It's been widely observed that in recent elections men have leaned Republican and women Democratic. A key element of that gender gap is often assumed to be a difference in attitudes to women's reproductive rights.

The perception that men and women have divergent views on abortion has persisted over time. The line popularized by Gloria Steinem that "if men could get pregnant, abortion would be a sacrament" proposes that a male-female divide over this social issue is more or less a biological given.

The polling confounds such stereotypes. The General Social Survey, which has been tracking American opinions for decades, includes the question of whether a woman should be allowed to get an abortion if she "wants it for any reason." In 17 of the 23 years that this question has been asked, men have answered "yes" to a greater extent than women. The average difference was about 1.5 percentage points — a small but consistent gender gap, if not the one people seem to expect.

So what is it about women that makes them less enthusiastic than men about abortion on demand? Again, the survey offers answers. Using a common statistical method, one can determine the effect of different variables on an outcome of interest — in this case, the odds that someone will agree or disagree with the question. This reveals that the difference between men and women is not, in fact, likely because of their gender, but because of other factors that happen to correlate with gender.

As it happens, religious attendance and biblical literalism, as well as political ideology, were all highly predictive of attitudes toward abortion. Being Hispanic was also associated with being opposed to abortion on demand (even allowing for other variables, such as religiosity).

In contrast, sex and age were usually not independently significant. Probably the mediating factor here is that, according to most surveys, women tend to be more religious than men.

While, on the whole, there isn't a major difference in the sexes' attitudes toward abortion, there is one when we separate men and women by ideology. If we look at the data since 2000 (to get a more contemporary perspective), on the liberal end of the ideological spectrum men are consistently less supportive of abortion on demand than women. On the conservative end of the spectrum, it's women who like abortion on demand less than men do.

In other words, conservative women are the most anti-abortion segment of the population, and liberal women are the most in favor of abortion rights. You might say that the more significant difference here is not between men and women, but among women.

It may be that some have generalized this difference — men being less enthusiastic about abortion on demand among liberals — to the whole population. The critic Pauline Kael's 1972 assertion that she personally knew only one person who had voted for President Richard Nixon has become a favorite illustration of the cultural isolation of liberal elites. But this may simply be the reality, that Americans are ideologically polarized and that they inhabit different and mutually exclusive social worlds.

Stereotypes flourish in ignorance. Liberal and conservative perceptions of one another can be ignorant and patronizing, because they have so little personal experience of one another. Intriguingly, research by the social psychologists Jesse Graham, Brian A. Nozek and Jonathan Haidt has shown that liberals exhibit the least accurate perception of those with opposing political views.

Our liking for black-and-white versions of reality is belied by their more shaded truths. Even among "extremely liberal" women in the General Social Survey, over 25 percent did not accept an unequivocal abortion-rights position. Meanwhile, among "extremely conservative" women, nearly one-fifth (18.2 percent) did.

So, yes, there is a large gap between these ideologically polarized positions, but we miss a substantial proportion of the electorate if all we apprehend is the stylized cartoon. Nuance goes out the window when slogans about the "war on women" or the "liberal media" dominate public discourse.

All of this has important consequences for a pluralistic society in which politics aspires to be the art of persuasion. Abortion is arguably the most polarizing social issue in the United States, and despite the data at our fingertips, many succumb to caricatures of their opponents.

A greater engagement with the facts would enable those who support abortion rights to consider why so many women do not, rather than dismissing their political opponents as motivated by misogyny or false consciousness. Equally, looking at the skewed racial demographics of abortion might encourage conservatives to reconsider the idea that reproductive justice is purely a concern of privileged white feminists.

We live in a world with a surfeit of information at our service. It is our choice whether we seek out data that reinforce our biases or choose to look at the world in a critical, rational manner, and allow reality to bend our preconceptions. In the long run, the truth will work better for us than our cherished fictions.

Razib Khan, a doctoral candidate in genomics at the University of California, Davis, writes about genetics, evolution, politics and philosophy. This article first appeared in the New York Times.