One of the defi ning features of addiction is an impairment of self-control: addicts are people who (to all appearance) fi nd it especially diffi cult to bring their behavior into line with their best judgments. Addicts oft en report a loss of control, and theorists have oft en used the language of loss of control to describe addiction. Indeed, loss of control over behavior has oft en been seen as defi nitive of addiction; the Diagnostic and Statistical Manual of Mental Disorders , fourth edition (DSM-IV) makes unsuccessful eff orts to control substance use and use for longer periods than intended two of the seven criteria for a diagnosis of substance dependence (any three of the seven must be present for a positive diagnosis).