Anne Fleur Kortekaas-Rijlaarsdam

137 SUMMARY AND DISCUSSION 7 Table 7.1 Overview of the thesis aims and corresponding key findings Aim Key findings 1 st aim Quantify the effects of MPH on academic performance assessed in terms of both productivity and accuracy while distinguishing between core academic subjects (math, reading and spelling) • MPH has small to medium sized positive effects on math accuracy and math productivity (Chapters 2, 3 and 6) and reading speed (Chapter 2) • MPH has no effect on reading accuracy and spelling (Chapters 2 and 3) • Overall academic effects of MPH are small compared to behavioral effects and limited to math (Chapters 2 and 3) 2 nd aim Unravel the mechanism behind MPH-effects on academic performance, thereby distinguishing between academic productivity and academic accuracy for math, reading and spelling • Children with ADHD have cognitive impairments (visuospatial working memory and lapses of attention), and are less intrinsically motivated for math (Chapter 4) • MPH has large effects on ADHD symptoms (Chapter 3) • There are no effects of MPH on cognition and motivation (Chapter 4) • The only evidence for mediating variables influencing MPH-effects on academic performance relates to improvements in ADHD symptoms (parent-rated) and improvements in parent reports of their child’s perceived competence. These effects are specific for MPH effect on math productivity (Chapters 3 and 4). • Evidence for moderating variables affecting MPH effects on academic performance is limited to math ability: Children with below-average math performance profit more fromMPH treatment than children with above-average math performance (Chapter 3). 3 rd aim Quantify the effects of MPH on feedback learning in children with ADHD and the interaction between MPH and reward on math performance in children with ADHD • Children with ADHD show intact acquisition of stimulus-reward associations and reversal learning compared to TD controls (Chapter 5) • Children with ADHD are impaired when acquired knowledge needs to be applied in novel contexts (Chapter 5) • MPH treatment improves learning of stimulus- reward associations and shows potential (trend effect) to improve generalization of knowledge (Chapter 5) • Parents of children with ADHD report differential responses of their children to punishment and reward, compared to parents of TD controls (Chapter 4) • Children with ADHD and TD controls profit equally from positive feedback and reward, resulting in better math performance (Chapter 6) • MPH treatment does not affect the ability to profit from feedback and reward on a math task (Chapter 6)