The author of the study is Kevin Lafferty, a biologist at the University of California at Santa Barbara. Lafferty made three straightforward observations.Lafferty's hypothesis predicted that the national cultures/characters of countries with high rates of Toxoplasma infection would have higher rates of characteristics such as neuroticism, uncertainty avoidance and "masculine" sex roles:
- Toxoplasma infection rates vary from country to country. South Korea has prevalance rate of only 4.3%, for example, while Brazil's rate is 66.9%. These rates are determined by many factors, from the eating habits in a country (steak tartar, anyone?) to its climate (Toxoplasma oocysts survive longer in warm tropical soil).
- Psychologists have measured some of the personality traits influenced by Toxoplasma in these countries. People with Toxoplasma tend to be more self-doubting and insecure, among other things. Among the differences in men, Toxoplasma is associated with less interest in seeking novelty. Toxoplasma-infected women are more open-hearted.
- A nation's culture can be described, at least in part, as the aggregation of its members' personalities.
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.
So--has Lafferty discovered why the French are neurotic (Toxo: 45%) and Australians are not (28%)? As he admits, this is just a first pass.
Lafferty also notes that many other factors shape a nation's culture--which actually raises another interesting question: what about other parasites? Do viruses, intestinal worms, and other pathogens that can linger in the body for decades have their own influence on human personality? How much is the national spirit the spirit of a nation's parasites?
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