Monetary Reinforcement Research Articles

ASYMMETRY OF REINFORCEMENT AND PUNISHMENT IN HUMAN CHOICE

The hypothesis that a penny lost is valued more highly than a penny earned was tested in human choice. Five participants clicked a computer mouse under concurrent variable-interval schedules of monetary reinforcement. In the no-punishment condition, the schedules arranged monetary gain. In the punishment conditions, a schedule of monetary loss was superimposed on one response alternative. Deviations from generalized matching using the free parameters c (sensitivity to reinforcement) and log k (bias) were compared in the no-punishment and punishment conditions. The no-punishment conditions yielded values of log k that approximated zero for all participants, indicating no bias. In the punishment condition, values of log k deviated substantially from zero, revealing a 3-fold bias toward the unpunished alternative. Moreover, the c parameters were substantially smaller in punished conditions. The values for bias and sensitivity under punishment did not change significantly when the measure of net reinforcers (gains minus losses) was applied to the analysis. These results mean that punishment reduced the sensitivity of behavior to reinforcement and biased performance toward the unpunished alternative. We concluded that a single punisher subtracted more value than a single reinforcer added, indicating an asymmetry in the law of effect.

Effect of transdermal nicotine replacement on alcohol responses and alcohol self-administration

Nicotine replacement is commonly used to treat tobacco use in heavy-drinking smokers. However, few studies have examined the effect of nicotine replacement on subjective and physiological responses to alcohol and alcohol drinking behavior. The primary aim of this within-subject, double-blind study was to examine whether transdermal nicotine replacement (0 mg vs 21 mg/day) altered response to a low-dose priming drink and subsequent ad libitum drinking behavior. Subjects (n=19) were non-treatment-seeking, non-dependent heavy drinkers who were daily smokers. Six hours after transdermal patch application, subjective and physiological responses to a priming drink [designed to raise blood alcohol levels (BALs) to 0.03 g/dl] were assessed. This was followed by a 2-h self-administration period where subjects could choose to consume up to eight additional drinks (each designed to raise BALs by 0.015 g/dl) or to receive monetary reinforcement for drinks not consumed. We found that 6 h after patch application, tobacco craving associated with withdrawal relief was decreased, and systolic blood pressure and heart rate were increased in the active patch condition compared to the placebo patch condition. Subjective intoxication in response to the priming drink was attenuated in the active nicotine patch condition compared to 6 h of nicotine deprivation (i.e., placebo patch). During the self-administration period, subjects had longer latencies to start drinking and consequently appeared to consume fewer drinks when administered the active patch compared to the placebo patch. In heavy drinkers, transdermal nicotine replacement compared to mild nicotine deprivation attenuated subjective and physiological alcohol responses and delayed the initiation of drinking.

Neural Evidence for Enhanced Error Detection in Major Depressive Disorder

Anomalies in error processing have been implicated in the etiology and maintenance of major depressive disorder. In particular, depressed individuals exhibit heightened sensitivity to error-related information and negative environmental cues, along with reduced responsivity to positive reinforcers. The authors examined the neural activation associated with error processing in individuals diagnosed with and without major depression and the sensitivity of these processes to modulation by monetary task contingencies. The error-related negativity and error-related positivity components of the event-related potential were used to characterize error monitoring in individuals with major depressive disorder and the degree to which these processes are sensitive to modulation by monetary reinforcement. Nondepressed comparison subjects (N=17) and depressed individuals (N=18) performed a flanker task under two external motivation conditions (i.e., monetary reward for correct responses and monetary loss for incorrect responses) and a nonmonetary condition. After each response, accuracy feedback was provided. The error-related negativity component assessed the degree of anomaly in initial error detection, and the error positivity component indexed recognition of errors. Across all conditions, the depressed participants exhibited greater amplitude of the error-related negativity component, relative to the comparison subjects, and equivalent error positivity amplitude. In addition, the two groups showed differential modulation by task incentives in both components. These data implicate exaggerated early error-detection processes in the etiology and maintenance of major depressive disorder. Such processes may then recruit excessive neural and cognitive resources that manifest as symptoms of depression.

