| This within-group, pretest posttest design study using archival data explored the effect of Contingency Management (CM) targeting substance use on intrinsic motivation to remain substance-free. Prior studies showed CM had no significant change in intrinsic motivation or had mixed results. However, all prior studies aggregated data of those who received rewards regardless of level of performances and compared them to alternative groups. Aggregation is a concern particularly under low-cost procedures because participants do not necessarily receive the same strength of reinforcement for the same level of performance and performance does not necessarily correlate with reinforcement strength. The current study used low-cost contingency management procedures to examine the impact of level of performance and strength of reinforcement on intrinsic motivation. Participants were in one of two groups: those theoretically expected increase (or no decrease) in intrinsic motivation based on performance and strength of reinforcement, and those expected to decrease. Intrinsic motivation was measured at pre-treatment, posttreatment, and three months posttreatment using the Client Motivation to Remain Substance-Free Scale (CMOTS-SF), a modified version of the Client Motivation for Therapy Scale (CMOTS). CMOTS and CMOTS-SF intake scores correlated significantly (r = .799; p = .01) and subscale scores for the CMOTS and CMOT-SF were comparable (.77 to .96 versus .63 to .93). Individual CMOTS-SF scores and score classification (e.g., decreased or not during the treatment phases) were dependent variables. The independent variables were group (expected increase or decrease) and phase of treatment (pre- to posttreatment; post- to three months posttreatment). Modal participants were White male adults in substance outpatient treatment. Analyses from pre- to posttreatment did not support the hypotheses. In fact, pre-treatment intrinsic motivation appeared preserved at post-treatment under CM. From posttreatment to three months posttreatment, however, the group expected to decrease did demonstrate decreased intrinsic motivation (t 25= -2.08; p = .048), but at the group level, failed to show significant change. The results suggest that CM interventions may not undermine intrinsic motivation during treatment, while removal of CM post-treatment needs examination. Future research would benefit from use of between-groups designs, larger samples for power, a no-treatment group, and reduced testing time. |
