Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 6 122 11 provided written informed consent before enrollment in the study. Children were instructed to work as fast and accurately as possible. After the practice phase (and determination of entry level for the experimental phase), the child was told that when a trial started with a green screen (motivation condition), rewarded feedback would be given occasionally in the case of a correct response and when a trial started with a white screen (neutral condition), feedback would be absent. It was explained that the absence of rewarded feedback in a small percentage of trials in the green (motivation) condition, did not always imply an incorrect response. Further, children were told that at the end of the task, they could exchange points earned for stickers (three points earned one sticker). The child was required to respond by typing the correct answer using a numerical keyboard – with answers confirmed by a press on the enter-key. Halfway through the task (after 14 trials, on average after 4 minutes), a short break was given, in which the child watched a short animation. Total task duration including the break was on average 10 minutes. Analyses Firstly, we validated the task in the TD population: We used Generalized Linear Mixed Model (GLMM) analyses to test the effects of condition (motivation versus neutral). In addition to testing the difference between conditions, we expected children to perform better at the end of the task, i.e. we expected improved math performance as Table 6.1 Difficulty levels for calculations Level Problem size Number of carry operations Formulation Example 1 0-9 0 A+B 2+7 2 10-19 0 AB+C 12+4 3 10-19 1 A+B 8+5 4 20-100 0 AB+C 54+3 5 20-100 0 AB+CD 17+42 6 20-100 0 ABC+D 125+4 7 20-100 1 AB+C 48+3 8 20-100 1 ABC+D 124+9 9 20-100 1 AB+CD 57+35 10 100-200 1 AB+CD 53+96 11 100-200 2 AB+CD 67+78 12 100-200 2 ABC+DEF 145+297 Note . The formulation of level 8 and 9 was switched.This was not planned but turned out to be in line with data from another sample (N=90, primary school children) indicating that accuracy is higher for ABC+D than for AB+CD in problem size range of 20-100 ( t (90)=3.76, p <.001).