On The Gist, a gift for your New Year's resolutions. Maria Konnikova of the New Yorker tells us what research has been done into various popular exercise methods. She's the author of The Confidence Game, now available for preorder. For the Spiel, the biggest news story in the world right now. Today's sponsor: Casper, the online retailer of premium mattresses for a fraction of the price. Get $50 toward any mattress purchase by visiting casper.com/gist and using the promo code GIST. Join Slate Plus! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today at slate.com/gistplus.

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