Model-based and model-free pain avoidance learning
Background: While there is good evidence that reward learning is underpinned by two distinct decision control systems – a cognitive 'model-based' and a habitbased 'model-free' system, a comparable distinction for punishment avoidance has been much less clear. Methods: We implemented a pain avoidance task that placed differential emphasis on putative model-based and model-free processing, mirroring a paradigm and modelling approach recently developed for reward-based decision-making. Subjects performed a two-step decision-making task with probabilistic pain outcomes of different quantities. The delivery of outcomes was sometimes contingent on a rule signalled at the beginning of each trial, emulating a form of outcome devaluation. Results: The behavioural data showed that subjects tended to use a mixed strategy – favouring the simpler model-free learning strategy when outcomes did not depend on the rule, and favouring a model-based when they did. Furthermore, the data were well described by a dynamic transition model between the two controllers. When compared with data from a reward-based task (albeit tested in the context of the scanner), we observed that avoidance involved a significantly greater tendency for subjects to switch between model-free and model-based systems in the face of changes in uncertainty. Conclusion: Our study suggests a dual-system model of pain avoidance, similar to but possibly more dynamically flexible than reward-based decision-making.
Additional Information© 2018 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 License (http://www.creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage). Article first published online: May 10, 2018; Issue published: January 1, 2018. Received: October 26, 2017; Accepted: April 02, 2018. O.W., S.L., J.O., B.S. and W.Y. conceived the experiment, O.W., B.S. and W.Y. conducted the experiment and O.W., S.L. and W.Y. analysed the results. All the authors reviewed the manuscript. We thank Kaori Nakamura for her help in scheduling and conducting the experiment. The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article. The study was supported by JSPS Grant-in-Aid for Young Scientists A (Grant number: JP25700016) and Grant-in-Aid for Scientific Research on Innovative Areas (Grant number: JP17H06314). The research is also supported by Arthritis Research UK (Ref: 21357).
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