Friday, March 30, 2007

Affective feeling and the perception of risk

It is clear that people base their assessments of risk on more that the actual data about specific risks. Trust, Emotion, Sex, Politics, and Science: Surveying the Risk-Assessment Battlefield by Paul Slovic explores these factors that modulate our perception of risk.

On page 6 of the article, Slovic discusses the ways in which our emotions change our perception of risk. He discusses the impact of affect, a term he uses to describe whether a person has a positive or negative view of the subject under discussion. According to Slovic:
Support for the conception of affect as an orienting mechanism comes from a study by Alhakami and Slovic. They observed that, whereas the risks and benefits to society from various activities and technologies ... tend to be positively associated in the world, they are inversely correlated in people’s minds [My comment: In other words, although activities that have high benefits have high risks, people tend to think that activities that they feel are highly beneficial have low risks and vice versa.]. Alhakami and Slovic found that this inverse relationship was linked to people’s reliance on general affective evaluations when making risk/ benefit judgments. When the affective evaluation was favorable (as with automobiles, for example), the activity or technology being judged was seen as having high benefit and low risk; when the evaluation was unfavorable (e.g., as with pesticides), risks tended to be seen as high and benefits as low. It thus appears that the affective response is primary, and the risk and benefit judgments are derived (at least partly) from it.
If Slovic is correct, it would go a long way toward explaining the disparity between homebirth advocates' perception of risk and the very different actual risks. So, for example, homebirth advocates strongly value homebirth. They think that it has high benefits, and therefore they assume that it has low risks. On the other hand, homebirth advocates are contemptuous of the use of pain relief in labor, and therefore grossly overestimate the risks of epidurals.

The reality is that homebirth has an excess neonatal mortality rate in the range of 1-2/1000 and epidural has an excess neonatal mortality rate of 0. Homebirth has an unknown risk of maternal mortality (not enough homebirths have been evaluated to reach a conclusion) and epidurals have an excess maternal mortality rate in the range of 7/1,000,000. So from a purely factual point of view, homebirth carries greater risk of death than epidurals.

Homebirth advocacy websites and publications are replete with condemnation for the "risks" of epidurals (including entirely fabricated risks like impairment of the mother-infant bond), yet they gloss over, fail to mention or are entirely dishonest about the risks of homebirth.


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