You walk into the grocery store with a five item list: milk, eggs, chicken breast, bread, tomatoes. You leave with 15 items, including the chocolate cookies that were too tempting to pass up and the trail mix you definitely didn't need. What happened? Turns out the grocery store is set up specifically to lure you into buying more than you meant to. In fact, one expert on the science of the supermarket says that during a single trip to the grocery store, most shoppers leave with 60% more than they intended to buy.