Left Behinds

The anti-andrewsullivan.com. Or, the Robin Hood (Maid Marian?) of bright pink Blogger blogs.

Tuesday, August 22, 2006

Awesome science,part IX (?): hypermasculinity is a sickness

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.
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.

Make your own jokes about, you know, people who might start unnecessary wars to sort out their daddy issues.

Seed article. Original journal abstract.


In response to Solomon's and my girlfriend's sputtering questions (his in the comments below, hers over the phone), I did a little internet research and now bring you the following information. First, what is Toxoplasma?

Toxoplasmosis results from infection by the parasite Toxoplasma gondii. Most domestic cats are or will be infected during their lives. The parasite reproduces within cats but is passed through their feces to intermediate hosts, particularly rats and humans. The parasites spread through the body, lodging primarily within the muscle and brain tissue, where they will remain throughout the host's life. When a cat eats an infected rat or bird or uncooked meat, the cat acquires the parasite, and the cycle continues. The rate of infection in humans ranges from 20%-80%, varying by country with France at the high end. Billions of people thus have parasites in their brains.
Toxoplasma gondii has been shown to affect the behavior of infected rats, who exhibit slower reaction times, reduced fear response, and a fatal attraction to cat scent. This last was demonstrated in a convincing paper [link via Future Pundit] by Berdoy, Webster, and Macdonald. They used rat, rabbit, and neutral scents as control for the cat scent and watched rats' foraging behavior over hundreds of hours under laboratory conditions. (I might have done the statistical analysis a bit differently, but their model and analysis are commonly used for this kind of data and should work well.) Berdoy et al. found that infected rats showed a stable preference for cat smells whereas uninfected [r]ats strongly avoided them.

CDC factsheet here. The quote above is from a mostly negative appraisal of Jaroslav Flegr's work by Carnegie Mellon University Professor of Statistics Christopher Genovese. Jaroslav Flegr is a Czech scientist who has investigated the behavior-altering properties of Toxoplasma in humans, using a common, 16-dimension survey to assess personality in infected and uninfected people. See some of his papers here and here. I got those links from Genovese, who links to many more. From the second link, here's a representative finding.

Two hundred and twenty-four men and one hundred and seventy women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma infected and uninfected subjects were observed (p < 0.01). For men the factors G (low superego strength [disregards rules, expedient], p<0.02), and possibly L (protension [suspecting, jealous, dogmatic]), O (guilt proneness), and A (sizothymia [reserved, detached, critical) prevailed in infected subjects. For women the prevailing factors were A (affectothymia [warmhearted, outgoing, easygoing], p<0.01), and possibly L (alaxia [trusting, accepting conditions, tolerant]) and N (shrewdness). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (p<0.02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.

Flegr has also found that Toxoplasma infection slows reaction times, which he suggests may lead to increased risk of traffic accidents (both links PDFs).

Most amusing is this characterization FuturePundit lifts from a London Times article no longer available online for free.

[W]omen infected with toxoplasma spent more money on clothes and were consistently rated as more attractive. “We found they were more easy-going, more warm-hearted, had more friends and cared more about how they looked,” he said. “However, they were also less trustworthy and had more relationships with men.”

By contrast, the infected men appeared to suffer from the “alley cat” effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. “They tended to dislike following rules,” Flegr said.

What Lafferty seems to have done is take preexisting country-level data on rates of Toxoplasma infection and personality scores in that same survey Flegr used, and analyzed them to see how they match up. "Neuroticism" appears to be a technical description related to some of the trait dimensions in the personality survey.


  • At 9:26 PM, Blogger Solomon Grundy said…

    You are fucking kidding me.

    I'm going to read those articles now.

    Which societies/regions are infected? Is there a cure???

  • At 9:29 PM, Blogger Solomon Grundy said…

    including the unusually neurotic nations of Hungary and China and the notably easygoing Turkey.

    oh my god how do you get rid of it???

    and how exactly did they clearly define and measure "neuroticism"?

  • At 9:32 PM, Blogger Solomon Grundy said…

    since when is turkey easygoing? haven't they been at war with / militarily oppressed greece and the kurds for like a millenium?

    though the one turk i ever dated was incredibly easygoing. such a cutie...

  • At 10:28 PM, Blogger Antid Oto said…

    See long update.

  • At 10:38 PM, Blogger Solomon Grundy said…

    ps i wasn't aware of it as i was writing, but my replies pretty clearly indicate that i have been infected with the virus

  • At 10:40 PM, Blogger Solomon Grundy said…

    the “alley cat” effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. “They tended to dislike following rules,” Flegr said.

    it's like he's singing my life with his words

  • At 10:49 PM, Blogger Antid Oto said…

    One minor point: it's actually a single-celled parasite, not a virus.

  • At 10:42 AM, Blogger Solomon Grundy said…

    Ah, which is easier to deal with, right? We can shoot Bush with some doxycycline and he'll lose that whole angry monkey thing...

  • At 1:03 PM, Blogger Antid Oto said…

    Not necessarily. It's not a bacterial infection. See here for example:

    Toxoplasma infections are especially difficult to treat because they recur. The disease operates in two stages, a proliferative stage and a latent stage. During the proliferative stage the infection can be treated, although there are many problems with available medicines, but the illness then progresses to a latent stage, where the cysts form that hold the parasites in a less active state. These cysts are untreatable as scientists can’t get medication inside the cyst. The cysts eventually rupture and release proliferating parasites, which can cause a recurrence of the illness if the immune system is weakened and in those with eye disease. Such recurrences can cause severe damage to the eye and nervous system.

    The medications they do use currently to treat active Toxoplasmosis infections seem to be kind of toxic, although frankly what do I know. I don't think they're as benign as doxycycline.

  • At 12:38 AM, Blogger Solomon Grundy said…

    Great. Like I didn't have enough to be a hypochondriac about. Next time I complain about how "my Toxoplasma cyst is feeling achey," you can just go ahead and blame yourself.

    Oh also, did you hear that fatness is caused by alien parasites in our large intestines?


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