Measurement of cognitive load (CL) is seen as a problematic issue since no consensus about appropriate instruments has been reached. In this study, a rating scale instrument to measure mental load (ML; 6 items) and mental effort (ME; 6 items) is evaluated using Item Response Theory. N=506 students self-reported their amount of ML and ME after working on a standardised multiple choice-test. The findings propose to separately measure ML and ME instead of CL in general. Furthermore, the 7-point rating scale had to be reduced post-hoc to a 3-point scale in order to reach consistent information. Finally, there was a significant (negative) correlation between ML and test performance, but not between ME and test performance.Peer Reviewe
