EFFECT OF REINFORCEMENT PROBABILITY AND PRIZE SIZE ON COCAINE AND HEROIN ABSTINENCE IN PRIZE‐BASED CONTINGENCY MANAGEMENT

Although treatment outcome in prize‐based contingency management has been shown to depend on reinforcement schedule, the optimal schedule is still unknown. Therefore, we conducted a retrospective analysis of data from a randomized clinical trial (Ghitza et al., 2007) to determine the effects of the probability of winning a prize (low vs. high) and the size of the prize won (small, large, or jumbo) on likelihood of abstinence until the next urine‐collection day for heroin and cocaine users ( N = 116) in methadone maintenance. Higher probability of winning, but not the size of individual prizes, was associated with a greater percentage of cocaine‐negative, but not opiate‐negative, urines.