America the Toxoplasmic

We at Phronesisaical have previously discussed my favorite parasite, the toxoplasma gondii. We have operated under the assumption, however, that toxoplasma does wacky things to rats and mosquitoes, and we neglected human beings in the discussion. I was wrong and am now prepared to welcome toxoplasma to the human body. And yet, I feel rather uncertain and guilty.

Approximately one-quarter of Americans host a parasite that has been shown to affect personality in both rodents and humans. According to a recent study, this single-celled organism may be able to shape entire cultures.

In a paper published in the online edition of Proceedings of the Royal Society, United States Geological Survey researcher Kevin Lafferty argues that a significant factor in why some countries exhibit higher levels of neuroticism than others may be the prevalence of the parasite Toxoplasma gondii. The study also indicates that it may influence a society's preference for strict laws, an expression of uncertainty avoidance, and its valuation of 'masculine' priorities such as competitiveness and financial success over 'feminine' values like relationship-building.

"Toxoplasma appears to explain 30% of the variation in neuroticism among countries, 15% of the uncertainty avoidance among Western nations and 30% of the sex role differences among Western nations," Lafferty said via e-mail...

Lafferty based his analysis on earlier research by Jaroslav Flegr, a parasitologist at Prague's Charles University, which showed that in humans, Toxoplasma infection correlates highly with certain personality traits: Infected men tended to have lower levels of intelligence, superego strength and novelty-seeking, while infected women exhibited higher levels of intelligence, superego strength and warmth. Infected people of both sexes tend to be susceptible to feelings of guilt.