Why some people think they know more than vaccine experts | Science News for Students

Why some people think they know more than vaccine experts

Those who cling to myths often don’t realize what they don’t know, study finds
Apr 4, 2019 — 6:40 am EST
a photo of a doctor applying a bandaid to the upper arm of a smiling teen with dark skin and curly hair

This teen has a reason to smile after getting a vaccine. Vaccines provide long-lasting protection against dangerous diseases.

Steve Debenport/E+/Getty Images

Vaccines save lives — millions every year. Yet some parents won’t let their children get this common treatment. New research suggests many of these people think they know more than the experts. That may make them more likely to fall for baseless myths, the study concludes

Matthew Motta is a political scientist at the University of Pennsylvania in Philadelphia. He studies science communication and the public-policy impacts of people rejecting science. Recently, he and others surveyed 1,310 U.S. adults on their knowledge of autism. Some websites wrongly appeal to parents’ fears that childhood vaccines may cause the complex brain condition — even though study after study has shown that there is no link. Motta’s group also asked how these people felt about government requirements that all children get vaccines.

More than a third of the people surveyed claimed they knew as much or more about the causes of autism than either doctors or scientists. In fact, the opposite was true. People who thought they knew more than the experts generally knew the least about autism. That overconfidence was also strongest among people who oppose vaccines.

The Dunning-Kruger effect helps explain the results, Motta says. Psychologists Justin Kruger and David Dunning first described the effect in 1999. At the time, both worked at Cornell University in Ithaca, N.Y.

a photo of a rash from the measles covering a patient's abdomen
Rashes from the measles, like the one in this 1958 photo of a patient’s abdomen, used to be a common sight before the measles vaccine was developed. Dangers from vaccine-preventable diseases are very real and growing again as more people reject doctors’ advice.
Heinz F. Eichenwald/CDC

“Some people have so little knowledge about a subject that they actually don’t know how much knowledge they lack,” Motta explains. In other words, people who don’t know what they don’t know can mistakenly think they know plenty. They’re wrong. Yet they feel quite confident that they know more than people who have spent their lives doing research in that field.

Motta’s group also had another finding. Overconfident people are more likely to think that actors or talk show hosts should influence public policy on vaccines. In fact, such celebrities have no expert training and or knowledge. Often they, too, are overconfident — and wrong.

The study appeared in the August 2018 issue of Social Science & Medicine.

Salil Benegal is a political scientist at DePauw University in Greenfield, Ind. He wrote a commentary on the study’s findings. It ran in the September 2018 issue of Social Science & Medicine. The new study, he says, helps explain how overconfidence can “amplify the effects of misinformation from non-expert sources.” He says it can have the same effect on exaggerating the believability of some political groups.

Indeed, Benegal says, the new findings may “be relevant to a lot of other areas where there is skepticism or misinformation about scientific facts.” He says that includes topics such as climate change or biotechnology.  

The new study, he adds, also highlights the problem some news outlets create when they look for comments from “both sides” — experts and non-experts — on matters of science. After all, science is about facts. And someone’s personal beliefs won’t change the facts.

What to do

The new findings don’t mean that overconfident people are stupid, Motta says. They may even know a lot about things other than vaccines. And telling people that they’re idiots would never change their minds anyway.

Some people might be willing to consider scientific evidence. Others might not listen. Ethan Lindenberger, 18, of Norwalk, Ohio, faced that problem. His mom wouldn’t let him get vaccinated. She rejected mounds of scientific evidence showing that vaccines are safe. “Her only response was: ‘That’s what they want you to think,’” Lindenberger said at a March 5 congressional hearing in Washington, D.C.

When talking about vaccines with someone, such as a parent, don’t give up, Motta urges teens and ‘tweens. “Make an effort to connect with your parents,” he suggests. “Talk with them on their own terms,” he says, “while staying true to the science.”

If a parent worries about side effects, Motta says, contrast the teeny risk of any true side effect with the much greater danger of getting a potentially lethal disease.

If a parent thinks vaccines are disgusting, Motta suggests that teens talk how getting a dangerous, preventable disease is much more disgusting. Describe the blotchy, ugly rashes of measles or skin scars of chickenpox. Describe the pain and spasms tetanus can cause or yucky diarrhea from rotavirus. Even the throat-clogging mucus from diphtheria (Dip-THEER-ee-uh).

