Thinking about default enrollment lowers vaccination intentions and public support in G7 countries.

Policymakers often face a conundrum between being transparent about policies and ensuring that those policies are effective. This challenge is particularly relevant for behavioral nudges, which are not usually disclosed. Rather than avoiding transparency, we suggest that policymakers encourage citizens to reflect on nudges to help them understand their own views and align those views with their behaviors. Using data from an online survey experiment with 24,303 respondents in G7 countries, we examine the impact of reflection on a hypothetical default nudge policy for COVID-19 booster appointments. Contrary to expectations, participants say they would be less likely to get the booster when automatically enrolled compared with a control condition. Similarly, encouraging citizens to think about the status quo (baseline) policy also reduces intentions for boosters. These interventions have no effect on approval of the policy. Further, encouraging people to think about automatic enrollment decreases approval of the policy and further decreases their intentions to get vaccinated. These findings suggest that reflection on a nudge can increase backlash from a nudge and also elicit policy disapproval, thereby aligning policy support with behavioral intentions.

Public support for more stringent vaccine policies increases with vaccine effectiveness.

Under what conditions do citizens support coercive public policies? Although recent research suggests that people prefer policies that preserve freedom of choice, such as behavioural nudges, many citizens accepted stringent policy interventions like fines and mandates to promote vaccination during the COVID-19 pandemic-a pattern that may be linked to the unusually high effectiveness of COVID-19 vaccines. We conducted a large online survey experiment (N = 42,417) in the Group of Seven (G-7) countries investigating the relationship between a policy's effectiveness and public support for stringent policies. Our results indicate that public support for stringent vaccination policies increases as vaccine effectiveness increases, but at a modest scale. This relationship flattens at higher levels of vaccine effectiveness. These results suggest that intervention effectiveness can be a significant predictor of support for coercive policies but only up to some threshold of effectiveness.

Interventions to counter misinformation: Lessons from the Global North and applications to the Global South.

We synthesize evidence from 176 experimental estimates of 11 interventions intended to combat misinformation in the Global North and Global South, which we classify as informational, educational, sociopsychological, or institutional. Among these, we find the most consistent positive evidence for two informational interventions in both Global North and Global South contexts: inoculation/prebunking and debunking. In a complementary survey of 138 misinformation scholars and practitioners, we find that experts tend to be most optimistic about interventions that have been least widely studied or that have been shown to be mostly ineffective. We provide a searchable database of misinformation randomized controlled trials and suggest avenues for future research to close the gap between expert opinion and academic research.

Subscriptions and external links help drive resentful users to alternative and extremist YouTube channels.

Do online platforms facilitate the consumption of potentially harmful content? Using paired behavioral and survey data provided by participants recruited from a representative sample in 2020 (n = 1181), we show that exposure to alternative and extremist channel videos on YouTube is heavily concentrated among a small group of people with high prior levels of gender and racial resentment. These viewers often subscribe to these channels (prompting recommendations to their videos) and follow external links to them. In contrast, nonsubscribers rarely see or follow recommendations to videos from these channels. Our findings suggest that YouTube's algorithms were not sending people down "rabbit holes" during our observation window in 2020, possibly due to changes that the company made to its recommender system in 2019. However, the platform continues to play a key role in facilitating exposure to content from alternative and extremist channels among dedicated audiences.

How do social media feed algorithms affect attitudes and behavior in an election campaign?

We investigated the effects of Facebook's and Instagram's feed algorithms during the 2020 US election. We assigned a sample of consenting users to reverse-chronologically-ordered feeds instead of the default algorithms. Moving users out of algorithmic feeds substantially decreased the time they spent on the platforms and their activity. The chronological feed also affected exposure to content: The amount of political and untrustworthy content they saw increased on both platforms, the amount of content classified as uncivil or containing slur words they saw decreased on Facebook, and the amount of content from moderate friends and sources with ideologically mixed audiences they saw increased on Facebook. Despite these substantial changes in users' on-platform experience, the chronological feed did not significantly alter levels of issue polarization, affective polarization, political knowledge, or other key attitudes during the 3-month study period.

Asymmetric ideological segregation in exposure to political news on Facebook.

