Impulsivity and rapid discounting of delayed hypothetical rewards in cocaine-dependent individuals.

In this study, crack/cocaine-dependent (CD) and non-drug-using matched control (MC) participants were presented with hypothetical immediate and delayed rewards, with 16 delay conditions ranging from 5 min to 25 years. All participants were presented with hypothetical monetary rewards; however, the CD group was also presented with hypothetical crack/ cocaine rewards. The objective value of the rewards ranged from $1 to $1,000. Hyperbolic discounting functions provided a good fit of the data. The CD group discounted monetary rewards at a higher rate than the MC group did, and the CD group discounted crack/cocaine rewards at a higher rate than it did monetary rewards. Moreover, scores on self-report measures indicated greater impulsivity in the CD group when compared with the MC group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay Discounting of Potentially Real and Hypothetical Rewards: II. Between- and Within-Subject Comparisons.

Prior studies comparing discounting of delayed hypothetical or potentially real rewards have reported no differences, but they used within-subjects designs. This raises the possibility that participants remembered their choices in one condition and repeated them in the other. In Experiment 1, between-subjects comparisons were made with an adjusting-amount procedure. No significant effect of reward type on delay discounting was detected. Experiment 2 increased the proportion of real rewards and made between- and within-subject comparisons. These comparisons also failed to reveal a significant effect of reward type. Although these findings are consistent with prior findings, caution is urged because choices involving hypothetical rewards have yet to be compared with choices involving real rewards (i.e., the consequences of every choice are obtained) in an experiment using forced-choice trials and steady-state methodology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Moderate drug use and delay discounting: A comparison of heavy, light, and never smokers.

Delay discounting was examined in light smokers (10 or fewer cigarettes per day) and compared with previously published delay discounting data for heavy and never smokers. Participants evaluated several hypothetical outcomes: money gains and loses ($10, $100, and $1,000), health gains and losses (durations of improved and impoverished health subjectively equivalent to $1,000), cigarette gains and losses (amounts subjectively equivalent to $1,000), and potentially real rewards ($10 and $100). Light smokers discounted money significantly more than never smokers, but light smokers did not differ from heavy smokers. The 3 groups did not statistically differ in discounting of health consequences. Similarly, the 2 smoking groups were not found to differ in discounting of cigarettes. Like heavy smokers, light smokers discounted cigarettes significantly more than money and health. Several significant, positive correlations were found between smoking rate and various discounting measures in the heavy smokers but not in the light smokers. Several previous findings were replicated, helping to validate the present results: the sign effect (greater discounting of gains than losses), the magnitude effect (greater discounting of smaller rewards), reliability of discounting measures over time, and the consistency of hypothetical and potentially real rewards. These data suggest that even moderate levels of drug use may be associated with high delay discounting levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of methylphenidate on discounting of delayed rewards in attention deficit/hyperactivity disorder.

Impulsivity is a central component of attention deficit/hyperactivity disorder (ADHD). Delay discounting, or a preference for smaller, immediate rewards over larger, delayed rewards, is considered an important aspect of impulsivity, and delay-related impulsivity has been emphasized in etiological models of ADHD. In this study, we examined whether stimulant medication, an effective treatment for ADHD, reduced discounting of delayed experiential and hypothetical rewards among 49 children (ages 9–12 years) with ADHD. After a practice day, participants completed a 3-day double-blind placebo-controlled acute medication assessment. Active doses were long-acting methylphenidate (Concerta), with the nearest equivalents of 0.3 and 0.6 mg/kg TID immediate-release methylphenidate. On each testing day, participants completed experiential (real-world money in real time) and hypothetical discounting tasks. Relative to placebo, methylphenidate reduced discounting of delayed experiential rewards but not hypothetical rewards. Broadly consistent with etiological models that emphasize delay-related impulsivity among children with ADHD, these findings provide initial evidence that stimulant medication reduces delay discounting among those with the disorder. The results also draw attention to task parameters that may influence the sensitivity of various delay discounting measures to medication effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discounting in current and former marijuana-dependent individuals.

