Graphical perception is a link between our visual system and statistical graphics. Inputs from the nervous system is what drives graphical perception. In this age of information explosion, it is important in understanding how graphics are perceived. From the past, people have come up with graphical perception theories to better understand graph design, presentation and interpretation. In 1984, Cleveland and McGill tested overall theories of graphical perception and had some interesting findings. They found that people were better at length judgements than area judgments and better at area judgements than volume judgements. This supports why people misinterpret the information in a pie chart. In fact, the root of this lies in the challenge of angular perception. Research on perception mechanics of pie charts showed that there is a difference in what people were seeing than what they were being shown (referred to as the absolute error). Different forms of pie charts (Donut, arc, area etc.) had different absolute error. Kosara and Skau found that pie charts are not read by central angle. They are read by arc length, area or a combination. We could look for other ways of quantifying the information in pie charts. Bar charts could be preferred over pie charts. Cleveland and McGill explain dot charts are superior to bar charts and pie charts.
Understanding how graphics is perceived should be taken into consideration before visualizing information. Otherwise, people consuming graphical information may have biased perceptions. With plenty of tools available now days to plot or graph the information, we should not be using any or every form of graphics. It becomes important to understand which graphs should be preferred over others so that the information is perceived with minimal absolute error.
References:
Cleveland, W. S., & McGill, R. Graphical Perception: Theory, Experimentation, and Application to the Development of Graphical Methods
http://flowingdata.com/2010/03/20/graphical-perception-learn-the-fundamentals-first/
http://www.win-vector.com/blog/2009/08/good-graphs-graphical-perception-and-data-visualization/