Uncertainty alters the balance between incremental learning and episodic memory
- Columbia University, United States
- Princeton University, United States
Abstract
A key question in decision making is how humans arbitrate between competing learning and memory systems to maximize reward. We address this question by probing the balance between the effects, on choice, of incremental trial-and-error learning versus episodic memories of individual events. Although a rich literature has studied incremental learning in isolation, the role of episodic memory in decision making has only recently drawn focus, and little research disentangles their separate contributions. We hypothesized that the brain arbitrates rationally between these two systems, relying on each in circumstances to which it is most suited, as indicated by uncertainty. We tested this hypothesis by directly contrasting contributions of episodic and incremental influence to decisions, while manipulating the relative uncertainty of incremental learning using a well-established manipulation of reward volatility. Across two large, independent samples of young adults, participants traded these influences off rationally, depending more on episodic information when incremental summaries were more uncertain. These results support the proposal that the brain optimizes the balance between different forms of learning and memory according to their relative uncertainties and elucidate the circumstances under which episodic memory informs decisions.
Data availability
All code, data, and software needed to reproduce the manuscript can be found here: https://codeocean.com/capsule/2024716/tree/v1; DOI: https://doi.org/10.24433/CO.1266819.v1
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Uncertainty alters the balance between incremental learning and episodic memoryCode Ocean, https://doi.org/10.24433/CO.1266819.v1.
Article and author information
Author details
Funding
National Science Foundation (1644869)
- Jonathan Nicholas
National Science Foundation (1822619)
- Nathaniel D Daw
National Science Foundation (1822619)
- Daphna Shohamy
National Institutes of Health (MH121093)
- Nathaniel D Daw
National Institutes of Health (MH121093)
- Daphna Shohamy
John Templeton Foundation (60844)
- Daphna Shohamy
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Michael J Frank, Brown University, United States
Ethics
Human subjects: Informed consent was obtained online with approval from the Columbia University Institutional Review Board (IRB #1488)
Version history
- Preprint posted: July 6, 2022 (view preprint)
- Received: July 7, 2022
- Accepted: December 1, 2022
- Accepted Manuscript published: December 2, 2022 (version 1)
- Version of Record published: January 3, 2023 (version 2)
Copyright
© 2022, Nicholas et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Uncertainty alters the balance between incremental learning and episodic memory
eLife 11:e81679.
https://doi.org/10.7554/eLife.81679
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We are unresponsive during slow-wave sleep but continue monitoring external events for survival. Our brain wakens us when danger is imminent. If events are non-threatening, our brain might store them for later consideration to improve decision-making. To test this hypothesis, we examined whether novel vocabulary consisting of simultaneously played pseudowords and translation words are encoded/stored during sleep, and which neural-electrical events facilitate encoding/storage. An algorithm for brain-state-dependent stimulation selectively targeted word pairs to slow-wave peaks or troughs. Retrieval tests were given 12 and 36 hr later. These tests required decisions regarding the semantic category of previously sleep-played pseudowords. The sleep-played vocabulary influenced awake decision-making 36 hr later, if targeted to troughs. The words’ linguistic processing raised neural complexity. The words’ semantic-associative encoding was supported by increased theta power during the ensuing peak. Fast-spindle power ramped up during a second peak likely aiding consolidation. Hence, new vocabulary played during slow-wave sleep was stored and influenced decision-making days later.
