After so many PBJs in a lifetime, we tend to make them without thinking. Peanut butter here, jelly there. But wait. There's a method to that madness.
Instinctively, many people slop peanut butter on the bottom slice and jelly on top. Why? John Kessler, food columnist for the Atlanta Journal-Constitution, has a theory: "Since taste buds are on the tongue, then the peanut butter goes on the underside so I can taste it first."
Kessler goes back and forth, until eventually, he has no idea why he does what he does. But he's got one thing certain: Relative weights and densities are an issue. Heavier ingredients logically go at the bottom, and peanut butter is heavy, while jelly is jiggly.
So where do you stand: Jelly-side up or jelly-side down? It's a very important issue.