Discounting of delayed rewards in opioid-dependent outpatients: Exponential or hyperbolic discounting functions?

Abstract

Recent theories of substance abuse have used value discounting of delayed rewards to partly explain the decision to take drugs. Normative-economic theory holds that an exponential function describes the effects of delay on discounting, whereas the matching law posits a hyperbolic discounting function. The ability of these functions to describe 18 human heroin-dependent individuals' monetary- and heroin-reward delay-discounting functions was assessed. In the 1st condition, participants chose between immediate and delayed hypothetical monetary rewards. Delayed rewards were $1,000, and the immediate reward amount was adjusted until choices reflected indifference. In the 2nd condition, participants chose between immediate and delayed heroin (the delayed amount was that which each participant reported he or she could purchase with $1,000). The hyperbolic function produced significantly higher R2 values and significantly lower sums of squared error values. Consistent with previous findings, delayed heroin rewards were discounted at a significantly higher rate than were delayed monetary rewards.

Methodological considerations in the study of delay discounting in intertemporal choice: A comparison of tasks and modes

“…The results provide good psychometric support for the hyperbolic discounting construct. Discount curves were described better by a hyperbolic decay function than by an exponential function, consistent across all conditions, and further solidified the evidence that supports the essential shape of the discounting function (e.g., Green, Myerson, & McFadden, 1997;Kirby & Marakovi , 1996;Madden et al, 1999). Furthermore, the $1,000 reward was discounted more than the $10,000 reward was, consistent with past magnitude effects (Chapman & Winquist, 1998;Kirby, 1997;Vuchinich & Simpson, 1998).…”

Behavioral and neuroeconomics of drug addiction: Competing neural systems and temporal discounting processes

“…Green et al, 1994). These curves have been documented in a variety of settings to be hyperbolic in form Madden et al, 1999;Myerson and Green, 1995).…”

Lorazepam dose-dependently decreases risk-taking related activation in limbic areas

“…For example, altered risk-taking behavior has been observed in substance dependence, where data show that these individuals are more likely to select actions associated with large short-term gains (and large long-term losses) preferentially to those with small short-term gains (and small long-term losses) (Bechara and Damasio, 2002;Grant, Contoreggi et al, 2000). Furthermore, they have a tendency to select risky options (Lane and Cherek, 2000) and show an altered temporal horizon of risks and benefits (i.e., a steeper temporal discounting function) (Petry, Bickel et al, 1998;Madden, Bickel et al, 1999).…”