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。     

Asymmetric discounting in intertemporal choice: a query-theory account

People are impatient and discount future rewards more when they are asked to delay consumption than when they are offered the chance to accelerate consumption. The three experiments reported here provide a process-level account for this asymmetry, with implications for designing decision environments that promote less impulsivity. In Experiment 1, a thought-listing procedure showed that people decompose discount valuation into two queries. Whether one considers delayed or accelerated receipt of a gift certificate influences the order in which memory is queried to support immediate versus delayed consumption, and the order of queries affects the relative number of patient versus impatient thoughts. Relative frequency and clustering of impatient thoughts predicts discounting and mediates the discounting asymmetry. Experiment 2 implicated query order causally: When participants listed reasons for immediate versus delayed consumption in the order used spontaneously in acceleration and delay decisions, the discounting asymmetry was replicated; reversing the order in which reasons were listed eliminated the asymmetry. The results of Experiment 3, which used an implicit-memory task, support a memory-interference account of the effect of query order.     

Koopmans’ constant discounting for intertemporal choice: A simplification and a generalization

Koopmans provided a well-known preference axiomatization for discounted utility, the most widely used model for maximizing intertemporal choice. There were, however, some technical problems in his analysis. For example, there was an unforeseen implication of bounded utility. Some partial solutions have been advanced in various fields in the literature. The technical problems in Koopmans’ analysis obscure the appeal of his intuitive axioms. This paper completely resolves Koopmans’ technical problems. In particular, it obtains complete flexibility concerning the utility functions that can be used. This paper, thus, provides a clean and complete preference axiomatization of discounted utility, clarifying the appeal of Koopmans’ intuitive axioms.     

Subadditive versus hyperbolic discounting: A comparison of choice and matching

Impulsive and myopic choices are often explained as due to hyperbolic discounting, meaning that people are impatient for outcomes available immediately, and become increasingly more patient the more the outcome is delayed. Recent research, however, has suggested that much experimental evidence for increasing patience is actually due to subadditive discounting: people are less patient (per-time-unit) over shorter intervals regardless of when they occur. Because previous research into subadditive discounting has used a choice elicitation procedure, the present paper tests whether it generalises to matching. We find strong evidence that it does, but also find weak evidence of increasing patience for matching. We suggest, however, that subadditive discounting alone may be sufficient to account for all of our results. We conclude by questioning the contribution that hyperbolic discounting makes to our understanding of time preference.     

Hierarchical Bayesian estimation and hypothesis testing for delay discounting tasks

A state-of-the-art data analysis procedure is presented to conduct hierarchical Bayesian inference and hypothesis testing on delay discounting data. The delay discounting task is a key experimental paradigm used across a wide range of disciplines from economics, cognitive science, and neuroscience, all of which seek to understand how humans or animals trade off the immediacy verses the magnitude of a reward. Bayesian estimation allows rich inferences to be drawn, along with measures of confidence, based upon limited and noisy behavioural data. Hierarchical modelling allows more precise inferences to be made, thus using sometimes expensive or difficult to obtain data in the most efficient way. The proposed probabilistic generative model describes how participants compare the present subjective value of reward choices on a trial-to-trial basis, estimates participant- and group-level parameters. We infer discount rate as a function of reward size, allowing the magnitude effect to be measured. Demonstrations are provided to show how this analysis approach can aid hypothesis testing. The analysis is demonstrated on data from the popular 27-item monetary choice questionnaire (Kirby, Psychonomic Bulletin & Review, 16(3), 457–462 2009), but will accept data from a range of protocols, including adaptive procedures. The software is made freely available to researchers.     

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.     

