Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 6 118 on cognitive, rather than academic tasks, we developed an ecologically valid motivation math task to substantiate effects of rewarded feedback and MPH on math performance. We hypothesized that math performance of TD children would be better in the motivation condition (consisting of rewarded feedback: for an explanation of the conditions, see Methods section) as reward and feedback are known to improve (academic) performance (Dihoff et al., 2004; Hattie & Timperley, 2007; Luwel et al., 2011; Narciss & Huth, 2006; Shute, 2008). We also validated our math task by assessing the relationship between performance on the newly developed task and similar academic math tasks. MAT E R I A L S AND ME T HODS Participants As part of a larger study (see Kortekaas-Rijlaarsdam, Luman, Sonuga-Barke, Bet, & Oosterlaan, 2017b), sixty-five children with ADHD were recruited between 2012 and 2014 through four mental health clinics in the Netherlands, the Dutch parent association for children with developmental problems, and the study’s website. Sixty- seven TD children were recruited in the same period through primary schools. Inclusion criteria for both groups were (1) age between 8 and 13 years, (2) at least one year of Dutch primary school education to ensure full understanding of test instructions, and (3) an estimated full-scale IQ of at least 70. Full-scale IQ was estimated using a short form of the most recent version available in the Netherlands, the Wechsler Intelligence Scale for Children, Third revised edition (WISC-III-R; including the subtests Information, Vocabulary, Block Design and Symbol Search: Wechsler, 2005) with excellent validity ( r = .91) and reliability ( r xx = .93) for estimating full-scale IQ (Sattler, 2001). In addition, children with ADHD met the following criteria: (1) a clinical diagnosis of ADHD confirmed by the Diagnostic Interview Schedule for Children for DSM-IV, parent version (DISC-IV-P; (Shaffer et al., 2000)), and (2) a score > 90 th percentile on the Inattentive and/or Hyperactive/Impulsive scale of both parent and teacher version of the Disruptive Behavior Rating Scale (DBDRS; (Oosterlaan, Scheres, Antrop, Roeyers, & Sergeant, 2005; Pelham, Evans, Gnagy, & Greenslade, 1992)) to ensure symptom severity and pervasiveness, (3) treatment with MPH or indication for treatment with MPH, and (4) no concomitant (parent reported) neurological disorders or autism spectrum disorder. Children in the TD group were included if they had no (parent reported) psychiatric or neurological disorder, including ADHD. To ensure