Twenty percent of Americans still doubt that President Barack Obama was born in the United States, years after the White House released his long-form birth certificate showing he was born in Hawaii. In 2012, 36 percent of Americans said that senior federal officials probably or certainly knew in advance about the terrorist attacks of Sept. 11, 2001 -- despite the fact that as best anyone can tell, the Bush administration received no specific warnings about 9/11 before it happened.

A newly published study sheds some light on why and how people believe conspiracy theories, even when all the evidence indicates they’re not true. It turns out that conservatives who believe conservative-leaning conspiracy theories are more politically knowledgeable than conservatives who don’t. However, among liberals, there doesn't seem to be concrete evidence of a correlation one way or the other between how well-informed someone is and how likely they are to believe conspiracy theories.

The background

Authors Joanne Miller, Kyle Saunders and Christina Farhart noticed that previous psychology studies had looked at how personality traits affect whether people believe conspiracy theories. But, they realized, no one had really looked into how a person's political traits -- like their ideological views, how much they generally trust authority and other people and their general knowledge about politics -- might be related to their readiness to accept conspiracy theories.

The researchers hypothesized that yes, of course ideological views matter -- they guessed liberals would be more likely to believe conspiracy theories that cast conservatives in a negative light, and conservatives would be more likely to believe theories that make liberals look bad. They also speculated that people who know more about politics are probably more likely to believe conspiracy theories, because they can use their knowledge to rationalize how the theory might be true.

The setup

The 2012 American National Election Study asked a representative sample of Americans about four different things that could be considered conspiracy theories -- two that were chosen to appeal to liberals, and two chosen to appeal to conservatives. Respondents were asked to weigh in on the following questions: whether the government knew about the 9/11 attacks before they happened; whether the government allowed the levees to be breached and the Hurricane Katrina flooding to become as devastating as it was; whether Obama was born in the United States; and whether the Affordable Care Act would have “death panels” to determine care for older patients.

The researchers also conducted their own study using Amazon Mechanical Turk, asking a non-representative sample of Americans about those four conspiracy theories, plus an additional four. Again, the four new questions included two believed to appeal to conservatives, and two thought to appeal to liberals: whether “global warming” is a hoax; whether Saddam Hussein was involved in 9/11; whether Republicans “stole” the 2004 presidential election; and whether the government lied about weapons of mass destruction in Iraq. Both studies showed very similar results.

The findings

Three characteristics come together to motivate belief in conspiracy theories. First: The conspiracy theory has to line up with what the person already believes. Conservatives aren’t going to jump on a conspiracy theory that makes other conservatives look bad, and liberals aren’t going to believe a theory that undermines liberal causes.

Second: Whether we're talking about liberals or conservatives, the people who are likely to believe conspiracy theories are less trusting of authority and other people than the people who dismiss the theories. That's about what you'd expect. A deep distrust of society seems to be correlated with a willingness to believe that what’s being reported isn’t the truth, or a tendency to believe that the government is always hiding something.

Third: People who believe in conspiracy theories are typically more knowledgeable about politics than the average American -- at least, that's true of conservative conspiracy theorists. Among liberals, there didn't seem to be any strong connection between how well-informed a person was about politics and how likely that person was to subscribe to conspiracy theories. The researchers weren’t expecting to find such a clear difference between ideologies.

The authors also didn’t expect to find that in general, conservatives are more likely to buy into conspiracy theories than liberals. But this is in fact what they concluded. Keep in mind, though, that the surveys were conducted in 2012 and 2013, and it's possible that the researchers might have found different results in, say, 2004 or 2005. It could be that conservatives were simply more motivated to believe conspiracy theories in 2012 and 2013 than liberals were -- since Obama, a Democrat, was in the White House at the time.

Another explanation could be that the specific theories the researchers asked about -- death panels, Hurricane Katrina, Obama's birthplace and so on -- were more polarizing for conservatives than for liberals. Out of the four theories chosen to appeal to conservatives, three were based on the Obama administration, which was in power at the time. By contrast, the items chosen to appeal to liberals had to do with older events and a presidential administration that had been out of power for a few years.

The takeaway

Don’t assume that people who believe in conspiracy theories are uninformed and simply need more information about a situation. Conservative conspiracy theorists are likely to be well-informed about politics, and liberal conspiracy theorists aren't necessarily poorly informed. Having said that -- climate change is real, Bush didn't do 9/11 and you should still vaccinate your kids.

Want more information on this study? Email natalie.jackson@huffingtonpost.com or the study authors.