Social Media, News Consumption, and Polarization: Evidence from a Field Experiment
中文摘要
在社交媒体上消费意识形态一致的新闻是否会加剧极化？我通过开展一项大型实地实验，随机向参与者提供在Facebook上订阅保守派或自由派新闻媒体的机会，以估计社交媒体新闻接触的影响。我收集了媒体影响因果链上的数据：对媒体的订阅、在Facebook上接触新闻、访问在线新闻网站、分享帖子，以及政治观点和态度的变化。主要发现有以下四点。第一，社交媒体上新闻接触的随机变动会显著影响个体所访问新闻网站的倾向。第二，接触与自身态度相悖的新闻会降低对对方政党的负面态度。第三，与对态度的影响相反，我未发现证据表明新闻媒体的政治倾向会影响政治观点。第四，在个体订阅相悖态度媒体的条件下，Facebook的算法更不可能向个体推送来自这些媒体的帖子。综合来看，这些结果表明，社交媒体算法可能限制了与自身态度相悖的新闻的接触，从而加剧极化。
Abstract
Does the consumption of ideologically congruent news on social media exacerbate polarization? I estimate the effects of social media news exposure by conducting a large field experiment randomly offering participants subscriptions to conservative or liberal news outlets on Facebook. I collect data on the causal chain of media effects: subscriptions to outlets, exposure to news on Facebook, visits to online news sites, and sharing of posts, as well as changes in political opinions and attitudes. Four main findings emerge. First, random variation in exposure to news on social media substantially affects the slant of news sites individuals visit. Second, exposure to counter-attitudinal news decreases negative attitudes toward the opposing political party. Third, in contrast to the effect on attitudes, I find no evidence that the political leanings of news outlets affect political opinions. Fourth, Facebook's algorithm is less likely to supply individuals with posts from counter-attitudinal outlets, conditional on individuals subscribing to them. Together, the results suggest that social media algorithms may limit exposure to counter-attitudinal news and thus increase polarization.