“We humans have only about 400 types of smell receptors,” [Pamela Dalton, a cognitive psychologist at Monell Chemical Senses Center] said. The particular combination of receptors each person has determines how a smell is experienced. In other words, my husband and I may not even be smelling the same candle. When you multiply a finite set of receptors by an infinite number of possible odor molecules, Dalton said, you get countless variations in how people experience scent. What registers in my brain as comforting might land in his as something cloying.

— Read more in Why It’s So Hard to Find a Crowd-Pleasing Scented Candle at The Wall Street Journal.