Melbourne School of Psychological Sciences - Theses
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ItemDevelopment of executive processes in early childhood( 2003-08)Although the paediatric literature in the area of executive function has expanded significantly over the past 20 years, there is still an imbalance of knowledge when compared to the adult literature. The present project sought to redress the balance in executive function research by (1) investigating the development of a wide range of executive processes in children between the ages of 3 and 7 years, and (2) examining the effects of early frontal lobe damage on the ongoing development of these skills.
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ItemDeveloping script-specific recognition ability - the case of learners of Japanese( 2006-11)Reading non-alphabetic script can be a serious challenge to second language (L2) learners with alphabetic backgrounds. Many L2 learners of Japanese or Chinese who are fluent in speaking the language do not necessarily acquire an advanced-level reading ability. The aim of my thesis was to investigate the development of L2 word recognition ability, one of the most important abilities that learners need to develop for efficient reading, among English-speaking learners of Japanese. By analysing the results of behavioural tests and a verbal protocol administered to both L1 and L2 readers of Japanese, the study described the changes in developing L2 learners’ kanji recognition skills and their awareness of the structure and function of characters at the different stages of L2 exposure. The overall findings suggest that the changes in processing patterns demonstrated by the participants in the present study may be fundamentally similar to those of L1 children, which have been found to be similar regardless of the types of script involved. The changes in L2 readers’ developing kanji recognition were accounted for by the transformation of the internal processing system; this transformation seems to occur by continuous link formation through learning corresponding information, and information processing based on the learned information. The process of transformation, which is affected by the frequency of exposure and the amount of practice, and therefore appears to be item-based, generally progresses on a stage-based developmental trajectory; the processing begins with local and incomplete information and progresses via intentional and analytical processing to develop into sophisticated attention-free processing. Although the developmental trajectory may be universal, the findings of the present study suggest that, when L1 and L2 are orthographically distant, L2 readers repeat the developmental phases due to lack of their ability to process script-specific information. L2 readers with alphabetic backgrounds cannot simply transfer the recognition skills and awareness that they have acquired in their L1 in the new environment of character recognition. The findings of the study suggest that script-specific recognition skills and awareness develop over time as the L2 readers’ internal processing system undergoes successive transformations. By identifying several critical skills and awareness, the present study has discussed the possibility of enhancing character recognition ability with the use of explicit instruction at critical moments.
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ItemDepression and immunity in adolescents: early precursors to disease?( 2012)Inflammation and immune dysfunction have been proposed to be mechanisms relevant to clinical depression. However, research on this topic is limited by the paucity of lifespan and longitudinal studies, making it difficult to address causality. This project aimed to examine inflammatory and depressive measures in adolescents from the community using both cross-sectional and prospective longitudinal designs. Experiment 1 was a cross-sectional, two-group study of 13 clinically depressed adolescents aged 13-18 years (11 females), and 13 age- and sex-matched healthy controls, both recruited from the community. Sixteen cytokines were measured in saliva and serum. Depressed adolescents displayed significantly elevated levels of C-reactive protein (CRP), Haptoglobin, Serum Amyloid P (SAP), and Alpha-2-macroglobulin (A2M) in saliva compared to controls, but not in serum, or for any other cytokine. Depressed adolescents also did not display a higher ratio of T helper cell 1- to T helper cell 2-type cytokines compared to controls. Experiment 2 was a prospective study of 67 adolescents (27 females) followed from 12-18 years of age and recruited from the community. Self-report depressive symptoms measured by the Center for Epidemiological Studies Depression Scale (CES-D) and Axis-I psychopathology measured by The Schedule for Affective Disorder and Schizophrenia for School-age Children (KSADS) were measured at four phases, and four salivary acute-phase proteins (CRP, Haptoglobin, SAP, and A2M) were measured at Phase II. Temperamental negative emotionality (NEM) was also assessed at age 12. Results showed that elevated CRP was significantly correlated with elevated CES-D scores cross-sectionally, but no inflammatory markers predicted the onset of a depressive illness or an increase in depressive symptoms over time. There was a significant Sex x CRP interaction effect on CES-D measured at Phase I, II, and IV, with a relationship between CRP and CES-D only apparent for females. Examining only females demonstrated significant associations between CRP and CES-D at all four phases, including CES-D measured two years prior to inflammation, suggesting that for females, depressive symptoms may precede elevated levels of CRP, however, further longitudinal research is required that measures inflammation at more than one time point. At Phase II, there were significant interactions of NEM temperament x CRP on CES-D, with a relationship between CRP and CES-D only for those with a high NEM score. Post-hoc analyses showed that body mass index (BMI) was also a significant moderator of the relationship between CRP and CES-D at Phase II, with a stronger association for participants with a higher BMI score. Measures of early-life stress and childhood trauma were not associated with inflammatory markers. These results suggest that salivary CRP is a marker of adolescent depression, but levels of this inflammatory marker do not predict the development of depressive illness. The results, along with other research, suggest that depressive symptoms may be a risk factor for chronic inflammation and associated medical diseases, especially for females. Furthermore, obesity may be another consequence of depression which can lead to this observed elevated inflammation. Finally, sex hormones should be considered in models of depression, obesity, and inflammation.