Perception of Risk

As discussed a few days ago, Robert is enjoying Daniel Kahneman’s book, Thinking, Fast and Slow.  In particular, it includes a good discussion of the differing views of risk perception and risk management held by Paul Slovic and Cass Sunstein.

Everyone agrees that people, and, perhaps, especially Americans, overestimate risks from certain categories of causes (e.g., chemical technologies, nuclear technologies, food preservatives) and tolerate high risk from other categories (e.g., skiing, bicycling, swimming). There are lots of folks who study the reasons for this.  The role of the media is a common focus. The question is what to do about it, and that is where there are differing schools of thought.

Anyhow, here’s a link to an old paper by Paul Slovic.  Here’s a link to an important paper by Sunstein and Kuran.

Sunstein proposes an “availability cascade” that causes the havoc. According to Sunstein:

“An availability cascade is a self-reinforcing process of collective belief
formation by which an expressed perception triggers a chain reaction that gives
the perception increasing plausibility through its rising availability in public
discourse. The driving mechanism involves a combination of informational and
reputational motives: Individuals endorse the perception partly by learning
from the apparent beliefs of others and partly by distorting their public responses
in the interest of maintaining social acceptance. Availability entrepreneurs–
activists who manipulate the content of public discourse-strive to trigger
availability cascades likely to advance their agendas. Their availability
campaigns may yield social benefits, but sometimes they bring harm, which
suggests a need for safeguards.”

Also, as a sort of illustration, here’s an excerpt from the wikipedia entry on the Fukushima nuclear power plant, err, disaster.


There were no casualties caused by radiation exposure, approximately 25,000 died due to the earthquake and tsunami. Predicted future cancer deaths due to accumulated radiation exposures in the population living near Fukushima are predicted to be extremely low to none.[31]

In 2013, two years after the incident, the World Health Organization indicated that the residents of the area who were evacuated were exposed to so little radiation that radiation induced health impacts are likely to be below detectable levels.[114] The health risks in the WHO assessment attributable to the Fukushima radiation release were calculated by largely applying the conservative Linear no-threshold model of radiation exposure, a model that assumes even the smallest amount of radiation exposure will cause a negative health effect.[115]

The WHO calculations using this model determined that the most at risk group, infants, who were in the most affected area, would experience an absolute increase in the risk of cancer(of all types) during their lifetime, of approximately 1% due to the accident. With the lifetime risk increase for thyroid cancer, due to the accident, for a female infant, in the most affected radiation location, being estimated to be one half of one percent[0.5%].[116][117] Cancer risks for the unborn child are considered to be similar to those in 1 year old infants.[118]

The estimated risk of cancer to people who were children and adults during the Fukushima accident, in the most affected area, was determined to be lower again when compared to the most at risk group – infants.[119] A thyroid ultrasound screening programme is currently[2013] ongoing in the entire Fukushima prefecture, this screening programme is, due to the screening effect, likely to lead to an increase in the incidence of thyroid disease due to early detection of non-symptomatic disease cases.[120] About one third of people[~30%] in industrialized nations are presently diagnosed with cancer during their lifetimes, radiation exposure can increase ones cancer risk, with the cancers that arise being indistinguishable from cancers resulting from other causes.[121]

No increase is expected in the incidence of congenital or developmental abnormalities, including cognitive impairment attributable to within the womb radiation exposure.[122] As no radiation induced inherited effects/heritable effects, nor teratogenic effects, have ever been definitely demonstrated in humans, with studies on the health of children conceived by cancer survivors who received radiotherapy, and the children of the Hibakusha, not finding a definitive increase in inherited disease or congenital abnormalities.[123] No increase in these effects are therefore expected in or around the Fukushima power plants.