Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 4 80 ADHD (Gut et al., 2012). Supporting this, low motivation for schoolwork has been shown to mediate the relation between ADHD symptoms and academic underperformance by decreasing study skills (DiPerna, Volpe, & Elliott, 2005; Volpe et al., 2006). Besides lower intrinsic academic motivation, children with ADHD also show altered sensitivity to punishment and reward ( Luman et al., 2005), which may alter the extrinsic motivation for school work. Extrinsic motivation is important to perform well at school because rewards and punishments, such as feedback and grades, are widely used methods to enhance academic performance. Children with ADHD have been shown to depend more on external rewards than TD children in terms of optimal cognitive functioning ( Luman et al., 2005). As the amount of feedback at school is usually comparable for all children, a lack in external rewards in class in addition to low intrinsic motivation may further impair academic performance. In addition to motivation for schoolwork, perceived academic competence has been shown to influence academic performance (Skinner, Wellborn, & Connell, 1990; Spinath, Spinath, Harlaar, & Plomin, 2006; Steinmayr & Spinath, 2009). Perceived academic competence includes beliefs about one’s own capacities and abilities, and has reciprocal relationships with academic performance, with higher competence improving performance and better performance increasing perceived competence (Guay et al., 2003). Perceived competence is theorized to precede intrinsic motivation, suggesting that children with ADHD with lower intrinsic academic motivation may also perceive their own competence as lower than TD children (Deci & Ryan, 1985; Harter, 1981; Wigfield & Eccles, 2000). Indeed, a study by Scholtens et al. (2013) showed that ADHD symptoms are negatively associated with self-rated perceived academic competence in adolescents with ADHD. Together, these findings suggest that besides cognitive deficits and low academic motivation, a reduction in perceived academic competence may further explain academic underperformance in children with ADHD. Accumulating evidence suggests that stimulant medication improves cognition, with small to medium effect sizes for working memory, large effect sizes for lapses of attention and moderate effect sizes for response inhibition (Coghill, Seth, et al., 2014; Pietrzak et al., 2006). Although studies into the effects of stimulants often report improvements in both cognition and academic performance, the relation between these is rarely studied. For example, both Murray and et al. (2011) and Wigal et al. (2011) show that methylphenidate-related improvements in reading and math are accompanied by improvements in attention, including fewer lapses of attention. However, it is unclear whether these improvements in attention mediate the effects of methylphenidate (MPH) on school performance. Studies into the effects of stimulant medication on motivational deficits and perceived competence in ADHD are scarce