Over decades of study, University of Virginia psychologist Dennis Proffitt has shown that we are each living our own personal version of Gulliver's Travels, where the size and shape of the things we see are scaled to the size of our bodies, and our ability to interact with them. Stairs look less steep as dieters lose weight, baseballs grow bigger in the eyes of good hitters, hills look less daunting if you're standing next to a close friend, and learning happens faster when you can talk with your hands. The better we can understand what our bodies are—what they excel at, what they need, what they must avoid—Proffitt explains here, the better we can live our lives.