Wednesday, May 1, 2013

A What Point Does More Detail = Less Understanding?

I enjoy visiting Martin Krzywinski's homepage at the BC Genome Sciences Centre from time to time, as it's fascinating collection of great design ideas for communicating scientific data.  This time around, a presentation on designing effective visualizations in the biological sciences was worth the visit.

One slide caught my eye with a warning that most people probably consider obvious: "DO NOT DIVIDE YOUR SCALE INTO MORE THAN 500 INTERVALS".  Regrettably, I can remember a few biologists that would disagree and try to put everything possible into one intricately prepared figure.

Slide 15 from "Designing Effective Visualizations"

You could half-jokingly claim that most hyperdetailed scales are of limited use, except perhaps for pointing out how not to design a scale.  A scientist might counter with "The figure contains all the data!" but as a tool to communicate a concept they fall short.

It also turns out that designing good biological data visualizations isn't just an aesthetic exercise; it actually has an ironic origin in biology.   The example above reminded me of a very similar example in a book I received as a gift many years ago.

In Hack #34, O'Reilly's Mind Hacks points out that there's a limit to the visual selective attention the mind gives to groups of crowded dots or lines.  Basically, when details are crammed together beyond this limit, the viewer can't willfully focus their attention on any particular detail.  

I tried the examples in Mind Hacks (again) and found that truly, I can't concentrate on something as simple as an individual dot on a crowded field.  The surrounding points draw my attention away from the points I look at, again, and again, and again.

Which leads me to believe that if you're cramming data into scatterplots, I probably won't be able to focus on the points you think are important.

Mind Hacks contains many fun examples of when the average person's perception starts to breaks down and is a good guide for becoming aware of some very basic limitations of your eyes and brain.