通过注意力锚点提升视觉语言模型跨模态对齐精度,减少幻觉。
AttAnchor: Guiding Cross-Modal Token Alignment in VLMs with Attention Anchors
- 用语义锚点将图文令牌分组,增强跨模态局部性。
- 在15个评测中13项提升,推理任务最高增32%,幻觉指标提15%。
- 无需额外参数,小模型(1B)可超越大模型(7B/3B),适合高效部署。
视觉语言模型(VLMs)常因图像与文本令牌直接拼接并采用无模态感知的位置编码,导致跨模态语义相关令牌间产生不必要的长距离注意力,从而引发幻觉且表现逊于纯语言模型。为此,我们提出参数无依赖的注意力锚点(AttAnchor)框架,通过在文本中插入靠近相关视觉区域的语义标记,构建内容导向的注意力引导信号,使模型聚焦正确图像区域,提升视觉问答(VQA)、MMBench和POPE等任务的准确性,同时保持提示语义连贯性。该方法在15个不同指标和基准测试中取得13项改进,推理任务最高提升32%,幻觉评估提升最高达15%。仅0.1%推理开销下,TinyLLaVA 1B在POPE上超越更大模型如LLaVA 7B和QwenVL 3B。据我们所知,这是首个研究混合模态联合分组的方法,即文本与图像令牌共同聚类为共享组,而非单模态内分组或事后对齐。
原文摘要 · Abstract (English)
A fundamental reason for the dominance of attention over RNNs and LSTMs in LLMs is its ability to capture long-range dependencies by modeling direct interactions between all tokens, overcoming the sequential limitations of recurrent architectures. Similarly, a key reason why today's vision language models (VLMs) hallucinate and underperform pure language models is that they rely on direct concatenation of image and text tokens with a modality-blinded positional encoding, which conveniently adopts the pretrained LLM backbone but forces unnecessary long-distance attention between semantically related tokens across modalities. This underscores the urgent need for mechanisms that efficiently enhance token locality and cross-modal alignment. In response, we propose Attention Anchor, a parameter-free framework that efficiently groups semantically similar tokens across modalities, improving cross-modal locality. By inserting text tokens near relevant visual patches, we create semantic signposts that reveal true content-based cross-modal attention scores, guiding the model to focus on the correct image regions for tasks such as VQA, MMBench and POPE. This improves answer accuracy and reduces hallucinations without disrupting the prompt's semantic flow. AttAnchor achieves improvements across 13 out of 15 different metrics and benchmarks, including up to 32% gains on reasoning tasks and up to 15% improvements on hallucination benchmarks. AttAnchor enables TinyLLaVA 1B to outperform much larger models like LLaVA 7B and QwenVL 3B on POPE with only 0.1% inference time overhead. To the best of our knowledge, this work is among the first to investigate mixed-modal token grouping, where text and image tokens are clustered jointly into shared groups rather than being grouped within a single modality or merely aligned post-hoc with additional alignment losses.
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