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Brain Parasites and the World Cup

July 7, 2010

Toxoplasma gondii was an obscure little protozoan parasite that has become prominent in recent years because of a series of scientific studies linking it to a wide variety of human behaviors. Now, Patrick House at Slate thinks he’s found one more:

What if I told you that last week I predicted all eight winners of a round of the World Cup? And that instead of rankings or divination all I did was look up how many people in each team’s home country had a tiny parasite lurking in their amygdalas? […]

If we set aside the qualifying rounds (in which teams can play to a draw) and focus on matches with a clear winner, the results are very compelling. In the knockout round of this year’s tournament, eight out of eight winners so far have been the teams whose countries had higher rates of Toxo infection. If we go back to the 2006 World Cup, seven out of eight knockout-round winners could be predicted by higher Toxo rates.

I don’t know about you, but I think this seems more plausible than the fortune-telling Octopus.

The effect of Toxo on the brains of other species – especially rodents, is pretty amazing. Toxo can infect many animals, but can only reproduce in the digestive system of cats. So, when it infects a rat for instance, it scurries up to the amygdala and mucks around with the circuitry, making the rat less fearful and less averse to the smells of cats. The rat is more likely to get eaten, and thus perpetuates the life-cycle of the parasite.

As the article describes, more recent research has linked toxoplasmosis to all kinds of human behaviors, but these reports are scant on causative links. This article seems to be riffing on this fact, self-consciously conflating correlation and causation, but it’s a great intro to this tiny, and possibly very influential parasite.

[h/t] Vaughan at Mind Hacks

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2 Comments leave one →
  1. Rachel permalink
    July 8, 2010 12:05 am

    Is the World Cup hypothesis saying that it’s a suppression of fear (or some such) in the players that makes them more likely to win? Any explanations as to why it seems to be such a general effect on humans but so specifically linked to cat-scent in rats?

    • kevbonham permalink*
      July 8, 2010 2:55 am

      Most of the scientific studies don’t actually examine the causal link between toxo and whatever trait they’re talking about, and this article is no different. The simplest answer to the general effect on humans (if there actually is a real cause-effect) vs rats is that Toxo evolved to have a specific effect on rats, and the effects on other hosts is just a by-product.

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