Anne Fleur Kortekaas-Rijlaarsdam

99 REINFORCEMENT LEARNING IN ADHD: EFFECTS OF MPH 5 compared to TD children (Frank et al., 2007; Groen et al., 2008; Luman et al., 2009), although we recognize that other studies showed otherwise (Luman et al., 2015). In addition, we hypothesized that children with ADHD would be less able to apply recently learned knowledge about stimulus-response associations to novel stimulus pairs (i.e. generalization of learning) in the test phase of the task (Frank et al., 2007). Further, we expected children with ADHD to show deficits in reversal learning (Alsop et al., 2016; Itami & Uno, 2002). Results from non-clinical studies suggest that MPH improves reversal learning in participants with deficits or symptoms commonly seen in ADHD (working memory deficits or impulsive traits) (Clatworthy et al., 2009; van der Schaaf, Fallon, Ter Huurne, Buitelaar, & Cools, 2013).We predicted positive effects of MPH on all outcomes (Alsop et al., 2016; Frank et al., 2007; Itami & Uno, 2002; Luman et al., 2015; Luman et al., 2009). MAT E R I A L S AND ME T HODS Participants As part of a larger study (see Kortekaas-Rijlaarsdam et al., 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 typically developing (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 Wechsler Intelligence Scale for Children, third edition (WISC-III; including the substest Information, Vocabulary, Block Design and Symbol Search; Wechsler, 1991), 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-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 et al., 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