The perception that personalities differ greatly across the world is widespread; name a country and people can probably give you a stereotype of its typical inhabitant. Although much of this is simple prejudice, real differences in averages on certain personality scores have been measured. A paper in Nature Human Behavior suggests that this variation is a response to local climatic conditions, and speculates about the implications of global warming.
“Humans constantly experience and react to ambient temperature,” wrote the team led by Columbia University and Peking University in China. “Because temperature varies markedly across the world, it is conceivable that temperature shapes the fundamental dimensions of personality by affecting the habitual behaviors that underlie personality traits.”
The idea is not new. Northern latitude intellectuals wedded to their culture's supposed superiority to other nations, but seeking to move away from racism, have sometimes attributed various desirable traits to colder environments. For example, rainy conditions are said to encourage introspection and intellectual pursuits, compared to the temptations of sunnier climes.
Few, however, have bothered to test the idea, particularly on the scale the researchers have done, using 5,587 Chinese university students' responses to personality tests. Respondents were assessed on what are sometimes called the Big Five personality traits: agreeableness, conscientiousness, emotional stability, extroversion, and openness to experience. The authors hypothesized that growing up in a nicer climate would encourage people to explore the outside world, promoting extroversion and openness to new experiences. Moreover, they thought, getting out and meeting more people would also encourage agreeableness, while having a consistently more enjoyable climate should encourage emotional stability.
The results matched these expectations, with milder temperatures being associated with higher scores on each of the Big Five personality measures.
The study was then repeated in the United States, but extended to the ZIP-code level and a sample size of 1.6 million. This time it used the location where people had spent most of their childhood, while the Chinese study used only participants who had spent their entire childhood in their parent's home region.
The American sample revealed no significant relationship for a variety of climatic conditions, such as humidity or wind speed. Nevertheless, just as in China, average temperature mattered. The closer a city's average daily maximum temperature was to 22 ºC (72 ºF), the higher its inhabitants scored on all five measures. The size of the effect was much smaller in the US than in China, however, barely reaching statistical significance on some measures.
The studies tested other variables, some of which also proved significant. Most notably, cities more prone to flu outbreaks had residents with lower scores on all Big Five factors, suggesting a universal influenza vaccine could change personalities as much as global warming.