Hart next tried offering these participants the choice between a low dose of meth and a small monetary voucher, at different times of day. The prediction was that, meth being a potent reinforcer, users would take it compulsively; what he found was that people would take it in the morning but not in the evening, when it would stop them sleeping -- using it to get through the day in the same way office workers self-administer caffeine; and if the monetary reward was large enough, they would pass up the dose. These findings call into question the notion that addiction is driven by the reward of a chemically induced euphoria and that meth -- legally prescribed to treat ADHD, narcolepsy and obesity -- is the destructive drug so maligned by the NIDA and the popular press. Hart's conclusion was that his subjects were indeed making rational choices about their drug use.