The question behind the map
Does climate leave a mark on personality? The idea is intuitively appealing. Long winters might reward sociability and cooperation, or perhaps encourage reserve. Warm climates might make outdoor contact easier, while harsh seasons could alter the costs and benefits of social behaviour. Europe offers a tempting test case because temperature, rainfall and geography vary substantially across a relatively compact continent.
But intuition is cheap, and geographic stories are easy to tell after seeing a map. So I re-analysed the question using population differences in a polygenic score for Extraversion. Do the scores follow an east-west or a north-south pattern? Does five millennia of winter temperature predict them better than summer temperature or rainfall? And does the answer survive when the SNP panel changes?