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Expert-Novice Differences and Adaptive Multimedia 207 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Introduction When the same digital multimedia materials are presented to novices and experts in a domain, these two categories of users would perceive the presentation rather differently. Imagine a sufficiently complex electrical wiring diagram displayed on a computer screen. Experienced electrical engineers, even if they have not seen this particular diagram before, may immediately recognize familiar functional parts and see the diagram as a representation of a whole device or system. They would be able to rapidly figure out how the circuit operates and what it is used for. On the other hand, first-year electrical trade apprentices may at best see only a set of familiar elements (resistors, switches, etc.) without understanding why all these elements are connected in this particular way. (Let us leave out laypersons that would see a collection of lines, circles, rectangles, and other strange symbols). Obviously, the apprentices need detailed explanations of the circuit operation to understand the diagram. Assume the above categories of users are provided with well-developed comprehensive multimedia instructions (for example, constructed according to multimedia design principles of Mayer, 2001, 2005). The instructions may have the diagram animated and include appropriately-placed (synchronized with animations) narrated auditory explanations. Such multimedia materials would certainly help the novice trainees to understand the operation of the circuit. However, when the same instructions are presented to the experienced engineers, they may find them rather annoying, especially if it is not possible to avoid the instructional details. If post-instruction test tasks are used to assess the understanding of the operation of the circuit, we could find that experts who were presented with the diagram-only format without any explanations outperform the experts who studied the multimedia instructional message. In fact, such relative declines in experts learning were observed on many occasions (see the following section for some references). The effect was related to changes in domain-specific knowledge base that people acquire as they become more experienced in the domain, and to the role this knowledge plays in guiding their cognitive performance. According to a large number of studies in cognitive psychology conducted over many decades, our knowledge base is the most important factor influencing our perception of incoming information. Some recent evidence of early vision that is independent of knowledge structures (e.g., see Pylyshyn, 1999, for an overview) would not change the general significance of the knowledge effect, especially during complex cognitive activities. According to another impressive set of cognitive studies initiated by investigations of the nature of chess expertise (de Groot, 1966), the knowledge base is a single most important factor determining expert-novice differences in cognitive performance (see Chi, Glaser, & Farr, 1988, for an overview). Finally, studies of information processing limitations imposed by the structure of human cognitive architecture (originated by Miller, 1956), and the ways we deal with these limitations by reorganizing our knowledge base and using multiple (e.g., visual and auditory) modalities, provide another theoretical framework and empirical evidence to complete the picture of expert-novice differences in perceiving multimedia messages. This chapter starts with a brief overview of major theoretical issues and empirical evidence that are essential for understanding multimedia design implications of expert-

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