Perception Essay
The subject of graphical methods for data analysis and for data presentation needs a scientific foundation. The graphical perception approach is the visual decoding of information encoded on graphs-and it includes both theory and experimentation to test the theory. The theory deals with a small but important piece of the whole process of graphical perception. The first part is an identification of a set of elementary perceptual tasks that are carried out when people extract quantitative information from graphs. The second part is an ordering of the tasks on the basis of how accurately people perform them. Elements of the theory are tested by experimentation in which subjects record their judgments of the quantitative information on graphs. The experiments validate these elements but also suggest that the set of elementary tasks should be expanded. The theory provides a guideline for graph construction: Graphs should employ elementary tasks as high in the ordering as possible. This principle is applied to a variety of graphs, including bar charts, divided bar charts, pie charts, and statistical maps with shading. The conclusion is that radical surgery on these popular graphs is needed, and as replacements alternative graphical forms-dot charts, dot charts with grouping, and framed-rectangle charts.
Also, despite the bad reputation in data visualization, pie and donut charts are commonly used in information graphics and many other areas. Studies have attempted to find out which visual encodings are important for reading values off of these charts by splitting them into their constituent parts. The results show that all three visual cues are important, but that arc length, in particular, seems to provide important information. Angle is clearly not a significant bearer of information in pie charts, and in particular, the central meeting point of the circle segments does not appear to be crucial. Donut charts thus appear to be no worse than pie charts. Note that despite the generally firmly held stance against pie charts, little actual research has looked into their underlying perceptual mechanisms or the impact of design variations. More work is clearly needed, especially because of these charts’ widespread use.
Reference Graphical Perception: Theory, Experimentation, and Application to the Development of Graphical Methods. Available from: https://www.researchgate.net/publication/229099907_Graphical_Perception_Theory_Experimentation_and_Application_to_the_Development_of_Graphical_Methods