You’ve heard of the placebo effect, how people can get better from a fake treatment, but did you know there’s also a nocebo effect? It’s just as strong: “More than two-thirds of 34 college students developed headaches when told that a non-existent electrical current passing through their heads could produce a headache.” (From Skeptic’s Dictionary.) Alexis Madrigal did a very readable feature about it for the Atlantic called The Dark Side of the Placebo Effect: When Intense Belief Kills. I found out about it from Olivia Fox Cabane’s new book The Charisma Myth. What you don’t know can hurt you.