Department of Psychology, University of Southern California, Los Angeles, California 90089, USA.
J Neurosci. 2009 Nov 25;29(47):14820-7. doi: 10.1523/JNEUROSCI.4261-09.2009.
Several theories of self-control [including intertemporal bargaining (Ainslie, 1992) and self-signaling (Bodner and Prelec, 2001)] imply that intertemporal decisions can be more farsighted than would be predicted by the incentive associated with rewards outside a decision context. We examined this hypothesis using behavior and functional neuroimaging. First, subjects expressed preferences between amounts of money delayed by 4 months and smaller amounts available that day. This allowed us to establish "indifference pairs" individualized to each participant: immediate and delayed amounts that were equally preferred. Participants subsequently performed a reaction time functional magnetic resonance imaging task (Knutson et al., 2001a) that provided them with distinct opportunities to win each of the rewards that comprised the indifference pairs. Anatomical region of interest analysis as well as whole-brain analysis indicated greater response recruited by the immediate rewards (relative to the preference-matched delayed rewards) in regions previously implicated as sensitive to incentive value using the same task (including bilateral putamen, bilateral anterior insula, and midbrain). Reaction time to the target was also faster during the immediate relative to delayed reward trials (p < 0.01), and individual differences in reaction time between immediate versus delayed reward trials correlated with variance in magnetic resonance signal in those clusters that responded preferentially to immediate rewards (r = 0.33, p < 0.05). These findings indicate a discrepancy in incentive associated with the immediate versus the preference-matched delayed rewards. This discrepancy may mark the contribution of self-control processes that are recruited during decision-making but that are absent when rewards are individually anticipated.
几种自我控制理论[包括跨期讨价还价(Ainslie,1992)和自我信号(Bodner 和 Prelec,2001)]表明,跨期决策可以比奖励之外的决策背景所预测的更有远见。我们使用行为和功能神经影像学来检验这一假设。首先,被试者在 4 个月后延迟的金额和当天可用的较小金额之间表达了偏好。这使我们能够为每个参与者建立个性化的“无差异对”:即时和延迟的金额同样受欢迎。参与者随后执行了一项反应时间功能磁共振成像任务(Knutson 等人,2001a),该任务为他们提供了独特的机会赢得构成无差异对的每个奖励。基于感兴趣的区域分析和全脑分析表明,在与偏好匹配的延迟奖励相比,与即时奖励相关的反应在以前使用相同任务表明对激励价值敏感的区域(包括双侧壳核、双侧前岛叶和中脑)中招募的反应更大。与延迟奖励相比,即时奖励的目标反应时间也更快(p < 0.01),即时奖励与延迟奖励之间的反应时间差异与这些对即时奖励反应更敏感的簇中的磁共振信号变化相关(r = 0.33,p < 0.05)。这些发现表明,即时奖励与偏好匹配的延迟奖励之间存在激励差异。这种差异可能标志着在决策过程中招募的自我控制过程的贡献,但在个别预期奖励时不存在。