成瘾人群的决策障碍：研究范式与神经机制

药物成瘾者和赌博成瘾者常常偏好即刻的奖赏而忽视将来的消极结果。在进行决策任务时, 他们倾向于做出不利的选择, 偏好短时的获益而不顾长期的损失, 这是一种决策障碍的表现。延迟折扣任务(DDT)、爱荷华赌博任务(IGT)和剑桥赌博任务(CGT)是研究决策障碍的三种常用方法和范式, 分别考察成瘾人群的冲动性决策、决策短视和决策时的冒险行为。近十几年来的研究表明, 前额叶皮层(PFC)在人类的决策活动中起重要作用。其中, 腹内侧前额叶(VMPFC)、眶额叶(OFC)、背外侧前额叶(DLPFC)等皮层的功能变化与成瘾人群的决策障碍有密切关系。     

时间贴现在神经和行为上的年龄特征

时间贴现的年龄发展具有阶段性。前额皮质, 边缘系统和多巴胺能系统的发展成熟是从儿童期到成人期时间贴现发展变化的神经生物基础。成人期到老年期时间贴现年龄特征的研究结果不一致。概率贴现、未来定向、延迟满足等被用来探讨时间贴现年龄发展特征。可以从大脑不同区域的发展轨迹, 延迟时段的心理意义来进一步深入研究。     

概率贴现和时间贴现在人脑中的分离

本研究运用ERP技术来检验概率贴现和时间贴现是否反映了相同的神经机制过程。在本研究中,我们在一个刺激中同时操纵概率贴现（风险vs.安全）和时间贴现（1个月后vs.今天）水平。通过对两个过程上的ERN以及全时间段的ERP分析来确定它们是否反映了相同的认知过程。结果发现,这两者在ERN上存在差异,同时这两个效应在ERP的时程和出现的电极点上都存在差异。这些差异表明这两者可能包含着不同的神经机制过程。     

时间洞察力对拖延行为的影响机制:时间折扣的中介作用

采用津巴多时间洞察力量表（ZTPI）、一般拖延量表（GPS）和跨期选择任务,考察了时间洞察力对拖延行为的影响,并从时间折扣视角检验了时间洞察力影响拖延行为的中介机制。结果表明（1）对553名大学生的测量数据进行逐步回归和优势分析,结果表明："未来"时间洞察力对拖延行为具有良好的预测力,解释率最高;（2）对121名大学生的测量数据进行中介分析,结果表明：时间折扣在时间洞察力影响拖延行为过程中起着中介作用。这些结果说明,"未来"时间洞察力对拖延行为具有较好的预测作用,而且未来时间洞察力对拖延行为的影响可能是通过时间折扣为中介实现的。     

拖延的决策模型

拖延是指尽管预见到该行为会带来不利后果,人们仍自愿推迟开始或完成某一计划好的行为。先前的研究对拖延的类型、影响因素、成因以及干预等方面进行了广泛的探讨,然而拖延的决策过程——"现在做还是以后做?"认知机制还非常不清楚。因此,本文提出拖延决策模型试图从三方面阐明"现在做还是以后做?"的决策机制:首先,拖延动机和不拖延动机的斗争是决定是否拖延的根本;其次,拖延动机的斗争可以进一步简化为任务负性过程和任务正性结果的权衡;最后,主动推迟任务使负性过程发生延迟折扣是拖延的核心目的。拖延决策模型不仅有助于探明拖延的核心认知机制,也能够帮助预测拖延行为的发生及解释各种影响因素的作用机制,因此未来的研究可以借此整合一个从拖延的核心发生机制到各种影响因素的理论系统。     

时间洞察力对跨期选择偏好的预测

利用津巴多时间洞察力问卷,采用跨期选择经典范式,考察“现在享乐型”和“未来定向型”两类时间洞察力个体在跨期选择上的偏好,从人格特质角度来探究跨期选择的认知机制。结果发现：(1)现在享乐定向组的延迟折扣率显著高于未来定向组;(2)未来定向组在时间洞察力量表“未来维度”得分与延迟折扣率显著负相关。这说明时间洞察力对个体延迟折扣率具有预测作用,支持了跨期选择的时间感知基础模型。     

Effects of acute and chronic flunitrazepam on delay discounting in pigeons

Delay to delivery of a reinforcer can decrease responding for that reinforcer and increase responding for smaller reinforcers that are available concurrently and delivered without delay; acute administration of drugs can alter responding for large, delayed reinforcers, although the impact of chronic treatment on delay discounting is not well understood. In this experiment, the effects of repeated administration of the benzodiazepine flunitrazepam were studied in 6 pigeons responding on one key to receive food that was delivered immediately and on a second key to receive a larger amount of food that was delivered following delays which increased across a single session. Pigeons responded predominantly for the large reinforcer when there were no delays and when delays were short; however, as delays increased, responding for the large reinforcer decreased. Acutely, flunitrazepam (0.32, 1.0 and 3.2 mg/kg) dose-dependently increased responding for the large reinforcer, shifting the discounting curve rightward and upward. Repeated administration of flunitrazepam (0.32, 1.0 and 3.2 mg/kg, each for six sessions, separated by one session during which vehicle was administered) did not markedly alter its effects on responding for the large reinforcer, indicating that the development of tolerance to this effect of flunitrazepam is modest under these conditions.     

The ecological rationality of delay tolerance: insights from capuchin monkeys

Both human and non-human animals often face decisions between options available at different times, and the capacity of delaying gratification has usually been considered one of the features distinguishing humans from other animals. However, this characteristic can widely vary across individuals, species, and types of task and it is still unclear whether it is accounted for by phylogenetic relatedness, feeding ecology, social structure, or metabolic rate. To disentangle these hypotheses, we evaluated temporal preferences in capuchin monkeys, South-American primates that, despite splitting off from human lineage approximately 35 million years ago, show striking behavioural analogies with the great apes. Then, we compared capuchins’ performance with that of the other primate species tested so far with the same procedure. Overall, capuchins showed a delay tolerance significantly higher than closely related species, such as marmosets and tamarins, and comparable to that shown by great apes. Capuchins’ tool use abilities might explain their comparatively high preference for delayed options in inter-temporal choices. Moreover, as in humans, capuchin females showed a greater delay tolerance than males, possibly because of their less opportunistic foraging style. Thus, our results shed light on the evolutionary origins of self-control supporting explanations of delay tolerance in terms of feeding ecology.     

Timing of retirement: Including a delay discounting perspective in retirement models

This research examined the influence of delay and anticipated health and enjoyment on the amount of retirement savings sacrificed for early retirement. In addition to testing and supporting predictions that willingness to sacrifice retirement savings would be less with shorter delays to retirement, greater anticipated health, and greater anticipated enjoyment, an individual difference delay discounting measure derived from experimental studies was used to extend the Beehr, Glazer, Nielson, and Farmer’s (2000) model of retirement age. We predicted and found that oldest preferred retirement age related to personal characteristics, current work factors, future retirement factors, and individual differences in delay discounting, with greater delay discounting being associated with a younger preferred retirement age. Findings suggest that delay discounting is an important consideration in retirement planning and also highlight the significance that retirement expectations and being tired of work have in affecting one’s preferred retirement age.     

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.