Effects of alternative reinforcer and craving on the choice to smoke cigarettes in the laboratory

We examined to what extent craving for cigarettes and the magnitude of an alternative monetary reinforcer were predictors of the choice to smoke in the human laboratory. Twelve non-treatment-seeking nicotine-dependent volunteers participated in a series of outpatient sessions during which they had repeated opportunities to select between three puffs of a cigarette and a variety of monetary alternatives ($0.50-3), responding under a progressive-ratio schedule. Level of cigarette craving was measured at baseline and between each choice opportunity. The probability of choosing a cigarette decreased significantly with the increase in the magnitude of the alternative reinforcer. Baseline level of craving did not significantly alter the probability of choosing a cigarette, but a craving component related to the anticipation of positive effects from smoking, assessed repeatedly between choice opportunities, was predictive of the choice to smoke. These results demonstrate that the cigarette puff self-administration procedure is sensitive to environmental manipulations and cigarette puff choice can be modified by the availability of an alternative reinforcer. This paradigm models the motivational component associated with choice to smoke and could be used to evaluate the effects of pharmacological and behavioral interventions to decrease cigarette smoking.

Efficacy of an Individualized Adherence Support Program with Contingent Reinforcement Among Nonadherent HIV-Positive Patients

To evaluate the efficacy of a program designed to improve adherence to antiretroviral therapy among patients with poor adherence. A randomized intervention trial was conducted among 90 HIV-positive patients experiencing treatment failure as a result of noncompliance with their medication regimen. Eligible participants were randomly assigned to an adherence case management intervention with monetary reinforcement (CM) or to a standard of care group (SC). The CM participants met regularly with a treatment advocate for individualized adherence support. Efficacy was measured in terms of reductions in viral load and improvements in immune function at weeks 12, 24, and 48. After 48 weeks, 55% (n=26) of those in the CM achieved at least a 1-log10 drop in viral load as compared to 28% (n=12) in the SC group (P=.0089). Furthermore, the mean CD4 count was 209 cells/mm3 for the CM group as compared to 150 cells/mm3 in the SC group (P=.0333). Based on logistic regression analysis, being in the CM was an independent predictor of reduction in viral load (odds ratio=2.49; P=.0514). The individualized adherence intervention is feasible and effective in reducing viral load and improving immune function.

Experimentally induced aggressiveness in heroin-dependent patients treated with buprenorphine: Comparison of patients receiving methadone and healthy subjects

Objective measures of experimentally induced aggressiveness were evaluated in heroin-dependent patients (HDP), 15 receiving buprenorphine (BUP) and 15 receiving methadone (METH) treatment. HDP were randomly assigned to BUP and METH groups. Fifteen healthy subjects (CONT) were included in the study as controls. During a laboratory task, the Point Subtraction Aggression Paradigm, subjects earned monetary reinforcement and could respond by ostensibly subtracting money from a fictitious subject (the aggressive response). Money-earning (points maintained) responses did not differ in BUP patients and in controls. In contrast, point-maintained responses were significantly lower in the group of HDP treated with METH than in both the BUP and CONT groups. Aggressive responses were significantly higher in the HDP group than in the CONT group. No significant differences in aggressive responses were found between the BUP and METH groups. Baseline concentrations of plasma adrenocorticotropic hormone (ACTH) and cortisol (CORT) were higher in HDP than in CONT. During the experimental task, ACTH and CORT increased significantly less in METH patients than in BUP patients and CONT. Norepinephrine (NE) and epinephrine (EPI) levels increased significantly more in HDP than in CONT, without any difference between the METH and BUP patients. PSAP aggressive responses positively correlated with NE and EPI changes, as well as with Buss–Durkee Hostility Inventory (BDHI) scores in both METH and BUP patients and also in CONT subjects. No correlation was found between the extent of heroin exposure, drug doses and aggressiveness levels. BUP, similarly to METH, does not seem to affect outward-directed aggressiveness, as aggressive responses related more to monoamine levels and personality traits than to the action of opioid agonists. Money-earning responses seemed to be unimpaired in BUP patients.

Contingency Management for the Treatment of Methamphetamine Use Disorders

Theory and some preliminary evidence suggest that contingency management may be an effective treatment strategy or adjunct to psychosocial treatment for methamphetamine use disorders. An experimentally rigorous investigation on the topic was provided by a large multisite trial conducted under the auspices of the Clinical Trials Network of the National Institute on Drug Abuse. The authors report data on 113 participants who were diagnosed with methamphetamine abuse or dependence. They were randomly assigned to receive 12 weeks of either treatment as usual or treatment as usual plus contingency management. Urine samples were tested for illicit drugs, and breath samples were tested for alcohol. The reinforcers for drug-negative samples were plastic chips, some of which could be exchanged for prizes. The number of plastic chips drawn increased with each week of negative samples but was reset to one after a missed or positive sample. The participants in both groups remained in treatment for equivalent times, but those receiving contingency management in addition to usual treatment submitted significantly more negative samples, and they were abstinent for a longer period of time (5 versus 3 weeks). These results suggest that contingency management has promise as a component in treatment strategies for methamphetamine use disorder.

