A recurring theme in the cognitive development literature is the notion that people restructure their task knowledge as they develop increasingly sophisticated strategies. A large body of empirical literature spanning several domains suggests that in some cases, the process of knowledge restructuring is best characterized by a process of sequentially replacing old strategies with newer ones. In other cases, restructuring appears to be better characterized as a process involving changes in the way partial knowledge elements are selectively applied to a task. Critically, the former, but not the latter position, suggests that it may be quite difficult for people to revert to using an old strategy after restructuring has already occurred. The three experiments reported herein suggest that knowledge restructuring observed in experimental settings is aptly characterized by a process of strategy retention. Specifically, people are shown to readily revert to using an old categorization strategy even after demonstrably having restructured their knowledge, suggesting that knowledge is best conceptualized as having a heterogeneous structure. Formal modeling further supports this interpretation of the empirical results, and highlights the important role of selective attention in determining the manifest response strategy. The implications of these findings are discussed in terms of an overarching mixture-of-experts framework of knowledge representation.

Science has been perceived as difficult to learn because of its nature and the methods by which it is usually taught. Most first-year science students entering higher education in South Africa today come from disadvantaged teaching and learning backgrounds. These students bring different “knowledge, skills or abilities” into the learning process. This knowledge, referred to as prior knowledge – or what the student already knows – is the single most important factor influencing learning (Ausubel, 1968). It is on the basis of this influence of prior knowledge on learning that the focus in this study is on understanding its manifestation in learning. Prior knowledge has both facilitating and inhibiting effects in learning. However, the focus in this study was only on inhibiting effects of prior knowledge on learning. To better understand prior knowledge qualitative methods (interview, observation, document review and the prior knowledge state test) were used. The aim was to specifically establish how students used their understanding of selected acid-base concepts and processes to construct understanding and to generate meaning of new concepts and/or knowledge. The study managed to highlight important aspects of the quality of prior knowledge and their manifestation in learning. The findings generally indicated that: <ul> <li>The quality of the knowledge that students possessed was in most instances incomplete. That is, in their description of concepts, students preferred to use summary and informal descriptions without understanding the meaning of the concepts they were describing.</li> <li> The quality of knowledge (e.g. incomplete knowledge) affected their ability to construct understanding and/or generate meaning as this knowledge was insufficient to access for the construction of scientifically valid meanings of concepts.</li> <li>The quality of students’ knowledge impeded their ability to reflect and/or to be aware of the knowledge they possessed. This made it difficult for students to access knowledge and to restructure it in order to construct new knowledge or prevent errors in their learning.</li> </ul> The study culminated in the development of a framework that may in future be used to assess prior knowledge and enhance meaningful teaching and learning based on the quality of students’ prior knowledge. / Thesis (PhD)--University of Pretoria, 2008. / Curriculum Studies / unrestricted