Warren K. Bickel

Impulsivity and cigarette smoking: delay discounting in current, never, and ex-smokers

Abstract Rationale: Impulsivity is implicated in drug dependence. Recent studies show problems with alcohol and opioid dependence are associated with rapid discounting of the value of delayed outcomes. Furthermore, discounting may be particularly steep for the drug of dependence. Objectives: We determined if these findings could be extended to the behavior of cigarette smokers. In particular, we compared the discounting of hypothetical monetary outcomes by current, never, and ex-smokers of cigarettes. We also examined discounting of delayed hypothetical cigarettes by current smokers. Methods: Current cigarette smokers (n=23), never-smokers (n=22) and ex-smokers (n=21) indicated preference for immediate versus delayed money in a titration procedure that determined indifference points at various delays. The titration procedure was repeated with cigarettes for smokers. The degree to which the delayed outcomes were discounted was estimated with two non-linear decay models: an exponential model and a hyperbolic model. Results: Current smokers discounted the value of delayed money more than did the comparison groups. Never- and ex-smokers did not differ in their discounting of money. For current smokers, delayed cigarettes lost subjective value more rapidly than delayed money. The hyperbolic equation provided better fits to the data than did the exponential equation for 74 out of 89 comparisons. Conclusions: Cigarette smoking, like other forms of drug dependence, is characterized by rapid loss of subjective value for delayed outcomes, particularly for the drug of dependence. Never- and ex-smokers could discount similarly because cigarette smoking is associated with a reversible increase in discounting or due to selection bias.

Impulsive and Self-Control Choices in Opiate-Dependent Patients and Non-Drug-Using Control Participants: Drug and Monetary Rewards

Delay discounting was investigated in opioid-dependent and non-drug-using control participants. The latter participants were matched to the former on age, gender, education, and IQ. Participants in both groups chose between hypothetical monetary rewards available either immediately or after a delay. Delayed rewards were

Remember the future: working memory training decreases delay discounting among stimulant addicts

1,000, and the immediate-reward amount was adjusted until choices reflected indifference. This procedure was repeated at each of 7 delays (1 week to 25 years). Opioid-dependent participants were given a second series of choices between immediate and delayed heroin, using the same procedures (i.e., the amount of delayed heroin was that which could be purchased with

Impulsivity : the behavioral and neurological science of discounting

1,000). Opioid-dependent participants discounted delayed monetary rewards significantly more than did non-drug-using participants. Furthermore opioid-dependent participants discounted delayed heroin significantly more than delayed money.

A clinical trial of buprenorphine: Comparison with methadone in the detoxification of heroin addicts

BACKGROUND Excessive discounting of future rewards has been observed in a variety of disorders and has been linked both to valuation of the past and to memory of past events. METHODS To explore the functionality of discounting and memory, we examined whether training of working memory would result in less discounting of future rewards. In this study, 27 adults in treatment for stimulant use were randomly assigned to receive either working memory training or control training according to a yoked experimental design. Measures of delay discounting and several other cognitive behaviors were assessed pre- and posttraining. RESULTS Rates of discounting of delayed rewards were significantly reduced among those who received memory training but were unchanged among those who received control training; other cognitive assessments were not affected by memory training. Discount rates were positively correlated with memory training performance measures. CONCLUSIONS To our knowledge, this is the first study demonstrating that neurocognitive training on working memory decreases delay discounting. These results offer further evidence of a functional relationship between delay discounting and working memory.

Excessive discounting of delayed reinforcers as a trans-disease process contributing to addiction and other disease-related vulnerabilities: emerging evidence.

This volume is an approachable, comprehensive overview of the behavioural science and neuroscience of our impulsive choices and their relation to delay discounting - the tendency to devalue temporally distant rewards or punishments, even though they may greatly outbalance the immediate benefit of our choices. The cutting-edge researchers who contributed to this volume have documented cross-species similarities in impulsive decision making and pioneered the neuroscience of impulsive choice. In this text they provide insights into harmless impulsive acts as well as those that dominate and destory lives.