Does Facebook enable ideological segregation in political news consumption? We analyzed exposure to news during the US 2020 election using aggregated data for 208 million US Facebook users. We compared the inventory of all political news that users could have seen in their feeds with the information that they saw (after algorithmic curation) and the information with which they engaged. We show that (i) ideological segregation is high and increases as we shift from potential exposure to actual exposure to engagement; (ii) there is an asymmetry between conservative and liberal audiences, with a substantial corner of the news ecosystem consumed exclusively by conservatives; and (iii) most misinformation, as identified by Meta's Third-Party Fact-Checking Program, exists within this homogeneously conservative corner, which has no equivalent on the liberal side. Sources favored by conservative audiences were more prevalent on Facebook's news ecosystem than those favored by liberals.

Reshares on social media amplify political news but do not detectably affect beliefs or opinions.

We studied the effects of exposure to reshared content on Facebook during the 2020 US election by assigning a random set of consenting, US-based users to feeds that did not contain any reshares over a 3-month period. We find that removing reshared content substantially decreases the amount of political news, including content from untrustworthy sources, to which users are exposed; decreases overall clicks and reactions; and reduces partisan news clicks. Further, we observe that removing reshared content produces clear decreases in news knowledge within the sample, although there is some uncertainty about how this would generalize to all users. Contrary to expectations, the treatment does not significantly affect political polarization or any measure of individual-level political attitudes.

Like-minded sources on Facebook are prevalent but not polarizing.

Many critics raise concerns about the prevalence of 'echo chambers' on social media and their potential role in increasing political polarization. However, the lack of available data and the challenges of conducting large-scale field experiments have made it difficult to assess the scope of the problem1,2. Here we present data from 2020 for the entire population of active adult Facebook users in the USA showing that content from 'like-minded' sources constitutes the majority of what people see on the platform, although political information and news represent only a small fraction of these exposures. To evaluate a potential response to concerns about the effects of echo chambers, we conducted a multi-wave field experiment on Facebook among 23,377 users for whom we reduced exposure to content from like-minded sources during the 2020 US presidential election by about one-third. We found that the intervention increased their exposure to content from cross-cutting sources and decreased exposure to uncivil language, but had no measurable effects on eight preregistered attitudinal measures such as affective polarization, ideological extremity, candidate evaluations and belief in false claims. These precisely estimated results suggest that although exposure to content from like-minded sources on social media is common, reducing its prevalence during the 2020 US presidential election did not correspondingly reduce polarization in beliefs or attitudes.

Time and skeptical opinion content erode the effects of science coverage on climate beliefs and attitudes.

Although experiments show that exposure to factual information can increase factual accuracy, the public remains stubbornly misinformed about many issues. Why do misperceptions persist even when factual interventions generally succeed at increasing the accuracy of people's beliefs? We seek to answer this question by testing the role of information exposure and decay effects in a four-wave panel experiment (n = 2,898 at wave 4) in which we randomize the media content that people in the United States see about climate change. Our results indicate that science coverage of climate change increases belief accuracy and support for government action immediately after exposure, including among Republicans and people who reject anthropogenic climate change. However, both effects decay over time and can be attenuated by exposure to skeptical opinion content (but not issue coverage featuring partisan conflict). These findings demonstrate that the increases in belief accuracy generated by science coverage are short lived and can be neutralized by skeptical opinion content.

Information From Same-Race/Ethnicity Experts Online Does Not Increase Vaccine Interest or Intention to Vaccinate.