Motta and others are now at work on a new study. They hope it will show this strategy can work. If so, it may one day help health experts and others fight the growing problem of preventable disease.

Ethan Lindenberger testifies at a March 5, 2019 hearing, in Washington, D.C., convened by the U.S. Senate Committee on Health, Education, Labor and Pensions. The teen describes growing up unvaccinated.
PBS NewsHour/YouTube

Power Words

(more about Power Words)

amplify     To increase in number, volume or other measure of responsiveness.

autism     (also known as autism spectrum disorders ) A set of developmental disorders that interfere with how certain parts of the brain develop. Affected regions of the brain control how people behave, interact and communicate with others and the world around them. Autism disorders can range from very mild to very severe. And even a fairly mild form can limit an individual’s ability to interact socially or communicate effectively.

climate change     Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

commentary     (in science) An opinion piece, often written to accompany — and add perspective to — a paper by others, which describes new research findings.

diarrhea     (adj. diarrheal) Loose, watery stool (feces) that can be a symptom of many types of microbial infections affecting the gut.

diphtheria      A bacterial infection where the germs produce a poison that destroys healthy tissue in the respiratory system. Within a few days, it can become hard to breathe. Other symptoms include weakness, fever and a very sore throat. If the poison enters the bloodstream it can eventually damage the heart, kidneys and nerves. There is a vaccine to prevent the disease. It is usually administered to children as part of a cocktail of vaccines that also target tetanus and pertussis (whooping cough).

Dunning-Kruger effect     This is a behavior that occurs when someone doesn’t know how bad they are at something. They initially overestimate how well they will do it. For example, a student might think they know enough chemistry to get a C on an exam, when in fact, they know almost nothing — so little that they end up with an F.

link     A connection between two people or things.

measles     A highly contagious disease, typically striking children. Symptoms include a characteristic rash across the body, headaches, runny nose, and coughing. Some people also develop pinkeye, a swelling of the brain (which can cause brain damage) and pneumonia. Both of the latter two complications can lead to death. Fortunately, since the middle 1960s there has been a vaccine to dramatically cut the risk of infection.

mucus     A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.

policy     A plan, stated guidelines or agreed-upon rules of action to apply in certain specific circumstances. For instance, a school could have a policy on when to permit snow days or how many excused absences it would allow a student in a given year.

political scientist     Someone who studies or deals with the governing of people, largely by elected officials and governments. 

psychologist     A scientist or mental-health professional who studies the human mind, especially in relation to actions and behaviors. 

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

side effects     Unintended problems or harm caused by a procedure or treatment.

social science     The scientific study of people and their relationships to each other.

strategy     A thoughtful and clever plan for achieving some difficult or challenging goal.

tetanus     An unusual type of bacterial infection that usually does not spread between infected individuals. The source of these germs is typically exposure to soil, dust or animal feces. The disease causes stiff, painful muscles throughout the body, including a cramping in the jaw (which is why it’s sometimes called “lockjaw”). Fevers, seizures, sweating and headaches may also occur.

tween     A child just approaching his or her teenage years. Tween is a term usually used for 11- to 12-years olds.

vaccine     (v. vaccinate) A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease. The injections used to administer most vaccines are known as vaccinations.


Hearing: United States Senate. Committee on Health, Education, Labor and Pensions. “Vaccines Save Lives: What Is Driving Preventable Disease Outbreaks?” Washington, D.C. March 5, 2019.

Journal: S. Benegal. Overconfidence and the discounting of expertise: A commentary. Social Science & Medicine. Vol. 213, September 2018, p. 95. doi: 10.1016/j.socscimed.2018.07.039.

Journal: M. Motta et al. Knowing less but presuming more: Dunning-Kruger effects and the endorsement of anti-vaccine policy attitudes. Social Science & Medicine. Vol. 211, August 2018, p. 274. doi: 10.1016/j.socscimed.2018.06.032.

Journal: D. Dunning. The Dunning-Kruger effect: On being ignorant of one’s own ignorance. Advances in Experimental Social Psychology. Vol. 44, 2011, p. 247. doi: 10.1016/B978-0-12-385522-0.00005-6.

Journal: J. Kruger and D. Dunning. Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments. Journal of Personality and Social Psychology. Vol. 77, December 1999, p. 1121.