A staged supervision recipe let a 3B vision-language model beat a frozen 32B model on dense-scene reasoning without changing any architecture
AspireAI community · arXiv
Lightweight vision-language models compete on standard benchmarks yet fail systematically in dense-scene reasoning, where multiple objects, attributes and relations must be grounded together. The authors introduce DRBench, a benchmark of 14,573 questions over 2,943 images spanning five task categories and three progressive reasoning layers, then propose DRScaffold, a supervised fine-tuning framework that decomposes the supervision target into four causally ordered stages so reasoning steps stay anchored to visual entities. On three lightweight VLMs the recipe produced substantial DRBench gains while preserving or improving general-purpose benchmark performance. The striking result: Qwen2.5-VL-3B trained with DRScaffold surpassed the frozen Qwen2.5-VL-32B under zero-shot direct-answer prompting on DRBench, so structured supervision substituted for a significant portion of model scale. The limitation is that the substitution is demonstrated on one dense-scene benchmark built by the same authors, so it does not yet show that scale stops mattering in general.
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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.