Political scientists spend a good deal of time studying “motivated reasoning,” i.e. people’s tendency to interpret new information in ways that are consistent with their prior preferences and/or predispositions. This phenomenon is hugely important to American politics because a large portion of the public has strong partisan loyalties, most of which were formed early in life and persist and even intensify as people get older. Partisans come to most issues already leaning toward one view. Because of motivated reasoning, they are unlikely to be swayed by new information because their prior prejudices on the issue shape how they interpret all new facts and arguments.

Tara Haelle from Double X Science provides a nice example of motivated reasoning in the medical field. For almost all American men, their circumcision status was determined before they were autonomous enough to participate in the decision. (It is very rare to be circumcised as an adult.) Circumcision is also the subject of a modest amount of medical debate about its benefits and drawbacks. A male doctor’s personal circumcision status is surely correlated with his parents’ attitudes toward circumcision and his cultural, ethnic and religious background. But all these things are present early in life, before a male doctor can learn for himself about any research on circumcision. In other words, for almost all men (including male doctors), their interpretation of the scientific research does not affect their own circumcision status. Yet Haelle reports that,

[A] 2010 study out of Canada asked 572 family doctors, urologists, obstetricians, pediatricians and family medicine residents what they use to make their decisions regarding circumcision. Just over three quarters of them (77%) said they base their circumcision decisions on medical evidence. However, the survey also asked the men about their circumcision status and about their attitude toward circumcision: 68% of the 125 circumcised males supported circumcision, and 69% of the 106 uncircumcised males opposed circumcision. This is a fairly small group (and nearly half of the original 1009 physicians contacted didn’t answer the survey), but clearly, male doctors’ own circumcision status may influence their decisions – and recommendations – even if they believe they are basing those decisions only on the medical evidence.

As I said, one can’t tell from this whether it is actually walking around with a circumcised or uncircumcised penis or whether it is men’s early developed opinions on this topic from their cultural background that causes them to interpret medical evidence differently. But, as with most political topics, predispositions are powerful shapers of opinions even among those (doctors) who are much more informed on the topic than the average person. The same psychological phenomenon explains why, on almost all contentious political topics, more information does not push all people toward one opinion. In many cases more information actually increased preference polarization because we interpret it in light of what we already believe.

I leave you with an obligatory Mel Brooks clip:

[Cross-posted at Mischiefs of Faction]

Our ideas can save democracy... But we need your help! Donate Now!