Studies have found that a variety of drug-dependent groups discount delayed rewards more than matched controls. This study compared delay discounting for a hypothetical $1,000 reward among dependent marijuana users, former dependent marijuana users, and matched controls. Discounting of marijuana was also assessed in the currently marijuana-dependent group. No significant differences in discounting were detected among the groups; however, currently dependent users showed a trend to discount money more than the other 2 groups. Within the dependent marijuana group, marijuana was discounted more than money, and discounting for money and marijuana was significantly and positively correlated. Regression analyses indicated that delay discounting was more closely associated with tobacco use than marijuana use. A variety of questionnaires were also administered, including impulsivity questionnaires. Dependent marijuana users scored as significantly more impulsive on the Impulsiveness subscale of the Eysenck Impulsiveness–Venturesomeness–Empathy questionnaire than controls. However, the 3 groups did not significantly differ on several other personality questionnaires, including the Barratt Impulsivity Scale—11. The Stanford Time Perception Inventory Present–Fatalistic subscale was positively correlated with money and marijuana discounting, indicating that a greater sense of powerlessness over the future is related to greater delay discounting. Results suggest that current marijuana dependence may be associated with a trend toward increased delay discounting, but this effect size appears to be smaller for marijuana than for previously examined drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imagining the future: Degraded representations of future rewards and events in schizophrenia.

Over the course of life, most people work toward temporally distant rewards such as university degrees or work-related promotions. In contrast, many people with schizophrenia show deficits in behavior oriented toward long-term rewards, although they function adequately when rewards are more immediately present. Moreover, when asked about possible future events, individuals with schizophrenia show foreshortened future time perspectives relative to healthy individuals. Here, we take the view that these deficits are related and can be explained by cognitive deficits. We compared the performance of participants with schizophrenia (n = 39) and healthy participants (n = 25) on tasks measuring reward discounting and future event representations. Consistent with previous research, we found that relative to healthy participants, those with schizophrenia discounted the value of future rewards more steeply. Furthermore, when asked about future events, their responses were biased toward events in the near future, relative to healthy participants' responses. Although discounting and future representations were unrelated in healthy participants, we found significant correlations across the tasks among participants with schizophrenia, as well as correlations with cognitive variables and symptoms. Further analysis showed that statistically controlling working memory eliminated group differences in task performance. Together these results suggest that the motivational deficits characteristic of schizophrenia relate to cognitive deficits affecting the ability to represent and/or evaluate distant outcomes, a finding with important implications for promoting recovery from schizophrenia. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Three-month stability of delay and probability discounting measures.

Psychopharmacologists are interested in delay and probability discounting because the tendency to discount the value of future and uncertain rewards has been linked with drug dependency. However, relatively little is known about the long-term stability of discounting measures typically studied in clinical psychopharmacology. To evaluate the stability of discounting over a 3-month period, the authors compared points of subjective equality (indifference points) with those collected from the same subjects 3 months earlier. Seven delay periods, ranging from 1 week to 25 years, and 7 probability values, ranging from .95 to .05, were assessed in an undergraduate sample (n=22, delay discounting; n=18, probability discounting). The authors examined both differential stability (stability of individual differences) and absolute stability (stability of the group mean) of delay and probability discounting measures as well as their respective indifference points. The results demonstrate that standard delay and probability discounting parameters (e.g., hyperbolic k and area under the curve) had both differential stability and absolute stability across 3 months. Moreover, most indifference points in the delay and probability discounting tasks demonstrated both differential and absolute stability. All together, these results suggest that delay and probability parameters are stable enough to predict future behavior, such as substance abuse. Additional findings indicated that a hyperbolic function fitted the data better than an exponential function and that delay and probability discounting parameters were not significantly correlated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison between two measures of delay discounting in smokers.

