Park Heyeon, Lee Daeyeol, Chey Jeanyung
Department of Psychology, Seoul National University, Seoul, Korea.
Department of Neuroscience, Department of Psychiatry, Yale School of Medicine, New Haven, United States of America.
PLoS One. 2017 Jul 19;12(7):e0180588. doi: 10.1371/journal.pone.0180588. eCollection 2017.
Previous studies found that stress shifts behavioral control by promoting habits while decreasing goal-directed behaviors during reward-based decision-making. It is, however, unclear how stress disrupts the relative contribution of the two systems controlling reward-seeking behavior, i.e. model-free (or habit) and model-based (or goal-directed). Here, we investigated whether stress biases the contribution of model-free and model-based reinforcement learning processes differently depending on the valence of outcome, and whether stress alters the learning rate, i.e., how quickly information from the new environment is incorporated into choices. Participants were randomly assigned to either a stress or a control condition, and performed a two-stage Markov decision-making task in which the reward probabilities underwent periodic reversals without notice. We found that stress increased the contribution of model-free reinforcement learning only after negative outcome. Furthermore, stress decreased the learning rate. The results suggest that stress diminishes one's ability to make adaptive choices in multiple aspects of reinforcement learning. This finding has implications for understanding how stress facilitates maladaptive habits, such as addictive behavior, and other dysfunctional behaviors associated with stress in clinical and educational contexts.
先前的研究发现，压力通过促进习惯形成来改变行为控制，同时在基于奖励的决策过程中减少目标导向行为。然而，目前尚不清楚压力如何扰乱控制奖赏寻求行为的两个系统（即无模型（或习惯）和基于模型（或目标导向））的相对贡献。在此，我们研究了压力是否会根据结果的效价不同地偏向无模型和基于模型的强化学习过程的贡献，以及压力是否会改变学习率，即新环境中的信息多快被纳入选择中。参与者被随机分配到压力组或对照组，并执行一个两阶段的马尔可夫决策任务，其中奖励概率会在没有通知的情况下定期反转。我们发现，只有在出现负面结果后，压力才会增加无模型强化学习的贡献。此外，压力会降低学习率。结果表明，压力会削弱一个人在强化学习的多个方面做出适应性选择的能力。这一发现对于理解压力如何促进不良习惯（如成瘾行为）以及临床和教育背景下与压力相关的其他功能失调行为具有重要意义。
