David Shiffman, an undergraduate at Duke University, was working with Dr. Dan Rittschof on stingray feeding behavior for his honors thesis, which required catching several rays of two different species and keeping them in captivity. While they were holding them in two different kinds of tank, they noticed to their surprise a color change in both species—a result completely incidental to research, but interesting enough for David to summarize for me thus:

The problem with this graphic is that it separates different individuals of the same species, and it’s a little confusing to see how the tank acts as a treatment and the ray color is the result. I suggested he rearrange the photos into a matrix, which is often a good way to show the interaction between factors (in this case, ray color and tank color).

I’d suggest some pretty standard changes: removing boxes around things wherever possible, paying attention to the typeface, and showing rather than labeling the tank color.

I’ve chosen here to make a swatch of the ray color, which can be an excellent way to show color change, but the sacrifice is the distinctive silhouettes of the two species, which make it much easier for us to follow what’s happened. The ideal situation would be better-quality photos of each ray, showing the whole fish without reflections to distract the reader. The rays should be photographed on a neutral background, or using each of the actual tanks as a background (the photos currently all use the same gray background, which just confuses things). The advantage of using the actual tanks is that you’d no longer need to label the colors—they’d be self-evident. The only text necessary would be the species names. Show, not tell.