Over the course of two experimental sessions, they were asked to light a cigarette and hold it as if they were going to smoke, but then extinguish it. This was meant to put their cravings on high alert. Then they were re-exposed to one of the 12 "olfactory cues" they'd been offered before—either their favorite of the scents, a tobacco odor, or plain-old air. They were allowed to sniff this sample over a five-minute period, rating how much they wanted to smoke on a scale from 0 to 100 at each minute mark. Researchers repeated this process the next day. The second time, however, participants were either assigned tobacco, a blank, or a pleasant smell other than their favorite for the five-minute sniff-and-rank trial.