This page contains the CT-skills tests and the CT-practice tasks of our experiment (in Dutch). Depending on the randomly assigned condition, participants (1) practiced with domain-specific problems once (practice once condition); (2) practiced with these problems for a second time after a week (practice twice condition); (3) practiced with these problems for a second time after a week and for a third time after two weeks (practice thrice condition). Additionally, English example items of the CT-skills tests and of each training condition are provided on this page.