Correlations between social dominance orientation and political attitudes reflect common genetic underpinnings

The paper, in plain language

The coherence of ideology as a genetic question

Social dominance orientation — preferring hierarchy between groups versus opposing it — correlates with a striking range of political positions. In this PNAS study led by Thomas Kleppestø and Lotte Thomsen, we asked whether that coherence is socially learned or reflects common genetic underpinnings, comparing identical and fraternal twins from the Norwegian Twin Registry on both SDO subdimensions and six political attitudes.

What the twins reveal

Both faces of SDO were heritable — 37 percent of variance for the dominance dimension, 24 for anti-egalitarianism — with no detectable influence of shared family environment. The striking figure is the source of the SDO-politics correlations: genetic correlations averaged .51 while environmental correlations averaged .08. The desire for or against group hierarchy looks like a genetically grounded behavioural syndrome that helps explain why political views cluster.

What this does not say

Heritability is a population statistic, not destiny, and this population was homogeneous: white Norwegians born 1945–1960 in one of the world's most egalitarian countries. Zero shared-environment effect within Norway does not mean environments don't matter between societies — the authors state that a cross-national twin sample would likely reveal exactly such effects. The design also cannot name mechanisms; genes act through development and experience, not around them.

Why it matters

Political psychology often treats ideology as downstream of upbringing and information; these data insist a developmental predisposition is in the mix. The follow-up study with the same twin cohort sharpened the point — right-wing authoritarianism and SDO turn out to be genetically two sides of the same coin — and my experimental work shows the same orientations respond to context, from perceived threat to group position. Predisposition and situation are not rivals; they are the two halves of the explanation.