The present thesis focuses on Type A behavior in children and its possible relation to hyperactivity/ADHD. Type A behavior in children has commonly been studied as the child equivalent behaviors of the adult pattern, in other words, competitive achievement-striving, impatience/time-urgency, and aggressiveness.
Study I investigated the convergent and discriminant validity of observationally assessed Type A behavior with regard to parent- and teacher-rated Type A behavior (Matthews Youth Test for Health [MYTH] questionnaire) and hyperactivity (questionnaire) among 8-year-olds. Study II was similar although these relations were studied longitudinally between 4 and 8 years of age, and hyperactivity was observationally assessed at age 4. The results of Studies I and II showed that Type A behavior is discernible already at age 4 and that it should be regarded as a phenomenon rather distinct from hyperactivity. Assessing aspects of Impatience, however, was found to be problematic, both in terms of discriminating between Type A behavior and hyperactivity, and in terms of showing stability over time. The MYTH was concluded to measure Type A behavior too indiscriminately, showing a substantial overlap with hyperactivity.
Study III attempted to differentiate Type A behavior (MYTH-defined) and hyperactivity/ADHD using observed motivation during a reaction time task. The results pointed to the MYTH as indiscriminant from hyperactivity measures with regard to observed motivation and task performance. The perception of Type A individuals as highly motivated to achieve was not evident in this study.
In Study IV, an observationally assessed Type A group was compared to a Type B group and an ADHD group on measures of inhibitory control and executive functioning. The results pointed to similarities between Type A and ADHD boys regarding overt displays of time-urgency and impatience. However, differences on other tasks of executive functioning lead to speculations concerning differing origins of overtly similar characteristics of Type A behavior and ADHD.