This thesis was designed to investigate differences in aggression between girls with and without attention-deficit/hyperactivity disorder (ADHD). Forty girls with ADHD and 43 girls without ADHD aged 9- to 12- years and their mothers and teachers participated. A multiassessment methodology was used to investigate these differences, employing mothers' reports, teachers' reports, and a laboratory aggression analogue task (a computer game involving simulated girls in other rooms). The results indicated that mothers and teachers saw girls with ADHD as having much higher levels of all types of aggression assessed, including overt, relational, proactive, and reactive aggression, than girls in the control group. On the lab task, girls with ADHD used a strategy that involved more threatening and bragging comments, and social exclusions of their co-players. Expected differences on some of the lab task measures did not emerge. Also, according to mothers, teachers, and the results from the lab task, girls with ADHD were significantly less prosocial than girls in the control group. Where significant group differences had been found, follow-up tests generally indicated that girls with ADHD and comorbid oppositional-defiant disorder (ODD) were more aggressive than girls in the control group, with girls with ADHD but not ODD falling in between. In sum, these results indicate substantial cause for concern for the concurrent and future psychosocial well-being of girls with ADHD.

Previous research has identified motor deficits within the ADHD population, and indicates that these individuals are at an increased risk for difficulties relating to their motor development. The present study, which utilized discriminant function analysis, was unable to document areas of motor impairment for individuals diagnosed with ADHD. Specifically, no evidence of motor impairment was identified on tasks of motor coordination, fine motor dexterity, motor speed and grip strength, which measures the integrity of the motor system at the basic output level. Interestingly, results identified that individuals with ADHD were more proficient in their motor abilities than the normative population. Two mitigating factors were controlled for in this study and were found to impact performance on motor tasks. First, higher level thinking skills such as verbal comprehension, attention control, cognitive sequencing, working memory and executive functions appear to be more responsible for documented performance deficits than an underlying motor deficit. Secondly, the high prevalence of comorbid psychiatric and medical disorders, inherent to the ADHD population, appears to negatively impact performance on motor tasks. In general, individuals with only a diagnosis of ADHD consistently outperformed individuals who had been diagnosed with ADHD and comorbid disorders.This study also examined the sensory and subcortical abilities of individuals with ADHD. Results indicate that these children are similar to their same age peers in their visual perception, visual acuity, auditory discrimination and tactile perception. Finally, this study was unable to identify evidence of impairment in the subcortical abilities of ADHD individuals. In fact, individuals with only a diagnosis of ADHD outperformed the control group across a majority of tasks assessing subcortical abilities. Comorbidity also appears to negatively impact performance on sensory and subcortical tasks, especially for individuals with comorbid medical conditions. Overall, results from this study impact the field of research which previously identified motor performance deficits in the ADHD population. Further research is needed to examine the sensory and motor abilities of ADHD individuals to understand the performance abilities of individuals with ADHD. / Department of Educational Psychology

The corpus callosum (CC) is the largest fiber¹ tract in the brain and connects homological regions of the two cerebral hemispheres. Research with split-brain patients, whose CC has been surgically severed, and neurologically intact groups has shown that the CC is important for sustained and divided attention. Due to its role in attention, the CC is of interest to clinical conditions in which attention is affected, such as attention deficit hyperactivity disorder (ADHD). Although the size of the CC has been examined in children and adolescents with ADHD, the results have been inconsistent. Therefore, the first of three studies in this thesis synthesized the current research in a metaanalysis, which analyzed the data from 13 studies that examined CC area in children and adolescents with ADHD, when compared to healthy controls. This study found that the splenium, the most posterior region of the CC, was smaller in ADHD and the rostral body, an anterior region, was smaller in boys with ADHD compared with controls. Thus, there is evidence for differences in area in both the anterior and posterior regions of the CC in ADHD. It was not known whether these differences persist into adulthood, however, because CC size had not been examined in adults with ADHD. Therefore, the second study examined CC area and structural integrity in young adults with ADHD compared with healthy controls using magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI), respectively. The difference in the size of the splenium was not present in this adult sample, although the genu (an anterior region of the CC) was smaller and two midposterior regions were larger in adults with ADHD when compared with controls. In addition, a reduction in the integrity of the genu and greater integrity in the splenium was found in ADHD. The relationship between CC morphology and measures of attention and IQ was also examined in young adults with ADHD and controls in order to assess the functional significance of differences in the CC. The integrity of the splenium was correlated with performance on the Stroop task, which requires attentional control. Hence, this study indicated that the morphology of the CC is atypical in young adults with ADHD and that these differences in the CC may impact on cognitive functioning. Interestingly, an estimate of performance IQ was negatively correlated with CC area in controls. This result conflicts with previous research on the relationship between IQ and the CC in healthy adults although the literature has yielded inconsistent findings. The third study, therefore, examined the relationship between IQ and both CC area and integrity in more detail in a larger sample of young adults. A negative correlation was found between the area of posterior regions of the CC and an estimate of performance IQ, while an estimate of verbal IQ was associated with decreased structural integrity in the genu. This study supports the hypothesis that differences in CC size and or integrity may have cognitive consequences. In summary, this thesis confirms the view that the development of the CC is atypical in children and young adults with ADHD. In addition, differences in CC integrity were associated with cognitive functioning in young adults with ADHD. Finally, the morphology of the CC is related to cognitive performance in healthy adults. ¹ American spelling is used throughout the thesis in order to be consistent with the published papers which have been published or prepared using American spelling. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1367349 / Thesis (Ph.D.) -- University of Adelaide, School of Psychology, 2009