Policy Points Mass vaccination is essential for bringing the COVID-19 pandemic to a close, yet substantial disparities remain between whites and racial and ethnic minorities within the United States. Online messaging campaigns featuring expert endorsements are a low-cost way to increase vaccine awareness among minoritized populations, yet the efficacy of same-race/ethnicity expert messaging in increasing uptake remains unknown. Our preregistered analysis of an online vaccine endorsement campaign, which randomly varied the racial/ethnic identity of the expert, revealed no evidence that information from same race/ethnicity experts affected vaccine interest or the intention to vaccinate. Our results do not rule out the possibility that other low-cost endorsement campaigns may be more effective in increasing vaccine uptake, but do suggest that public health campaigns might profitably focus on issues of access and convenience when targeting minoritized populations in the United States. CONTEXT: The COVID-19 pandemic in the United States has been unequally experienced across racial and ethnic groups. Mass vaccination is the most effective way to bring the pandemic to an end and to manage its public health consequences. But the racialization of public health delivery in the United States has produced a sizable racial/ethnic gap in vaccination rates. Closing this gap in vaccine uptake is therefore essential to ending the pandemic. METHODS: We conducted a preregistered, well-powered (N = 2,117) between-subjects survey experiment, fielded March 24 to April 5, 2021, in which participants from YouGov's online panel-including oversamples of Black (n = 471), Hispanic/Latino/a (n = 430), and Asian American (n = 319) participants-were randomly assigned to see COVID-19 vaccine information endorsed by same- or different-race/ethnicity experts or to a control condition. We then measured respondents' vaccination intentions, intention to encourage others to get vaccinated, and interest in learning more information and sharing information with others. FINDINGS: Same-race/ethnicity expert endorsements had no measurable effect on nonwhite or white respondents' willingness to get the COVID-19 vaccine, to encourage others to get the vaccine, or to learn more or share information with others. CONCLUSIONS: Our study provides empirical evidence suggesting online endorsements from same-race/ethnicity experts do not increase vaccine interest, advocacy, or uptake, though same-race/ethnicity endorsements may be effective in other venues or mediums.

Political audience diversity and news reliability in algorithmic ranking.

Newsfeed algorithms frequently amplify misinformation and other low-quality content. How can social media platforms more effectively promote reliable information? Existing approaches are difficult to scale and vulnerable to manipulation. In this paper, we propose using the political diversity of a website's audience as a quality signal. Using news source reliability ratings from domain experts and web browsing data from a diverse sample of 6,890 US residents, we first show that websites with more extreme and less politically diverse audiences have lower journalistic standards. We then incorporate audience diversity into a standard collaborative filtering framework and show that our improved algorithm increases the trustworthiness of websites suggested to users-especially those who most frequently consume misinformation-while keeping recommendations relevant. These findings suggest that partisan audience diversity is a valuable signal of higher journalistic standards that should be incorporated into algorithmic ranking decisions.

The ephemeral effects of fact-checks on COVID-19 misperceptions in the United States, Great Britain and Canada.

Widespread misperceptions about COVID-19 and the novel coronavirus threaten to exacerbate the severity of the pandemic. We conducted preregistered survey experiments in the United States, Great Britain and Canada examining the effectiveness of fact-checks that seek to correct these false or unsupported beliefs. Across three countries with differing levels of political conflict over the pandemic response, we demonstrate that fact-checks reduce targeted misperceptions, especially among the groups who are most vulnerable to these claims, and have minimal spillover effects on the accuracy of related beliefs. However, these reductions in COVID-19 misperception beliefs do not persist over time in panel data even after repeated exposure. These results suggest that fact-checks can successfully change the COVID-19 beliefs of the people who would benefit from them most but that their effects are ephemeral.

Minimal effects from injunctive norm and contentiousness treatments on COVID-19 vaccine intentions: evidence from 3 countries.

Does information about how other people feel about COVID-19 vaccination affect immunization intentions? We conducted preregistered survey experiments in Great Britain (5,456 respondents across 3 survey waves from September 2020 to February 2021), Canada (1,315 respondents in February 2021), and the state of New Hampshire in the United States (1,315 respondents in January 2021). The experiments examine the effects of providing accurate public opinion information to people about either public support for COVID-19 vaccination (an injunctive norm) or public beliefs that the issue is contentious. Across all 3 countries, exposure to this information had minimal effects on vaccination intentions even among people who previously held inaccurate beliefs about support for COVID-19 vaccination or its perceived contentiousness. These results suggest that providing information on public opinion about COVID vaccination has limited additional effect on people's behavioral intentions when public discussion of vaccine uptake and intentions is highly salient.

Evaluating the effects of vaccine messaging on immunization intentions and behavior: Evidence from two randomized controlled trials in Vermont.

