Dynamic persuasion: decay and accumulation of partisan media persuasion

Abstract Both academic researchers and political pundits have generally accepted two 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 suggesting 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 cumulative effect from multiple doses of partisan media—let alone one powered to detect cumulative effects among subgroups of the population—would require an unrealistic number of respondents. These cumulative effects are thus difficult to test in an experimental setting with limited resources.