Brendan Nyhan

Effective Messages in Vaccine Promotion: A Randomized Trial

OBJECTIVES: To test the effectiveness of messages designed to reduce vaccine misperceptions and increase vaccination rates for measles-mumps-rubella (MMR). METHODS: A Web-based nationally representative 2-wave survey experiment was conducted with 1759 parents age 18 years and older residing in the United States who have children in their household age 17 years or younger (conducted June–July 2011). Parents were randomly assigned to receive 1 of 4 interventions: (1) information explaining the lack of evidence that MMR causes autism from the Centers for Disease Control and Prevention; (2) textual information about the dangers of the diseases prevented by MMR from the Vaccine Information Statement; (3) images of children who have diseases prevented by the MMR vaccine; (4) a dramatic narrative about an infant who almost died of measles from a Centers for Disease Control and Prevention fact sheet; or to a control group. RESULTS: None of the interventions increased parental intent to vaccinate a future child. Refuting claims of an MMR/autism link successfully reduced misperceptions that vaccines cause autism but nonetheless decreased intent to vaccinate among parents who had the least favorable vaccine attitudes. In addition, images of sick children increased expressed belief in a vaccine/autism link and a dramatic narrative about an infant in danger increased self-reported belief in serious vaccine side effects. CONCLUSIONS: Current public health communications about vaccines may not be effective. For some parents, they may actually increase misperceptions or reduce vaccination intention. Attempts to increase concerns about communicable diseases or correct false claims about vaccines may be especially likely to be counterproductive. More study of pro-vaccine messaging is needed.

Redefine Statistical Significance

We propose to change the default P-value threshold for statistical significance from 0.05 to 0.005 for claims of new discoveries.

Does correcting myths about the flu vaccine work? An experimental evaluation of the effects of corrective information.

Seasonal influenza is responsible for thousands of deaths and billions of dollars of medical costs per year in the United States, but influenza vaccination coverage remains substantially below public health targets. One possible obstacle to greater immunization rates is the false belief that it is possible to contract the flu from the flu vaccine. A nationally representative survey experiment was conducted to assess the extent of this flu vaccine misperception. We find that a substantial portion of the public (43%) believes that the flu vaccine can give you the flu. We also evaluate how an intervention designed to address this concern affects belief in the myth, concerns about flu vaccine safety, and future intent to vaccinate. Corrective information adapted from the Centers for Disease Control and Prevention (CDC) website significantly reduced belief in the myth that the flu vaccine can give you the flu as well as concerns about its safety. However, the correction also significantly reduced intent to vaccinate among respondents with high levels of concern about vaccine side effects--a response that was not observed among those with low levels of concern. This result, which is consistent with previous research on misperceptions about the MMR vaccine, suggests that correcting myths about vaccines may not be an effective approach to promoting immunization.

The hazards of correcting myths about health care reform.

Context:Misperceptions are a major problem in debates about health care reform and other controversial health issues. Methods:We conducted an experiment to determine if more aggressive media fact-checking could correct the false belief that the Affordable Care Act would create “death panels.” Participants from an opt-in Internet panel were randomly assigned to either a control group in which they read an article on Sarah Palin’s claims about “death panels” or an intervention group in which the article also contained corrective information refuting Palin. Findings:The correction reduced belief in death panels and strong opposition to the reform bill among those who view Palin unfavorably and those who view her favorably but have low political knowledge. However, it backfired among politically knowledgeable Palin supporters, who were more likely to believe in death panels and to strongly oppose reform if they received the correction. Conclusions:These results underscore the difficulty of reducing misperceptions about health care reform among individuals with the motivation and sophistication to reject corrective information.

