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Reading the entropy of a model's own attention maps was enough to decide when chain-of-thought would help, and doing so cut wasted reasoning without retraining

AspireAI community · arXiv
Indiscriminate chain-of-thought prompting can hurt multimodal models by inducing reasoning that is not needed, a failure the authors call overthinking; in reasoning segmentation it shows up as reasoning that drifts from the query's intent and the visual grounding. Difficulty-Aware Chain-of-Thought (DA-CoT) is a training-free framework that triggers CoT selectively based on the input's intrinsic difficulty. The key observation is that the entropy of the model's attention maps tracks that difficulty: low entropy indicates confident, localized grounding, while high entropy suggests uncertainty and potential benefit from CoT. DA-CoT adds a Bidirectional Rethinking mechanism that lets the model flip its reasoning decision when the initial output fails, recovering from both overthinking and underthinking. The method reaches state-of-the-art performance on reasoning segmentation benchmarks while improving inference efficiency. The limitation is that it has been validated on reasoning segmentation only, so the attention-entropy signal is not yet shown to separate difficulty reliably across other multimodal task families.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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.
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