Data shown are for the conflict effects residualized on age and thalamic k3). Left column: low caudate DA group. Right column: normal caudate DA group. (A, C) Cortical k3 was a significant predictor of conflict effects in all cases except for the Stroop conflict effect in the normal caudate DVR group (p = .06, other p’s < .0001). This association between cortical k3 and conflict effects were stronger in low caudate DVR group (A, C) than normal caudate DVR (B, D) group. The fit lines are based on the least squares (solid) and robust regression (dashed) results. The b*, t-value, and DF: t-test results are for the robust regression coefficients.