Fall is here, and that means an explosion of pumpkin spice-flavored products. Starbucks sells $500 million worth of pumpkin spice lattes every year—and at other retailers, pumpkin spice goes way beyond hot beverages. There are pumpkin spice cookies, candles, and even cleansers. The number of pumpkin spice products has increased more than 80 percent since 2011. But what is pumpkin spice?

The mix may vary in different products, but the recipe is intended to evoke the memory of pumpkin pie. Pumpkin pie spices, such as cinnamon, nutmeg, ginger, and allspice, contain more than 300 flavor compounds—substances made of two or more elements. But natural spices are expensive and vary in quality. A mixture of a dozen or so key compounds can trick our brains into thinking we’re experiencing real spices. “It’s our brain, not our tongue or our nose, that tells us what a flavor is,” says food scientist Kantha Shelke of the Institute of Food Technologists.