Measuring delay discounting in a crowdsourced sample: An exploratory study

Delay discounting is a measure of preferences for smaller immediate rewards over larger delayed rewards. Discounting has been assessed in many ways; these methods have variably and inconsistently involved measures of different lengths (single vs. multiple items), forced‐choice methods, self‐report methods, online and laboratory assessments, monetary and non‐monetary compensation. The majority of these studies have been conducted in laboratory settings. However, over the past 20 years, behavioral data collection has increasingly shifted online. Usually, these experiments involve completing short tasks for small amounts of money, and are thus qualitatively different than experiments in the lab, which are typically more involved and in a strongly controlled environment. The present study aimed to determine how to best measure future discounting in a crowdsourced sample using three discounting measures (a single shot measure, the 27‐item Kirby Monetary Choice Questionnaire, and a one‐time Matching Task). We examined associations of these measures with theoretically related variables, and assessed influence of payment on responding. Results indicated that correlations between the discounting tasks and conceptually related measures were smaller than in prior laboratory experiments. Moreover, our results suggest providing monetary compensation may attenuate correlations between discounting measures and related variables. These findings suggest that incentivizing discounting measures changes the nature of measurement in these tasks.     

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.     

A comparison of bounded diffusion models for choice in time controlled tasks

The Wiener diffusion model (WDM) for 2-alternative tasks assumes that sensory information is integrated over time. Recent neurophysiological studies have found neural correlates of this integration process in certain neuronal populations. This paper analyses the properties of the WDM with two different boundary conditions in decision making tasks in which the time of response is indicated by a cue. A dual reflecting boundary mechanism is proposed and its performance is compared with a well-established absorbing boundary in the cases of the WDM, the WDM with extensions, and the WDM with prior probability. The two types of boundary influence the dynamics of the model and introduce differential weighting of evidence. Comparisons with Ornstein-Uhlenbeck models are also done, and it is shown that the WDM with both types of boundary achieves similar performance and produces similar fits to existing behavioural data. Further studies are proposed to distinguish which boundary mechanism is more consistent with experimental data.     

Delay discounting of monetary gains and losses in adolescents with ADHD: Contribution of delay aversion to choice

Adolescents with attention-deficit/hyperactivity disorder (ADHD) are known to have stronger preferences for smaller immediate rewards over larger delayed rewards in delay discounting tasks than their peers, which has been argued to reflect delay aversion. Here, participants performed a delay discounting task with gains and losses. In this latter condition, participants were asked whether they were willing to wait in order to lose less money. Following the core assumption of the delay aversion model that individuals with ADHD have a general aversion to delay, one would predict adolescents with ADHD to avoid waiting in both conditions. Adolescents (12–17 years) with ADHD (n = 29) and controls (n = 28) made choices between smaller immediate and larger delayed gains, and between larger immediate and smaller delayed losses. All delays (5–25 s) and gains/losses (2–10 cents) were experienced. In addition to an area under the curve approach, a mixed-model analysis was conducted to disentangle the contributions of delay duration and immediate gain/delayed loss amount to choice. The ADHD group chose the immediate option more often than controls in the gain condition, but not in the loss condition. The contribution of delay duration to immediate choices was stronger for the ADHD group than the control group in the gain condition only. In addition, the ADHD group scored higher on self-reported delay aversion, and delay aversion was associated with delay sensitivity in the gain condition, but not in the loss condition. In sum, we found no clear evidence for a general aversion to delay in adolescents with ADHD.     

The need of young adults to text now: Using delay discounting to assess informational choice

This study examined the value of responding immediately to a text or call and the ability to wait. The willingness to delay texting or calling for a larger monetary reward was compared with delay tolerance for monetary rewards alone. The results of two experiments showed no differences in the qualitative shape of the delay discounting functions, indicating a similar decision-making process for informational (texting or calling) and monetary decisions. Data in the second experiment showed that the degree of delay tolerance varied as a function of the social distance of the texting partner, indicating a strategic decision-making process in informational decisions. However, the time course of loss of value for informational versus monetary rewards revealed substantial quantitative differences. While money loses value on the time span of weeks, information loses value within minutes, which may explain why behaviors like texting often occur in inappropriate situations and may seem like addictions.     

