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Questioning Representational Optimism in Deep Learning: The Fractured Entangled Representation Hypothesis

Akarsh Kumar, Jeff Clune, Joel Lehman, Kenneth O. Stanley

2025 · arXiv

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Much of the excitement in modern AI is driven by the observation that scaling up existing systems leads to better performance. But does better performance necessarily imply better internal representations? While the representational optimist assumes it must, this position paper challenges that view. We compare neural networks evolved through an open-ended search process to networks trained via conventional stochastic gradient descent (SGD) on the simple task of generating a single image. This minimal setup offers a unique advantage: each hidden neuron's full functional behavior can be easily visualized as an image, thus revealing how the network's output behavior is internally constructed neuron by neuron. The result is striking: while both networks produce the same output behavior, their internal representations differ dramatically. The SGD-trained networks exhibit a form of disorganization that we term fractured entangled representation (FER). Interestingly, the evolved networks largely lack FER, even approaching a unified factored representation (UFR). In large models, FER may be degrading core model capacities like generalization, creativity, and (continual) learning. Therefore, understanding and mitigating FER could be critical to the future of representation learning.

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vatsachak
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"Animals experience pressure for a lot more "general" intelligence because of the highly multi-task and even actively adversarial multi-agent self-play environments they are min-max optimized within, where failing at any task means death. In a deep optimization pressure sense, LLM can't handle lots of different spiky tasks out of the box (e.g. count the number of 'r' in strawberry) because failing to do a task does not mean death." Point to me a task that a human should be able to perform and I will point to you a human who cannot perform that task, yet has kids. Survival is not a goal, it is a constraint. Evolution evolves good abstractions because it is not chasing a goal, but rather it creates several million goals with each species going after it's own. https://arxiv.org/abs/2505.11581
kmeisthax
Neutral mention · rule
If there aren't any five-legged dogs in your trainset, it's safer[0] to just remember that all dogs are four-legged than to actually recognize and count legs. After all, you might have a few images of dogs in your trainset that are misleading enough to look five-legged (e.g. because a dog is in front of another dog). Overrepresentation is a different source of bias. That's what gives you, say, image generators that always draw "golden 1970s sci-fi robot" as C3-PO even when given additional instructions to draw something else. Both of these problems are manifestations of the difference between training and deployment distributions. Ok, I guess you could say that…
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four-legged dogs are "overrepresented" in the training set, but that's because four-legged dogs are also overrepresented in reality. The deployment distribution doesn't have five-legged dogs in it. What we've done is instead concoct an adversarial distribution to force a train/deploy gap where none would exist. Releasing the vision encoder won't help because weights are opaque. Stochastic gradient descent does not yield functional internal representations[1]; it fills the bucket of parameters with one distribution and one distribution only. We could tell if, say the vision encoder produces identical embeddings for dogs regardless of leg count, or some other counterfactuals; but not much more than that. [0] Lower loss and possibly lower L2-norm [1] https://arxiv.org/abs/2505.11581

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