The "Unfriending" Problem: The Consequences of Homophily in Friendship Retention for Causal Estimates of Social Influence

Abstract An increasing number of scholars are using longitudinal social network data to try to obtain estimates of peer or social influence effects. These data may provide additional statistical leverage, but they can introduce new inferential problems. In particular, while the confounding effects of homophily in friendship formation are widely appreciated, homophily in friendship retention may also confound causal estimates of social influence in longitudinal network data. We provide evidence for this claim in a Monte Carlo analysis of the statistical model used by Christakis, Fowler, and their colleagues in numerous articles estimating “contagion” effects in social networks. Our results indicate that homophily in friendship retention induces significant upward bias and decreased coverage levels in the Christakis and Fowler model if there is non-negligible friendship attrition over time.

One Vote Out of Step? The Effects of Salient Roll Call Votes in the 2010 Election

We investigate the relationship between controversial roll call votes and support for Democratic incumbents in the 2010 midterm elections. Consistent with previous analyses, we find that supporters of health care reform paid a significant price at the polls. We go beyond these analyses by identifying a mechanism for this apparent effect: constituents perceived incumbents who supported health care reform as more ideologically distant (in this case, more liberal), which in turn was associated with lower support for those incumbents. Our analyses show that this perceived ideological difference mediates most of the apparent impact of support for health care reform on both individual-level vote choice and aggregate-level vote share. We conclude by simulating counterfactuals that suggest health care reform may have cost Democrats their House majority.

The science of fake news

Addressing fake news requires a multidisciplinary effort The rise of fake news highlights the erosion of long-standing institutional bulwarks against misinformation in the internet age. Concern over the problem is global. However, much remains unknown regarding the vulnerabilities of individuals, institutions, and society to manipulations by malicious actors. A new system of safeguards is needed. Below, we discuss extant social and computer science research regarding belief in fake news and the mechanisms by which it spreads. Fake news has a long history, but we focus on unanswered scientific questions raised by the proliferation of its most recent, politically oriented incarnation. Beyond selected references in the text, suggested further reading can be found in the supplementary materials.

Scandal Potential: How Political Context and News Congestion Affect the President's Vulnerability to Media Scandal

Despite its importance in contemporary American politics, presidential scandal is poorly understood within political science. Scholars typically interpret scandals as resulting from the disclosure of official misbehavior, but the likelihood and intensity of media scandals is also influenced by the political and news context. This article provides a theoretical argument for two independent factors that should increase the presidents vulnerability to scandal: low approval among opposition party identifiers and a lack of congestion in the news agenda. Using new data and statistical approaches, I find strong support for both claims. These results suggest that contextual factors shape the occurrence of political events and how such events are interpreted.

The Role of Social Networks in Influenza Vaccine Attitudes and Intentions Among College Students in the Southeastern United States

PURPOSE To investigate whether support for vaccines among ones health discussants is associated with beliefs in vaccine safety and intention to vaccinate among college students. METHODS Ordered logistic regression analysis was conducted of data collected from 1,019 undergraduates at a large public university in 2009 and 2010. RESULTS Having health discussion networks that support vaccination is a significant predictor of beliefs of H1N1 vaccine safety (adjusted odds ratio [aOR] = 2.32) and intention (aOR = 1.78) in 2009 and of influenza vaccine safety (aOR = 1.85) and intention (aOR = 1.74) in 2010. These relationships are strongest among parents, friends, and spouses. CONCLUSIONS Perceptions of flu vaccine attitudes among health discussants were strongly related to vaccination intent and beliefs about flu vaccine safety among survey respondents.

Displacing Misinformation about Events: An Experimental Test of Causal Corrections

Misinformation can be very difficult to correct and may have lasting effects even after it is discredited. One reason for this persistence is the manner in which people make causal inferences based on available information about a given event or outcome. As a result, false information may continue to influence beliefs and attitudes even after being debunked if it is not replaced by an alternate causal explanation. We test this hypothesis using an experimental paradigm adapted from the psychology literature on the continued influence effect and find that a causal explanation for an unexplained event is significantly more effective than a denial even when the denial is backed by unusually strong evidence. This result has significant implications for how to most effectively counter misinformation about controversial political events and outcomes.