Mild opioid deprivation increases the degree that opioid-dependent outpatients discount delayed heroin and money

The efficacy of buprenorphine and methadone was compared in the outpatient detoxification of heroin addicts. Forty‐five patients were randomized to receive either sublingual buprenorphine or oral methadone under double‐dummy and double‐blind conditions to study the pharmacology of buprenorphine in a 90‐day detoxification protocol. The patients were administered either 2 mg buprenorphine or 30 mg methadone for 3 weeks followed by 4 weeks of dose reductions and 6 weeks of placebo medication. No significant between‐group differences were seen on measures of treatment retention, drug use, or symptom report. During the hydromorphone challenge, methadone attenuated opioid effects to a greater extent than did buprenorphine on both physiologic (pupil constriction) and self‐report measures. However, this did not result in greater abuse of illicit opioid drugs by subjects taking buprenorphine. The results of this clinical trial indicated that buprenorphine was acceptable to patients and as effective as methadone in the detoxification treatment of heroin addicts.

An Algorithm for Identifying Nonsystematic Delay-Discounting Data

Delay discounting describes the devaluation of a reinforcer as a function of the delay until its receipt. Although all people discount delayed reinforcers, one consistent finding is that substance-dependent individuals tend to discount delayed reinforcers more rapidly than do healthy controls. Moreover, these higher-than-normal discounting rates have been observed in individuals with other behavioral maladies such as pathological gambling, poor health behavior, and overeating. This suggests that high rates of delay discounting may be a trans-disease process (i.e., a process that occurs across a range of disorders, making findings from one disorder relevant to other disorders). In this paper, we argue that delay discounting is a trans-disease process, undergirded by an imbalance between two competing neurobehavioral decision systems. Implications for our understanding of, and treatment for, this trans-disease process are discussed.

Deconstructing relative reinforcing efficacy and situating the measures of pharmacological reinforcement with behavioral economics : a theoretical proposal

HeadingAbstractRationale. A growing literature suggests that excessive temporal discounting of delayed rewards may be a contributing factor in the etiology of substance abuse problems. Little is known, however, about how drug deprivation may affect temporal discounting of delayed rewards by drug-dependent individuals.Objective. To examine the extent to which opioid deprivation affects how opioid-dependent individuals discount small, medium and large quantities of delayed heroin and money.Methods. Thirteen opioid-dependent individuals maintained on buprenorphine completed a hypothetical choice task in which they choose between a constant delayed reward amount and an immediate reward amount that was adjusted until they expressed indifference between both outcomes. The task was completed for three values of heroin and money rewards during eight sessions under conditions of opioid deprivation (four sessions) and satiation (four sessions).Results. Across conditions, hyperbolic functions provided a good fit for the discounting data. Degree of discounting was significantly higher when subjects were opioid deprived. Consistent with previous findings, degree of discounting was higher for heroin than money and inversely related to the magnitude of the reward.Conclusion. Opioid deprivation increased the degree to which dependent individuals discounted delayed heroin and money. Understanding the conditions that affect how drug-dependent individuals discount delayed rewards might help us understand the myopic choices made by such individuals and help improve treatment outcomes.

Reframing Health Behavior Change With Behavioral Economics

Several [corrected] discounting studies have use the R2 measure to identify data [corrected] with poor fits to a mathematical discounting model as nonsystematic data to be eliminated [corrected] Data from three previous delay-discounting studies (six separate groups, with a total of 161 individuals) were used to demonstrate why using R2 to assess the fits of discounting data is problematic. A significant, positive correlation between discounting rate parameter and R2 was found in most groups, showing that R2 is more stringent as a measure of fit for low discounting rates than for high discounting rates. Furthermore, it is suggested that identifying nonsystematic data based on any measure of fit to a mathematical discounting model may be problematic because it confounds discounting rate comparison with the issue of discounting model assessment. Therefore, a model-free method to identify nonsystematic data is needed. An algorithm for identifying nonsystematic data is presented that is based on the expectation of a monotonically decreasing discounting function. This algorithm identified 13 cases out of the 161 reanalyzed data sets as nonsystematic. These nonsystematic data are presented, along with examples of data not identified as nonsystematic. This algorithm, or modifications of it, may be useful in a variety of human and nonhuman animal discounting studies (e.g., delay discounting, probability discounting) as an alternative to the R2 measure for identifying nonsystematic data. The algorithm may be used in empirical investigations to improve discounting methodology, and may be used to identify outliers to be removed from analyses.