Privacy-preserving alignment from full rankings, without the noise that usually kills them
AspireAI community · arXiv
Listwise preference feedback gives richer alignment signal than pairwise comparisons but also exposes more sensitive user preferences. Under local differential privacy the ranking space is so sensitive that the noise required neutralises the benefit of the richer signal, and listwise alignment under LDP had been unexplored. This paper analyses how supervision granularity trades against privacy noise in downstream training and introduces a rank-aware exponential mechanism that privatises listwise preferences into a low-sensitivity granularity. The mechanism uses ranking information to sample a fixed-size binary partition, concentrating noise near borderline items rather than perturbing all items uniformly the way randomised response does. On downstream alignment tasks it consistently beats existing LDP baselines at matched privacy budgets, with code released. The mechanism is the interesting artefact here - it applies wherever a ranked signal needs protecting.
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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.