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Start free trial →The Cognitive Revolution" | AI Builders, Researchers, and Live Player Analysis · AI Research & Frontier Labs · November 2026
The host asked where facts live if each neuron has roughly one core role, since a model with millions of neurons clearly stores far more facts than that. Goodfire's Curt Tigges answers that knowledge lives in the wiring, not in single neurons.
Let's maybe do a little lightning round if such a thing is possible in this context on just like how this work interacts with, or maybe should cause me to update my understanding of some other parts of what I
…of always knew that was somewhat of a general, you know, an oversimplification. How would you update my thinking about facts? Like, do they, do we still think they live in the MLPs? Do they like this sort of one core role per neuron does leave me like, okay, then where are the facts in this thing?
Yeah, that's a frequent question because, you know, a model might have 5 million neurons, but no, way more than 5 million facts, right? But that's because you don't have a fact in a neuron. A neuron is not a fact, but the fact is in the connections between neurons. And you can have exponentially more connections between neurons than you have individual neurons. So, you know, a set of 10 neurons networked together can represent way more than 10 facts just because the number of possible paths between them is just so high. So yeah, from what we've seen, certainly we haven't found every single fact that's in the model and can say 100% are only in the MLPs, but we find so many facts in the MLPs just implemented by these connections that it seems like the natural place for them to be. Like the post-impressionism thing, you know, that's a whole bunch of artists and a whole bunch of concepts and in a smaller set of neurons than there are things that could be elaborated from that community.
Do we see a different profile of factual recall degradation with sparsity as compared to like arc style tests? They can even do better with sparsity, reasoning they do worse. My gut would say factual would also be like significantly affected by sparsity, but what did you actually observe?
So we did test some MMLU data sets and we're able to recover performance on those pretty well. And that does test factual recall. We do have some tests that we're still working on for like medicine knowledge or chemistry knowledge. But for the most part, we really haven't seen much degradation.…
Yeah, interesting. I guess that really just speaks to like localization, which then brings to mind the nature of experts. The old story about experts was the experts themselves are also not interpretable bad news. You know, it's, we can't really identify what role the experts are playing. It seems…