Do Large Language Models Perform Latent Multi-Hop Reasoning without Exploiting Shortcuts?

LLM Latent Reasoning CoT
我们评估了大型语言模型(LLMs)在回答多跳查询时隐式回忆和组合事实的能力,例如“斯嘉丽·约翰逊出生那年,夏季奥运会的举办国是”。评估这一能力的一个主要挑战是,LLMs可能通过在相同的训练序列中遇到头实体“斯嘉丽·约翰逊”和答案实体“美国”而发展出捷径,或者仅仅基于频率优先级来猜测答案。为了防止这些捷径,我们排除了预训练语料库中头实体和答案实体共同出现的测试查询。通过仔细选择关系和事实,并系统地移除模型可能猜测答案或利用部分匹配的情况,我们构建了一个评估数据集SOCRATES(无捷径的隐式推理)。我们观察到,LLMs在不利用捷径的情况下展示了有希望的隐式多跳推理能力,但仅限于某些类型的查询。对于需要隐式回忆国家作为中间答案的查询,最佳模型达到了80%的隐式组合能力,但对于回忆年份的查询,这一比例降至5%。与链式思维组合能力的比较突显了模型隐式推理和显式推理能力之间的显著差距。分析显示,在隐式组合能力较高的查询中,中间答案的隐式表示构建得更频繁,并且在预训练过程中出现了隐式多跳推理。
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 evaluating this ability is that LLMs may have developed shortcuts by encounters of 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 co-appear in pretraining corpora. 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 composability 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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