SignificanceComplex adaptive systems exhibit characteristic dynamics near tipping points such as critical slowing down (declining resilience to perturbations). We studied Twitter and Google search data about measles from California and the United States before and after the 2014–2015 Disneyland, California measles outbreak. We find critical slowing down starting a few years before the outbreak. However, population response to the outbreak causes resilience to increase afterward. A mathematical model of measles transmission and population vaccine sentiment predicts the same patterns. Crucially, critical slowing down begins long before a system actually reaches a tipping point. Thus, it may be possible to develop analytical tools to detect populations at heightened risk of a future episode of widespread vaccine refusal.

Can the media effectively hold politicians accountable for making false claims? Journalistic fact-checking assesses the accuracy of individual public statements by public officials, but less is known about whether this process effectively imposes reputational costs on misinformation-prone politicians who repeatedly make false claims. This study therefore explores the effects of exposure to summaries of fact-check ratings, a new format that presents a more comprehensive assessment of politician statement accuracy over time. Across three survey experiments, we compared the effects of negative individual statement ratings and summary fact-checking data on favorability and perceived statement accuracy of two prominent elected officials. As predicted, summary fact-checking had a greater effect on politician perceptions than individual fact-checking. Notably, we did not observe the expected pattern of motivated reasoning: co-partisans were not consistently more resistant than supporters of the opposition party. Our findings suggest that summary fact-checking is particularly effective at holding politicians accountable for misstatements.