Delay-discounting probabilistic rewards: Rates decrease as amounts increase

The independence of delay-discounting rate and monetary reward size was tested by offering subjects (N = 621) a series of choices between immediate rewards and larger, delayed rewards. In contrast to previous studies, in which hypothetical rewards have typically been employed, subjects in the present study were entered into a lottery in which they had a chance of actually receiving one of their choices. The delayed rewards were grouped into small ($30–$35), medium ($55–$65), and large amounts ($70–$85). Using a novel parameter estimation procedure, we estimated discounting rates for all three reward sizes for each subject on the basis of his/her pattern of choices. The data indicated that the discounting rate is a decreasing function of the size of the delayed reward (p < .0001), whether hyperbolic or exponential discounting functions are assumed. In addition, a reliable gender difference was found (p = .005), with males discounting at higher rates than females, on average.     

Within-subject comparison of real and hypothetical money rewards in delay discounting

A within-subject design, using human participants, compared delay discounting functions for real and hypothetical money rewards. Both real and hypothetical rewards were studied across a range that included $10 to $250. For 5 of the 6 participants, no systematic difference in discount rate was observed in response to real and hypothetical choices, suggesting that hypothetical rewards may often serve as a valid proxy for real rewards in delay discounting research. By measuring discounting at an unprecedented range of real rewards, this study has also systematically replicated the robust finding in human delay discounting research that discount rates decrease with increasing magnitude of reward. A hyperbolic decay model described the data better than an exponential model.     

海洛因戒除者的行为冲动性： 基于DDT和IGT任务反应模式的探讨

以61名男性海洛因戒除者和32名正常成年男性为被试,探讨了海洛因戒除者在延迟折扣任务和Iowa赌博任务两种决策条件下的冲动性反应模式及其关系。结果发现,海洛因戒除者的决策行为受其对即时强化的超敏感性或“即时收益优先”模式控制,其高冲动性特质既表现为对强化物长远价值的非敏感性,又表现为对强化物潜在风险的耐受性;该类人群上述两方面的特征虽有一定关联,但二者分别反应了其行为冲动性的两个相对独立的维度,且具有跨戒除时相的相对稳定性     

海洛因延迟强化物超快速折扣倾向的心理机制

以124名处于不同戒除时相的男性海洛因戒除者为被试, 采用金钱和海洛因延迟折扣任务(DDT), 并以基于线索暴露的渴求感测量为效度指标, 探讨了该类人群对海洛因延迟强化超快速折扣倾向及其心理机制。结果发现: (1) 相对于金钱延迟强化, 戒除者对海洛因延迟强化表现出显著的超快速折扣倾向, 且该倾向不随戒除期的延长而改变; (2) 戒除者对海洛因延迟强化的超快速折扣行为可能是其冲动性特质与海洛因相关线索共同作用的结果, 海洛因相对于金钱折扣率的增量部分可能反映了海洛因及其相关线索对该类人群主观渴求感的诱发效应。     

Impulsivity in borderline personality disorder: reward-based decision-making and its relationship to emotional distress

Impulsivity in Borderline Personality Disorder (BPD) has been defined as rapid and unplanned action. However, a preference for immediate gratification and discounting of delayed rewards might better account for the impulsive behaviors that appear to regulate emotional distress in BPD. To investigate this, a delay discounting task was administered to 30 outpatients diagnosed with BPD and 28 healthy community controls (all aged 15-24) before and after a mood induction. Trait impulsivity was measured with the Barratt Impulsiveness Scale. The results showed that the BPD group had a greater preference for immediate gratification and higher rate of discounting the delayed reward than the control group. Although the mood induction resulted in increased feelings of rejection and anger in all participants, and the rate of delay discounting changed significantly in the control group, the rate of discounting did not change for the BPD group. There was no evidence of rapid decision-making in the BPD group as response times were similar between the two groups during both trials. Finally, greater general impulsiveness and nonplanning impulsiveness were associated with greater rates of discounting in the BPD group. Together these findings suggest that BPD is characterized by a preference for immediate gratification and tendency to discount longer-term rewards. This characteristic appears to exist independent of feelings of rejection and anger, rather than being reactive to this, and to be related to trait impulsivity.     

