We provide an NLP framework to uncover four linguistic dimensions of political polarization in social media: topic choice, framing, affect and illocutionary force. We quantify these aspects with existing lexical methods, and propose clustering of tweet embeddings as a means to identify salient topics for analysis across events; human evaluations show that our approach generates more cohesive topics than traditional LDA-based models. We apply our methods to study 4.4M tweets on 21 mass shootings. We provide evidence that the discussion of these events is highly polarized politically and that this polarization is primarily driven by partisan differences in framing rather than topic choice. We identify framing devices, such as grounding and the contrasting use of the terms "terrorist" and "crazy", that contribute to polarization. Results pertaining to topic choice, affect and illocutionary force suggest that Republicans focus more on the shooter and event-specific facts (news) while Democrats focus more on the victims and call for policy changes. Our work contributes to a deeper understanding of the way group divisions manifest in language and to computational methods for studying them.

本文提出了一种基于NLP的框架，通过分析话题选择、表达方式、情感和言语作用等四个维度来研究社交媒体中的政治极化。作者通过现有的词汇方法量化这些方面，并提出了利用聚类技术识别分析主题的方法。作者将这些方法应用于对21起大规模枪击事件中的4.4M条推文进行研究，发现这些事件的讨论在政治上高度极化。结果表明，共和党更关注枪手和事件特定事实，而民主党则更关注受害者和政策变化的呼吁。同时，作者还发现了一些引导言论极化的表达方式，诸如“基础事实”以及“恐怖分子”和“疯子”这两个术语的不同使用。该研究深入了解了语言中的群体分裂表现方法，并提供了计算方法来研究这些现象。

在社交媒体中分析极化趋势：以21起大规模枪击事件中的推文为例