不确定性容忍度对跨期选择的影响及其情景依赖性

采用2(不确定性容忍度：高、低)×2(跨期日期：今天/14天、今天/180天)×2(延迟奖赏值：200元、1000元)混合实验设计,探讨不同任务特征下不确定性容忍度对跨期选择的影响。结果表明：跨期日期为180天时,不确定性容忍度主效应边缘显著;不确定性容忍度与延迟奖赏值交互作用显著：在200元时低容忍度个体对延迟奖赏的折扣程度大于高容忍度个体,在1000元时无此效应;跨期日期为14天时,不确定性容忍度的主效应及其与延迟奖赏值交互作用均不显著。这表明,不确定性容忍度对跨期选择存在影响,但这种影响受到跨期日期和延迟奖赏值的调节,具有情景依赖性。     

A Measure of Delay Discounting Within the Academic Domain

It is important to better understand the decision‐making processes involved in student procrastination, in order to develop interventions that reduce this common problem. Students may procrastinate because studying produces delayed reinforcers; however, no task measuring delay discounting of academic outcomes currently exists. In Experiment 1, we developed and piloted a measure of academic discounting modeled on titrating‐amount tasks successfully used in the discounting literature. Participants made hypothetical choices between working for money (the smaller, sooner reinforcer) and working on an assignment that was due at various times (the larger, later reinforcer). Participants showed systematic decreases in the subjective value of the assignment as a function of delay, and the hyperbolic and hyperboloid models described the shape of this decrease in value well. In general, larger delayed rewards are discounted less steeply than smaller delayed rewards (the magnitude effect). In Experiment 2, we observed the magnitude effect in academic discounting: Participants discounted a “not important” assignment more steeply than an “important” assignment. In the hyperboloid model, this change was captured by an increase in the s parameter. Results provide support for the validity of the academic discounting task. Copyright © 2018 John Wiley & Sons, Ltd.     

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.     

Modeling the effect of reward amount on probability discounting

The present study with college students examined the effect of amount on the discounting of probabilistic monetary rewards. A hyperboloid function accurately described the discounting of hypothetical rewards ranging in amount from $20 to $10,000,000. The degree of discounting increased continuously with amount of probabilistic reward. This effect of amount was not due to changes in the rate parameter of the discounting function, but rather was due to increases in the exponent. These results stand in contrast to those observed with the discounting of delayed monetary rewards, in which the degree of discounting decreases with reward amount due to amount-dependent decreases in the rate parameter. Taken together, this pattern of results suggests that delay and probability discounting reflect different underlying mechanisms. That is, the fact that the exponent in the delay discounting function is independent of amount is consistent with a psychophysical scaling interpretation, whereas the finding that the exponent of the probability-discounting function is amount-dependent is inconsistent with such an interpretation. Instead, the present results are consistent with the idea that the probability-discounting function is itself the product of a value function and a weighting function. This idea was first suggested by Kahneman and Tversky (1979), although their prospect theory does not predict amount effects like those observed. The effect of amount on probability discounting was parsimoniously incorporated into our hyperboloid discounting function by assuming that the exponent was proportional to the amount raised to a power. The amount-dependent exponent of the probability-discounting function may be viewed as reflecting the effect of amount on the weighting of the probability with which the reward will be received.     

社会贴现:一种测量利他行为的新任务

社会贴现指的是人际交往过程中利他行为随着个人之间的社会距离增加而逐渐减少的现象。其研究任务首次将社会距离进行了量化,以个体愿意舍弃金额的数量换取他人获得定额的行为作为利他的标准。解释水平理论为社会贴现的内涵提供了理论基础,并解释了其内部机制。未来研究可以从自我结构的角度对社会贴现进行解释,也可以尝试使用社会支持相关的指标代替金钱,以避免金钱概念的启动所导致个体偏向自私的结论。     

Sex Differences in Psychological Factors Associated with Social Discounting

The social discounting paradigm is a powerful means of quantifying altruism in humans, who are typically willing to forgo some amount of personal earnings in exchange for increased earnings for another person. The amount of money that people are willing to forgo decreases with increasing social distance. In this study, we examined variables related to sex, intolerance of uncertainty, and empathy, all of which are theorized to affect the social discounting rate. Participants (27 men and 28 women) completed measures of intolerance of uncertainty, empathy, and social discounting. We found sex differences in psychological predictors of social discounting: in women, empathy (but not intolerance of uncertainty) predicts the social discounting rate, while in men, social discounting is associated with intolerance of uncertainty (but not empathy). Possible neurobiological, social, and cognitive explanations for this sex difference are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Discounting of food,sex, and money

