Fuzzy Contrastive Decoding to Alleviate Object Hallucination in Large Vision-Language Models

Large vision-language models (LVLMs) often exhibit object hallucination, a phenomenon where models generate descriptions of non-existent objects within images. Prior methods have sought to mitigate this issue by adjusting model logits to reduce linguistic bias, but they often lack precise control over visual uncertainty, sometimes exacerbating hallucinations instead of mitigating them. To address this limitation, we propose a novel decoding strategy called fuzzy contrastive decoding (FuzzyCD) that uses Takagi-Sugeno fuzzy inference to refine hallucination control. FuzzyCD adaptively assigns weights to high-hallucination logits while mitigating unnecessary linguistic bias. Specifically, it transforms the log-probabilities of top-1 tokens from both standard and hallucination logits into a \textit{confidence} linguistic fuzzy set. Through Takagi-Sugeno fuzzy inference, it dynamically adjusts hallucination logits to prevent the model from over-relying on spurious linguistic patterns. Experimental results on object hallucination datasets demonstrate that hallucination is mitigated by 11\%p compared to conventional LVLMs. In-depth analyses highlight the effectiveness of FuzzyCD in enhancing the reliability of vision-language models.