Cited by 228Reinforcement Learning in RoboticsDomain Adaptation and Few-Shot LearningAdvanced Bandit Algorithms Research

Towards Continual Reinforcement Learning: A Review and Perspectives

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Khetarpal, Khimya, Riemer, Matthew, Rish, Irina, Precup, Doina·2022·Journal of Artificial Intelligence Research

Abstract

In this article, we aim to provide a literature review of different formulations and approaches to continual reinforcement learning (RL), also known as lifelong or non-stationary RL. We begin by discussing our perspective on why RL is a natural fit for studying continual learning. We then provide a taxonomy of different continual RL formulations by mathematically characterizing two key properties of non-stationarity, namely, the scope and driver non-stationarity. This offers a unified view of various formulations. Next, we review and present a taxonomy of continual RL approaches. We go on to discuss evaluation of continual RL agents, providing an overview of benchmarks used in the literature and important metrics for understanding agent performance. Finally, we highlight open problems and challenges in bridging the gap between the current state of continual RL and findings in neuroscience. While still in its early days, the study of continual RL has the promise to develop better incremental reinforcement learners that can function in increasingly realistic applications where non-stationarity plays a vital role. These include applications such as those in the fields of healthcare, education, logistics, and robotics.

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  • Affordance theory in RL holds that the environment constrains and suggests possible actions, and agents learn which actions are afforded in each situation.

    “Another line develops affordance theory in RL, where the environment constrains and suggests possible actions (Graves et al., 2022; Khetarpal et al., 2020). Rather than treating all actions as always available, agents learn which are afforded in each situation, mirroring selective, skillful responses in enactive perception.”

    From Toward Enactive Artificial Intelligence (2026) · cites this paper as Khetarpal et al., 2020

    In “The Agent-Environment Boundary” (page unavailable), the review says the space of affordances may change over time and may emerge through agent–environment interaction. Section 2.2 also notes that action availability can change over time. These passages support the idea that possible actions depend on the situation, but they do not say that the environment suggests actions or that agents learn which actions are afforded in each situation. (LLM, conf=0.76)

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Cited by

Sorted by citations

Authors
Khetarpal, K., Riemer, M., Rish, I., & Precup, D.
Affiliations
  • McGill University (CA)
  • Mila - Quebec Artificial Intelligence Institute (CA)
Venue
Journal of Artificial Intelligence Research
Published
2022-12-22
Volume
75
Pages
1401-1476
ISSN
1076-9757 (ISSN-L)
OpenAlex
W3117215073
Cited by
224
References
474
Citations by year
2026: 37 · 2025: 54 · 2024: 72 · 2023: 28 · 2022: 11 · 2021: 22
FWCI
13.57
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Journal of Artificial Intelligence Research (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • Canadian Institute for Advanced Research
  • Canada Excellence Research Chairs, Government of Canada
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Reinforcement Learning in Robotics
  • Physical Sciences › Computer Science › Artificial Intelligence › Domain Adaptation and Few-Shot Learning
  • Social Sciences › Decision Sciences › Management Science and Operations Research › Advanced Bandit Algorithms Research
Keywords
continual reinforcement learning, lifelong learning, incremental learning

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