If you use a narrow definition like “RL is exactly those algorithms that are on arxiv cs.AI right now with an RL label”, then the brain is not RL.
If you use a broad definition like “RL is anything with properties like Thorndike’s law of effect”, then, well, remember that “reinforcement learning” was a psychology term long before it was an AI term!
If it helps, I was arguing about this with a neuroscientist friend (Eli Sennesh) earlier this year, and wrote the following summary (not necessarily endorsed by Eli) afterwards in my notes:
Eli doesn’t like the term “RL” in a brain context because of (1) its implication that “reward” is stuff in the environment as opposed to an internal “reward function” built from brain-internal signals, (2) its implication that we’re specifically maximizing an exponentially-discounted sum of future rewards.
…Whereas I like the term “RL” because (1) If brain-like algorithms showed up on GitHub, then everyone in AI would call it an “RL algorithm”, put it in “RL textbooks”, and use it to solve “RL problems”, (2) This follows the historical usage (there’s reinforcement, and there’s learning, per Thorndike’s Law of Effect etc.).
When I want to talk about “the brain’s model-based RL system”, I should translate that to “the brain’s Bellman-solving system” when I’m talking to Eli, and then we’ll be more-or-less on the same page I think?
…But Eli is just one guy, I think there are probably dozens of other schools-of-thought with their own sets of complaints or takes on “RL”.
Oh, it’s definitely controversial—as I always say, there is never a neuroscience consensus. My sense is that a lot of the controversy is about how broadly to define “reinforcement learning”.
If you use a narrow definition like “RL is exactly those algorithms that are on arxiv cs.AI right now with an RL label”, then the brain is not RL.
If you use a broad definition like “RL is anything with properties like Thorndike’s law of effect”, then, well, remember that “reinforcement learning” was a psychology term long before it was an AI term!
If it helps, I was arguing about this with a neuroscientist friend (Eli Sennesh) earlier this year, and wrote the following summary (not necessarily endorsed by Eli) afterwards in my notes:
…But Eli is just one guy, I think there are probably dozens of other schools-of-thought with their own sets of complaints or takes on “RL”.