RecruitingOutcome Inference in the Sensory Preconditioning Task in Opioid-Use DisorderBackground: People with addictions often find it hard to choose the long-term benefits of abstinence over the short-term effects of using drugs. Researchers think this is partly due to parts of the brain involved in certain types of learning and decision-making. Researchers want to test these basic functions using a simple task with pictures and odors. Objective: To see if performance in a learning task differs between people who have opioid-use disorder and people who don t. Eligibility: Adults 21-60 years old who are willing to fast for at least 6 hours and smell food odors. Those with an opioid-use disorder must either not use for at least 3 weeks or be in treatment. Design: Participants will have 1 visit that will take up to 5 hours. Before the visit, participants will be asked to not eat or drink anything except water for at least 6 hours. At the visit, participants will be checked for signs of intoxication. Participants will give urine and breath samples. Participants will have tests of learning and behavior. They will look at shapes on a computer screen. The shapes will be paired with different food odors. The odors will come from a sterile tube placed under the nose. Participants will have their breathing monitored with a belt around the upper abdomen. About 30 days and 60 days later, participants will be called and asked about their drug use over the past 30 days.