Classic sales tactics weave through her method like subtle threads: Kondo’s signature technique, in which you hold an item to see whether it “sparks joy” before deciding whether to throw it out, has echoes of consumer decision-making research. “Consumer psychology says that if you touch an item in the store, you are more likely to buy it,” says Joseph Ferrari, a professor of psychology at DePaul University who has studied the psychology of possessions. “If you pick up the item, you are more likely to keep it. So she’s misinforming people.”