The deepening gender gap in American voting, with men favoring the Republican Party and women favoring the Democrats, is well known, if not well understood. So what explains the presence of millions of men in the Democratic Party and millions of women in the Republican Party? What distinguishes these two constituencies, whose partisanship runs against the grain?

An additional variable predicting Republican partisanship is social dominance orientation, or having a preference for group-based hierarchy and inequality. Arnold Ho is a professor of psychology at the University of Michigan and the lead author of the 2015 paper “The Nature of Social Dominance Orientation: Theorizing and Measuring Preferences for Intergroup Inequality Using the New SDO7 Scale.” He wrote that he and his colleagues found “consistent gender differences across all samples, with men having higher levels of social dominance orientation than women” and that there are “moderate to strong correlations between SDO and political conservatism across all samples, such that greater conservatism is associated with higher levels of SDO.”

Ho measured conservatism on the basis of political affiliation — Democratic liberal, Republican conservative and self-identification as a social and economic liberal or conservative.

Read the full article at The New York Times.