as measured by self-report questionnaires (p < .05). The results l end external validity to the delay-discounting rate as a measure of impulsi veness, a characteristic associated with substance abuse.