Agreement between computer and questionnaire measures of delay discounting in smokers was compared. Correlations between measures for small, medium, or large rewards were significant. Log κ values decreased as the reward delay increased, with values lower for the computer task than the questionnaire, with significant differences for small rewards. The 2 measures were related to smoking rate but not to age, gender, or obesity. The Bland-Altman test of agreement indicated large within-subject differences in κ values between the 2 measures. The size of the difference between the log κ values and magnitude of the log κ values were positively related. Results suggest κ values from the 2 measures are related but may not be used interchangeably. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discounting of cocaine by rhesus monkeys.

The present, subjective value of a reinforcer typically decreases as a function of the delay to its receipt, a phenomenon termed delay discounting. Delay discounting, which is assumed to reflect impulsivity, is hypothesized to play an important role in drug abuse. The present study examined delay discounting of cocaine injections by rhesus monkeys. Subjects were studied on a discrete-trials task in which they chose between 2 doses of cocaine: a smaller, immediate dose and a larger, delayed dose. The immediate dose varied between 0.012 and 0.4 mg/kg/injection, whereas the delayed dose was always 0.2 mg/kg/injection and was delivered after a delay that varied between 0 and 300 s in different conditions. At each delay, the point at which a monkey chose the immediate and delayed doses equally often (i.e., the ED50) provided a measure of the present, subjective value of the delayed dose. Dose-response functions for the immediate dose shifted to the left as delay increased. The amount of the immediate dose predicted to be equal in subjective value to the delayed dose decreased as a function of the delay, and hyperbolic discounting functions provided good fits to the data (median R2 = .86). The current approach may provide the basis for an animal model of the effect of delay on the subjective value of drugs of abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discounting of hypothetical and potentially real outcomes in nicotine-dependent and nondependent samples.

Discounting is a behavioral phenomenon in which the value of an outcome diminishes as a function of its increased delay or decreased probability and is related to substance abuse research because of its theoretical ties with behavioral models of impulsive choice. Research to date suggests that hypothetical outcomes used in discounting research yield data that are indistinguishable from those using potentially real outcomes. However, the extant literature focuses primarily on delay discounting in non-drug-using humans and has not examined whether hypothetical outcomes yield disproportionate numbers of nonsystematic response patterns. In two experiments, we compared hypothetical and potentially real monetary outcomes in delay and probability discounting tasks in terms of rates of discounting and the frequency of nonsystematic response patterns. In Experiment 1, 61 adults reported no smoking, binge drinking, or illicit drug use in the past year. Experiment 2 included a community sample of nicotine-dependent adults (N = 36). In both experiments, discounting for hypothetical and potentially real outcomes yielded similar data, replicating and extending a growing literature pointing to the empirical equivalence of these outcomes. These findings are relevant to research on discounting that is frequently used in the study of substance use and other impulse-control behaviors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Pathological gamblers discount probabilistic rewards less steeply than matched controls.

Nineteen treatment-seeking men meeting Diagnostic and Statistical Manual for Mental Disorders (4th ed.) criteria for pathological gambling and 19 demographically matched controls participated. Participants provided demographic information, information about their recent drug use and gambling activities, and biological samples (to confirm drug abstinence). They also completed the Eysenck Personality Questionnaire, the South Oaks Gambling Screen (SOGS), and 2 questionnaires designed to separately quantify probability and delay discounting. Pathological gamblers discounted probabilistic rewards significantly less steeply than matched controls. A significant correlation revealed that more shallow probability discounting was associated with higher SOGS scores. Across groups, there was no significant difference in delay discounting, although this difference approached significance when education and ethnicity were included as covariates. These findings, collected for the 1st time with pathological gamblers, are consistent with previous reports that problem-gambling college students discount probabilistic rewards less steeply than controls. The nature of the relation between probability discounting and severity of problem gambling is deserving of further study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypothetical intertemporal choice and real economic behavior: Delay discounting predicts voucher redemptions during contingency-management procedures.

