Past research into optimism and pessimism has tended to view these constructs as polar opposites of a fixed personality trait that function in mutually exclusive ways. In the field of child development in particular, this has led to theory-driven work that not only accepts this dichotomy but also uses it to drive and explicate larger issues of resilience and vulnerability. The current thesis challenges the assumptions underpinning this conceptual framework, and, through the use of divergent methodologies, seeks to establish children’s optimism as a dynamic and adaptive process with predictive value during the developmental period. In the first two studies, predictors and correlates of putative dispositional optimism and pessimism in children and adolescents were examined. A significant age-related decline in optimism was found, but importantly a degree of functional independence between optimism and pessimism was also observed. The third study elicited more specific optimistic expectancies using a vignette methodology. This was seen to share some congruence with the earlier measures of dispositional optimism, but the study also elucidated some of the parameters and realism constraining children’s optimism. Again an age-related decline in optimism was demonstrated that was distinct from any associated changes in pessimism. The fourth and final study involved a pilot examination of the dimensionality of the optimism construct, confirming its functional independence from pessimism, and also demonstrating the fluidity and receptivity of children’s optimistic processes from an intervention perspective. From these various studies, it is concluded that optimistic and pessimistic processes in children and adolescents reflect functionally distinct pathways and drive different aspects of vulnerability and well-being. A reconfiguration of the extant theory in this area seems warranted. Based on this conceptual and methodological critique, a preliminary proposal is put forward towards a more substantive approach to the development of optimism and pessimism during childhood and adolescence. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1317136 / Thesis (Ph.D.) -- University of Adelaide, School of Psychology, 2008