Great episode.
1) In the songbird, the RL circuit used for imitation is pretty well understood
pmc.ncbi.nlm.nih.gov/article…
It indeed doesn't have direct supervision of motor actions token by token, but rather learns by RL to adjust its motor output to match the sound of a stored memory of a tutor song.
1.1) Note that this is an ethologically-specific, evolved reward function.
"Song is learned not for external reinforcement but instead by matching vocal performance to the memory of a tutor song (Marler, 1997, 1970)." (
elifesciences.org/reviewed-p…)
Here is a bit about the reward function:
pmc.ncbi.nlm.nih.gov/article…
It has a dedicated circuit to store the tutor song memory too, so it can then use it as part of this reward function. Thus the reward function is custom designed by evolution and built up in a sequence of evolved steps -- each with specific, identifiable brain circuitry -- to enable an evolved cultural transmission process in an animal.
1.2) Evolution probably puts a lot of its programming into the reward function. That's probably why the brainstem and hypothalamus constitute most of the brain cell type diversity in the mammalian brain.
nature.com/articles/s41586-0…
Connectomics can reveal specific details of how this works
elifesciences.org/articles/2…
1.3) Probably a lot of these are intrinsic, non-behaviorist
lesswrong.com/posts/FNJF3SoN…
reward functions programmed by evolution to help humans bootstrap, notably, social instincts
lesswrong.com/posts/kYvbHCDe…
Those social instincts can drive a bias to learn by imitation of other humans. This Ullman paper is excellent on that
pnas.org/doi/10.1073/pnas.12…
and inspired me to go nuts nearly a decade ago writing about how specific evolved reward/cost functions could guide animals to take on specific learning trajectories / curricula that simpler costs/objectives wouldn't bias them to
arxiv.org/abs/1606.03813
2) Of course it won't be just about RL. The model used for model-based RL can be learned by self-supervised prediction, as in
arxiv.org/abs/1803.10760
and in LeCun's cake diagram. There are probably smarter tricks than just backprop through a multi-layer system that the cortico-thalamic system is using to drive efficient world model learning and inference. Work from Dileep George and others takes inspiration from songbird circuits to try to model this. This model can then be used for model based RL.
3) Taking into account that AI may converge to this type of design is important for AI safety scenario planning
osf.io/preprints/osf/fe36n_v…