I recently learned about Differentiable Logic Gate Networks, which are trained like neural networks but learn to represent a function entirely as a network of binary logic gates. See the original paper about DLGNs, and the "Recap - Differentiable Logic Gate Networks" section of this blog post from Google, which does an especially good job of explaining it.

It looks like DLGNs could be much more interpretable than standard neural networks, since they learn a very sparse representation of the target function. Like, just look at this DLGN that learned to control a cellular automaton to create a checkerboard, using just 6 gates (really 5, since the AND gate is redundant):

So simple and clean! Of course, this is a very simple problem. But what's exciting to me is that in principle, it's possible for a human to understand literally everything about how the network works, given some time to study it.

What would happen if you trained a neural network on this problem and did mech interp on it? My guess is you could eventually figure out an outline of the network's functionality, but it would take a lot longer, and there would always be some ambiguity as to whether there's any additional cognition happening in the "error terms" of your explanation.

It appears that DLGNs aren't yet well-studied, and it might be intractable to use them to train an LLM end-to-end anytime soon. But there are a number of small research projects you could try, for example:

• Can you distill small neural networks into a DLGN? Does this let you interpret them more easily?
• What kinds of functions can DLGNs learn? Is it possible to learn decent DLGNs in settings as noisy and ambiguous as e.g. simple language modeling?
• Can you identify circuits in a larger neural network that would be amenable to DLGN distillation and distill those parts automatically?
• Are there other techniques that don't rely on binary gates but still add more structure to the network, similar to a DLGN but different?
• Can you train a DLGN to encourage extra interpretability, like by disentangling different parts of the network to be independent of one another, or making groups of gates form abstractions that get reused in different parts of the network (like how an 8-bit adder is composed of many 1-bit adders)?
• Can you have a mixed approach, where some aspects of the network use a more "structured" format and others are more reliant on the fuzzy heuristics of traditional NNs? (E.g. the "high-level" is structured and the "low-level" is fuzzy.)

I'm unlikely to do this myself, since I don't consider myself much of a mechanistic interpreter, but would be pretty excited to see others do experiments like this!

There's been a widespread assumption that training reasoning models like o1 or r1 can only yield improvements on tasks with an objective metric of correctness, like math or coding. See this essay, for example, which seems to take as a given that the only way to improve LLM performance on fuzzy tasks like creative writing or business advice is to train larger models.

This assumption confused me, because we already know how to train models to optimize for subjective human preferences. We figured out a long time ago that we can train a reward model to emulate human feedback and use RLHF to get a model that optimizes this reward. AI labs could just plug this into the reward for their reasoning models, reinforcing the reasoning traces leading to responses that obtain higher reward. This seemed to me like a really obvious next step.

Well, it turns out that DeepSeek r1 actually does this. From their paper:

2.3.4. Reinforcement Learning for all Scenarios

To further align the model with human preferences, we implement a secondary reinforcement learning stage aimed at improving the model’s helpfulness and harmlessness while simultaneously refining its reasoning capabilities. Specifically, we train the model using a combination of reward signals and diverse prompt distributions. For reasoning data, we adhere to the methodology outlined in DeepSeek-R1-Zero, which utilizes rule-based rewards to guide the learning process in math, code, and logical reasoning domains. For general data, we resort to reward models to capture human preferences in complex and nuanced scenarios. We build upon the DeepSeek-V3 pipeline and adopt a similar distribution of preference pairs and training prompts. For helpfulness, we focus exclusively on the final summary, ensuring that the assessment emphasizes the utility and relevance of the response to the user while minimizing interference with the underlying reasoning process. For harmlessness, we evaluate the entire response of the model, including both the reasoning process and the summary, to identify and mitigate any potential risks, biases, or harmful content that may arise during the generation process. Ultimately, the integration of reward signals and diverse data distributions enables us to train a model that excels in reasoning while prioritizing helpfulness and harmlessness.

This checks out to me. I've already noticed that r1 feels significantly better than other models at creative writing, which is probably due to this human preference training. While o1 was no better at creative writing than other models, this might just mean that OpenAI didn't prioritize training o1 on human preferences. My Manifold market currently puts a 65% chance on chain-of-thought training outperforming traditional LLMs by 2026, and it should probably be higher at this point.

We need to adjust our thinking around reasoning models - there's no strong reason to expect that future models will be much worse at tasks with fuzzy success criteria.

Adapted from my previously-posted question [LW · GW], after cubefox [LW · GW] pointed out that DeepSeek is already using RLHF.