How Parasites Warp the Human Mind
What’s the Latest Development?
“The enemy within” is a salient cultural trope readily found in the most successful thriller movies, where adversaries shock audiences by appearing from supposedly safe and secure places. The concept has a strong biological correlative in the parasite, which makes its living by exploiting others’. “Take grasshoppers infected with hairworm. One day they are going about their business; the next they find themselves compelled to jump into pools of water. The parasite essentially makes grasshoppers suicidal to ensure they can reproduce.”
What’s the Big Idea?
Some biologists think humans may be more commonly infected with mind-altering parasites than is typically believed by psychologists, who examine mental defects as purely behavioral phenomena. “A 2006 study, for example, suggested that infection [with a single-celled brain parasite Toxoplasma gondii] could cause subtle but significant personality changes—potentially affecting everything from guilt, intelligence and affection.” When rats become infected with Toxoplasma gondii, they suddenly lose their fear and act irrationally. Some believe as many as a third of humans are similarly infected.
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