Ethan Porter

The spread of misinformation about COVID-19 vaccines threatens to prolong the pandemic, with prior evidence indicating that exposure to misinformation has negative effects on intent to be vaccinated. We describe results from randomized experiments in the United States (n = 5,075) that allow us to measure the effects of factual corrections on false beliefs about the vaccine and vaccination intent. Our evidence makes clear that corrections eliminate the effects of misinformation on beliefs about the vaccine, but that neither misinformation nor corrections affect vaccination intention. These effects are robust to formatting changes in the presentation of the corrections. Indeed, corrections without any formatting modifications whatsoever prove effective at reducing false beliefs, with formatting variations playing a very minor role. Despite the politicization of the pandemic, misperceptions about COVID-19 vaccines can be consistently rebutted across party lines.

Despite the increasing sums devoted to online political advertising, our understanding of the persuasive effects of such advertising is limited. We report the results of a ZIP code level randomized field experiment conducted over Facebook and Instagram during the 2018 U.S. midterm elections in Florida. The ads, produced by a Democratic-leaning political action committee, were designed to spur Democratic vote share and were seen more than 1.1 million times with over 100,000 full views. This wide saturation notwithstanding, we find that these advertisements had very small estimated effects on Democratic vote share at the precinct level (−0.04 percentage points, SE: 0.85 points). Our results underline the challenges of political persuasion via digital advertisements, particularly in competitive electoral contexts.