Stress enhances model-free reinforcement learning only after negative outcome

PLoS One. 2017 Jul 19;12(7):e0180588. doi: 10.1371/journal.pone.0180588. eCollection 2017.

Abstract

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.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Cold Temperature
  • Female
  • Goals*
  • Humans
  • Male
  • Reinforcement, Psychology*
  • Reversal Learning / physiology*
  • Reward*
  • Stress, Physiological / physiology*
  • Stress, Psychological / psychology*
  • Young Adult

Grants and funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (No. 2011-0005029). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.