The first threats may seem worse, but the second threats are far more likely. Why are people often more afraid of relatively low risks, and less afraid of bigger ones? Research into the perception of risk has revealed that, in addition to rationally considering the probabilities about a risk, human beings rely on intuitive faculties and emotions when subconsciously deciding what to fear, and how fearful to be. By understanding the factors that influence people's perception of risk, public health communicators can more effectively encourage them to make healthier choices.
David Ropeik, director of Risk Communication at Harvard Center for Risk Analysis (HCRA) and a former television journalist, lectures on this topic to HSPH students as well as government officials, reporters, and public health practitioners. As described in the book he co-authored in 2002 with HCRA Executive Director George Gray, RISK! A Practical Guide to What's Really Safe and What's Really Dangerous in the World Around You, several factors shape people's perception of risks:
Trust. The more we trust the people informing us about a risk, or the institution or company exposing us to the risk, or the government agencies that are supposed to protect us, the less afraid we'll be. The less we trust them, the greater our fear.
Control. The more control we have over a risk, the less threatening it seems. This explains why it feels safer to drive than fly, though the risk of death from motor vehicle crashes is much higher.
Dread. The more dreadful the nature of the harm from a risk, the more worried we'll be. Cancer is generally considered a more dreadful way to die than heart disease, yet heart disease kills roughly 25 percent more Americans.
Risk vs. benefit. The more we get a benefit from a choice or behavior, like using a cell phone when we drive or that "nice, healthy-looking tan" from the sun, the less concerned we are about any associated risk.
Human-made vs. natural. Natural risks seem less scary. Solar radiation causes an estimated 7,100 melanoma deaths in the U.S. per year. Yet many sunbathers worry more about nuclear radiation. Among more than 90,000 survivors of Hiroshima and Nagasaki, only about 500 cancer deaths have been attributed to radiation exposure over the past 59 years.
"Could it happen to me?" Statistical probabilities like one in a million are often used in risk communication, usually to no avail. One in a million is too high if you think you could be "the one." That is why the public sometimes demands additional regulations to cut already low risks to zero.
New or familiar. New threats--for example, West Nile virus when it first appears in a community--generate concern. After residents have lived with the risk for a while, familiarity lowers their fear.
Children. Any risk to a child seems more threatening in the eyes of adults than the same risk does to them.
Uncertainty. The less we know, or understand, about a risk, the scarier it seems.
Perceiving risk through these emotional and intuitive lenses, which have been identified by researchers Paul Slovic, Baruch Fischhoff, and others, is natural human behavior, but "It can lead us to make dangerous personal choices," Ropeik says. Driving may have felt safer than flying after September 11, 2001, but those who opted to drive rather than fly were actually raising their risk. Risk misperception can threaten health by making us too afraid, or not afraid enough.
Finally, as George Gray points out, failing to keep risk in perspective leads us to "pressure government for protection against relatively small risks, which diverts resources from bigger ones."
"By understanding and respecting the way people relate to risk," Gray says, "risk communicators can play a vital role in improving the public's health."