"Of those assigned to reward-based programs, 90.0% accepted the assignment, as compared with 13.7% of those assigned to deposit-based programs.... Reward-based programs were associated with higher abstinence rates than deposit-based programs ... However, ... the rate of abstinence at 6 months was 13.2 percentage points higher in the deposit-based programs than in the reward-based programs among the estimated 13.7% of the participants who would accept participation in either type of program."  MORE >>