What do you do when a parent wrongly believes that standard vaccinations pose a health risk to his or her child? In some senses, it’s just like other forms of public misunderstandings of science, like climate-change or evolution denialism. The difference is that because of the concept of herd immunity (the idea that you need a certain percentage of the population to be vaccinated or certain diseases will have the opportunity to spread wildly), anti-vaccine parents pose a much more immediate threat to others — not to mention to their own kids — than do other sorts of deniers.
The problem is that it’s tough to debunk these sorts of beliefs. In fact, when you present people with evidence pointing the other way, they’ll often simply dig in further — the so-called backfire effect. Psychologists are very interested in finding a way around this, and a new study in Proceedings of the National Academy of Sciences offers one possible route.
To slightly oversimplify the procedure, a team led by Zachary Horne of the University of Illinois asked a bunch of parents about their vaccination beliefs, gave them one of three interventions, and then asked them about their beliefs again. One group read “a paragraph written from a mother’s perspective about her child contracting measles,” viewed photos of children with measles, mumps, and rubella, and then read some short statements about how important it is to vaccinate children. Another group read a statement from the CDC attempting to debunk the idea of a link between vaccines and autism. Finally, a control group “read an unrelated vignette about a scientific topic.”
Overall, among those in the “disease risk” condition — that is, those presented not with challenges to anti-vaccine beliefs, but with reasons to vaccinate — there was a sizable, significant change in attitude that pointed in a pro-vaccination direction. There was little change in either the debunking or control group, and no statistically significant difference between the effects of the intervention on those two groups.
This doesn’t mean that emphasizing the importance of vaccines to skeptical parents works, full-stop. This was one study, and it dealt not with actual behavior vis-à-vis vaccination, but with purported beliefs. There’s no way to know from the experiment how long the positive effects persist, or if they’d cause parents, who would not have otherwise vaccinated their kids, to do so.
But it still highlights some important, nuanced points about debunking. Namely, explaining to someone why they’re wrong to hold a given belief doesn’t usually work. People hold beliefs for reasons other than “just” factual evidence, and the underlying cognitive structures holding up those false beliefs are pretty resistant to change. So replacing may sometimes be better than debunking — don’t attack a belief in a way that will cause someone to dig in; instead, replace it with a belief that will have the same desired effect.