DAVID GREENE, HOST:
All right. Here's an assumption that seems pretty safe. If something feels more risky, we are less likely to do it. Well, NPR's social science correspondent Shankar Vedantam is here to tell us why that might not be right.
Shankar, it seems pretty intuitive.
SHANKAR VEDANTAM, BYLINE: It does seem pretty intuitive, David. I was speaking with economist Jason Kerwin at the University of Minnesota. He wanted to test the idea that telling people that they are at risk would prompt them to take steps to protect themselves. Now, that rational approach is true most of the time, but there are some important exceptions.
JASON KERWIN: Telling people that an activity is extremely risky can sometimes paradoxically cause them to be less safe. So it can scare them to death instead of scaring them straight.
GREENE: OK. So he's talking about when people tell us not just that something is risky but something is really, really risky. That's when something strange happens.
VEDANTAM: Exactly. So let's say you believe the risk of something bad happening to you is close to 100 percent. Rather than inducing a feeling that there's something that you can do to protect yourself, this may induce a sense of fatalism. You tell yourself the risk is so high, there's really nothing I can do to protect myself. Kerwin was recently in Malawi. This is a country in southern Africa where there's a very high prevalence of HIV infection. In southern Malawi, about 1 in 5 adults, 20 percent of the population, is HIV positive - staggering number.
Kerwin observed that many adults, men in particular, believed their risk of HIV infection was close to 100 percent. They also believed, for example, that one act of sexual intercourse with an infected person was sure to give them HIV infection as well. Now, Malawi also happens to be a place where few of these men are actually practicing safe sex or changing their sexual behaviors, which led Kerwin to wonder whether the high sense of risk was leading to fatalism rather than leading people to take action to protect themselves. Here's Kerwin.
KERWIN: Men, in particular, they don't bother with condoms or with avoiding risky partners because, based on their history, they're just really sure that they've already got HIV.
GREENE: So how did they actually test this and decide that fatalism is really at play here?
VEDANTAM: Well, Kerwin divided volunteers in Malawi into groups, and he gave one of the groups information about the actual risk of HIV infection, which was much lower than people thought it was. So if you have unprotected sex with an infected partner for a year, your risk of catching HIV may be around 10 percent.
GREENE: Oh, not even close to the 100 percent that a lot of people were assuming.
VEDANTAM: No, no. Now, it's still high, but it's much, much lower than many people believe. Kerwin found that people who believed their risk was lower than they previously had thought became more likely to practice safe sexual behaviors. In effect, they were thinking, OK. I'm not doomed. There's something that I can do that might help keep me safe.
GREENE: So what does that mean if you're in the field of public health - you should be really careful not to make something seem too, too bleak?
VEDANTAM: I think that's right. I mean, when we want to change behavior, we often present people with a fearful picture. Now that can be justified, but it really is important that the fear actually correspond with reality. If it doesn't, inducing fear can actually backfire and make the problem worse.
GREENE: Interesting stuff, as always. Thanks, Shankar.
VEDANTAM: Thanks, David.
GREENE: Shankar Vedantam is NPR's social science correspondent, and he's also the host of a podcast that explores the unseen patterns in human behavior. It is called Hidden Brain.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.