Human and Machine Perception 4: Communication, Interaction, and Integration edited by V. Cantoni et al., World Scientific, Singapore, 2005 111 VISUAL ATTENTION MECHANISMS FOR INFORMATION VISUALIZATION ROBERTO MARMO Dipartimento Informatica, Università di Pavia, via Ferrata 1, 27100 Pavia, Italy email: marmo@vision.unipv.it MARIO VALLE Visualization Group, Swiss National Supercomputing Centre (CSCS) Via Cantonale Galleria 2, 6928 Manno, Switzerland, email: mvalle@cscs.ch Due to the overwhelming amount of information contained in the images produced by an information visualization tool, an important requirement for any visualization technique is that they should support rapid, accurate, and effortless visual exploration. We address this goal converting information into a graphical representation that takes better advantage of the human visual attention mechanisms. 1. Information Visualization In 1983, Edward Tufte [32] noted “often the most effective way to describe, explore, and summarize a set of numbers, even a very large set, is to look at pictures of those numbers”. Information visualization provides techniques for transforming data and information that are not inherently spatial into a visual form, facilitating their understanding [4,5]. Unfortunately, often there are nice visualizations that do not help understanding and do not create insight, because they ignore the human visual perception rules and are so complex that all the attention is wasted in understanding the image and not in extracting information from the data. We approach information visualization by defining a set of requirements for each visualization technique: 1. shared data: the technique should be able to display independent data values simultaneously; 2. speed: users should be able to obtain information about any of the data values quickly; 3. accuracy: information should accurately represent structures and relationship between data values. 2. Visual Attention Mechanisms The processing capabilities of the visual system are resource-limited and it is not conceivable to deal in exhaustive mode with the huge amount of visual