Anne Fleur Kortekaas-Rijlaarsdam

91 MPH EFFECTS ON MATH PERFORMANCE: INFLUENCE OF COGNITION, MOTIVATION AND PERCEIVED COMPETENCE 4 underperformance (Biederman et al., 2004; Mayes & Calhoun, 2007b; Preston et al., 2009; Thorell, 2007). There are however, many more ADHD-related cognitive processes that we have not included in our study and that may show methylphenidate-related improvements relevant for academic performance. For self-perceived academic competence, differences between children with ADHD and TD children were large and corroborated by all informants (self-rated, parents and teachers). However, only parent-rated self-perceived academic competence improved significantly with MPH. A possible explanation for this finding is that parent-rated self-perceived competence relies more on symptom improvements than on actual academic performance and that parents are more sensitive to detect such behavioral improvements in diverse settings than teachers (Shemmassian & Lee, 2012). In a previous study, we showed that parent-rated symptom improvements mediated math productivity (Kortekaas-Rijlaarsdam et al., 2017b). There may have been room for bias here: If parents observed symptom improvements in their child, they may have been more prone to rate their child’s self-perceived competence as higher. However, although parent-rated academic competence and parent-rated symptom improvements correlate significantly ( r = .53) in our sample, parent-rated academic competence significantly predicted math performance over and above parent-rated symptom improvements when entered together in a model ( t (76.3) = 2.54, β = 0.48, p = .013). Our results show that parent-rated self-perceived academic competence mediates the positive effects of MPH on math productivity. This is an important finding, as motivation and self-perceived competence are especially important for school performance of children with ADHD (Gut et al., 2012). Given the reciprocal relationship between academic competence and performance (Guay et al., 2003), the finding that parent-rated self-perceived academic competence increases over such a short period (7 days) is promising; higher perceived competence is not only directly related to better academic outcomes (DuPaul et al., 2004; Volpe et al., 2006), but may also precede motivational changes in the child, which in turn, may improve study skills and thereby further improve academic performance (DiPerna et al., 2005; Wigfield & Eccles, 2000). The fact that parent-rated self-perceived competence only mediated MPH-related improvements in math productivity is also in line with the findings by Skinner et al. (1990). In that study, a relation was observed between self-perceived competence and classroom participation. Such improved classroom participation is likely to directly result in higher productivity but does not necessarily result in higher accuracy. The fact that we found a mediating effect for self-perceived competence only is also in line with findings from Steinmayr et al. (2009), showing that self-perceptions of ability are