Comparison among the BICs across all mixture models suggested that the 5-class solution that constrained variation in impulsivity to be equal within class but allowed variation to be different across classes (see Martinez and Martinez, 2004) best fit the data. Mean-level changes in impulsivity by trajectory group are displayed in Fig. 1. All classes except Class 1 and Class 5 exhibited significant decreases in impulsivity between ages 18 and 25. Notably, Class 3 exhibited striking decreases in impulsivity from ages 18 to 25 (see Fig. 1) and demonstrated the sharpest reductions in impulsivity compared to all other impulsivity classes across this time span, suggesting Class 3 may represent a “developmentally limited” impulsivity group. Between ages 25 and 29, Class 4 and 5 displayed modest, though significant, decreases in impulsivity.2
