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arXiv 2604.03556cs.CVcs.AIcs.CL
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重点至关重要:面向视觉语言模型中幻觉的相位感知抑制

Focus Matters: Attention-Value Dynamics for Efficient Hallucination Mitigation in Vision-Language Models

Pusan National University(釜山大学);Pukyong National University(釜庆大学)

Sohyeon Kim, Sang Yeon Yoon, Kyeongbo Kong

AI总结:

本文提出一种轻量级干预方法,在视觉编码器的聚焦阶段选择性抑制低关注的token,通过单次前向传递统计信息和DPP保留多样视觉线索,减少幻觉的同时保持caption质量,且推理延迟低。

摘要:

大型视觉语言模型(LVLMs)在多模态推理中取得了显著进展,但仍然容易产生对象幻觉,即生成不存在于输入图像中的对象描述。近期方法试图通过抑制视觉编码器中的不可靠视觉信号来缓解幻觉,但许多方法依赖于每次输入的迭代优化,导致显著的推理延迟。本文研究了LVLMs中视觉编码器的内部注意力动态,并识别出视觉信息处理的三个阶段:扩散、聚焦和再扩散。我们的分析揭示,幻觉行为对聚焦阶段接收低关注的token特别敏感。受此启发,我们提出了一种轻量级的推理时间干预方法,在聚焦阶段选择性地抑制这些token。该方法通过单次前向传递的统计信息以无训练的方式运行,并采用决定性点过程(DPP)来保留多样的视觉线索同时过滤冗余token。在多个LVLM backbone和解码策略上的广泛实验表明,所提出的方法在减少幻觉度量的同时保持了竞争性的caption质量。此外,与对抗性不确定性估计方法相比,我们的方法在具有可忽略的额外推理延迟的情况下实现了可比的幻觉缓解效果。

英文摘要:

Large Vision-Language Models (LVLMs) have achieved impressive progress in multimodal reasoning, yet they remain prone to object hallucinations, generating descriptions of objects that are not present in the input image. In this work, we investigate hallucination from the perspective of attention-value dynamics inside LVLM vision encoders. We identify a consistent three-phase structure of visual processing---diffusion, focus, and rediffusion---and show that the focus phase is where attention most clearly separates strongly and weakly supported visual tokens. However, low attention does not necessarily imply negligible downstream influence: low-attention tokens in the focus phase can still exert non-negligible value-side influence on the attention output relative to their small attention mass. Through controlled phase-wise value interventions, we find that hallucination behavior is particularly sensitive to the value content of low-attention tokens during this phase. Replacing or neutralizing these values reduces hallucination metrics while largely preserving grounded object evidence. A token-level teacher-forcing analysis further shows that the intervention reduces the probability of hallucinated object tokens with much smaller effects on ground-truth object tokens. In addition, Visual Attention Ratio (VAR) analysis shows that focus-phase intervention is accompanied by increased attention to visual tokens during decoding. Based on these observations, we instantiate a simple training-free inference-time intervention that replaces focus-phase low-attention values with an image-level mean value vector using statistics from a single forward pass. Experiments across multiple LVLM backbones demonstrate that this analysis-derived intervention reduces object hallucination with negligible additional runtime and remains compatible with existing inference-time mitigation methods.

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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