It seems easy to figure out what data visualization charts are bad. They’re the ones crammed with too much text, unnecessary ornamentation, garish colors, and cheap clip art.
Edward Tufte, the noted design expert, derided such decorations as redundant at best, useless at worst. He called them “chart junk.” But the debate still goes on between visualization experts: Could these derided extra elements serve a purpose?
Yes, the same design elements that attract so much criticism, a new study reports, can also make a chart more memorable.
Communicating Complex Information
“I spend a lot of my time reading these scientific papers,” said lead author Michelle Borkin, “so I have to wonder, when I walk away from my desk, what am I going to remember? Which of the figures and visualizations in these publications are going to stick with me?”
Working at the interface of computer science and psychology, Borkin specializes in the visual representation of data, looking for the best ways to communicate and interpret complex information.
Borkin and her advisor, Professor Hanspeter Pfister, turned to Aude Oliva, a research scientist at MIT’s Computer Science and Artificial Intelligence Lab, and a cognitive psychologist by training.
Faces vs. Landscapes
Oliva’s lab has been studying visual memory for about six years now. Her team has found that in photographs, faces and human-centric scenes are typically easy to remember while landscapes are not.
“All of us are sensitive to the same kinds of images, and we forget the same kind as well,” Oliva says. “We like to believe our memories are unique, that they’re like the soul of a person, but in certain situations it’s as if we have the same algorithm in our heads that is going to be sensitive to a particular type of image. So when you find a result like this in photographs, you want to know: is it generalizable to many types of materials—words, sound, images, graphs?”
For Oliva’s group, the research would provide more evidence of cognitive similarities in the brain’s visual processing, from person to person. For Pfister’s group, it could suggest that certain design principles make visualizations inherently more memorable than others.
Together, the team designed a large-scale study in the form of an online game.
In order to rigorously measure the memorability of a wide variety of visualizations, they collected more than 5,000 charts and graphics from scientific papers, design blogs, newspapers, and government reports and manually categorized them by a wide range of attributes.
Serving the graphics up in brief glimpses of just one second each to participants via Amazon Mechanical Turk, the researchers tested the influence of features like color, density, and content themes on users’ ability to recognize which ones they had seen before.
What Makes for a Memorable Chart?
“A visualization will be instantly and overwhelmingly more memorable if it incorporates an image of a human-recognizable object—if it includes a photograph, people, cartoons, logos—any component that is not just an abstract data visualization,” says Pfister. “We learned that any time you have a graphic with one of those components, that’s the most dominant thing that affects the memorability.”
Visualizations that were visually dense proved memorable, as did those that used many colors. Other results were more surprising.
“You’d think the types of charts you’d remember best are the ones you learned in school—the bar charts, pie charts, scatter plots, and so on,” Borkin says. “But it was the opposite.”
Unusual types of charts, like tree diagrams, network diagrams, and grid matrices, were actually more memorable.
“If you think about those types of diagrams—for example, tree diagrams that show relationships between species, or diagrams that explain a molecular chemical process—every one of them is going to be a little different, but the branching structures feel very natural to us,” explains Borkin. “That combination of the familiar and the unique seems to influence the memorability.”