发现视觉推理中的潜在中间步骤实际没用,模型根本没依赖它们。
What's Holding Back Latent Visual Reasoning?

- 用无意义的假符号替代潜在视觉符号,模型准确率不变,说明其不关键。
- 真实数据中中间步骤信息量不足,无法简化任务,导致模型直接跳过。
- 推理时生成的潜在符号与理想表示差距大,严重偏离正确方向。
人类解决复杂视觉问题时会通过心理模拟中间视觉步骤,而非仅依赖语言推理。受此启发,近期一些视觉-语言模型尝试用连续潜在符号作为中间视觉想象步骤,实现链式思维推理。本文研究发现:当用无意义的假符号替换潜在符号时,模型准确率几乎不受影响,表明这些符号在最终预测中几乎不发挥因果作用。分析显示,当前大多数数据集中的理想潜在符号所提供的额外信息有限,无法显著简化任务,导致模型训练时忽略它们,并在推理时直接绕过。而在一个诊断数据集上微调后,模型可真正依赖这些符号。此外,推理时生成的潜在符号与理想表示存在显著偏差,聚集于狭窄区域,进一步阻碍了其有效性。研究指出,未来提升潜在视觉推理的关键在于构建提供充分支持的高质量数据集和更精准的潜在符号生成方法。
原文摘要 · Abstract (English)
Humans can approach complex visual problems by mentally simulating intermediate visual steps, rather than reasoning through language alone. Inspired by this, several works on Vision-Language Models have recently explored chain-of-thought reasoning with continuous latent tokens as intermediate visual imagination steps. In this work, we investigate how recent models leverage such latent tokens. Surprisingly, we find that model accuracy is unaffected when latent tokens are replaced by uninformative dummy tokens. This indicates that latent tokens play a minimal causal role in the model's final prediction. To better understand this phenomenon, we analyze both the training signal provided by oracle latent representations and the quality of the latent tokens generated at inference time. Our experiments reveal two crucial issues holding back latent visual reasoning: First, in most existing datasets, oracle latent tokens provide limited additional information beyond the original image and do not substantially simplify the task, leading models to ignore them during training and effectively bypassing them at inference time. When fine-tuned on a diagnostic dataset, in which latent tokens provide sufficient support for the final prediction, we show that models can causally rely on them. Second, the latent tokens produced at inference time deviate from their corresponding oracle representations, collapsing to a narrow region and preventing benefits even when the model relies on them. Overall, our findings suggest that future progress in latent visual reasoning depends on two key pillars: high-quality datasets with informative intermediate steps and more precise latent token prediction.
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