Delay discounting rates are predictive of drug use status, the likelihood of becoming abstinent, and a variety of health behaviors. Rates of delay discounting may also be related to other relevant behaviors associated with addiction, such as the frequency at which individuals redeem contingency management voucher earnings. This study examined the discounting rates of 152 participants in a buprenorphine treatment program for opioid abuse. Participants received up to 12 weeks of buprenorphine treatment combined with contingency management. Participant's drug use was measured via urine specimens submitted three times a week. Successive negative urine specimens were reinforced with increasing amounts of money. After each negative urine specimen, a participant could either redeem his or her earnings or accumulate it in an account. Analysis of the frequency of redemptions showed that participants with higher rates of delay discounting at study intake redeemed their earnings significantly more often than participants with lower rates of discounting. Age and income also predicted redemption rates. We suggest that delay discounting rates can be used to predict redemption behaviors in a contingency management treatment program and that these findings are consistent with the recent theory of the competing neurobehavioral decision systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perception of anticipatory time in temporal discounting.

The current article focuses on the role of anticipatory time perception in temporal discounting. We propose a perceived-time–based model and demonstrate that 2 aspects of time perception are relevant to hyperbolic discounting. Specifically, our model states that diminishing sensitivity to longer time horizons (i.e., how long individuals perceive short time horizons to be relative to long time horizons) and the level of time contraction overall (i.e., how long or short individuals perceive time horizons to be overall) contribute to the degree of hyperbolic discounting. We estimate individual differences in the degree of diminishing sensitivity to time and the degree of time contraction, and demonstrate that each significantly predicts the degree of hyperbolic discounting. These results empirically confirm two unique aspects of anticipatory time perception in determining individuals’ temporal discounting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discounting is associated with treatment response among cocaine-dependent outpatients.

Delay discounting (DD) describes the rate at which reinforcers lose value as the temporal delay to their receipt increases. Steeper discounting has been positively associated with vulnerability to substance use disorders, including cocaine use disorders. In the present study, we examined whether DD of hypothetical monetary reinforcers is associated with the duration of cocaine abstinence achieved among cocaine-dependent outpatients. Participants were 36 adults who were participating in a randomized controlled trial examining the efficacy of voucher-based contingency management (CM) using low-magnitude (N = 18) or high-magnitude (N = 18) voucher monetary values. DD was associated with the number of continuous weeks of cocaine abstinence achieved, even after adjusting for treatment condition during the initial 12-week, t(33) = 2.48, p = .045 and entire recommended 24-week of treatment, t(33) = 2.40, p = .022. Participants who exhibited steeper discounting functions achieved shorter periods of abstinence in the Low-magnitude voucher condition (12-week: t(16) = 2.48, p = .025; 24-week: t(16) = 2.68, p = .017), but not in the High-magnitude voucher condition (12-week: t(16) = 0.51, p = .618; 24-week: t(16) = 1.08, p = .298), although the interaction between DD and treatment condition was not significant (12-week: t(32) = ?1.12, p = .271; 24-week: t(32) = ?0.37, p = .712). These results provide further evidence on associations between DD and treatment response and extend those observations to a new clinical population (i.e., cocaine-dependent outpatients), while also suggesting that a more intensive intervention like the High-magnitude CM condition may diminish this negative relationship between DD and treatment response. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Now or later? Striatum and insula activation to immediate versus delayed rewards.

Neuroimaging studies on delay discounting tasks that use reward delays ranging from minutes to days have implicated the insula and striatum in the processing of intertemporal decisions. This study aimed at assessing whether these brain regions would also be involved in decision-making when subjects have to wait through the delays within the range of seconds. Using functional MRI in 13 healthy volunteers, we repeatedly presented monetary options with delays that differed within the range of multiple seconds. Using a region-of-interest approach, we found significant activation in the bilateral anterior insula and striatum when subjects chose either the immediate (smaller) or delayed (larger) option. In particular, insular activation was observed after the response and the delay, when the outcome of the immediate or the delayed choice was shown. Significantly greater activation was observed in the ventroanterior striatum while subjects chose the immediate, as opposed to the delayed, options and also after receiving the outcome of waiting through the longer delay option. The evidence presented here indicates that both the ventral striatum and the insula are involved in the processing of choosing delay options as well as the consequences of choices with delays in the seconds' range. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discounting predicts postpartum relapse to cigarette smoking among pregnant women.

