测试大模型是否能无捷径地进行隐式多跳推理,发现仅对特定类型有效。
Do Large Language Models Perform Latent Multi-Hop Reasoning without Exploiting Shortcuts?
- 构建无捷径数据集SOCRATES,排除训练中共现实体干扰
- 国家类中间答案隐式组合率达80%,年份类仅5%
- 揭示预训练中隐式多跳推理能力逐步出现的机制
我们评估大语言模型(LLMs)在回答如“斯嘉丽·约翰逊出生那年夏季奥运会举办国是?”这类多跳问题时,能否通过隐式回忆和组合事实完成推理。主要挑战在于模型可能因在训练中同时见过头实体“斯嘉丽·约翰逊”和答案实体“美国”而形成捷径,或仅凭频率先验猜测答案。为防止此类捷径,我们排除了测试集中头实体与答案实体在训练中曾共现的情况。通过精心选择关系与事实,并系统剔除可能被猜测或部分匹配利用的样本,构建了无捷径推理评估数据集SOCRATES(ShOrtCut-fRee lATent rEaSoning)。结果表明,当不依赖捷径时,某些查询下模型仍展现出良好的隐式多跳推理能力,但仅限特定类型:需隐式回忆国家作为中间答案的查询中,最优模型达到80%的隐式可组合性;而需回忆年份的查询中,该指标仅为5%。与链式思维(Chain-of-Thought)对比显示,模型在隐式推理与显式推理之间存在显著差距。分析进一步表明,高隐式可组合性查询更倾向于生成中间答案的隐式表示,且隐式多跳推理能力在预训练过程中逐步显现。
原文摘要 · Abstract (English)
We evaluate how well Large Language Models (LLMs) latently recall and compose facts to answer multi-hop queries like "In the year Scarlett Johansson was born, the Summer Olympics were hosted in the country of". One major challenge in such evaluation is that LLMs may have developed shortcuts by encountering the head entity "Scarlett Johansson" and the answer entity "United States" in the same training sequences or merely guess the answer based on frequency-based priors. To prevent shortcuts, we exclude test queries where the head and answer entities might have co-appeared during training. Through careful selection of relations and facts and systematic removal of cases where models might guess answers or exploit partial matches, we construct an evaluation dataset SOCRATES (ShOrtCut-fRee lATent rEaSoning). We observe that LLMs demonstrate promising latent multi-hop reasoning abilities without exploiting shortcuts, but only for certain types of queries. For queries requiring latent recall of countries as the intermediate answer, the best models achieve 80% latent composability, but this drops to just 5% for the recall of years. Comparisons with Chain-of-Thought highlight a significant gap between the ability of models to reason latently versus explicitly. Analysis reveals that latent representations of the intermediate answer are constructed more often in queries with higher latent composability, and shows the emergence of latent multi-hop reasoning during pretraining.
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