Anti-Vaxx’ers Prove the Dunning-Kruger Test

People who think they know more than medical experts are more likely to trust information about vaccines from non-expert sources, such as celebrities
women gossiping looking at an iphone
(Precision Vaccinations)

One of the most contentious areas of health policy in the past decades has been vaccination safety.

Vaccinations have protected millions from the ravages of tetanus, whooping cough, and even chicken pox.

And yet, many Americans refuse or delay the vaccination of their children out of fear that vaccines could lead to autism, even though scientific consensus refutes this claim.

The growing “anti-vaxx” movement in the UK has even seen pet owners refusing to vaccinate their dogs. This fake-news forced the British Veterinary Association to issue a statement in April 2018 that dogs cannot develop autism.

Specifically, building on past research, our research team contends that some U.S. adults might support anti-vaxx policy positions in part because they believe they know more than medical experts.

We wanted to test this theory.

Could the inability of anti-vaxxers to accurately appraise their own knowledge and skills compared to those of medical experts play a role in shaping their attitudes about vaccines?

This inability to accurately appraise one’s own knowledge is called the Dunning-Kruger effect, first identified in social psychology.

Dunning-Kruger effects occur when individuals’ lack of knowledge about a particular subject leads them to inaccurately gauge their expertise on that subject.

Ignorance of one’s own ignorance can lead people who lack knowledge on a subject, think of themselves as more expert, than those who are comparatively better informed.

We refer to this as “overconfidence.”

To test our hypothesis, our researchers asked more than 1,300 Americans in December 2017 to compare their own perceived levels of knowledge about the causes of autism to those of medical doctors and scientists.

We found that 34 percent of U.S. adults in our sample feel that they know as much or more than scientists about the causes of autism.

Slightly more, or 36 percent, feel the same way about their knowledge relative to that of medical doctors.

We also found strong evidence of Dunning-Kruger effects in our sample.  

Sixty-two percent of those who performed worst on our autism knowledge test believe that they know as much or more than both doctors and scientists about the causes of autism, compared to only 15 percent of those scoring best on the knowledge test.

Likewise, 71 percent of those who strongly endorse misinformation about the link between vaccines and autism feel that they know as much or more than medical doctors about the causes of autism, compared to only 28 percent of those who most strongly reject that misinformation.

Our research also finds that these Dunning-Kruger effects have important implications for vaccine policy.

In addition to gauging autism knowledge, our survey asked respondents to share their opinions on several aspects of vaccine policy.

For example, we asked respondents whether or not they support parents’ decisions to not vaccinate their children before sending them to public schools.

We found that 30 percent of people who think that they know more than medical experts about the causes of autism strongly support giving parents the latitude to not vaccinate their children. 

In contrast, 16 percent of those who do not think that they know more than medical professionals felt the same way.

Our study also finds that people who think they know more than medical experts are more likely to trust information about vaccines from non-expert sources, such as celebrities.

These individuals are also more likely to support a strong role for non-experts in the process of making policies that pertain to vaccines and vaccination.

Ultimately, our results point to the uphill battle that the scientific community faces as it confronts growing anti-vaxx sentiment from the public and politicians alike.

Even as the mountain of evidence on the safety and importance of vaccines from doctors and scientists continues to grow, many Americans think they know more than the experts trying to correct their misperceptions.

Therefore, finding new ways to present scientific consensus on vaccines to an audience skeptical of medical experts should be a priority.

Our research suggests that one interesting area for future research could be to examine whether pro-vaccine information from non-expert sources like celebrities could persuade those with anti-vaccine policy attitudes to change their minds.

This article is an excerpt from The

These authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment: Matthew Motta, Postdoctoral fellow, University of Pennsylvania; Steven Sylvester, Assistant professor, public policy, Utah Valley University; Timothy Callaghan, Assistant Professor, Texas A&M University School of Public Health, Texas A&M University.