Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 6 128 need for pharmacological interventions. Although the use of such motivational strategies is more demanding for teachers, our results suggest that not only children with ADHD profit from this approach, but also TD children. Thus, such motivational strategies should be exercised within regular classrooms more often for the benefit of all students. Interestingly, despite their inferior math performance at entry, children with ADHD during placebo and TD children profited equally from rewarded feedback. Thus, children with ADHD were not more sensitive to reward than TD children during placebo, which opposes existing theories on altered reinforcement processing in ADHD (Luman et al., 2005) as well as experimental studies on the reward threshold of children with ADHD when off-medication (Liddle et al., 2011; Wilkison et al., 1995). The latter may be explained by placebo effects, which can be large in randomized controlled clinical trials (Krogsbøll et al., 2009). Taken together, our findings imply that the effects of rewarded feedback and MPH on math performance are independent and may act through different mechanisms. This mechanism behind reward and feedback related improvements in academic performance should be topic of future research. MPHmay work by improving behavior within classrooms (Kortekaas-Rijlaarsdam et al., 2017b). In addition, MPH may improve math performance in children with ADHD by improving attention (e.g. by decreasing attentional lapses: Castellanos et al. 2005) or by improving executive functions (Tamminga, Reneman, Huizenga, & Geurts, 2016), but see Kortekaas- Rijlaarsdam et al., 2017a, Luman, Sonuga-Barke, Bet, & Oosterlaan, 2017a. However, reward as well as feedback are also likely to impact behavior important for math performance, including task persistence (Deci, Koestner, & Ryan, 1999; Fyfe & Rittle- Johnson, 2017). Moreover, rewarded feedback has potential to improve cognitive performance of children with ADHD, including working memory (Dovis et al., 2012) and response inhibition (Rosch et al., 2016). There is evidence that cognitive performance is important for e.g. math performance (Ashcraft & Krause, 2007), although the mediating effects of such cognitive improvements on reward-related improvements in academic performance remains to be investigated. The current study has a number of limitations. Firstly, as we aspired to measure the effects of rewarded feedback on actual school performance in an ecologically valid manner, we used a newly developed task. Although the first results (condition effects) suggest validity, more research with this task is required to confirm it psychometric value. Furthermore, our treatment intervention was relatively short (7 days placebo