Supplementary file 1_An affinity-based opinion dynamics model for the evolving pattern of political polarization.docx

Political polarization has attracted many studies in recent years. We developed an opinion dynamics model with affective homophily effect and national social norm effect to describe this phenomenon. The time evolution of the polarization between the two parties and the spread of opinions within each party are affected by three factors: the repulsive effect between the two parties, the attractive and repulsive effects between the members in each party, and the national social norm effect that pulls the opinions of all members towards a common norm. The model is internally consistent and is applied to the simulation of the symmetric patterns of polarization and spread of the opinion distributions in the U.S. Congress, and the results align well with 154 years of recorded data. The time evolution of the strength of the national social norm effect is obtained and is consistent with the important historical events that occurred during the past 150 years.

近年来，政治极化现象已引发众多学术研究关注。本研究构建了融合情感同质性效应（affective homophily effect）与国家社会规范效应（national social norm effect）的舆论动力学模型，以刻画该现象。两党间极化态势与各党派内部舆论传播的时间演化，受三类因素共同影响：一是两党间的排斥效应，二是各党派内部成员间的吸引与排斥效应，三是将全体成员观点拉向统一规范的国家社会规范效应。该模型具备内在一致性，被用于模拟美国国会（U.S. Congress）中极化态势与舆论分布传播的对称模式，所得结果与154年的历史记录数据高度吻合。本研究推导得到的国家社会规范效应强度的时间演化曲线，其变化趋势与过去150年间发生的重大历史事件高度契合。