November 5, 2015 5:38 AM EST

Society tends to treat conspiracy theorists as quacks or cranks. But in his new book, Rob Brotherton argues that all of us–no matter our age, gender or education level–are actually hardwired to find patterns in unrelated events. According to several polls and estimates, half of U.S. citizens think the government is concealing facts about 9/11, nearly 40% believe that climate change might not be real, and one-third even think the government is hiding evidence of alien life. These conclusions–typically drawn from a hodgepodge of unverified photos and news reports–have only been amplified by the Internet, which helps connect people with similar mind-sets. But their genesis is biological: when we’re faced with events we cannot understand, it’s natural for our brains to create a narrative–even if it means “casting the world in terms of ‘us versus them'” to potentially dangerous ends, as Brotherton puts it. “There are more conspiracy theorists out there than you might expect,” he writes. “Chances are you know some. Chances are you are one.”

–SARAH BEGLEY

This appears in the November 16, 2015 issue of TIME.

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