Wednesday, August 29, 2007

Flaws in reasoning

Both lack of basic knowledge about childbirth, and lack of understanding of statistics contribute to the belief in the myths and falsehoods of homebirth advocacy. There is another factor, as well: flaws in reasoning. A recent article on the flaws in reasoning of vaccine rejectionists gives us insight into the flaws in reasoning of various "natural" health movements.

According to A taxonomy of reasoning flaws in the anti-vaccine movement, flaws in reasoning can be divided into two types: cognitive determinants such as the difficulty in detecting and correcting biases in incomplete and unrepresentative data and motivational-social determinants such as wishful thinking and self-serving distortions of reality and exaggerated impressions of social support.

For example:
One can readily point to two of the most common misconceptions regarding vaccination used by the anti-vaccine movement in its literature. The first is that the diseases against which we vaccinate had already begun to disappear before vaccination and were going to disappear anyway regardless of the adoption of routine vaccination. The second is that vaccine-preventable diseases are no longer threats from which one must protect oneself.

These twin misconceptions are commonly said to be the product of vaccination’s own success. By reducing the risk of the disease, the occurrence rates of that disease drop dramatically. As a result, over time, new generations of parents are vaccinating their children against diseases for which the parents lack direct experience or even awareness. For example, it has been generations since the vast majority of parents in highly developed countries have experienced a case of diphtheria, infantile pertussis, or tetanus. Contemporary parents may incorrectly presume from the absence or reduced occurrence of disease that the disease is no longer circulating and hence is no longer a threat...
A very similar phenomenon occurs among homebirth advocates. Because of the success of modern obstetrics in lowering mortality and complication rates, "new generations of parents lack direct experience or even awareness" of the inherent dangers of childbirth. Because it has been generations since parents in highly developed countries have had direct experience with neonatal or maternal death, contemporary parents incorrectly assume that the risk of neonatal or maternal death has virtually disappeared. However, the inherent risks remain the same. Modern obstetrics has modified the outcome.

As the authors write in regard to vaccine rejectionism:
These beliefs represent cognitive flaws arising from the difficulty in detecting and correcting biases in incomplete and unrepresentative data. The absence of disease does not mean the virus or bacteria is eradicated or that the disease is not a threat.
Similarly, the beliefs of homebirth advocates "represent cognitive flaws arising from the difficulty in detecting and correcting biases in incomplete and unrepresentative data." Low neonatal and maternal mortality rates do not mean that childbirth is not inherently dangerous.

In addition:
Mistaken beliefs arise not just from cognitive flaws in reasoning, but also from motivational and social determinants of questionable belief...There are three major forms of this ... the first of which is wishful thinking and self-serving distortions of reality... [such as] the anti-vaccine movement’s belief in a vast conspiracy of physicians, public health officials, and the pharmaceutical industry. The argument goes that this triad will of course suppress information regarding ... adverse events ... When a public health official or a physician or an industry representative defends vaccines, the believer in this conspiracy senses a cover-up...

Other common themes of the anti-vaccine movement readily play to this motivational determinant. A Dutch survey ... described a pair of prevalent negative beliefs among parents regarding vaccines that influences their decisions to allow vaccination of their children. Parents in this survey commonly held the belief that children receive
too many vaccines at once and that the vaccinations interfere with natural development...

The belief that vaccines interfere with natural development appeals to an attractive logic that medical interventions in general, and vaccinations in particular, are artificial and therefore unnatural, unwelcome, and unnecessary. Thus, that a medical intervention and especially a combination of medical interventions might overwhelm one’s system is that much more unnatural, unwelcome, and unnecessary.
These motivational and social determinants have parallels in homebirth advocacy. Homebirth advocates constantly claim that doctors are motivated by desire for profit above safety, that there are "too many" interventions and that these interventions "interfere" with the maternal-infant bond.

The third of these motivational and social determinants of
questionable beliefs is the exaggerated impression of social support.
Homebirth advocates repeatedly claim that homebirth is a growing movement despite the opposition of doctors. The fact is, however, that homebirth with direct entry midwives is a fringe movement, accounting for less than 1% of births in the US, the rate remaining unchanged over the past 25 years.

Homebirth advocacy is based in large part on a myriad of erroneous beliefs. In attempting to correct these erroneous beliefs, it is important to understand the flaws in reasoning that lead homebirth advocates to accept claims that are patently untrue.


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