Yi Richard, Gatchalian Kirstin M, Bickel Warren K
Department of Psychiatry, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
Exp Clin Psychopharmacol. 2006 Aug;14(3):311-7. doi: 10.1037/1064-1297.14.3.311.
Drug use, abuse, and addiction are common behavioral manifestations of impulsiveness. A useful and popular laboratory analogue of impulsiveness is temporal discounting. Temporal discounting refers to the reduction in the present, subjective value of outcomes that are temporally distant in the future. The extensive literature on temporal discounting indicates hyperbolic discounting, the magnitude effect, and the sign effect. It is possible that the same principles may apply to other dimensions of psychological distance, including past temporal distance. The purpose of the present study was to examine the possibility that outcomes in the past are discounted hyperbolically and at a similar rate to outcomes in the future. The magnitude and sign effects were also examined in past discounting. Indifference points of college students were determined from a paper-and-pencil questionnaire of future and past discounting. The results demonstrate that humans discount temporally distant past outcomes similarly to future outcomes. Discounting of the future and past are qualitatively and quantitatively similar; discounting of past outcomes is orderly, hyperbolic, and consistent with most empirical observations from studies of future discounting, including the magnitude and sign effects. The present study indicates that the discounting of past outcomes is a quantifiable phenomenon, and the results are similar to observations from the established future-discounting literature. Past discounting may be of use in the study of drug-dependent and other impulsive populations. Implications of a relationship between future and past discounting are discussed.
药物使用、滥用和成瘾是冲动性的常见行为表现。一种有用且流行的冲动性实验室模拟是时间折扣。时间折扣是指未来在时间上遥远的结果在当前主观价值上的降低。关于时间折扣的大量文献表明存在双曲线折扣、量级效应和符号效应。同样的原则可能适用于心理距离的其他维度，包括过去的时间距离。本研究的目的是检验过去的结果是否以双曲线方式进行折扣，且折扣率与未来的结果相似这一可能性。在过去折扣中也考察了量级效应和符号效应。大学生的无差异点是通过一份关于未来和过去折扣的纸笔问卷确定的。结果表明，人类对时间上遥远的过去结果的折扣方式与对未来结果的折扣方式相似。对未来和过去的折扣在质和量上都是相似的；对过去结果的折扣是有序的、双曲线的，并且与未来折扣研究中的大多数实证观察结果一致，包括量级效应和符号效应。本研究表明，对过去结果的折扣是一种可量化的现象，其结果与已有的未来折扣文献中的观察结果相似。过去折扣可能在药物依赖和其他冲动人群的研究中有用。讨论了未来折扣与过去折扣之间关系的意义。