Magnitude effect contributes to the domain specificity in delay discounting

Discounting is a useful framework for understanding temporal choices. A person who prefers $50 immediately over $100 in 1 month exhibits a higher discount rate than a person deciding to wait for the higher payoff. Although previous research shows that discount rates are domain-specific, we propose an alternative to the domain specificity account. We suggest that differences in discounting alternatives across various domains may result not so much from the domains' nature per se but from differences in perceived attractiveness of the discounted alternatives. We replicated that an illustrative study evidencing domain specificity in discounting (Experiment 1) showed that people's subjective values of the payoffs in domains discounted in this experiment were different (Experiment 2) and used a novel method to match the attractiveness of the available alternatives across domains (Experiment 3). Finally, Experiment 4 showed that when matching was applied, the domain effect disappeared. We conclude that a magnitude effect can, at least partially, explain domain specificity in delay discounting.     

Pathological gamblers, with and without substance use disorders, discount delayed rewards at high rates

Pathological gambling is classified as a disorder of impulse control, yet little research has evaluated behavioral indices of impulsivity in gamblers. The rates at which rewards delayed in time are subjectively devalued may be a behavioral marker of impulsivity. This study evaluated delay discounting in 60 pathological gamblers and 26 control participants. Gamblers were divided into those with (n = 21) and without (n = 39) substance use disorders. A hypothetical $1,000 reward was delayed at intervals ranging from 6 hr to 25 years, and immediate rewards varied from $1 to $999. Pathological gamblers discounted delayed rewards at higher rates than control participants, and gamblers with substance use disorders discounted delayed rewards at higher rates than non-substance-abusing gamblers. These data provide further evidence that rapid discounting of delayed rewards may be a feature central to impulse control and addictive disorders, including pathological gambling.     

Temporal discounting of monetary rewards in children and adolescents with ADHD and autism spectrum disorders

It has been difficult to differentiate attention‐deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in terms of some aspects of their cognitive profile. While both show deficits in executive functions, it has been suggested that they may differ in their response to monetary reward. For instance, children with ADHD prefer small immediate over large delayed rewards more than typically developing controls. One explanation for this is that they discount the value of rewards to a higher degree as they are moved into the future. The current study investigated whether children with ADHD can be differentiated from those with ASD in terms of reward discounting. Thirty‐nine children (8–16 y) with ADHD, 34 children with ASD and 46 typically developing controls performed a hypothetical monetary temporal discounting task. Participants were instructed to make repeated choices between small variable rewards (0, 5, 10, 20, 30€) delivered immediately and large rewards delivered after a variable delay. Children with ADHD but not ASD discounted future rewards at a higher rate than typically developing controls. These data confirm steeper discounting of future rewards in ADHD and add to a small but growing literature showing that the psychological profile of ADHD can be distinguished from that of ASD in terms of disrupted motivational processes.     

Contextual control of delay discounting by pathological gamblers

The present study demonstrated the relative impact of gambling and nongambling contexts on the degree of delay discounting by pathological gamblers. We used a delay-discounting task with 20 pathological gamblers in and out of the natural context in which they regularly gambled. For 16 of the 20 participants, it appeared that the difference of context altered the subjective value of delayed rewards, thereby producing relative changes in delay-discounting rates that were generally consistent with a hyperbolic model of intertemporal choice. The current data suggest that empirically derived k values from delay-discounting tasks are context sensitive and are not constant across various settings for the individual. Implications for future transitional research on addictive disorders generally, and gambling specifically, are discussed.     

Tests of an indifference rule in variable‐delay and double‐reward choice procedures with humans

Four hundred and fifty participants were recruited from Amazon Mechanical Turk across 3 experiments to test the predictions of a hyperbolic discounting equation in accounting for human choices involving variable delays or multiple rewards (Mazur, 1984, 1986). In Experiment 1, participants made hypothetical choices between 2 monetary alternatives, 1 consisting of a fixed delay and another consisting of 2 delays of equal probability (i.e., a variable‐delay procedure). In Experiment 2, participants made hypothetical monetary choices between a single, immediate reward and 2 rewards, 1 immediate and 1 delayed (i.e., a double‐reward procedure). Experiment 3 also used a double‐reward procedure, but with 2 delayed rewards. Participants in all 3 experiments also completed a standard delay‐discounting task. Finally, 3 reward amounts were tested in each type of task ($100, $1000, and $5000). In the double‐reward conditions (Experiments 2 and 3), the results were in good qualitative and quantitative agreement with Mazur's model (1984, 1986). In contrast, when participants made choices involving variable delays (Experiment 1), there was relatively poor qualitative and quantitative agreement with this model. These results, along with our previous findings, suggest the structure of questions in hypothetical tasks with humans can be a strong determinant of the choice pattern.     