Modeling the effect of alcohol on smoking lapse behavior

The primary aim of this project was to examine the role of alcohol use in smoking lapse behavior, as alcohol consumption is a known risk factor for poor smoking cessation outcomes. We have developed a novel human laboratory model to examine two primary aspects of alcohol-mediated tobacco relapse: (1) Does alcohol facilitate the initiation of the first cigarette? (2) Once the first cigarette is initiated, does alcohol facilitate subsequent smoking? Using a within-subject design, 16 daily smokers who were also heavy social drinkers received a priming drink (0.03 g/dl or taste-masked placebo) and then had the option of initiating a tobacco self-administration session or delaying initiation by 5-min increments for up to 50 min in exchange for monetary reinforcement. Subsequently, the tobacco self-administration session consisted of a 1-h period in which subjects could choose to smoke their preferred brand of cigarettes using a smoking topography system or receive monetary reinforcement for cigarettes not smoked. Alcohol craving, tobacco craving, subjective reactivity to alcohol, and nicotine withdrawal were assessed as secondary outcomes. Results demonstrated that after consuming the alcohol beverage, subjects were less able to resist the first cigarette and initiated their smoking sessions sooner, and smoked more cigarettes compared to the placebo beverage. These findings have implications for smoking cessation in alcohol drinkers and model development to assess smoking lapse behavior.

Nicotine self-administration: cigarette versus nicotine gum diurnal topography

The few extant reports examining the relationship between diurnal patterns of pre-cessation smoking and cessation nicotine replacement use suggest that this relationship may be important in preventing smoking relapse. The current study evaluated three interventions to increase nicotine gum use: standard treatment (ST, N = 31), ST plus brief feedback about nicotine attitudes and knowledge (BF, N = 32), or BF plus contingent monetary reinforcement for nicotine gum use (CM, N = 34). Subsets of the 97 randomized subjects were selected based on availability of adequate data for analyses: baseline phase (i.e., 6-7 days of ad libitum smoking, N = 63) or the treatment phase (i.e., 13-15 days of treatment, N = 47). For both cigarettes and nicotine gum, participants showed a characteristic pattern of increasing use during the morning hours, followed by stable use in the afternoon and evening, with a steep decrease prior to sleep onset. Patterns of diurnal gum use did not differ by compliance intervention. Greater morning use of cigarettes or gum was associated with smoking relapse while greater evening and night use of cigarettes or gum was associated with abstinence. Understanding of diurnal patterns of smoking and NRT use may ultimately inform tailored scheduling of NRT.

Methadone doses of 100 mg or greater are more effective than lower doses at suppressing heroin self‐administration in opioid‐dependent volunteers

Methadone maintenance has been an effective pharmacotherapy for the treatment of heroin dependence for nearly four decades. Recent clinical research suggests that methadone doses larger than those used in most clinics are more effective at suppressing illicit heroin use. This greater efficacy may result from greater cross-tolerance to the reinforcing effects of heroin. The purpose of this double-blind, within-subject study was to examine the relationship between methadone maintenance dose and the reinforcing effects of heroin. Participants were stabilized on 50, 100 and 150 mg methadone (ascending order) during separate outpatient periods before being admitted to an inpatient research unit for testing at each maintenance dose. Five opiate-dependent volunteers completed the study. During each 4-week inpatient testing period, participants sampled three doses of heroin (0, 10, or 20 mg; random order; one dose per week) and were subsequently allowed seven opportunities to choose between another injection of that week's heroin dose and varying amounts of money (dollars 2-38). The number of heroin injections chosen decreased as methadone dose was increased. Larger alternative monetary reinforcers were required to suppress heroin self-administration during maintenance on 50 compared to 100 or 150 mg methadone. Larger methadone doses also completely blocked the subjective effects of heroin and produced greater withdrawal suppression during the outpatient periods. These results support other clinical and laboratory-based research indicating that persistent heroin use may be reduced by providing larger methadone maintenance doses that produce more effective cross-tolerance to heroin.

