Delay Discounting and the Choice to Take a Drug

描述（由申请人提供）：行为与其强化者之间的延迟通常会降低强化者的主观价值，这种现象称为延迟折扣。有一个完善的定量模型，双曲折现函数，它描述了延迟折现。关于延迟折扣的研究为我们理解药物滥用做出了实质性的理论贡献。例如，药物滥用者对药物价值的折扣率比对货币强化物的折扣率要快，这表明折扣率可能取决于强化物的性质。然而，在一个假设的选择情境中，比较药物折扣和金钱折扣的实验研究了每种强化因素的单一量级。在人类中，延迟强化的大小是折现率的关键决定因素。对非人类的研究开始有助于我们理解延迟对药物选择的影响。最近，我们发现猴子对非药物强化物的反应比对可卡因的反应更强烈，这与在药物滥用者身上观察到的结果相反。这种差异可能是由于所研究的特定强化物的性质，或者是对猴子的真实强化物和对人类的假设强化物的使用。或者，它可能是强化物相对大小差异的结果。我们建议研究在给予同种（即药物/非药物）选择时，强化物的大小和延迟对药物和非药物强化物折现率的影响。目的1是在立即注射可卡因和延迟提供食物之间进行选择时，建立可卡因的剂量反应函数。将为不同数量的食物提供不同的折扣功能。这种同形选择情境（即即时药物vs延迟食物）类似于对药物滥用的潜在折扣解释：假设滥用药物者冲动地选择即时药物强化物，而不是更大的延迟非药物强化物。迄今为止，对这种同形选择的研究很少。目标2是建立在立即提供食物和延迟注射可卡因之间进行选择时食物的大小反应函数。将为不同剂量的可卡因建立折扣功能，并有不同的延迟。这种同形选择情况很重要，因为药物滥用也可能涉及在更直接的非药物强化物和延迟的药物强化物之间进行选择，正如药物滥用者经常投入大量时间和精力来获取药物的事实所证明的那样。这种情况在贴现文献中几乎没有得到讨论。我们对这两个目标的假设是，延迟强化的折现率将由双曲函数很好地描述，折现率将与延迟强化的数量成反比。研究结果将对理解药物选择的决定因素，以及在治疗背景下使用延迟强化具有重要意义。

DESCRIPTION (provided by applicant): Delay between a behavior and its reinforcer usually decreases the subjective value of the reinforcer, a phenomenon termed delay discounting. There is a well-established quantitative model, the hyperbolic discounting function, which describes delay discounting. Research with delay discounting has made substantial theoretical contributions to our understanding of drug abuse. For example, drug abusers discount the value of drugs more rapidly than they do monetary reinforcers, suggesting that discounting rate may depend on the nature of the reinforcer. However, experiments comparing discounting of drugs and money have studied a single magnitude of each reinforcer in a hypothetical choice situation. In humans, magnitude of a delayed reinforcer is a crucial determinant of discounting rate. Research with non-humans is beginning to contribute to our understanding of the effects of delay on drug choice. Recently, we found that monkeys discounted non-drug reinforcers more steeply than they did cocaine, a result opposite to that observed in drug abusers. This difference may be due to the nature of the specific reinforcers studied, or to the use of real reinforcers with monkeys vs. hypothetical reinforcers with humans. Alternatively, it may be a consequence of differences in the relative magnitudes of the reinforcers. We propose to investigate the effect of reinforcer magnitude and delay on the rate of discounting of drug and non-drug reinforcers in monkeys given allomorphic (i.e., drug/non-drug) choices. Aim 1 is to establish dose-response functions for cocaine when the choice is between an immediate injection of cocaine and the delayed presentation of food. Discounting functions will be established for different amounts of food available with various delays. This allomorphic choice situation (i.e., immediate drug vs. delayed food) is analogous to the one underlying discounting interpretations of drug abuse: drug abusers are assumed to impulsively choose immediate drug reinforcers over larger, delayed non-drug reinforcers. Such allomorphic choice has received little study to date. Aim 2 is to establish magnitude-response functions for food when the choice is between the presentation of an immediate amount of food and a delayed injection of cocaine. Discounting functions will be established for different doses of cocaine available with various delays. This allomorphic choice situation is important because drug abuse also can involve choosing between more immediate non-drug reinforcers and delayed drug reinforcers, as exemplified by the fact that drug abusers often devote considerable time and effort to procuring drugs. This situation has received virtually no discussion in the discounting literature. Our hypotheses for both Aims are that the discounting of the delayed reinforcer will be well described by the hyperbolic function and that rate of discounting will vary inversely with the amount of the delayed reinforcer. The results will have important implications for understanding the determinants of drug choice and, potentially, for the use of delay to reinforcement in a therapeutic context.