Intertemporal Similarity: Discounting as a Last Resort

Standard models of intertemporal choice assume that individuals discount future payoffs by integrating reward amounts and time delays to generate a discounted value. Alternative models propose that, rather than integrate across them, individuals compare within attributes (amounts and delays) to determine if differences in one attribute outweigh differences in another attribute. For instance, the similarity model 1) compares the two reward amounts to determine whether they are similar, 2) compares the similarity of the two time delays, and then 3) makes a decision based on these similarity judgments. Here, I tested discounting models against attribute‐based models that use similarity judgments to make choices. I collected intertemporal choices and similarity judgments for the reward amounts and time delays from participants in three experiments. All experiments tested the ability of discounting and similarity models to predict intertemporal choices. Model generalization analyses showed that the best predicting models started with similarity judgments and then, if similarity failed to make a prediction, resorted to discounting models. Similarity judgments also matched intertemporal choice data demonstrating both the magnitude and sign effects, thereby accounting for behavioral data that contradict many discounting models. These results highlight the possibility that attribute‐based models such as the similarity models provide alternatives to discounting that may offer insights into the process of making intertemporal choices. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

物质成瘾领域延迟折扣研究中的外部效度问题

物质成瘾者的跨期决策缺陷已被大量使用金钱延迟折扣任务的研究所证实。然而近年来, 来自金钱延迟折扣任务变式(成瘾物质延迟折扣任务、性延迟折扣任务和跨类别延迟折扣任务)的发现表明, 在物质成瘾领域的延迟折扣研究中单一使用金钱延迟折扣任务存在一定的局限性。首先, 物质成瘾者对金钱的延迟折扣水平可能并不能完全代表其对成瘾物质、性和其它自然奖赏的延迟折扣水平; 其次, 仅使用单一延迟折扣任务可能存在对物质成瘾者跨期决策过程的过度简化; 最后, 金钱延迟折扣任务较其变式对物质成瘾者的一些临床特征不够敏感。未来研究应进一步丰富、拓展物质成瘾领域的跨类别延迟折扣研究, 并对可能影响跨期决策的时间因素进行深入探索。     

人们如何设想未来：未来情景思维对个体心理和行为的影响

未来情景思维(Episodic Future Thinking, EFT)主要指人们基于当前情景或过去经历来思考、想象未来的过程, 是人们对于未来的一种设想。根据已有的行为实验和神经影像学等多个方面的研究结果, 系统论述了未来情景思维的概念和特征, 以及个体过去的生活经历及相应记忆和个体生活目标对其的影响, 通过概括和分析行为和脑神经两方面的证据来论述未来情景思维会对人们具体生活实践产生积极与消极的双向影响。当然, 未来还需要进一步加强未来情景思维研究的广度和深度, 特别是要细化未来情景思维的类型, 探讨未来情景思维可能导致的不适应行为以及影响个体心理和行为的作用机制, 从而为人们如何更积极地适应未来提供更充分的实证证据和理论构想。     

Concurrent relations between inhibitory control,vocabulary and internal state language in 18- and 24-month-old Italian-speaking infants

The aim of this study was to investigate the concurrent relations between 18- and 24-month-olds' performance on tasks measuring inhibitory control, word production, and internal state vocabulary. Two tasks were used to measure inhibitory control, the Reverse Categorization task (a conflict task), and the Gift task (a delay task). Expressive vocabulary was assessed with the Italian version of the MacArthur Communicative Development Inventory (Words and Sentences), and internal state vocabulary was assessed with a checklist of 78 mental state terms adapted from the English Internal State Language Questionnaire. Expressive vocabulary was associated to Internal State Language and to the Reverse Categorization task, but not to the Delay task. Our findings document internal state language abilities in a sample of 61 Italian-speaking children, and show that internal state vocabulary is significantly and specifically related only to performance on the conflict measure of inhibitory control, even when vocabulary size is controlled for. Results of our study extend to an Italian sample of children previous findings on an early association between self-control and theory of mind and suggest that a link between inhibitory control processes and internal state language may be present at a very young age.     

Smokers discount their drug of abuse in the same way as other consumable rewards

Recent research shows that drug abusers discount delayed monetary rewards more than nonabusers do, and they discount delayed substances of abuse (e.g., drugs) more than delayed money. Furthermore, non-drug-abusers discount food and substances of abuse (e.g., alcohol), more than money. Here, we compare the delay and probability discounting of money with that of a directly consumable reward (chocolate) and with that of a substance of abuse (cigarettes), in a drug-using population (smokers). In line with previous research, we found in two experiments that delay discounting differentiated between smokers and nonsmokers, and between money and a nonabused directly consumable reward (chocolate). In addition, our results show that there appears to be no difference in the extent to which smokers discount their abused substance compared to another directly consumable reward. These findings support the contention that drugs and food are part of the same category of primary reinforcers, whereas money is discounted differently, as a conditioned reinforcer.     

Is focusing on unknown items while studying a beneficial long-term strategy?

The amount students learn is influenced by the decisions they make while they study. Prior research shows that when people decide what to study (and what not to), they almost universally prioritise information they do not know over information they do know. We found that focusing on unknown items was beneficial when memory was tested immediately after studying, but not when memory was tested after a delay of one or two weeks. These findings support a model in which studying unknown items causes many items to rise above a recall threshold, which results in a short-term advantage, but also leaves the items vulnerable to forgetting. Studying known items, by contrast, moves items farther above threshold, such that they remain above threshold for longer. These findings have implications for students and teachers who want to maximise long-term learning.     

Delay discounting as emotional processing: An electrophysiological study

Both theoretical models and functional imaging studies implicate the involvement of emotions within the delay discounting process. However, defining this role has been difficult to establish with neuroimaging techniques given the automaticity of emotional responses. To address this, the current study examined electrophysiological correlates involved in the detection and evaluation of immediate and delayed monetary outcomes. Our results showed that modulation of both early and later ERP components previously associated with affective stimuli processing are sensitive to the signalling of delayed rewards. Together with behavioural reaction times that favoured immediacy, we demonstrated, for the first time, that time delays modify the incentive value of monetary rewards via mechanisms of emotional bias and selective visual attention. Furthermore, our data are consistent with the hypothesis that delayed and thus intangible rewards are perceived less saliently, and rely on emotion as a common currency within decision making. This study provides a new approach to delay discounting and highlights a potential novel route through which delay discounting may be investigated.