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Some skills training is well supported by empirical evidence. People who take piano lessons observably improve their ability to play piano, on average, even though some don't, even though they often regress after they stop, and even though some people improve without taking lessons. Similar remarks apply to golf lessons, JavaScript bootcamps, calculus courses, and plumbing apprenticeships.

Most kinds of therapy, by contrast, are closer in their empirically measured effectiveness to studying geography through astral travel or studying history through past-life regressions. CBT and exposure therapy are among the few exceptions.