July 5, 2014

Once is accident, twice is coincidence

By

Back in 2010, a piece in Slate pointed out that a country’s success in the 2010 and 2006 World Cup knock-out rounds was strongly correlated with the proportion of the population infected by Toxoplasma gondii.  In 2010, Toxoplasma seroprevalence predicted all eight knockout-round wins; in 2006 it predicted seven of eight.

Toxoplasma, in case you weren’t introduced when you met it, is a single-celled organism that can live, and reproduce asexually, in pretty much any warm-blooded animal, but can only reproduce sexually in the guts of cats. That’s not the interesting part. The interesting part is that in rodents the parasite has effects on the brain, making the animal less cautious and more likely to end up in the gut of a cat. There’s some evidence Toxoplasma also has effects on human behaviour, though that’s still controversial.

Now, in 2014, I see a Tweet from Australian biologist Michael Whitehead

So, three times is enemy action?

There are good reasons to be sceptical: the football rankings haven’t changed all that much since 2006, so this isn’t really three independent tests. Also, the seroprevalence data is for the countries as a whole, not for the team members.  Still, in contrast to the predictions using Octopus vulgaris in the last World Cup, it’s not completely out of the question that there could be a real effect.

avatar

Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »