Dynamic Persuasion: Decay and Accumulation of Partisan Media Persuasion

The single shot nature of experiments on the effects of partisan media on public opinion may limit the relevance of estimates that such studies produce for politics and policy. For example, there might be cumulative effects from multiple doses of partisan media such that the combined effect of repeated exposures on political attitudes is much greater than that of a single dose. Similarly, the persuasive effect of partisan media might be temporary and decay quickly after a single exposure. We implement a novel multi-wave experiment that allows us to examine these concerns. We find that the persuasive effects demonstrate substantial durability, decaying only mildly over the course of a week following treatment. Additionally, we find no evidence of cumulative effects of repeated exposure to partisan media, and instead slight moderation. Together, these results suggest that partisan media’s influence on public opinion is persistent, but the additive effects of “filter bubbles” are limited. We appreciate the research assistance of Grace Chao, Henry Feinstein, and Kaitlin Tucci, and funding from the National Science Foundation (SES-1528487) and the Political Experiments Research Lab (PERL) at MIT. ∗PhD student, Department of Political Science, Massachusetts Institute of Technology, zmarko@mit.edu †Kalb Professor, John F. Kennedy School of Government, Harvard University, Matthew Baum@harvard.edu ‡Mitsui Professor, Department of Political Science, Massachusetts Institute of Technology, berinsky@mit.edu §Assistant Professor, Department of Political Science, Boston University, jdbk@bu.edu ¶Associate Professor, Department of Political Science, Massachusetts Institute of Technology, teppei@mit.edu