Creating Causal Embeddings for Question Answering with Minimal Supervision
Rebecca Sharp, Mihai Surdeanu, Peter A. Jansen, Peter E. Clark, Michael Hammond · 2016
A common model for question answering (QA) is that a good answer is one that is closely related to the question, where relatedness is often determined using generalpurpose lexical models such as word embeddings.We argue that a better approach is to look for answers that are related to the question in a relevant way, according to the information need of the question, which may be determined through task-specific embeddings.With causality as a use case, we implement this insight in three steps.First, we generate causal embeddings cost-effectively by bootstrapping cause-effect pairs extracted from free text using a small set of seed patterns.Second, we train dedicated embeddings over this data, by using task-specific contexts, i.e., the context of a cause is its effect.Finally, we extend a state-of-the-art reranking approach for QA to incorporate these causal embeddings.We evaluate the causal embedding models both directly with a casual implication task, and indirectly, in a downstream causal QA task using data from Yahoo! Answers.We show that explicitly modeling causality improves performance in both tasks.In the QA task our best model achieves 37.3% P@1, significantly outperforming a strong baseline by 7.7% (relative).