Daniel Engber in Slate: What's the Deal With "Cat Ladies"? - Are there "cat gentlemen," too?
Engber considers the prevalence of "cat hoarders" (who are usually women) without considering the most obvious -- at least to my intuition -- cause: toxoplasmosis infection.
Toxoplasmosis is a disease caused by a protozoa parasite whose lifecycle can cross cats and other animals, but only sexually reproduces inside cats. There's strong evidence that toxo-infected rats and mice have their behavior affected by the parasite in ways that make them more likely to be captured by cats: their reactions are slower, they're less fearful of new situations, and they even seem to be drawn to the smell of cat urine (whereas non-infected cat prey will wisely avoid all cat smells).
There's also evidence toxo-infection can have analogous effects on infected humans -- subtly altering their personality and making them more prone to, among other things, dangerous accidents. This writeup (which I believe is an uncreditted reprint of a New Scientist article) is a good summary. Let's compare Engber's observations about "cat ladies" with the observed effects of toxoplasmosis on mammals:
The cats aren't just a symptom of 'cat hoarding'... they're also an original cause.«»
One can even invoke evolution to explain such effects. Toxoplasmosis infected female humans have an increased probability of becoming cat horders. This increases the survival probability of infected cats. Cats living in such conditions have an increased probability of getting infected. This increases the the survival probability of the parasite. Such a positive feedback loop can drive evolution (co-evolution).
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