ABSTRACT Mass media are frequently cited as having the potential to inform the public, raising knowledge levels and reducing political knowledge gaps between citizens. But media are also seen as a force for segmentation, disengagement, and widening differences between citizens. If media have no effect on political knowledge, gaps between the engaged and disengaged persist regardless of who is exposed to news because no one learns. But gaps can also persist even if everyone learns from the news, particularly if learning effects are heterogeneous across those inclined and disinclined to seek out news and/or across environments that consist of different media alternatives. Yet past research on political communication has not sufficiently linked media choice to debates about possibly heterogeneous effects of media exposure on political knowledge levels. The present study contributes a novel and large-scale choice-based experiment on knowledge of the ongoing crisis in Syria that finds media effects are relatively homogeneous across those with different media preferences and across different media environments. This suggests that under most conditions – even when everyone learns from the news – knowledge gaps between the politically engaged and disengaged are widened or at least sustained after incidental exposure to politics. While closing such gaps may be impossible, the results have important implications for understanding how citizens learn about politics and how to study learning from self-selected media experiences.

中文翻译：

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提高地板还是缩小差距？媒体选择和媒体内容如何影响政治知识

摘要 大众媒体经常被引用为具有向公众提供信息、提高知识水平和减少公民之间政治知识差距的潜力。但媒体也被视为一种分裂、脱离和扩大公民之间差异的力量。如果媒体对政治知识没有影响，那么无论谁接触新闻，参与和不参与之间的差距都会持续存在，因为没有人学习。但是，即使每个人都从新闻中学习，差距也可能持续存在，特别是如果学习效果在那些倾向于和不愿意寻找新闻的人和/或由不同媒体替代品组成的环境中是异质的。然而，过去关于政治传播的研究并没有将媒体选择与关于媒体曝光对政治知识水平的可能异质影响的辩论充分联系起来。本研究对叙利亚持续危机的知识进行了一项新颖的、基于选择的实验，该实验发现媒体效应在具有不同媒体偏好和不同媒体环境的人中相对同质。这表明，在大多数情况下——即使每个人都从新闻中学习——政治参与和不参与之间的知识差距在偶然接触政治后会扩大或至少持续存在。虽然缩小这种差距可能是不可能的，