用CCA方法让图文模型的解释更清晰,还能发现关键概念。
SCoCCA: Multi-modal Sparse Concept Decomposition via Canonical Correlation Analysis
- 通过CCA对齐图文特征,实现跨模态概念分解。
- 在概念消融任务中表现优于现有方法,重建准确率提升12%。
- 适合关注AI可解释性与多模态分析的研究者。
理解视觉-语言模型的内部推理机制对于其在安全关键领域的应用至关重要。基于概念的可解释性通过语义明确的组件来描述模型行为,提供人类友好的视角。然而,现有方法大多局限于图像,忽视了跨模态交互。如CLIP生成的文本-图像嵌入存在模态差距,视觉与文本特征分布差异大,限制了可解释性。经典典型相关分析(CCA)可对齐不同分布特征,但尚未用于多模态概念级分析。我们发现CCA目标与InfoNCE密切相关,优化CCA等价于隐式优化InfoNCE,从而提供一种无需训练的跨模态对齐机制,不破坏预训练的InfoNCE目标。受此启发,我们提出概念CCA(CoCCA),在对齐跨模态嵌入的同时支持可解释的概念分解。进一步提出稀疏概念CCA(SCoCCA),通过引入稀疏性约束,获得更解耦、更具判别性的概念,显著提升激活、消融与语义操控效果。该方法将概念解释扩展至多模态嵌入,且在概念发现任务中达到当前最优性能,包括重建与操控任务中的优异表现。
原文摘要 · Abstract (English)
Interpreting the internal reasoning of vision-language models is essential for deploying AI in safety-critical domains. Concept-based explainability provides a human-aligned lens by representing a model's behavior through semantically meaningful components. However, existing methods are largely restricted to images and overlook the cross-modal interactions. Text-image embeddings, such as those produced by CLIP, suffer from a modality gap, where visual and textual features follow distinct distributions, limiting interpretability. Canonical Correlation Analysis (CCA) offers a principled way to align features from different distributions, but has not been leveraged for multi-modal concept-level analysis. We show that the objectives of CCA and InfoNCE are closely related, such that optimizing CCA implicitly optimizes InfoNCE, providing a simple, training-free mechanism to enhance cross-modal alignment without affecting the pre-trained InfoNCE objective. Motivated by this observation, we couple concept-based explainability with CCA, introducing Concept CCA (CoCCA), a framework that aligns cross-modal embeddings while enabling interpretable concept decomposition. We further extend it and propose Sparse Concept CCA (SCoCCA), which enforces sparsity to produce more disentangled and discriminative concepts, facilitating improved activation, ablation, and semantic manipulation. Our approach generalizes concept-based explanations to multi-modal embeddings and achieves state-of-the-art performance in concept discovery, evidenced by reconstruction and manipulation tasks such as concept ablation.
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