A TEST OF THE FORMAL AND MODERN THEORIES OF MATCHING

The present study tested a formal, or purely mathematical, theory of matching, and a modern account derived by McDowell (1986) that incorporates deviations from strict matching-bias and sensitivity. Six humans pressed a lever for monetary reinforcers on five concurrent variable interval (VI) schedules of reinforcement. All schedules were presented during each session. The magnitude on one alternative remained constant, and five magnitudes were presented across sessions on the other alternative. To test the formal account, two absolute response rate equations were fitted to the response and reinforcement rates at each alternative at each magnitude. Although the equations accounted for a high percentage of variance, there was a significant negative correlation between the standardized residuals and the predicted response rates. To test the modern account, an ensemble of four equations was fitted to the data. The equations predicted relative and absolute responding, and the independent variables in each equation were adjusted for bias and sensitivity. The equations accounted for a high percentage of variance, and the standardized residuals were not correlated with the predicted response rates. The values of the parameters were consistent with empirical findings and theoretical predictions, including the prediction that k should remain constant across changes in reinforcer magnitude. The results suggest that the formal theory of matching does not describe the data, and that the modern theory may provide an accurate and coherent description of concurrent and single-alternative responding.

Performance of heavy marijuana-smoking adolescents on a laboratory measure of motivation

Marijuana smoking produces effects that may persist for hours or days beyond the period of acute intoxication. Despite evidence that adolescence represents a period of heightened exposure to marijuana, little research exists regarding possible impairment in adolescents who smoke marijuana regularly, and none exists regarding basic behavioral processes. In the present study, adolescents who smoked marijuana on a regular basis (near daily) were compared to a control group of adolescents on a two-option experimental task designed to measure motivation. The contingencies were arranged such that one option (work), which required systematically increasing response output, initially produced greater rates of monetary reinforcement than an alternative option (non-work) that required no response output to earn money. Switching to the non-work option was interpreted as a measure of reduced motivation. Significant differences were found between the groups: the marijuana-smoking participants switched earlier to the non-work option, and derived a greater percentage of their earnings from the non-work option. These differences existed when controlling for differences in cognitive aptitude, gender, and the presence of conduct disorder. A significant correlation between cannabinoid levels and percent of earnings derived from the non-work option suggests that these effects could be associated with the presence of cannabinoids in the marijuana-smoking group.

Exploring the limits and utility of operant conditioning in the treatment of drug addiction

This article describes a research program to develop an operant treatment for cocaine addiction in low-income, treatment-resistant methadone patients. The treatment's central feature is an abstinence reinforcement contingency in which patients earn monetary reinforcement for providing cocaine-free urine samples. Success and failure of this contingency appear to be an orderly function of familiar parameters of operant conditioning. Increasing reinforcement magnitude and duration can increase effectiveness, and sustaining the contingency can prevent relapse. Initial development of a potentially practical application of this technology suggests that it may be possible to integrate abstinence reinforcement into employment settings using salary for work to reinforce drug abstinence. This research illustrates the potential utility and current limitations of an operant approach to the treatment of drug addiction. Similar research programs are needed to explore the limits of the operant approach and to develop practical applications that can be used widely in society for the treatment of drug addiction.

Modification of performance on the Span of Apprehension Task in a group of young people with early onset psychosis.

The aim of the study was to examine the effect of contingent monetary reinforcement and enhanced instructions on Span of Apprehension (SPAN) performance in a group of young people with early onset psychosis. Twenty-five participants (mean age 16.7) received a 3- and 12-letter version of the SPAN task six times: baseline, three x intervention, post-test, and 10-day follow-up. No significant effects of time were found in the 3-letter condition, indicating a ceiling effect for accuracy. In the 12-letter condition detection rates improved significantly reaching a maximum at the third intervention (p < 0.001). Performance showed a temporary decline at post-test, but performance returned to the maximum level at the 10-day follow-up. The study suggests that SPAN performance can be improved in young people with early onset psychosis using relatively simple interventions and that performance gains are relatively durable.

Discounting of Delayed Reinforcers: Measurement by Questionnaires Versus Operant Choice Procedures

The ability of a reinforcer to maintain behavior decreases as a hyperbolic function of its delay. This discounted value can help explain impulsivity defined as the choice of an immediate, small reinforcer over a delayed, large reinforcer. Human operant studies using consumable reinforcers such as videos have found impulsivity with delays under 1 min. However, measures of discounting rates using questionnaires that describe hypothetical amounts of monetary reinforcers and delays of days, months, or years have found discounting rates that are much too low to explain impulsive choice in operant procedures. A comparison of discounting rates across questionnaire and operant studies indicates that questionnaires produce slower discounting because of the absence of both reinforcement and consumption processes. Combining reinforcement with questions about future reinforcers could facilitate the integration of questionnaire research into a behavioral framework.