PREFERENCE REVERSALS DUE TO MYOPIC DISCOUNTING OF DELAYED REWARD

Abstract— A basic stationarity axiom of economic theory assumes stable preference between two deferred goods separated by a fixed time. To test this assumption, we offered subjects choices between delayed rewards, while manipulating the delays to those rewards. Preferences typically reversed with changes in delay, as predicted by hyperbolic discounting models of impulsiveness. Of 36 subjects, 34 reversed preference from a larger, later reward to a smaller, earlier reward as the delays to both rewards decreased. We conclude that the stationarity axiom is not appropriate in models of human choice.     

Time discounting and time preference in animals: A critical review

Animals are an important model for studies of impulsivity and self-control. Many studies have made use of the intertemporal choice task, which pits small rewards available sooner against larger rewards available later (typically several seconds), repeated over many trials. Preference for the sooner reward is often taken to indicate impulsivity and/or a failure of self-control. This review shows that very little evidence supports this assumption; on the contrary, ostensible discounting behavior may reflect a boundedly rational but not necessarily impulsive reward-maximizing strategy. Specifically, animals may discount weakly, or even adopt a long-term rate-maximizing strategy, but fail to fully incorporate postreward delays into their choices. This failure may reflect learning biases. Consequently, tasks that measure animal discounting may greatly overestimate the true discounting and may be confounded by processes unrelated to time preferences. If so, animals may be much more patient than is widely believed; human and animal intertemporal choices may reflect unrelated mental operations; and the shared hyperbolic shape of the human and animal discount curves, which is used to justify cross-species comparisons, may be coincidental. The discussion concludes with a consideration of alternative ways to measure self-control in animals.     

Sources and types of social support in youth physical activity.

This study examines the influence of sources and types of social support on youth physical activity. The sample comprised 372 youth (mean age=12.05 years, SD=1.63). Youth were 76% White and 50.3% female. The annual household income for the sample was 20% under $30,000; 30% $30,000-$49,999; 25% $50,000-$69,999; 13% $70,000-$89,999; and 12% $90,000 and above. Results revealed that friends who support and watch youth engage in activities are significantly and positively related to youth physical activity. Significant correlations existed among the type factors. Future research should examine the sources and nature of support and the mechanisms through which social support influences youth physical activity.     

Priming the ant or the grasshopper in people's mind: How regulatory mode affects inter‐temporal choices

The present study examined the influence of two regulatory mode concerns—a locomotion concern with movement from state to state and an assessment concern with making comparisons—on choices between immediate and delayed (from 2 to 6 weeks) money rewards. Regulatory mode orientation was induced by means of a priming procedure. We predicted that the choices in the assessment condition would be less impulsive and more far‐sighted than those in the locomotion condition. After taking into account the effects of amount of early reward, length of delay and increase in delayed reward—all of which were in the direction of previous studies—this regulatory mode prediction was supported. Our findings suggest that it might be possible to induce more far‐sighted (or economically rational) inter‐temporal choices by means of instructions that induce an assessment orientation independent of stable inter‐individual differences in discount rate. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparing Delay Discounting Rates When Using the Fill-in-the-Blank and Multiple-Choice Methods

Several methods have been devised to measure delay discounting. The present study recruited university students to complete a delay-discounting task involving five different outcomes (finding a dating partner, free cigarettes, winning $100,000, being owed $100,000, and obtaining one's ideal body image) that was administered using either the fill-in-the blank (FITB) or multiple-choice (MC) method. Results showed that the different administration methods sometimes produced significantly different rates of discounting, the direction of which differed by outcome. Hyperbolic discounting and the area under the discounting curve were nearly always significantly correlated when the FITB method was used but were never significantly correlated when the MC method was used. Discounting across the five outcomes produced a two-factor solution when the FITB data were factor analyzed. The MC data were described by a one-factor solution. The present results illustrate that procedural variables have a potentially profound impact on delay-discounting data, and generalizing from studies on delay discounting should be done with caution until those variables are fully understood.     

