Original article: Motivated Numeracy and Enlightened Self-Government.
Easy-to-read summary of the results: Science Confirms: Politics Wrecks Your Ability to Do Math.
Easier-to-read summary of the summary: A group including both liberals and conservatives were first tested for numeracy, then given either fictional stats on the efficacy of a rash treatment (how many people get better/worse, with/without the treatment) or quantitatively identical fictional stats on gun regulation and crime (in how many cities crime went up/down, with/without gun control laws). They had to say whether, according to the stats, the treatment was effective or whether the laws reduced crime. (In half of the cases the answer was yes, in half no). For the rash problem, numerate people did better in giving the right answer, irrespectively of their politics. For the gun control problem, numerate people (of both political sides) were much better at giving the right answer when it agreed with their political beliefs; when the conclusion implied by the stats disagreed with their political beliefs, they did no better than innumerate people.