Anne Fleur Kortekaas-Rijlaarsdam

117 EFFECTS OF MPH AND REWARD ON MATH PERFORMANCE 6 optimal approach to stimulate the classroom performance of children with ADHD. Although studies on the synergy between effects of reward and MPH are scarce, the evidence for positive effects reward, including positive feedback, on math performance in TD children is robust (Dihoff, Brosvic, Epstein, & Cook, 2004; Luwel, Foustana, Papadatos, & Verschaffel, 2011; Narciss & Huth, 2006). Supportive positive performance feedback and rewards are thought to be crucial for all children leading to positive effects on achievement and motivation for learning (Hattie & Timperley, 2007; Shute, 2008). However, feedback frequency in typical classrooms is low (Bond et al., 2000) and providing optimal feedback in an appropriate way requires considerable training (Hattie & Timperley, 2007). Moreover, previous research suggests that children with ADHD profited more from rewards in terms of working memory than typical controls (Dovis, Van Der Oord, Wiers, & Prins, 2012). As working memory is an important cognitive skill for math (Ashcraft & Krause, 2007), these results imply that the use of rewards may even have a higher potential to improve math skills in children with ADHD than in TD children. However, to the best of our knowledge, evidence on this topic is lacking so far. As current estimations indicate that one or two children in every classroom are currently treated with stimulant medication for ADHD (Dutch Health Council, 2014; The Lab Express Scripts, 2014), more knowledge on the interplay between the effects of reward/feedback and stimulant treatment is crucial to determine the most effective approach to maximize school performance in children with ADHD. Therefore, the main aim of this study was to investigate the synergy between the effects MPH and rewarded feedback (feedback coupled to reward) on an ecologically valid math task. To this end, we investigated whether children with ADHD and TD children profited equally from rewarded feedback. We hypothesized that both children with ADHD and TD controls would perform better when rewarded feedback was presented contingent on their performance (Hattie & Timperley, 2007; Shute, 2008). As children with ADHD show increased sensitivity to external rewards (Luman et al., 2005), we expected children with ADHD to profit more from rewarded feedback than TD children, in line with previous findings (Dovis et al., 2012; Strand et al., 2012). Secondly, we hypothesized that MPH treatment would result in better math performance compared to placebo, albeit with small effect sizes (Kortekaas-Rijlaarsdam et al., 2018). Concerning the synergy between the effects of rewarded feedback and MPH, we predicted that the combination of rewarded feedback and MPH treatment would result in better math outcomes than either treatment alone (Pelham et al., 1986; Rosch et al., 2016; Strand et al., 2012). The second aim of this study was to validate a novel motivation math task. As previous research on the effects of reward and feedback on performance focuses