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November / December 2011
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According to human development professor Valerie Reyna, if public health officials want to counter the anti-vaccination movement, they need to understand how people process risk

Cornell Alumni Magazine: What do you study?

Valerie Reyna: I study risky decision-making in children, adolescents, and adults. The canonical example is the teenager who takes risks—who speeds or gets into a car with a driver who's been drinking. Or think about the hundreds of thousands of people who die from smoking every year; almost every one initiates that behavior in adolescence. Certain personality types are what we call sensation-seeking—the fact that something bad might happen makes it thrilling—and many people go through a period like that in adolescence. But the cognition of risk changes fundamentally from adolescence to adulthood.

Valerie Reyna

CAM: Could you give an example?

VR: Take unprotected sex. There's the possibility of HIV infection, and most adults would say it's not worth it. From the point of view of an adolescent, there are benefits to having sex and the chances of HIV infection are objectively low, so it makes sense to take a risk. But as you go from adolescence to adulthood, there's what we call a "gist-based intuitive process." That's a mouthful, but what it boils down to is this: if there's a non-negligible possibility of a really bad thing, don't do it.

CAM: How does that thinking apply in areas where people are quite bad at assessing risk? People ride in cars every day but are terrified to fly, even though the odds of dying in a car accident are much higher than in a plane crash.

VR: In fact, the joke in my profession is that people drive to the airport, and then they worry.

CAM: So why do people think like that?

VR: Risk perception is affected by things like familiarity and control. Essentially, if you have less control over something or it's less familiar, you're more fearful.

CAM: Given your specialty, why were you interested in studying immunization?

VR: It involves a major public health problem, and also it's a question of risk. Vaccines are low-risk, but they do have some risk; there's the very remote possibility that you will have a severe reaction or even die. Parents have to decide whether to vaccinate their children—but there are major public health consequences if they don't. There have been recurrences of some diseases, like measles, that we thought were conquered.

CAM: What are the most common worries about vaccination? VR: There has been concern about narcolepsy associated with certain vaccines in Europe; in the U.S., some people continue to see a connection (wrongly) between autism and childhood vaccinations. And the prevalence rate for autism—one in seventy for boys—is very high. As more people talk about this in the media, more people are concerned that there is a link. They think, I got my child vaccinated and he began to exhibit these symptoms; they connect the dots.

CAM: In general, are people good at assessing risk?

VR: It depends if they've had adequate opportunity to experience the outcome. People who lived before the polio vaccine knew people who had polio; they saw friends die, they saw people in iron lungs. The research shows that if you have exposure to outcomes, you're able to estimate probabilities very well. But in today's world, if everybody gets vaccinated, you don't observe the bad event.

CAM: What is happening in people's minds when they decide whether or not to vaccinate?

VR: One thing that's obvious is that official sources of information about vacci-nation risks and benefits—government websites, for example—are difficult for laypeople to understand. It's not that they necessarily use big words; it's that the concepts—like "herd immunity"— make no sense. The sites just tell facts; they don't explain them. My theory says that you can encode facts in a rote fashion—what we call "verbatim representation"—but those representations are not what you use to make decisions; to make decisions, you use what we call "gist representations."

CAM: What are gist representations? VR: They capture the bottom-line meaning. If you don't understand what you're reading, your gist is impoverished. And these websites don't explain; they exhort. They say, "You should get vaccinated." Why? "Because you should." They don't really explain the risks, the mechanisms of the vaccines, or the process by which they're approved in a way that people understand and therefore trust. On the other hand, if you go to an anti-vaccination website, it's very explanatory. There's a coherent narrative.

CAM: Do the anti-vaccination sites also tend to be more compelling? They can tell a story like, "My son Billy was three years old and developing normally and now he's autistic because of this vaccine."

VR: That's precisely correct. We're seeing stories that are not only emotionally evocative, but also more coherent.

CAM: As a researcher, do you have to be neutral about whether vaccines really cause autism?

VR: Being objective does not necessarily mean being completely open-minded about things for which there are established facts. For example, mercury was removed from vaccines—so if mercury caused autism, you'd see a drop in autism, and in fact it continues to be diagnosed at a higher rate. I would not presume that someone who's anti-vacci-nation is irrational; on the other hand, there are consequences. If you decide not to vaccinate, what about the child that sits next to yours in school?

CAM: Given that part of the problem is that one side offers more compelling messages, what can public health officials learn from your research to make a more effective case?

VR: The recommendation would be to focus on the gist instead of reporting facts that public health officials assume are self-evident—"this is FDA approved, you should just do it." The gist-based approach says that, to make a decision, people have to understand what they're being told. It might be temping to conclude, "The government will put the facts out there about vaccination, heart disease, cancer, or smoking, and that will solve the problem." But it's not facts that determine a decision; it's the mental representation of those facts. It's what's in the mind, not what's on the page, that determines what you do. In terms of public health, that's where the rubber meets the road.

— Beth Saulnier

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