Hat tip to Bryan Caplan, blogger for the Library of Economics and Liberty, for this story.
In a nutshell, even people good with number and analytical skills seem to either lose those skills, or shade the results, when faced with a conclusion that runs counter to their ideological positions.
Study respondents were asked to analyze a set of data and report the results – they were given a reasonably difficult problem that turned on their ability to draw valid causal inferences from empirical data.
All participants were given the same set of numbers. Two groups of subjects was told that the numbers represented the results of a skin-rash study, and told that the study showed sometime the treatment cured the skin rash, and sometimes it made it worse. They were asked to assess whether the treatment, overall, was curing more than it was worsening. As the study’s authors put it:
Of the skin rash group, half had the column headings for the numbers reversed – that is, half were given numbers that supported “rash better,” and half “rash worse.”
The other half of the study participants were given the exact same numbers, but this time they were told the numbers represented a city government that was trying to decide whether to pass a law banning private citizens from carrying concealed handguns in public. Government officials, subjects were told, were unsure whether the law will be more likely to decrease crime by reducing the number of people carrying weapons or increase crime by making it harder for law-abiding citizens to defend themselves from violent criminals. They were shown two sets of data purportedly from two similar cities, one with and one without a ban, and again divided into two groups, one of which had data that supported the idea that the ban reduced crime and one that did not – again not by changing the data, but merely by changing the headings on each column of data.
Basically there were four experimental conditions reflecting opposite experiment results for both the skin-rash version of the problem and the gun-ban version of the problem.
As expected, the study’s authors report, subjects who had previously rated highly in “numeracy,” which the study authors describe as “a measure of the ability and disposition to make use of quantitative information,” did better in the task than subjects who rated poorly in this skill. No surprises there. In other words, when the subject was skin rashes, they expected that the more skilled people in numeracy would get the right answer more often than the lesser-skilled people, and that’s exactly what happened.
As to the gun ban answers:
In other words, they predicted that when the subject was changed to the gun ban, the political outlook of the study participant would color his analysis.
And they were right.
What’s fascinating to me is the low-skilled people are more likely to get the mathematically correct answer than the highly-skilled people when the issue runs against their beliefs.