Are conservatives more likely to stick to a diet than liberals? The answer might be yes.
In a paper published Monday in Proceedings of the National Academy of Sciences, researchers say there is a link between political ideology and the ability to exert self-control.
In a series of three studies with more than 300 participants, the authors found that people who identify as conservative perform better on tests of self-control than those who identify as liberal regardless of race, socioeconomic status and gender.
They also report that participants' performance on the tests was influenced by how much they believed in the idea of free will, which the researchers define as the belief that a person is largely responsible for his or her own outcomes.
For example, conservatives who are more likely to embrace the idea of free will overwhelmingly agreed with statements like "Strength of mind can always overcome the body's desires" and "People can overcome any obstacles if they truly want to."
"Conservatives tend to believe they had a greater control over their outcomes, and that was predicting how they did on the test," said Joshua Clarkson, a consumer psychologist at the University of Cincinnati and the lead author of the paper.
To screen for self-control, Clarkson and his colleagues relied on the Stroop test that asks participants to look at a list of color words such as "red" or "blue" that are printed in mismatching color fonts. (Picture the word "orange" printed in green letters.) Volunteers were asked to read the words, ignoring the color of the font, which can be challenging.
"If you see the word 'red' in blue type your mind wants to say 'blue' right away, but you have to suppress that," Clarkson said. "That's why it is a strong indicator of self regulation."
The authors found that while both liberals and conservatives were able to accurately read the words, conservatives generally were able to do it faster than liberals.
There was, however, one instance when liberals outperformed conservatives on the test.
During one of the experiments, participants were given a fake research article that suggested believing in free will is an obstacle to achieving personal goals. The volunteers were asked to read it before taking the test.
The fake article argued that people who take full responsibility for their outcomes can suffer from more frustration, anxiety and guilt compared with people who put less faith in free will. It concluded that those negative feelings are counter-productive to self-control performance.
After reading the article, conservatives did worse on the test and liberals did better.
Clarkson said one possible explanation for this result is that the article put doubt in the minds of the conservatives.
"For conservatives, their default when they experience struggle is to dig deep," he said. "But if all of a sudden you have a struggle, and then you think you are getting in your own way, you may start second-guessing yourself."
And that second-guessing takes up brain power that might otherwise be applied to the task at hand, he said.
Liberals, on the other hand, may have performed better on the test after reading that embracing free will is bad, because it allows them to better focus on the test, he said.
"You tell liberals that belief in free will is bad and they are like, 'Good, I don't have it anyway,' " he said.
The researchers ran a similar test with a different fake article that argued belief in free will is useful for self-control and can lead to better and increased effort. After reading that article, conservatives outperformed liberals once again on the test.
Clarkson said that the research team, which includes members from Saint Louis University, Indiana University and the University of North Florida, come from different places on the political spectrum.
"We've got liberals, conservatives, libertarians and people who aren't sure," he said. "We are not saying that conservatives are better in general. We just think this study gives us a novel way to think about self-control."