厌恶和恐惧情绪对跨期选择的不同影响：基于ERP的研究

本研究运用事件相关电位技术(ERPs)考察厌恶和恐惧情绪对跨期选择的影响。其中,厌恶和恐惧情绪采用情绪面孔图片进行启动,分析跨期选择任务中评估阶段所诱发的ERP成分。行为结果发现,与中性面孔相比,厌恶面孔启动使个体倾向于选择立即奖赏。ERP结果发现,在选项评估阶段,厌恶面孔比中性和恐惧面孔启动诱发更大的P2、P3和LPP波幅。这说明,厌恶情绪促使个体投入更多的注意和动机资源对跨期选项进行评估,进而使个体倾向即时满足。     

厌恶和恐惧情绪对跨期选择的不同影响：基于ERP的研究

本研究运用事件相关电位技术(ERPs)考察厌恶和恐惧情绪对跨期选择的影响。其中,厌恶和恐惧情绪采用情绪面孔图片进行启动,分析跨期选择任务中评估阶段所诱发的ERP成分。行为结果发现,与中性面孔相比,厌恶面孔启动使个体倾向于选择立即奖赏。ERP结果发现,在选项评估阶段,厌恶面孔比中性和恐惧面孔启动诱发更大的P2、P3和LPP波幅。这说明,厌恶情绪促使个体投入更多的注意和动机资源对跨期选项进行评估,进而使个体倾向即时满足。     

跨期选择单维占优模型的过程检验

跨期选择需要决策者在眼前与未来的损益之间做出权衡与取舍。主流跨期选择理论认为, 跨期选择是把未来价值折扣到现在, 根据折扣后的价值进行选择的过程; 而单维占优模型则认为决策者把“结果”维度上的差异和“延迟”维度上的差异进行比较(维度间差异比较), 然后根据差异更大的维度(即占优势的维度)进行决策。跨期选择众理论之争无果的原因之一或是研究者未能找到揭示其心理过程的令人信服的证据。为此, 本研究采用过程检验而非结果拟合的方法, 首创了“直观模拟天平”任务, 对维度间差异比较的大小进行测量, 从而为验证单维占优模型提供了支持性的证据。实验1A证明了维度间差异大小中介了选择结果, 被试认为“结果”维度上的差异相对于“延迟”维度上的差异越大, 越倾向于选择延迟长、结果大的选项; 反之, 被试认为“延迟”维度上的差异相对于“结果”维度上的差异越大, 越倾向于选择延迟短、结果小的选项。实验1B证明了维度间差异比较是在选择时实时(而不是在选择后)进行的。实验1C通过调整实验程序消减了共同方法偏差对结果的影响。实验2进一步证明维度间差异比较可以解释众多的跨期选择异象。通过4个实验, 本研究揭示了维度间差异比较构成了跨期选择的重要(尽管可能不是唯一)决策过程, 为支持单维占优模型提供了重要的过程验证证据。     

Decision biases in intertemporal choice and choice under uncertainty: Testing a common account

Two experiments were performed to test a psychophysical account of parallels between biases in risky choice and intertemporal choice. Experiment 1 demonstrated the common difference effect in intertemporal choice and the common ratio effect in risky choice. As was predicted, these two biases were uncorrelated with each other, although each was correlated across monetary/health domains. This result is consistent with the supposition that these two biases result from psychophysical properties of two different dimensions (time and probability, respectively). Experiment 2 examined the magnitude effect in intertemporal choice and the peanuts effect in risky choice. These two biases were correlated with each other but were uncorrelated across monetary/health domains. This result is consistent with the supposition that these two biases result from psychophysical properties of the same dimension (utility of money or health).     

