Wednesday, October 10, 2007

Risk perception: control, choice and cause

One of the interesting things about risk perception is that it is often unrelated to the actual level of risk. You can see this at work in homebirth advocacy, where the risks of homebirth itself are far greater than advocates understand, and the "risks" that advocates are trying to protect themselves from are far smaller than they appreciate.

David Ropeik, Director of Risk Communication at the Harvard Center for Risk Analysis, discusses the causes of misperception of risk in his article The Consequences of Fear. In particular, he mentions three factors, control, choice and origin, that are especially relevant for understanding the misperception of risk among homebirth advocates.

Take the issue of choice, for example. It is widely accepted among scholars of risk analysis that risks over which we feel as though we exercise control are perceived to be smaller than risks that are imposed from outside.
We sometimes fail to take adequate precautions against relatively larger risks that do not cause elevated concern. Roughly 20% of Americans still do not wear safety belts in motor vehicles. The risk perception literature would suggest that this is, in part, because we have a sense of control when we are behind the wheel, and the risk of crashing is both familiar and chronic—factors that make risks seem less threatening. Consider the public health ramifications here. The US National Highway Traffic Safety Administration estimates that if safety belt usage increased to 85%, 2,700 lives would have been saved in 2002...
In other words, people not only tolerate the substantial risk of not wearing a seatbelt, but they perceive the risk to be relatively small, when, in fact, it is relatively large compared to risks that evoke more fear, like the risk of a plane crash or a terrorist attack.

A second factor that modifies perception of risk is a sense of control. Risks that are deliberately chosen seem smaller than risks that are imposed by external forces.
many Americans sought a sense of control and safety after 9/11 by driving instead of flying. Air arrivals in Las Vegas were down 6.5% and motor vehicle arrivals were up 7.3% at the end of April 2002, compared with the same period in 2001, according to the Las Vegas Convention and Visitors Authority. Consider the public health ramifications of such a choice. Driving is far more likely to result in injury or death. A study by Michael Sivak and Michael Flannagan of the Human Factors Division at the University of Michigan Transportation Research Institute found that roughly 1,000 more Americans died in road accidents during October–December 2001 than would have been expected based on a comparison between figures from January–August 2000 and January–August 2001.
Similarly, there is a sense of control that comes from giving birth at home, which is safe and familiar, as opposed to giving birth in the hospital, which is a strange and psychologically uncomfortable place. Ahtough the risks of homebirth are far higher than the "risks" (real or imagined) of hospital birth, that is not how they are perceived by homebirth advocates. Homebirth advocates claim that an advantage of homebirth is the fact that a baby cannot acquire MRSA or other "superbugs" at home, although MRSA is almost unheard of in a newborn nursery. In reality, homebirth has a risk of neonatal death that is orders of magnitude higher than any risk posed by MRSA in the newborn nursery.

The third factor is that risks of technology are widely perceived to be greater than risks from nature, even though in many cases they are not.
...many people fail to protect themselves adequately from the sun, in part because the sun is natural and because, for some of us, the benefit of a healthy glowing tan outweighs the risks of solar exposure. However, solar radiation is widely believed to be the leading cause of melanoma, which will kill an estimated 7,910 Americans this year.
It is axiomatic among homebirth advocates that childbirth is inherently safe because it is natural. This is not and has never been true.

Homebirth advocates are absolutely certain that the risks of homebirth are so small as to be trivial and are far outweighed by the risks of hospital birth. This is a misperception of the risk. Because homebirth encourages a sense of control, because homebirth is freely chosen, and because birth is natural, homebirth advocates misperceive the real risks.


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