Emotion-cause span extraction: a new task to emotion cause identification in texts

摘要

Emotional cause identification (ECI) is an important task for emotion analysis, aiming to identify the causes behind a certain emotion expressed in the text. Most of the previous studies are restricted to the clause-level binary classification, which have ignored an important fact that not all words in the clause are useful cause information for people to express emotions. In this work, we propose a new task: emotion-cause span extraction (ECSE), which is capable of obtaining more accurate and effective emotion causes. Inspired by recent advances in using joint learning approaches to ECI, we propose a novel joint learning framework for emotion-cause span extraction and span-based emotion classification so as to better address the ECSE task. Taken as the default backbone network, the Bidirectional Encoder Representations from Transformers (BERT) is used to encode multiple words and serve contextualized token representations. Furthermore, we also propose a multi-attention mechanism with emotional context awareness and a relative position learning mechanism on word-level, which is able to further capture the mutual interactions between the emotion clauses and candidate spans. According to the experimental results on a benchmark emotion cause corpus, it proves the reliability of the ECSE task and the effectiveness of our approach. In addition, through an in-depth analysis of traditional ECI task by converting ECSE into the clause-level binary classification task, we achieve the best performance among the systems in comparison, which further demonstrates the feasibility of the new ECSE task.