Years of psychological research have suggested that people who are politically conservative are happier than their liberal counterparts. This so-called “ideological happiness gap” has inspired elaborate theories for why conservatives enjoy life more than liberals do.

But there may be no happiness gap at all. According to a new study published online today in Science, the tiny differences found in previous studies may have resulted from a slight tendency on the part of political conservatives to “self-enhance,” or view themselves in an unrealistically positive light.

Happiness is hot stuff in psychology. One reason is that the tool used by nearly all studies in this field—surveys asking people to self-report their happiness on numerical scales—is cheap and easy to implement. Plus, the results matter to policymakers: People’s happiness correlates with important life outcomes such as health, wealth, and even life expectancy.

So researchers have combed through demographic data in search of factors associated with lesser and greater happiness. Some of those factors seem obvious: Living in destitution in an affluent nation is strongly associated with unhappiness. Others factors are more puzzling.

The purported happiness gap between liberals and conservatives has attracted considerable media attention. Conservative Americans, Canadians, and Europeans all seem to be happier than their liberal compatriots. Those results are generally based on surveys that ask respondents, for example, to rate on a scale of 1 to 7 how well a statement applies to them. Examples include: “The conditions of my life are excellent. If I could live my life over, I would change almost nothing. I am satisfied with my life.”

Psychologists have proposed myriad hypotheses to explain the gap. Conservatives could be more content with the status quo, according to one argument, or liberals may be prone to anxious self-reflection.

But there could be a simpler explanation. Rather than truly being happier than liberals, conservatives may be more prone to put a positive spin on their lives. To test that possibility, Sean Wojcik, a psychologist at the University of California, Irvine, and colleagues devised a study that aimed to assess not just happiness but also people’s tendency to self-enhance.

To get enough subjects to nail down this tiny statistical effect, the researchers used a website—YourMorals.org—open to people of any political persuasion. A total of 1433 people filled out and submitted not only the standard happiness questionnaire but also a series of questions called the Balanced Inventory of Desirable Responding. That instrument measures “the tendency to engage in self-deceptive enhancement.” For example, people who highly agree with statements such as “I am fully in control of my own fate,” or, “I never regret my decisions,” are deemed to be self-enhancing.

Sure enough, the new study finds that people’s political conservatism was slightly correlated with their tendency to self-enhance. That effect is tiny, but still big enough to explain away the happiness gap, according to the researchers.

The researchers also used two other measures to gauge the happiness of liberals and conservatives, neither of which indicated greater conservative happiness. First they used language-processing software to measure the positive and negative emotions of 47,257 tweets. People who follow the Republican Party on Twitter were somewhat more likely to use emotionally negative words than were followers of the Democratic Party. Second, the researchers hired an expert in facial expression analysis to examine the photos of current members of Congress. Democratic members were scored as having slightly more genuine smiles than Republicans.

“Conservatives don't seem to be any happier than liberals,” concludes Dan Kahan, a psychologist at Yale University who was not involved in the study but has waded through battles about the minds of liberals versus conservatives himself. The study, he says, “raises questions about the validity of happiness self-report measures generally.” Kahan wonders if happiness surveys “are truly measuring what we care about.”

For his part, Wojcik is optimistic about the future of happiness research. But he agrees that “this research quickly raises philosophical questions about what it means to be happy at all.”