Risk perception is a fascinating field it seeks to study the reasons for rifts between the opinions of experts on a subject and the general public. Notable example include:
* The Safety of Nuclear Energy
* The Danger Posed by Climate Change
* The Health benefits or dangers of gluten
* The danger posed to the US by self monitoring person who may have been exposed to ebola.
One of the key features of risk perception is that there is always a kernel of truth to the popular belief, but due possibly to one of several statistical fallacies the importance of that kernel is overestimated.
A group of policemen have breathalyzers displaying false drunkenness in 5% of the cases tested. However, the breathalyzers never fail to detect a truly drunk person. 1/1000 of drivers are driving drunk. Suppose the policemen then stops a driver at random, and force them to take a breathalyzer test. It indicates that he or she is drunk. We assume you don't know anything else about him or her. How high is the probability he or she really is drunk?
Most people will answer as as high as 95%, but the correct answer is 2%. This is because drunk drivers are very rare, so even though the breathalyzer is accurate the likelihood that a random driver just happens to be drunk is still very small, even if they test positive.
A person claims to a group of friends that those who drive red cars receive more speeding tickets. The group agrees with the statement because a member of the group drives a red car and frequently receives speeding tickets.
Many people will depend on personal experiences or exceptional cases that garner a great deal of media attention. For example, after seeing news stories about child abductions, people may judge that the likelihood of this event is far greater than it actually is. In fact, most Americans believe that crime and teen pregnancy are on the rise when in fact both of these things have been falling in most cities for nearly a decade.
In the past few weeks we have seen differences in risk perception that have been some of the most stark ever recorded. An overwhelming majority of experts rejecting quarantine measures while 70% or more Americans favor them in polls. Why is this happening?
Differences in risk perception are not just about how well people understand the subject or the statistics. There are cultural factors as well. I believe cultural values are a key factor in the rift on ebola policy.
Public Health experts think of an epidemic as something to solve at the macro level. The more people that die the worse it is. So, when they weigh a vanishingly small risk of Ebola in the US against thousands of deaths in West Africa the choice is very simple.
In contrast to this most members of the American public are thinking first of their own safety. The foreign, and stigmatized nature of ebola along with its use in horror movies makes any risk no matter how small or luddicurrsly indirect or even imagined unacceptable. (Keep in mind, a risk of zero is not something that exists even with quarantines.) Thinking about the epidemic as a whole is not a part of the American calculus on this topic.
The scary thing about all of this is that is it precisely a failure to stop a raging epidemic that could pose the greatest real health threat to Americans, but since that threat is not "today" but rather in the future it is not urgent enough to warrant concern. (see: global warming)
This is why quarantine measures are described over and over as "common sense" two words that ought to cause anyone to stop and reexamine what was just said more carefully as they are often a screen of the least sensible ideas of all.