Discounting is a useful framework for understanding choice involving a range of delayed and probabilistic outcomes (e.g., money, food, drugs), but relatively few studies have examined how people discount other commodities (e.g., entertainment, sex). Using a novel discounting task, where the length of a line represented the value of an outcome and was adjusted using a staircase procedure, we replicated previous findings showing that individuals discount delayed and probabilistic outcomes in a manner well described by a hyperbola-like function. In addition, we found strong positive correlations between discounting rates of delayed, but not probabilistic, outcomes. This suggests that discounting of delayed outcomes may be relatively predictable across outcome types but that discounting of probabilistic outcomes may depend more on specific contexts. The generality of delay discounting and potential context dependence of probability discounting may provide important information regarding factors contributing to choice behavior.     

Integrated versus segregated accounting and the magnitude effect in temporal discounting

Temporal discounting rates in humans generally decrease as the amount of reward increases, a phenomenon known as themagnitude effect. In the present study, we examined whether temporal discounting and the magnitude effect are related to segregation of choices in terms of gains or losses for waiting for or expediting receipt of a reward. Subjects (N = 24) responded to a series of hypothetical choices about amounts of money available either immediately or after a delay. The immediate and delayed amounts either were presented as integrated amounts in the baseline condition or were segregated as differential gains or losses for choosing delayed or expedited consumption (delay and speedup conditions, respectively). Temporal discounting rates decreased in the segregated conditions, in accord with the standard discounted utility model but contrary to the hypothesis that the subjects were choosing on the basis of reward differentials in the baseline condition. The size of the magnitude effect was comparable in the baseline and the delay conditions but decreased in the speed-up condition. These results challenge explanations of the magnitude effect in terms of an increasing proportional sensitivity property of the utility function (Loewenstein & Prelec, 1992) and the hypothesis that subjects choose on the basis of differentials even when the rewards are presented as integrated amounts.     

Temporal discounting and preference reversals in choice between delayed outcomes

Subjects chose between pairs of hypothetical amounts of money available after different delays. When smaller, more immediate amounts were selected over larger, more delayed amounts, the addition of a constant delay to both outcomes resulted in reversals of preference, contrary to the standard discounted utility model of economics. The delays at which preference reversed were determined for three pairs of amounts ($20 vs. $50, $100 vs. $250, and $500 vs. $1,250). The relation between the delay to the larger amount and the delay to the smaller amount at preference reversal was well fit by both linear and quadratic functions. Intercepts increased with amount, strongly suggesting that rate of discounting decreases with amount. The presence of significant negative curvature in the data from the majority of individual subjects poses problems for exponential and hyperbolic models of temporal discounting in self-control, both of which predict a linear relation between the delays to the larger and smaller amounts.     

Diminishing marginal value as delay discounting.

The fundamental law underlying economic demand and exchange is the tendency for value of marginal units to diminish with increasing amounts of a commodity. The present paper demonstrates that this law follows from three still-more-basic psychological assumptions: (a) limited consumption rate, (b) delay discounting, and (c) choice of highest valued alternative. Cases of diminishing marginal value apparently due to pure intensity of reward may plausibly be attributed to the above three factors. The further assumption that maximum consumption rate may vary within and across individuals implies that some substances may be unusually addictive and that some individual animals may be unusually susceptible to addiction.     

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。     

跨期决策中的负折扣现象及其机制

主流跨期决策模型认为, 跨期决策存在一个时间折扣过程。时间折扣是指人们会根据将来获益或损失的延迟时间对其效用进行折扣, 折扣后的效用小于原来的效用, 而负折扣现象违背了时间折扣过程。负折扣现象出现在金钱、非金钱的获益与损失领域, 其可能的解释机制为预期情绪。目前关于负折扣现象的研究, 较少验证其影响机制, 未来的研究可以结合眼动追踪和fMRI技术探讨其机制, 并丰富对负折扣现象的影响因素研究。     

负折扣现象:跨期决策中的自我-他人决策差异

负折扣现象作为一种违背时间折扣假定的现象越来越多地引起研究者关注。本文通过两种指标考察了为自己决策和为他人决策在负折扣现象上的差异。实验1运用二择一选择范式考察人们在为自己决策和为他人决策时对于何时发生负性事件的时间偏好。结果发现,相比较于为他人决策,为自己决策时被试更倾向于选择早些发生负性事件,即更容易产生负折扣现象。实验2运用测量时间折扣率的经典范式考察了人们在为自己决策和为他人决策时的时间折扣率。结果发现,为自己决策时比为他人决策时的时间折扣率更小,更容易出现负折扣率。总体结果表明,为自己决策比为他人决策更容易出现负折扣现象。从情绪卷入的角度看,我们推测,为自己决策时由于更多的预期负性情绪卷入,从而导致更容易产生负折扣现象。     

