Can personality polygenic scores travel across populations?

Genes are one reason people differ in personality. Twin and family studies put the heritability of broad personality traits at roughly 40 percent, and molecular studies now identify many of the common variants involved. If genetic differences help make one person more outgoing, anxious or conscientious than another, an obvious next question follows: do they also contribute to average personality differences between ethnic groups and national populations?

National stereotypes certainly assume that such differences exist. Americans are said to be outgoing and brash, the British reserved, Germans orderly, Italians expressive and Finns quiet. These portraits might contain observation, caricature or both. In a famous 49-culture study, national-character stereotypes were internally consistent but generally failed to match the average personality scores reported by the people who lived in those countries.

The measurement problem runs deeper than inaccurate stereotypes. When people answer a statement such as ‘I am outgoing’, they rarely compare themselves with humanity as a whole. They compare themselves with friends, colleagues and other people around them. An Italian and a Finn with the same observable behaviour may therefore choose different answers because each is judging against a different local norm. Psychologists call this the frame-of-reference, or reference-group, effect. It can compress, erase or even reverse apparent differences between countries in self-report data.

Until recently, the genetic side of the comparison was also too weak for a serious test. That changed with the new Nature personality GWAS. It is large enough to identify 1,260 lead variants across the Big Five, making it possible to ask whether population differences in those variants predict population differences in reported personality. I tested that question globally, in Europe, and in a broader whole-genome frequency panel.

Explore the results yourself: Open the interactive Extraversion map to switch between the aggregate-frequency and individual-level genotype maps, zoom around the world, and compare genetic and self-reported scores.

Only one trait survived every test. Which countries came out on top, and did the stereotypes get it right? Upgrade to see the full global and European results.