Mediation analyses. First, we established an effect of positive urine status (i.e., CUD+ versus controls) on metacognitive accuracy (c-paths). Second, we found an effect of positive urine status on the bilateral rACC GMV (a-paths). Third, controlling for positive urine status (where effects of CUD+ fell below significance: c′-paths), the (A) left rACC and (B) right rACC ROIs remained significant predictors of metacognitive accuracy (b-paths). Both indirect effects were significant, tested with bootstrapping, indicating mediation (see Results for statistics).