Aggressive responding in abstinent heroin addicts: neuroendocrine and personality correlates

Objective measures of experimentally induced aggressiveness were evaluated in 20 abstinent heroin-dependent subjects, in comparison with 20 normal healthy male subjects. All the subjects were preliminarily submitted to DSM-IV interviews, Buss–Durkee Hostility Inventory (BDHI) and Minnesota Multiphasic Personality Inventory (MMPI II). During a laboratory task, the Point Subtraction Aggression Paradigm (PSAP), subjects earned monetary reinforcers with repeated button presses and were provoked by the subtraction of money, which was attributed to a fictitious other participant. Subjects could respond by ostensibly subtracting money from the fictitious subject (the aggressive response). Money-earning responses were not different in drug-free heroin addicts and controls during the first two sessions and significantly lower during the third session in heroin-dependent subjects ( t=2.99, P<.01). Aggressive responses were significantly higher ( F=4.9, P<.01) in heroin addicted individuals, in comparison with controls. During the experimentally induced aggressiveness, plasma adrenocorticotropic hormone (ACTH) and cortisol (CORT) concentrations increased less significantly, and norepinephrine (NE) and epinephrine (EPI) levels, together with heart rate (HR), increased more significantly in abstinent heroin-dependent subjects than in healthy subjects. PSAP aggressive responses positively correlated with catecholamine changes, BDHI “direct” and “irritability” scores, MMPI “psychopathic deviate” scores in heroin-dependent subjects and controls, and with CORT responses only in healthy subjects. No correlation was found between heroin-exposure extent (substance abuse history duration) and aggressiveness levels. The present findings suggest that heroin-dependent patients have higher outward-directed aggressiveness than healthy subjects, in relation with monoamine hyperreactivity, after long-term opiate discontinuation. Aggressiveness in heroin addicts seems to be related more to the personality traits than to drug effects. The impairment of hypothalamus–pituitary–adrenal (HPA) axis in abstinent addicted individuals could be due to a long-lasting action exerted by opiates on proopiomelanocortin (POMC) or to a premorbid psychobiological condition, in association with increased sympathetic arousal.

THE ROLE OF REINFORCEMENT IN CYCLE ERGOMETRY

PURPOSE The purpose of this study was to investigate the influence of music and/or money on exercise time and pedal rate. METHODS Twenty-five college students exercised on a cycle ergometer until they were too tired to continue or for a maximum duration of 45 minutes. Each subject exercised at 60% of their age-predicted-max-heart rate under each of four conditions: control (no reinforcement), self-selected music, money (15 cents was earned for every 40 pedal revolutions), and self-selected music + money. Each reinforcement was continuously applied during the exercise session. The order of the reinforcement was completely counterbalanced. Each session was scheduled 1 to 3 days apart. RESULTS The money reinforcement and the music + money reinforcement significantly increased both exercise time and the subjects' pedal rate (p < .05). The control and music reinforcement did not produce significant differences in exercise time or pedal rate. CONCLUSION Monetary reinforcement can significantly increase work output and exercise time.

The Conjunction Effect: New Evidence for Robustness

Five studies investigated the conjunction effect (or conjunction fallacy), in which participants report that the conjunction of two events is more rather than less likely than one of the events alone. There was no evidence that feedback or monetary reinforcement for correct answers affected students' performance on conjunction problems. Under some circumstances the context in which the conjunction problem was presented (after questions emphasizing logic or questions emphasizing opinions) affected occurrence of the effect. Location of the conjunction among the statements being rated had a significant effect. The effect occurred with or without a framing description and whether the conjunction consisted of two or three simple statements. However, statements representing the conjunction of three simple statements were (appropriately) judged less likely than those representing the conjunction of two simple statements. The substantial incidence of the effect, even without the descriptive frame and even when incentive and feedback were provided for correct answers, argues for its robustness.

Contingent monetary reinforcement of smoking reductions, with and without transdermal nicotine, in outpatients with schizophrenia.

Contingent monetary reinforcement of smoking reductions, with and without transdermal nicotine, in outpatients with schizophrenia.

Human Schedule Performance with Hypothetical Monetary Reinforcement

Experiments examined the effect of variable ratio (VR) and variable interval (VI) schedules between a response (an investment made in the context of a game) and an outcome (a return on the investment) on human response rates and judgments of the causal effectiveness of the response. In Experiment 1, the time between successive outcomes obtained on a VR schedule became the successive interval criterion for a yoked VI schedule. Response rates and ratings of causal efficacy were higher on the VR than the VI schedule. In Experiment 2, the number of responses required per outcome on a VR schedule was matched to that on a master VI 40-s schedule. Both response rate and the ratings of causal effectiveness were higher in the VR schedule. However, these findings only held when the cost of a response was relatively high, but not when it was low.