As the worm turns

Carl Zimmer reviews an upcoming paper titled: "Can the common brain parasite, Toxoplasma gondii, influence human culture?"

So [Kevin] Lafferty wondered, is there a relationship between a country's prevalence of Toxoplasma and its culture?

The answer, he argues, is yes. He selected a few key features of human personality that Toxoplasma appears to influence, and which have been measured on a national scale--such as neuroticism, uncertainty avoidance, and "masculine" sex roles. Lafferty predicted that in countries with higher Toxoplasma rates, these features would all be stronger. He gathered data from studies on 39 countries in from all five continents. He corrected for various factors, for example including per capita gross domestic product as a variable. He found a signficiant correlation between high levels of the parasite and high levels of neuroticism. There was a positive but weak correlation between Toxoplasma and levels of uncertainty avoidances and masculine sex roles. However, if he excluded the non-Western countries of China, South Korea, Japan, Turkey, and Indonesia, the correlations of both personality measurements with Toxoplasma got much stronger.