Anne Fleur Kortekaas-Rijlaarsdam

115 EFFECTS OF MPH AND REWARD ON MATH PERFORMANCE 6 I N T RODUC T I ON Children with attention-deficit/hyperactivity disorder (ADHD) often underperform in school, with largest impairments in math and reading (Frazier et al., 2007). Methylphenidate (MPH) is the most common treatment for ADHD (Wright et al., 2015). However, improvements in academic performance with MPH are small (Kortekaas-Rijlaarsdam, Luman, Sonuga Barke, & Oosterlaan, 2018). Besides the behavioral problems of children with ADHD, a variety of factors are hypothesized to add to their academic problems, including cognitive and motivational impairments (Mayes & Calhoun, 2007; Preston, Heaton, McCann, Watson, & Selke, 2009; Thorell, 2007DuPaul et al., 2004; Gut, Heckmann, Meyer, Schmid, & Grob, 2012; Langberg, Arnold, Hinshaw, & Swanson, 2012). There is accumulating evidence of motivational factors influencing school performance, including findings of lower intrinsic motivation for school in children with ADHD compared to typically developing (TD) controls (Carlson, Booth, Shin, & Canu, 2002; Kortekaas-Rijlaarsdam, Luman, Sonuga-Barke, Bet, & Oosterlaan, 2017a). Further, reports show altered sensitivity to reinforcement in children with ADHD. Specifically, cognitive task performance of children with ADHD seems more dependent (i.e. better performance) on external rewards compared to performance of TD children (Luman et al., 2005). As it is difficult to alter a child’s intrinsic motivation for schoolwork (Ryan & Deci, 2000), most potential for motivational strategies therefore lies in increasing extrinsic motivation. Besides evidence for positive effects of reward on cognitive performance of children with ADHD (Luman et al., 2005), reward as well as performance feedback may further improve academic performance by increasing task interest and persistence (Deci et al., 1999; Fyfe & Rittle-Johnson, 2017). As ADHD treatment with stimulant medication is common in regular classrooms and previous research suggests that stimulants may affect the ability to profit from feedback and reward, it is important to study the interplay between the effects of stimulants and rewarded feedback. Such knowledge is necessary to determine how school performance in children with ADHD can be optimized. The results of existing literature on the synergy between the effects of stimulant medication and reward or feedback is inconsistent. There is evidence that treatment with MPH affects the motivational threshold of children with ADHD: For example, when off-medication, children with ADHD were more sensitive to rewarded feedback (feedback coupled to reward such as points) than typically developing (TD) children on a inhibitory control task (Liddle et al., 2011; Sonuga-Barke & Castellanos, 2007).