  Causality extraction from natural language texts is a challenging open
problem in artificial intelligence. Existing methods utilize patterns,
constraints, and machine learning techniques to extract causality, heavily
depending on domain knowledge and requiring considerable human effort and time
for feature engineering. In this paper, we formulate causality extraction as a
sequence labeling problem based on a novel causality tagging scheme. On this
basis, we propose a neural causality extractor with the BiLSTM-CRF model as the
backbone, named SCITE (Self-attentive BiLSTM-CRF wIth Transferred Embeddings),
which can directly extract cause and effect without extracting candidate causal
pairs and identifying their relations separately. To address the problem of
data insufficiency, we transfer contextual string embeddings, also known as
Flair embeddings, which are trained on a large corpus in our task. In addition,
to improve the performance of causality extraction, we introduce a multihead
self-attention mechanism into SCITE to learn the dependencies between causal
words. We evaluate our method on a public dataset, and experimental results
demonstrate that our method achieves significant and consistent improvement
compared to baselines.
