Why are 'cat ladies' so crazy? A common parasite may be to blame

Study finds that infected humans show fewer inhibitions

Toxoplasma gondii—a common parasite that infects humans who own cats or eat raw steak—may make people more social and reckless, according to a study in the European Journal of Personality.

The parasite can be hosted by humans, but it requires a cat or rodent host to survive its full life cycle. Infected rodents lose their fear of cats, which increases their chances of being eaten and transfers the parasite to the feline predators.

Meanwhile, humans can become infected when they handle cat litter, or when they consume undercooked meat or unwashed fruits and vegetables.

In the latest study, researchers tested participants for the parasite and asked them to complete personality questionnaires. They found that infected participants showed fewer inhibitions. Moreover, the longer a person was infected, the less conscientious they appeared (Rodriguez, Scientific American, 9/24; Slate, 9/24).

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