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Acknowledgement is made for the support and advice given by my academic supervisor, Professor Robert Solman, at the University of New South Wales in the conducting and reporting of this research. The friendly and professional guidance of Robert in the planning and conducting of all aspects of the research and the presentation of this thesis is deeply appreciated. Robert has had many articles published in high criterion journals and his untiring work in co-authoring two papers with me based upon my doctoral research has been invaluable. The first, based on the Experiments 1 to 5 reported in this thesis and entitled "The influence of technical illustrations on students' comprehension in geography", will appear in Reading Research Quarterly, 26 (July-August, 1991). The second paper based on the Experiments 6 to 9 reported in this thesis and co-authored also with Professor John Sweller is under review with Instructional Science. Robert has devoted a great deal of his time and energy to me throughout both my doctoral research and the two papers for publication in higher criterion journals based upon my research. so supportive throughout my doctoral studies. Sandra's kindness, love and xi patience set a framework in which I could work effectively at all times on my research, and in writing the two papers and this thesis. The extra work Sandra did at home, particularly in the final stages of writing this thesis, and her loyalty and . encouragement throughout my research contributed a great deal to getting me through all aspects of my studies.

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Instructional techniques commonly used in geographical and environmental education ignore the critical factor of the limited processing capacity of working memory. Illustrations are frequently presented in ways which cause readers to have to mentally integrate mutually referring information prior to learning the content. The three studies reported here examined the effects of presentation format of technical illustrations based upon schema theory and cognitive load theory (Sweller, 1988(Sweller, , 1989) and extend the work of Purnell, Solman and Sweller (1991) in geography. The effects of splitting attention between an illustration and a key were examined. One hundred and fiftyfour students in secondary schools participated in the studies. Negative effects on performance were found in all three studies where attention was split between mutually referring information as there was extraneous cognitive load to the main learning tasks. This applied both to the direct recall of that information and also to the recall of that information which required inferences to be made. To enhance learning, the data supports modern perceptions of cognitive architecture such as Sweller (1993). That is, instruction should maximise the use of long-term memory through schema acquisition and automation of cognitive processes, and thereby reduce cognitive load on working memory to facilitate learning.