Eight models could be probed for the answer and still got it wrong at generation time
AspireAI community · arXiv
This paper asks whether a model's encoded information actually governs its behaviour, and finds a gap. Using parametric CAD to separate failures of encoding, expression and activation-level control, it shows that pretraining contributes much more to linearly decoding local relations than to decoding global constraint status - which is already highly decodable from random representations. Strong local decodability did not translate into the models' zero-shot predictions, which stayed far below supervised probe performance. Restoring clean internal activations repaired probe predictions, while simple activation steering did not give reliable targeted control, and low-rank fine-tuning on only 400 labelled relation pairs substantially improved generation on three representative models. The methodological point is the one worth carrying: decodability is not evidence that encoded information will be expressed or controllable in behaviour.
Read the story and explore more from the AspireAI community.
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.