Conspiracies: 11-18-year-olds encountered online or in-person "the moon landing being a hoax and that the earth is flat."
Conspiracy. Just saying the word in conversation can make people politely edge away, looking for someone who won't corner them with wild theories about how Elvis, John F. Kennedy and Bigfoot are cryogenically frozen in an underground bunker.

Conspiracies are sometimes real. The Watergate break-in is a good example of a political conspiracy that actually happened. But thanks to the social-media algorithms that push users toward ever-more-emotional, conspiratorial content, it's probably never been easier for false conspiracy theories to spread.

All conspiracy theories must have certain necessary elements: a conspiracy between two or more people, a secret action, and a motive, said Karen Douglas, a professor of social psychology at the University of Kent in the U.K. But the ones that take off usually have something extra.