There’s a familiar scene that plays out every morning in offices, kitchens, and coffee shops: one person can finish a third cup before noon and still feel sluggish, while someone else gets restless halfway through a single latte. If caffeine has ever seemed to pass right through you, leaving you wondering why your coffee does so little, you’re not imagining it. A new study published in the peer-reviewed journal Brain and Behavior offers a new piece of the puzzle. Researchers discovered that caff
