“…Contingency management interventions are rooted in research that suggests drug addiction is operant behavior that is maintained and modifiable by its consequences and should be modifiable through the strategic use of alternative reinforcement (Bigelow & Silverman, 1999). Based on these principles, Higgins and colleagues developed voucher-based reinforcement intervention in which patients receive monetary vouchers exchangeable for goods and services for providing drug-free urine samples (Higgins et al, 1991). Voucher-based reinforcement can increase abstinence from a wide range of drugs (Lussier, Heil, Mongeon, Badger, & Higgins, 2006) and has been identified as a highly effective behavioral treatment for drug addiction (Castells et al, 2009; Dutra et al, 2008; Knapp et al, 2007; Pilling, Strang, Gerada, & NICE, 2007).…”