On The Gist, Maria Konnikova of the New Yorker explains how our birth order influences personality and intelligence for a game we call "Is That Bulls--t?" Does IQ go down after the firstborn? Her new book, The Confidence Game, is now available for preorder. For the Spiel, Mike's takeaways form the CNN Republican presidential debate last night. Read more of Slate's coverage of the GOP primary. Today's sponsors: Stamps.com, where you can buy and print official U.S. postage right from your desk using your own computer and printer. Use the promo code THEGIST to get a no-risk trial and a $110 bonus offer. Shari's Berries. Fresh berries dipped in chocolate, starting at just $19.99 are a great last-minute gift, and double your berries for just $10. Visit berries.com, click on the microphone, and use the 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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