Belief Polarization

Evidence that fits with our beliefs is quickly waved through at the mental border control. Counter evidence, on the other hand, must submit to close interrogation and even then will probably not be allowed in. As a result, people can wind up holding their beliefs even more strongly after seeing counterevidence. It’s as if we think, “Well, if that’s the best that the other side can come up with then I must really be right.” This phenomenon is called belief polarization.

In 1956, a physician named Alice Stewart published a preliminary report of a vast survey of children who had dies of cancer. The results from her work were clear. Just one x-ray of an unborn baby doubled the risk of childhood cancer. A mere 24 years later (1980), the major U.S.  medical associations officially recommended that zapping pregnant women with ionizing radiation no longer be a routine part of prenatal care. Britain took a little longer still.

Why did it take so long? Unfortunately, a later study run by a different researcher failed to find a link between prenatal x-rays and childhood cancer. Even though the design of this study has substantial defects- as the researcher himself later admitted- the medical community gleefully acclaimed it as proof that they were right and Alice Stewart was wrong. The similarity of this story to the experimental demonstrations of biased evaluation of evidence is, well, dramatic.

By 1977, there was a huge amount of research showing the link between prenatal x-rays and childhood cancer. Yet the US NAtional Council on Radiation Protection remained stubbornly concvivned that x-rays were harmless. They suggested an alternative explanation:  It wasn’t the radiation that caused cancer. No, the relationship between x-rays and cancer was due to the supernatural prophetic diagnostic powers of the obstetricians. The obstetricians were x-raying babies they somehow knew would get cancer.” (Fine)


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