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Maximilian Puelma Touzel

puelmatm@mila.quebec
Collaborateur·rice de recherche
Superviseur⋅e principal⋅e
Irina Rish
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Publications

Performance-gated deliberation: A context-adapted strategy in which urgency is opportunity cost
Maximilian Puelma Touzel
Paul Cisek
Guillaume Lajoie
Finding the right amount of deliberation, between insufficient and excessive, is a hard decision making problem that depends on the value we… (voir plus) place on our time. Average-reward, putatively encoded by tonic dopamine, serves in existing reinforcement learning theory as the opportunity cost of time, including deliberation time. Importantly, this cost can itself vary with the environmental context and is not trivial to estimate. Here, we propose how the opportunity cost of deliberation can be estimated adaptively on multiple timescales to account for non-stationary contextual factors. We use it in a simple decision-making heuristic based on average-reward reinforcement learning (AR-RL) that we call Performance-Gated Deliberation (PGD). We propose PGD as a strategy used by animals wherein deliberation cost is implemented directly as urgency, a previously characterized neural signal effectively controlling the speed of the decision-making process. We show PGD outperforms AR-RL solutions in explaining behaviour and urgency of non-human primates in a context-varying random walk prediction task and is consistent with relative performance and urgency in a context-varying random dot motion task. We make readily testable predictions for both neural activity and behaviour.
2022-05-01
PLoS Comput. Biol. (published)
doi.org
Performance-gated deliberation: A context-adapted strategy in which urgency is opportunity cost
Maximilian Puelma Touzel
Paul Cisek
Guillaume Lajoie
2022-05-01
PLoS Comput. Biol. (publié)
doi.org
Summarizing Societies: Agent Abstraction in Multi-Agent Reinforcement Learning
Amin Memarian
Maximilian Puelma Touzel
Matthew D Riemer
Rupali Bhati
Irina Rish
Agents cannot make sense of many-agent societies through direct consideration of small-scale, low-level agent identities, but instead must r… (voir plus)ecognize emergent collective identities. Here, we take a first step towards a framework for recognizing this structure in large groups of low-level agents so that they can be modeled as a much smaller number of high-level agents—a process that we call agent abstraction. We illustrate this process by extending bisimulation metrics for state abstraction in reinforcement learning to the setting of multi-agent reinforcement learning and analyze a straightforward, if crude, abstraction based on experienced joint actions. It addresses non-stationarity due to other learning agents by improving minimax regret by a intuitive factor. To test if this compression factor provides signal for higher-level agency, we applied it to a large dataset of human play of the popular social dilemma game Diplomacy. We find that it correlates strongly with the degree of ground-truth abstraction of low-level units into the human players.
2022-04-21
ICLR.cc/2022/Workshop/Cells2Societies (poster)
openreview.net
openreview.net
Continual Learning In Environments With Polynomial Mixing Times
Matthew D Riemer
Sharath Chandra Raparthy
Ignacio Cases
Gopeshh Raaj Subbaraj
Maximilian Puelma Touzel
Irina Rish
The mixing time of the Markov chain induced by a policy limits performance in real-world continual learning scenarios. Yet, the effect of mi… (voir plus)xing times on learning in continual reinforcement learning (RL) remains underexplored. In this paper, we characterize problems that are of long-term interest to the development of continual RL, which we call scalable MDPs, through the lens of mixing times. In particular, we theoretically establish that scalable MDPs have mixing times that scale polynomially with the size of the problem. We go on to demonstrate that polynomial mixing times present significant difficulties for existing approaches that suffer from myopic bias and stale bootstrapped estimates. To validate the proposed theory, we study the empirical scaling behavior of mixing times with respect to the number of tasks and task switching frequency for pretrained high performing policies on seven Atari games. Our analysis demonstrates both that polynomial mixing times do emerge in practice and how their existence may lead to unstable learning behavior like catastrophic forgetting in continual learning settings.
openreview.net