[论文解读] Why Are Some Countries More Politically Fragmented Online Than Others?

Yuan Zhang, Laia Castro+2 more|arXiv (Cornell University)|Jan 8, 2026

Social Media and Politics被引用 0

一句话总结

作者们使用马尔可夫稳定性在政治影响者的co-following网络上开发了一个多尺度碎片化度量，比较巴西、西班牙和美国，并显示碎片化因国家和意识形态而异，由社会排序推动。

ABSTRACT

Online political divisions, such as fragmentation or polarization, are a growing global concern that can foster radicalization and hinder democratic cooperation; however, not all divisions are detrimental, some reflect pluralism and healthy diversity of opinion in a democracy. While prior research has predominantly focused on polarization in the United States, there remains a limited body of research on political divides in multiparty systems, and no universal method for comparing fragmentation across countries. Moreover, cross-country comparison is rare. This study first develops a novel measure of structural political fragmentation built on multi-scale community detection and the effective branching factor. Using a dataset of 18,325 political influencers from Brazil, Spain, and the United States, we assess online fragmentation in their Twitter/X co-following networks. We compare the fragmentation of the three countries, as well as the ideological groups within each. We further investigate factors associated with the level of fragmentation in each country. We find that political fragmentation differs across countries and is asymmetric between ideological groups. Brazil is the most fragmented, with higher fragmentation among the left-wing group, while Spain and the United States exhibit similar overall levels, with the left more fragmented in Spain and the right more fragmented in the United States. Additionally, we find that social identity plays a central role in political fragmentation. A strong alignment between ideological and social identities, with minimal overlap between ideologies, tends to promote greater integration and reduce fragmentation. Our findings provide explanations for cross-national and ideological differences in political fragmentation.

研究动机与目标

• 推动超越左右极化的跨国碎片化比较的必要性。
• 引入基于多层社区检测和有效分支因子的新的碎片化分数。
• 将该方法应用于巴西、西班牙和美国的大型 Twitter/X 意见领袖共同关注网络。
• 考察意识形态立场和社会身份如何与碎片化模式相关。
• 识别与碎片化相关的因素并评估意识形态群体之间的对称性。

提出的方法

• 构建双模关注网络（用户与政治影响者），并投影到影响者的共同关注图。
• 应用多尺度社区检测（Markov Stability），并使用自动尺度选择来识别层级社区。
• 使用在各层级中的有效社区数（ENC）定义碎片化分数（FRAG），并计算相邻层级之间的有效分支因子。
• 将 FRAG 扩展到左倾和右倾子图，以比较按意识形态的碎片化。
• 计算社区之间意识形态向量和社会身份向量的余弦相似度，并检验是否在各层级之间出现相似社区并集成。
• 通过人工编码者和LLM基于个人资料自我呈现对意识形态和社会身份进行注释，以分配意识形态与社会身份。

实验结果

研究问题

• RQ1 RQ1：哪些国家更碎片化或更统一？
• RQ2 RQ2：碎片化在意识形态群体之间是否对称？
• RQ3 RQ3：与碎片化相关的因素有哪些？

主要发现

• 巴西是碎片化最严重的国家（FRAG ~ 2.8），碎片化更深入（五个层级）而西班牙和美国分别为三层级。
• 西班牙和美国总体碎片化相似（FRAG ~1.8 和 1.7），但西班牙呈左倾主导碎片化，美国呈右倾主导碎片化。
• 基于再分配的议会席位的实质性党派数与线下选举分裂一致，但在线碎片化显示巴西的社媒用户比席位分布所示更两极化。
• 在意识形态层面，巴西和西班牙的左倾碎片化更高，而美国的右倾碎化更高；西班牙偏左主导，美国偏右主导。
• 与意识形态或社会身份相似的社区更可能在各层级之间合并，表明社会排序影响碎片化。
• 意识形态立场与社会身份的一致性越高，碎片化越低（排序越强 → 碎片化越低）。