Dynamic Persuasion: Decay and Accumulation of the Persuasive Effects of Partisan Media

Both academic researchers and political pundits have generally accepted several over-time features of persuasion by partisan media: that the persuasive effects of partisan media might be temporary and decay quickly after a single exposure, and that these effects accumulate from multiple exposures. That effects decay may serve to ameliorate concerns about the broad impact of such media on partisan polarization. Yet the assumption that persuasive effects accumulate may raise larger concerns from real-world repeat exposure. To explore these possibilities, we implement a novel set of multiwave experiments that allow us to examine concerns about media effects over time. We present estimates from three studies which suggest that the persuasive effect of exposure to just a short article or video clip can persist for up to a week. In contrast to this persistence, our results suggest that an experiment adequately powered to detect the accumulative effect from multiple doses of partisan media – let alone one powered to detect accumulative effects among subgroups of the population – would require an unrealistic number of respondents, suggesting that such effects are difficult to test in an experimental setting with limited resources.