The corpus callosum (CC) is the largest fiber¹ tract in the brain and connects homological regions of the two cerebral hemispheres. Research with split-brain patients, whose CC has been surgically severed, and neurologically intact groups has shown that the CC is important for sustained and divided attention. Due to its role in attention, the CC is of interest to clinical conditions in which attention is affected, such as attention deficit hyperactivity disorder (ADHD). Although the size of the CC has been examined in children and adolescents with ADHD, the results have been inconsistent. Therefore, the first of three studies in this thesis synthesized the current research in a metaanalysis, which analyzed the data from 13 studies that examined CC area in children and adolescents with ADHD, when compared to healthy controls. This study found that the splenium, the most posterior region of the CC, was smaller in ADHD and the rostral body, an anterior region, was smaller in boys with ADHD compared with controls. Thus, there is evidence for differences in area in both the anterior and posterior regions of the CC in ADHD. It was not known whether these differences persist into adulthood, however, because CC size had not been examined in adults with ADHD. Therefore, the second study examined CC area and structural integrity in young adults with ADHD compared with healthy controls using magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI), respectively. The difference in the size of the splenium was not present in this adult sample, although the genu (an anterior region of the CC) was smaller and two midposterior regions were larger in adults with ADHD when compared with controls. In addition, a reduction in the integrity of the genu and greater integrity in the splenium was found in ADHD. The relationship between CC morphology and measures of attention and IQ was also examined in young adults with ADHD and controls in order to assess the functional significance of differences in the CC. The integrity of the splenium was correlated with performance on the Stroop task, which requires attentional control. Hence, this study indicated that the morphology of the CC is atypical in young adults with ADHD and that these differences in the CC may impact on cognitive functioning. Interestingly, an estimate of performance IQ was negatively correlated with CC area in controls. This result conflicts with previous research on the relationship between IQ and the CC in healthy adults although the literature has yielded inconsistent findings. The third study, therefore, examined the relationship between IQ and both CC area and integrity in more detail in a larger sample of young adults. A negative correlation was found between the area of posterior regions of the CC and an estimate of performance IQ, while an estimate of verbal IQ was associated with decreased structural integrity in the genu. This study supports the hypothesis that differences in CC size and or integrity may have cognitive consequences. In summary, this thesis confirms the view that the development of the CC is atypical in children and young adults with ADHD. In addition, differences in CC integrity were associated with cognitive functioning in young adults with ADHD. Finally, the morphology of the CC is related to cognitive performance in healthy adults. ¹ American spelling is used throughout the thesis in order to be consistent with the published papers which have been published or prepared using American spelling. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1367349 / Thesis (Ph.D.) -- University of Adelaide, School of Psychology, 2009

Thesis (Psy. D.)--Wheaton College Graduate School, 2005. / Abstract. Includes bibliographical references (leaves 39-46).

Thesis (Psy. D.)--Wheaton College Graduate School, 2005. / Abstract. Includes bibliographical references (leaves 39-46).

Thesis (Ph. D.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Psychology." Includes bibliographical references (p. 51-66).

Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--Duquesne University, 2004. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 196-208).