The Found Art of Thank-You Notes

When Jimmy Fallon sits down to write his weekly thank-you notes on “The Tonight Show,” he is both ribbing and breathing life into a custom many felt was headed the way of the dodo. “Thank you, cotton candy,” Mr. Fallon scribbles on a correspondence card, “for making my grandmother’s hair look delicious.” Thank you, “bowling, for giving me an excuse to drink with somebody else’s shoes on.”

“Thank you, Chris Christie,” he writes, “for going back for seconds.”

Mr. Fallon’s routine is a hoot, of course, a joke that points up the truth that the boring stuff your parents made you do never actually goes out of fashion and that also inadvertently supports recent scientific findings linking gratitude to increased optimism, stress reduction and a better night’s sleep. Few who sit down to write a bread-and-butter note are likely to be aware that by doing so they are not only on trend but also on their way to becoming happier and more sociable people. Apparently, what Emily Post termed good manners (science prefers “gratitude intervention”) has all kinds of unexpected benefits. And as it happens, the handwritten gratitude intervention seems to be experiencing a moment of vogue.