November 12, 2010
Gravity isn’t just for the physicists. The force, or at least the notion of it, actually influences how we interpret scientific data, so much so that when shown a donut chart, some people thought it might actually roll away, says Robert Kosara, a researcher at UNC Charlotte.
Kosara and his graduate student found that people interpret charts that had an unequal distribution of "weight,” or darker and lighter colors, as unstable. The donut can roll away because gravity can turn the color imbalance into movement. The question why or how we do this has no scientific answers, yet. Researchers in information visualization, InfoVis, should focus on building the theory of visualization as much as they focus on creating new systems and developing new techniques to represent data, Kosara argued while presenting the Nov. 12 Visualization Friday Forum lecture.
Data visualization is a standard practice in the scientific method. Changing numbers into pictures lets scientists use their human prowess with reading visual data to spot patterns, trends and outliers, Kosara says. But visualizing data is also becoming a popular trend in the media. It produces pretty pictures for publications and provides another way to tell a story.
Because scientists do not yet know how and why some visualizations work and some don’t, it’s hard to know which visualizations to use. Kosara illustrated this point with a bar graph and a line graph charting sex versus height. When shown the bar graph, subjects interpret that, on average, males are taller than females. When shown a line graph representing the same data, subjects argue that as one becomes more male, he or she, becomes taller.
“That’s bad,” Kosara says. The subjects are attaching meaning to the representation rather than the actual data. The example is an exaggeration, but sheds light on the challenge of deciding what graph or picture best represents more complex data sets. If he can determine scientifically why men do better looking at tree graphs compared to females or how people rationalize gravity in an abstract donut chart, Kosara says, it might better transform scientific numbers into real-world stories.
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