Social Discounting and Cigarette Smoking During Pregnancy

In this study, we examined the association between social discounting and smoking status in a cohort of pregnant cigarette smokers (n = 91), quitters (n = 27), or never‐smokers (n = 30). The smokers and quitters were participants in clinical trials on smoking cessation and relapse prevention, whereas the never‐smokers were controls in a study on nicotine withdrawal during pregnancy. Social discounting was assessed using a paper‐and‐pencil task that assesses the amount of hypothetical money a person is willing to forgo in order to share with individuals in their social network ranging from the person who is emotionally closest to them to a mere acquaintance. The amount that women were willing to forgo in order to share decreased hyperbolically as a function of social distance, with smokers exhibiting steeper discounting functions (i.e., less generosity) than quitters or never‐smokers; discounting functions of quitters and never‐smokers did not differ significantly. In multivariate analyses controlling for potential sociodemographic and other confounds, social discounting remained a significant predictor of smoking status among smokers versus quitters. Overall, these results suggest that individual differences in social discounting may be a factor influencing the choices that women make about quitting smoking upon learning of a pregnancy. Copyright © 2011 John Wiley & Sons, Ltd.     

Delay discounting by pathological gamblers

Discounting of delayed rewards by pathological gamblers was compared to discounting of delayed rewards by matched control nongambling participants. All participants completed a hypothetical choice task in which they made repeated choices between dollars 1,000 available after a delay and an equal or lesser amount of money available immediately. The delay to the large amount of money was varied from 1 week to 10 years across conditions. Indifference points between immediate money and delayed money were identified at each delay condition by varying the amount of immediate money across choice trials. For the majority of participants, indifference points decreased monotonically across delays. Overall, gamblers discounted the delayed rewards more steeply than did control participants.     

Delay or probability discounting in a model of impulsive behavior: effect of alcohol

Little is known about the acute effects of drugs of abuse on impulsivity and self-control. In this study, impulsivity was assessed in humans using a computer task that measured delay and probability discounting. Discounting describes how much the value of a reward (or punisher) is decreased when its occurrence is either delayed or uncertain. Twenty-four healthy adult volunteers ingested a moderate dose of ethanol (0.5 or 0.8 g/kg ethanol: n = 12 at each dose) or placebo before completing the discounting task. In the task the participants were given a series of choices between a small, immediate, certain amount of money and $10 that was either delayed (0, 2, 30, 180, or 365 days) or probabilistic (i.e., certainty of receipt was 1.0, .9, .75, .5, or .25). The point at which each individual was indifferent between the smaller immediate or certain reward and the $10 delayed or probabilistic reward was identified using an adjusting-amount procedure. The results indicated that (a) delay and probability discounting were well described by a hyperbolic function; (b) delay and probability discounting were positively correlated within subjects; (c) delay and probability discounting were moderately correlated with personality measures of impulsivity; and (d) alcohol had no effect on discounting.     

Temporal discounting when the choice is between two delayed rewards

The present experiments extend the temporal discounting paradigm from choice between an immediate and a delayed reward to choice between 2 delayed rewards: a smaller amount of money available sooner and a larger amount available later. Across different amounts and delays, the data were consistently well described by a hyperbola-like discounting function, and the degree of discounting decreased systematically as the delay to the sooner reward increased. Three theoretical models (the elimination-by-aspects, present-value comparison, and common-aspect attenuation hypotheses) were evaluated. The best account of the data was provided by the common-aspect attenuation hypothesis, according to which the common aspect of the choice alternatives (i.e., the time until the sooner reward is available) receives less weight in the decision-making process.     

Conditioned Reflex and Perception: The Concept of Syncretism

Delay discounting occurs when the subjective value of an outcome decreases because its delivery is delayed. Past research has shown that how steeply participants discount an outcome varies inversely with the value of previously discounted outcomes. In the present study, participants discounted the same hypothetical monetary outcome ($1,000) after their hypothetical annual income was halved (Experiment 1) or doubled (Experiment 2). Rates of discounting decreased and increased, respectively, after these manipulations (although a similar change in discounting was observed for the control and treatment groups in Experiment 2). These results suggest that altering the context in which the discounting task is framed alters the subjective value of the outcome itself, in this case money. This result has implications for understanding contrast effects that are observed in rates of discounting, as well as for researchers and practitioners who are interested in determining methods for altering how individuals discount delayed outcomes.