It’s hard to look at climate change deniers as being anything other than willfully ignorant. The numbers are right there: As surely as greenhouse gas emissions are rising, so are global temperatures. To discount all that is to choose to be stupid.

But according to Yale law professor Dan Kahan, it’s easier than we think for reasonable people to trick themselves into reaching unreasonable conclusions. Kahan and his team found that, when it comes to controversial issues, people’s ability to do math is impacted by their political beliefs.

The study pitted over 1,000 participants against a tricky math problem. In one version, the question involved a clinical trial of a skin cream that sometimes helped heal rashes, and sometimes made them worse. Using a set of raw data, the participants had to do some complex calculations to decide whether or not the cream was effective. It was difficult enough that 59 percent of the participants got the problem wrong.

Then things got interesting. The researchers took the same exact question and reframed it. Now, instead of being about skin cream, the numbers in question referred to the effectiveness of concealed carry laws. And this time, whether or not people got the question right […]