Deep Emotion Recognition in Textual Conversations: A Survey

While Emotion Recognition in Conversations (ERC) has seen a tremendous advancement in the last few years, new applications and implementation scenarios present novel challenges and opportunities. These range from leveraging the conversational context, speaker and emotion dynamics modelling, to interpreting common sense expressions, informal language and sarcasm, addressing challenges of real time ERC and recognizing emotion causes. This survey starts by introducing ERC, elaborating on the challenges and opportunities pertaining to this task. It proceeds with a description of the main emotion taxonomies and methods to deal with subjectivity in annotations. It then describes Deep Learning methods relevant for ERC, word embeddings, and elaborates on the use of performance metrics for the task and methods to deal with the typically unbalanced ERC datasets. This is followed by a description and benchmark of key ERC works along with comprehensive tables comparing several works regarding their methods and performance across different datasets. The survey highlights the advantage of leveraging techniques to address unbalanced data, the exploration of mixed emotions and the benefits of incorporating annotation subjectivity in the learning phase.