All of beren's Comments + Replies

While I agree with a lot of points of this post, I want to quibble with the RL not maximising reward point. I agree that model-free RL algorithms like DPO do not directly maximise reward but instead 'maximise reward' in the same way self-supervised models 'minimise crossentropy' -- that is to say, the model is not explicitly reasoning about minimising cross entropy but learns distilled heuristics that end up resulting in policies/predictions with a good reward/crossentropy. However, it is also possible to produce architectures that do directly optimise for... (read more)

4Alex Turner
Agree with a bunch of these points. EG in Reward is not the optimization target  I noted that AIXI really does maximize reward, theoretically. I wouldn't say that AIXI means that we have "produced" an architecture which directly optimizes for reward, because AIXI(-tl) is a bad way to spend compute. It doesn't actually effectively optimize reward in reality.  I'd consider a model-based RL agent to be "reward-driven" if it's effective and most of its "optimization" comes from the direct part and not the leaf-node evaluation (as in e.g. AlphaZero, which was still extremely good without the MCTS).  "Direct" optimization has not worked - at scale - in the past. Do you think that's going to change, and if so, why? 

afaict, a big fraction of evolution's instructions for humans (which made sense in the ancestral environment) are encoded as what you pay attention to. Babies fixate on faces, not because they have a practical need to track faces at 1 week old, but because having a detailed model of other humans will be valuable later. Young children being curious about animals is a human universal. Etc.
 

This is true but I don't think is super important for this argument. Evolution definitely encodes inductive biases into learning about relevant things which ML archit... (read more)

I always say that the whole brain (including not only the basal ganglia but also the thalamocortical system, medulla, etc.) operates as a model-based RL system. You’re saying that the BG by itself operates as a model-free RL system. So I don’t think we’re disagreeing, because “the cortex is the model”?? (Well, we definitely have some disagreements about the BG, but we don’t have to get into them, I don’t think they’re very important for present purposes.)
 

I think there is some disagreement here, at least in the way I am using model-based / model-free ... (read more)

2Steve Byrnes
Seems like just terminology then. I’m using the term “model-based RL” more broadly than you. I agree with you that (1) explicit one-timestep-at-a-time rollouts is very common (maybe even universal) in self-described “model-based RL” papers that you find on arxiv/cs today, and that (2) these kinds of rollouts are not part of the brain “source code” (although they might show up sometimes as a learned metacognitive strategy). I think you’re taking (1) to be evidence that “the term ‘model-based RL’ implies one-timestep-at-a-time rollouts”, whereas I’m taking (1) to be evidence that “AI/CS people have some groupthink about how to construct effective model-based RL algorithms”. Hmm, I think the former is a strict subset of the latter. E.g. I think “learning through experience that I should suck up to vain powerful people” is the latter but not the former. Yeah I agree with the “directly” part. For example, I think some kind of social drives + the particular situations I’ve been in, led to me thinking that it’s good to act with integrity. But now that desire / value is installed inside me, not just a means to an end, so I feel some nonzero motivation to “act with integrity” even when I know for sure that I won’t get caught etc. Not that it’s always a sufficient motivation …

1. Evolution needed to encode not only drives for food or shelter, but also drives for evolutionary desirable states like reproduction; this likely leads to drives which are present and quite active, such as "seek social status" => as a consequence I don't think the evolutionary older drives are out of play and the landscape is flat as you assume, and dominated by language-model-based values
 

Yes, I think drives like this are important on two levels. At the first level, we are experience them as primary rewards -- i.e. as social status gives direct ... (read more)

1Charlie Steiner
afaict, a big fraction of evolution's instructions for humans (which made sense in the ancestral environment) are encoded as what you pay attention to. Babies fixate on faces, not because they have a practical need to track faces at 1 week old, but because having a detailed model of other humans will be valuable later. Young children being curious about animals is a human universal. Etc. Patterns of behavior (some of which I'd include in my goals) encoded in my model can act in a way that's somewhere between unconscious and too obvious to question - you might end up doing things not because you have visceral feelings about the different options, but simply because your model is so much better at some of the options that the other options never even get considered.

My understanding is that after a lot of simplifications, policy gradients just takes a noisy gradient step in the direction of minimising Bellman error, and so in the limit of infinite data/computation/visiting all states in the world, it is 'guaranteed' to converge to an optimal policy for the MDP. Q learning and other model-free algorithms have similar guarantees. In practice, with function approximation, and PPOs regularisation bits, these guarantees do not hold anymore, but the fundamental RL they are built off of does have them. The place to go deeper into this is Sutton and Bart's textbook and also Bertsekas' dynamic programming textbook

2Alex Turner
Yeah, I've read those books, although I admit to heavily skimming Bertsekas. 

I broadly agree with a lot of shard theory claims. However, the important thing to realise is that 'human values' do not really come from inner misalignment wrt our innate reward circuitry but rather are the result of a very long process of social construction influenced both by our innate drives but also by the game-theoretic social considerations needed to create and maintain large social groups, and that these value constructs have been distilled into webs of linguistic associations learnt through unsupervised text-prediction-like objectives which is ho... (read more)

2Alex Turner
FWIW I don't consider myself to be arguing against planning over a world model. 
2Alex Turner
Can you give me some examples here? I don't know that I follow what you're pointing at. 

I feel like this is a good point in general but I think there is an important but subtle distinction between the two examples. In the first case of the GAN it is that there is the distinction between the inner optimization loop of the ML algorithm and the outer loop of humans performing an evolutionary search process to get papers/make pretty pictures. 

 

In the wire-heading case this feels different in that you have essentially two separate value functions -- a cortical LM based one which can extrapolate values in linguistic/concept space and a cl... (read more)

2Steve Byrnes
I guess I want to call the second one “the actual value function defined in the agent’s source code” and the first one “the agent’s learned concept of ‘value function’” (or relatedly, “the agent’s learned concept of ‘pleasure’” / “the agent’s learned concept of ‘satisfaction’” / whatever). Other than that, I don’t think we’re in disagreement about anything, AFAICT.