Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls.

TLDR

The discounting model of impulsiveness predicts that higher delay‑discounting rates reflect greater impulsivity. In a 1‑in‑6 chance task, 56 heroin addicts and 60 matched controls chose between immediate and delayed monetary rewards, and their discount rates were estimated from the pattern of choices. Heroin addicts exhibited discount rates twice those of controls, and these rates were positively correlated with self‑reported impulsivity, supporting discounting as a valid measure of impulsiveness.

Abstract

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.