The change in total-CON degree also showed a trend of positive correlation with the improvement in Block Design test in both groups combined [ r = 0.25, t (49) = 1.80, p = 0.078; Figure 6 , left, black line] as well as in the training group alone [ r = 0.38, t (23) = 1.98, p = 0.06; Figure 6 , left, blue line], but not in the control group ( r = 0.04, p = 0.86; Figure 6 , left, orange line).
Although it may be difficult to find strong effects from short-term behavioral intervention that was implemented for a relatively short period of time, especially on highly plastic adolescent brains going through substantial maturational and developmental changes, the observed changes were modest and in some cases did not reach statistical significance.
This stable within-CON degree suggests that the training led to increases in PC in the training group compared with the control group that were insufficient to reach significance level in the group and time interaction, even though a slight trend toward increased PC was observed in the training group.