The effectiveness of vaccines in reducing child morbidity and mortality worldwide relies on public acceptance. However, relatively little is known about the effects of vaccine communication on vaccine attitudes and immunization behavior. Previous research suggests that common communication approaches may be ineffective or even counterproductive, especially among vaccine-hesitant parents. However, these studies typically rely on observational data or self-reported measures of vaccination intention. Using novel research designs, we tested the attitudinal and behavioral effects of messages encouraging vaccination in both a survey experiment conducted among a large sample of parents in Vermont who expressed hesitancy about childhood immunizations and a field experiment among parents whose children were overdue for vaccines. We find that neither a message promoting immunization as a social norm nor a message correcting common misperceptions about vaccines was measurably more effective than a standard public health message at improving parents' attitudes toward vaccines, intention to vaccinate their children, or compliance with the recommended vaccine schedule. Our results highlight the need for more research on approaches to successfully reducing vaccine hesitancy among parents.

Elite rhetoric can undermine democratic norms.

Democratic stability depends on citizens on the losing side accepting election outcomes. Can rhetoric by political leaders undermine this norm? Using a panel survey experiment, we evaluate the effects of exposure to multiple statements from former president Donald Trump attacking the legitimacy of the 2020 US presidential election. Although exposure to these statements does not measurably affect general support for political violence or belief in democracy, it erodes trust and confidence in elections and increases belief that the election is rigged among people who approve of Trump's job performance. These results suggest that rhetoric from political elites can undermine respect for critical democratic norms among their supporters.

Overconfidence in news judgments is associated with false news susceptibility.

We examine the role of overconfidence in news judgment using two large nationally representative survey samples. First, we show that three in four Americans overestimate their relative ability to distinguish between legitimate and false news headlines; respondents place themselves 22 percentiles higher than warranted on average. This overconfidence is, in turn, correlated with consequential differences in real-world beliefs and behavior. We show that overconfident individuals are more likely to visit untrustworthy websites in behavioral data; to fail to successfully distinguish between true and false claims about current events in survey questions; and to report greater willingness to like or share false content on social media, especially when it is politically congenial. In all, these results paint a worrying picture: The individuals who are least equipped to identify false news content are also the least aware of their own limitations and, therefore, more susceptible to believing it and spreading it further.

Why the backfire effect does not explain the durability of political misperceptions.

Previous research indicated that corrective information can sometimes provoke a so-called "backfire effect" in which respondents more strongly endorsed a misperception about a controversial political or scientific issue when their beliefs or predispositions were challenged. I show how subsequent research and media coverage seized on this finding, distorting its generality and exaggerating its role relative to other factors in explaining the durability of political misperceptions. To the contrary, an emerging research consensus finds that corrective information is typically at least somewhat effective at increasing belief accuracy when received by respondents. However, the research that I review suggests that the accuracy-increasing effects of corrective information like fact checks often do not last or accumulate; instead, they frequently seem to decay or be overwhelmed by cues from elites and the media promoting more congenial but less accurate claims. As a result, misperceptions typically persist in public opinion for years after they have been debunked. Given these realities, the primary challenge for scientific communication is not to prevent backfire effects but instead, to understand how to target corrective information better and to make it more effective. Ultimately, however, the best approach is to disrupt the formation of linkages between group identities and false claims and to reduce the flow of cues reinforcing those claims from elites and the media. Doing so will require a shift from a strategy focused on providing information to the public to one that considers the roles of intermediaries in forming and maintaining belief systems.

The sources and correlates of exposure to vaccine-related (mis)information online.

OBJECTIVES: To assess the quantity and type of vaccine-related information Americans consume online and its relationship to social media use and attitudes toward vaccines. METHODS: Analysis of individual-level web browsing data linked with survey responses from representative samples of Americans collected between October 2016 and February 2019. RESULTS: We estimate that approximately 84% of Americans visit a vaccine-related webpage each year. Encounters with vaccine-skeptical content are less frequent; they make up only 7.5% of vaccine-related pageviews and are encountered by only 18.5% of people annually. However, these pages are more likely to be published by untrustworthy sources. Moreover, skeptical content exposure is more common among people with less favorable vaccine attitudes. Finally, usage of online intermediaries is frequently linked to vaccine-related information exposure. Google use is differentially associated with subsequent exposure to non-skeptical content, whereas exposure to vaccine-skeptical webpages is associated with usage of webmail and, to a lesser extent, Facebook. CONCLUSIONS: Online exposure to vaccine-skeptical content is relatively rare, but vigilance is required given the potential for exposure among vulnerable audiences.