Delay discounting (DD), a measure of impulsivity, describes the rate at which rewards lose value as the delay to their receipt increases. Greater discounting has been associated with cigarette smoking and various other types of drug abuse in recent research. The present study examined whether DD predicts treatment outcome among cigarette smokers. More specifically, the authors examined whether baseline discounting for hypothetical monetary rewards predicted smoking status at 24 weeks postpartum among women who discontinued smoking during pregnancy. Participants were 48 pregnant women (10.5 = 4.1 weeks gestational age at study entry) who participated in a clinical trial examining the use of incentives to prevent postpartum relapse. Several sociodemographic characteristics (being younger, being less educated, and reporting a history of depression) assessed at study entry were associated with increased baseline DD, but in multivariate analyses only DD predicted smoking status at 24 weeks postpartum. Greater baseline DD was a significant predictor of smoking status at 24 weeks postpartum. DD was reassessed periodically throughout the study and did not significantly change over time among those who eventually resumed smoking or those who sustained abstinence. The results extend the association of DD with risk for substance abuse to pregnant and recently postpartum cigarette smokers and demonstrate a significant relationship between DD and treatment outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal discounting of rewards in patients with bipolar disorder and schizophrenia.

Patients with bipolar disorder (BD) and schizophrenia (SZ) often show decision-making deficits in everyday circumstances. A failure to appropriately weigh immediate versus future consequences of choices may contribute to these deficits. We used the delay discounting task in individuals with BD or SZ to investigate their temporal decision making. Twenty-two individuals with BD, 21 individuals with SZ, and 30 healthy individuals completed the delay discounting task along with neuropsychological measures of working memory and cognitive function. Both BD and SZ groups discounted delayed rewards more steeply than did the healthy group even after controlling for current substance use, age, gender, and employment. Hierarchical multiple regression analyses showed that discounting rate was associated with both diagnostic group and working memory or intelligence scores. In each group, working memory or intelligence scores negatively correlated with discounting rate. The results suggest that (a) both BD and SZ groups value smaller, immediate rewards more than larger, delayed rewards compared with the healthy group and (b) working memory or intelligence is related to temporal decision making in individuals with BD or SZ as well as in healthy individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Concave utility, transaction costs, and risk in measuring discounting of delayed rewards.

Research has consistently found that the decline in the present values of delayed rewards as delay increases is better fit by hyperbolic than by exponential delay-discounting functions. However, concave utility, transaction costs, and risk each could produce hyperbolic-looking data, even when the underlying discounting function is exponential. In Experiments 1 (N=45) and 2 (N=103), participants placed bids indicating their present values of real future monetary rewards in computer-based 2nd-price auctions. Both experiments suggest that utility is not sufficiently concave to account for the superior fit of hyperbolic functions. Experiment 2 provided no evidence that the effects of transaction costs and risk are large enough to account for the superior fit of hyperbolic functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personal relative deprivation, delay discounting, and gambling.

Several lines of research have provided evidence for a relation between personal relative deprivation and gambling. Despite this knowledge, little is known about possible psychological mechanisms through which personal relative deprivation exerts its influence on gambling. The authors of this research sought to examine one such mechanism: the desire for immediate rewards. Using complementary approaches to studying psychological mechanisms, they tested in four studies the general hypothesis that personal relative deprivation translates into gambling urges and behavior in part via increased desires for immediate, even if smaller, rewards. Study 1 showed that an experimental manipulation of personal relative deprivation increased participants' preferences for smaller-sooner over larger-later rewards during a delay-discounting task. Studies 2 and 3 showed that a decreased willingness to delay gratification led to increased gambling behavior. Study 4 showed that preferences for smaller-sooner over larger-later rewards statistically mediated the relation between self-reported personal relative deprivation and gambling urges among a community sample of gamblers. The implications and potential applications of these findings are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)