As we kick off a new season of Proof, we dig into the psychology and science behind our fascination with food shapes. From popcorn to square watermelons, you'll learn that there's a reason behind the choices we make when it comes to what our food looks like. Eliza Rothstein reports.

Try making your own sweet and salty popcorn at home, with our recipe for Spicy Caramel Popcorn.

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