• In both the U.S. and Denmark intelligence failed to predict standard party choice.
• This was due to opposing effects of intelligence on economic and social ideology.
•Denmark’s multi-party system allows non-standard representations of party choice.
•In Denmark, significant systematic intelligence differences observed between parties.

Intelligence is rarely studied as a predictor of vote choice, and at first glance our data supports this neglect: In samples from the U.S. and Denmark (Ns = 1419 and 953), intelligence does not predict the standard operationalization of vote choice in which parties are placed on a single left-vs-right dimension. (Standardized coefficients predicting right-wing vote choice were 0.05 and −0.03, respectively.)

However, this apparent non-effect in fact reflects approximately equal and opposite effects of intelligence on vote choice as transmitted through social and economic ideology. In both countries, higher ability predicts left-wing social and right-wing economic views.

The impact of intelligence on vote choice is thus most visible in true multi-party systems like Denmark, in which parties do not simply pair similar levels of social and economic conservatism, but instead provide diverse combinations of social and economic ideology.

Comparing the parties closest to representing authoritarian egalitarianism (social-right plus economic-left) and libertarianism (social-left plus economic-right), we observed a 0.9 SD intelligence gap.