arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2602.23136cs.CLcs.AIcs.LG
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模态崩溃作为不匹配解码:多模态大语言模型的信息论限制

Modality Collapse as Mismatched Decoding: Information-Theoretic Limits of Multimodal LLMs

Yahoo(雅虎);Nuance;BBN

Jayadev Billa

AI总结:

研究揭示多模态大语言模型中模态崩溃现象的信息论限制,指出解码器评分规则决定了可访问信息量,通过LoRA干预验证了训练目标对情绪检测性能的提升作用。

摘要:

大量研究表明,多模态大语言模型在处理语音和图像方面表现良好,但在非直观的方式上失败,导致诸如物体计数等简单任务不可靠。我们从信息论的角度研究这种行为,将多模态大语言模型推理视为不匹配解码问题:一个主要在文本上训练的解码器只能提取沿文本对齐方向的信息(移除模态特定(非文本)方向上的高达98%的变异性可以改善解码器损失),并且可访问的信息量受广义互信息(GMI)的限制。我们显示信息损失随着源数据与文本数据之间的分布不匹配程度以及解码器的敏感性增加而被限制。这个界限是模型评分规则的函数,而不是其架构。我们验证了五个跨越语音和视觉的模型的预测。一项受控研究(两个仅在编码器文本对齐方面不同的Prismatic VLMs)显示,瓶颈在于解码器的评分规则,而不是编码器的文本对齐或学习的投影。一项LoRA干预显示,仅仅用与情绪相关的目标进行训练可以将情绪检测的准确率从17.3%提高到61.8%,而不会影响其他属性,证实了训练目标决定了什么变得可访问。

英文摘要:

Numerous studies have shown that multimodal LLMs process speech and images well but fail in non-intuitive ways rendering trivial tasks such as object counting unreliable. We investigate this behavior from an information-theoretic perspective by framing multimodal LLM inference as a mismatched decoder problem: a decoder trained primarily on text can only extract information along text-aligned directions (removing up to 98% of the variation in modality-specific (non-text) directions improves decoder loss) and the amount of accessible information is bounded by the Generalized Mutual Information (GMI). We show that information loss is bounded as the distributional mismatch between the source data and the text data increases, and as the sensitivity of the decoder increases. This bound is a function of the model's scoring rule not its architecture. We validate the predictions across five models spanning speech and vision. A controlled study (two Prismatic VLMs differing only in encoder text-alignment) shows that the bottleneck lies in the scoring rule of the decoder rather than the text-alignment of the encoder or the learned projection. A LoRA intervention demonstrates that simply training with an emotion-related objective improves emotion detection from 17.3% to 61.8% task accuracy without affecting other attributes, confirming that the training objective determines what becomes accessible.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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