Social discounting and delay discounting

Social discounting was measured as the amount of money a participant was willing to forgo to give a fixed amount (usually $75) to another person. In the first experiment, amount forgone was a hyperbolic function of the social distance between the giver and receiver. In the second experiment, degree of social discounting was an increasing function of reward magnitude whereas degree of delay discounting was a decreasing function of reward magnitude. In the third experiment, the shape of the function relating delayed rewards to equally valued immediate rewards for another person was predicted from individual delay and social discount functions. All in all, the studies show that the social discount function, like delay and probability discount functions, is hyperbolic in form. Copyright © 2007 John Wiley & Sons, Ltd.     

Good things come to those who wait: Time discounting differences between adult offenders and nonoffenders

Criminal behavior has been explained by the idea that offenders have a lack of self-control. Yet, Wilson and Daly reported that juvenile offenders exhibit time-discounting tendencies similar to those of nonoffending juveniles. As no previous study has compared time-discounting behavior of adult offenders with nonoffenders, we raise the question, do adult offenders exhibit shorter time horizons or the tendency to discount future rewards? To answer this question, 89 offenders (ex-prisoners and prisoners) and 106 nonoffenders completed a time-discounting measure containing 27 different monetary choices. Our results show that, counter to findings with juvenile offenders, adult offenders (ex-prisoners) exhibit significantly shorter time horizons and discount more than nonoffenders as delayed payoffs increase to medium and large rewards. Furthermore, both offenders and nonoffenders are less likely to discount as the reward of future gains increases to medium and large.     

Cognitive Constraints on How Economic Rewards Affect Cooperation

ABSTRACT— Cooperation often fails to spread in proportion to its potential benefits. This phenomenon is captured by prisoner's dilemma games, in which cooperation rates appear to be determined by the distinctive structure of economic incentives (e.g., $3 for mutual cooperation vs. $5 for unilateral defection). Rather than comparing economic values of cooperating versus not ($3 vs. $5), we tested the hypothesis that players simply compare numeric values (3 vs. 5), such that subjective numbers (mental magnitudes) are logarithmically scaled. Supporting our hypothesis, increasing only numeric values of rewards (from $3 to 300¢) increased cooperation ( Study 1 ), whereas increasing economic values increased cooperation only when there were also numeric increases ( Study 2 ). Thus, changing rewards from 3¢ to 300¢ increased cooperation rates, but an economically identical change from 3¢ to $3 elicited no gains. Finally, logarithmically scaled reward values predicted 97% of variation in cooperation, whereas the face value of economic rewards predicted none. We conclude that representations of numeric value constrain how economic rewards affect cooperation.     

Feelings of dread and intertemporal choice

It frequently has been observed that people discount future rewards relative to present rewards. However, the literature on intertemporal choices involving emotional upsets and losses is fraught with inconsistencies, with some studies finding similar discounting of gains and losses, and others reporting that participants elect to undergo negative experiences sooner rather than later. To help resolve these contradictions, time preferences for different types of aversive experiences (social rejection, embarrassment, pain, monetary and property loss) were examined in five studies. Most participants preferred to postpone monetary and property losses, but intertemporal choices for other unpleasant experiences showed highly variable responses, with some participants deferring them as long as possible, and many electing to experience them immediately. Time preferences for these negative experiences were correlated, but were independent of time preference for rewards. It is argued (following Loewenstein, 1987 ) that anticipation of dread plays a key role in many people's choices about timing of aversive experiences. This interpretation was supported by choices about when to learn of a very unpleasant event whose timing was fixed (Study 3), and by a novel preference reversal (Study 4). Study 5 examined how actual and hypothetical experiences of dread unfolded over time; the results were consistent with a dread‐based interpretation of choices in the preceding studies. Copyright © 2010 John Wiley & Sons, Ltd.