跨期决策中的维度差异偏好：眼动证据

在跨期决策研究领域,虽然基于维度的跨期模型得到了一些源自结果检验和过程检验的证据支持,但此类模型所假设的维度间差异比较的心理过程尚缺乏直接的过程证据。本研究通过两个眼动实验,系统考察了相关眼动指标对维度差异偏好的预测效应。结果发现,根据基于维度的权衡模型可有效拟合出个体在跨期决策中的维度差异偏好,并且反应时、眼跳注视熵和静态注视熵等指标均与维度差异偏好负相关,而基于维度的注意分配与维度差异判断正相关。这些研究发现支持了本研究所提出的跨期眼动模型的相关假设,证实了维度差异偏好与跨期决策的认知加工过程之间的联系,为基于维度的跨期模型提供了更直接的过程证据,并为今后跨期决策的眼动模型发展指明了新方向。     

Behavioral trainings and manipulations to reduce delay discounting: A systematic review

In everyday decision-making, individuals make trade-offs between short-term and long-term benefits or costs. Depending on many factors, individuals may choose to wait for larger delayed reward, yet in other situations they may prefer the smaller, immediate reward. In addition to within-subject variation in the short-term versus long-term reward trade-off, there are also interindividual differences in delay discounting (DD), which have been shown to be quite stable. The extent to which individuals discount the value of delayed rewards turns out to be associated with important health and disorder-related outcomes: the more discounting, the more unhealthy or problematic choices. This has led to the hypothesis that DD can be conceptualized as trans-disease process. The current systematic review presents an overview of behavioral trainings and manipulations that have been developed to reduce DD in human participants aged 12 years or older. Manipulation studies mostly contain one session and measure DD directly after the manipulation. Training studies add a multiple session training component that is not per se related to DD, in between two DD task measurements. Ninety-eight studies (151 experiments) were identified that tested behavioral trainings and manipulations to decrease DD. Overall, results indicated that DD can be decreased, showing that DD is profoundly context dependent and changeable. Most promising avenues to pursue in future research seem to be acceptance-based/mindfulness-based trainings, and even more so manipulations involving a future orientation. Limitations and recommendations are discussed to identify the mechanistic processes that allow for changes in discount rate and behavior accordingly.

     

Evaluating the effect of delay spacing on delay discounting: carry‐over effects on steepness and the form of the discounting function

Most delay discounting studies use tasks that arrange delay progressions in which the spacing between consecutive delays becomes progressively larger. To date, little research has examined delay discounting using other progressions. The present study assessed whether the form or steepness of discounting varied across different delay progressions. Human participants completed three discounting tasks with delay progressions that varied in the time between consecutive delays: a standard (increasing duration between delays), linear (equal duration between delays), and an inverse progression (decreasing duration between delays). Steepness of discounting was generally reduced, and remained so, following experience with the inverse progression. Effects of the delay progression on the best fitting equation were order‐dependent. Overall the hyperbola model provided better fits, but the exponential model performed better with data from the inverse progression. Regardless, differences in which model fit best were often small. The finding that the best fitting model was dependent, in some cases, on the delay progression suggests that a single quantitative model of discounting may not be applicable to describe discounting across all procedural contexts. Ultimately, changes in steepness of discounting following experience with the inverse progression appeared similar to anchoring effects, whose mechanism will require further study to delineate.     

Spontaneous discounting of availability in frequency judgment tasks

Discounting is a causal-reasoning phenomenon in which increasing confidence in the likelihood of a particular cause decreases confidence in the likelihood of all other causes. This article provides evidence that individuals apply discounting principles to making causal attributions about internal cognitive states. In particular, the three studies reported show that individuals will fail to use the availability heuristic in frequency estimations when salient causal explanations for availability exist. Experiment 1 shows that fame is used as a cue for discounting in estimates of surname frequency. Experiment 2 demonstrates that individuals discount the availability of their own last name. Experiment 3, which used individuals' initials in a letter-frequency estimation task, demonstrates that simple priming of alternative causal models leads to discounting of availability. Discounting of cognitive states can occur spontaneously, even when alternative causal models are never explicitly provided.