“…As differences in education history (subjects with ADHD more often attend special schools, repeat grades, more often receive special educational services and are less likely to graduate from school, Murphy, Barkley, & Bush, 2002;Taanila, Hurtig, Miettunen, Ebeling, & Mailanen, 2009), self-esteem, and control beliefs (subjects with ADHD have a more external locus of control and suffer from lower self-esteem, Carlson, Mann, & Alexander, 2000;Niederhofer, 2008;Rucklidge, Brown, Crawford, & Kaplan, 2007) may differentially affect task-related motivation in both experimental groups, the QCM was considered to be a possible covariate of interest in the present study in order to rule out motivational explanations other than DA, which could cause group differences in experimental choice behavior.…”