Gaze data reveal distinct choice processes underlying model-based and model-free reinforcement learning

Nat Commun. 2016 Aug 11:7:12438. doi: 10.1038/ncomms12438.

Abstract

Organisms appear to learn and make decisions using different strategies known as model-free and model-based learning; the former is mere reinforcement of previously rewarded actions and the latter is a forward-looking strategy that involves evaluation of action-state transition probabilities. Prior work has used neural data to argue that both model-based and model-free learners implement a value comparison process at trial onset, but model-based learners assign more weight to forward-looking computations. Here using eye-tracking, we report evidence for a different interpretation of prior results: model-based subjects make their choices prior to trial onset. In contrast, model-free subjects tend to ignore model-based aspects of the task and instead seem to treat the decision problem as a simple comparison process between two differentially valued items, consistent with previous work on sequential-sampling models of decision making. These findings illustrate a problem with assuming that experimental subjects make their decisions at the same prescribed time.

MeSH terms

  • Choice Behavior
  • Decision Making
  • Eye Movements*
  • Female
  • Fixation, Ocular*
  • Humans
  • Learning*
  • Least-Squares Analysis
  • Male
  • Models, Neurological
  • Models, Psychological
  • Nerve Net
  • Probability
  • Regression Analysis
  • Reinforcement, Psychology*
  • Reward