Teaching Tuesday: Interpreting figures

When I was an undergraduate, I experienced one of those aha moments in my upper-level plant ecology class. At that point I’d taken a few ecology courses and thought I knew my stuff or at least the basics. I’d spent time reading primary literature and had to write papers and reports for various courses. I knew how to make figures and thought I knew how to interpret them. Then I came to my first mid-term exam and sitting there on the front page was a figure. The figure had to do with plant colonization following a glacier receding and although I can no longer recall the details, the fact that I can remember anything after all these years suggests the deep impression this question made on me.  Anyway, I looked at the figure, came up with an interpretation and completely missed the main point. Importantly I thought I’d understood the figure and answered the question correctly. So when I got the exam back and saw my major mistake, I realised how little effort I usually put into interpreting figures. Usually I let the paper, the caption or the speaker tell me what the figure showed.

Ecology is a figure heavy science. We often cram a lot into figures, and that isn’t a bad thing. Many figures have multiple comparisons all within one panel and then there are the multi-panels. Sometimes the interpretation is quick and easy, more of one thing in the treatment vs. control and that sort of thing. But often it takes a moment or two to appreciate all a figure is presenting to you. So I think that being able to understand data and how it is presented in figures is a crucial piece of understanding ecology. The vast majority of 214 ecologists that responded to my survey on teaching in ecology also agree.

a prime example of a super simple figure

But how to teach students the art and science of interpreting figures? Well one thing is to expose students to figures in lectures; another approach is to have them make their own for labs/field exercises. I think these methods are common to many ecology classes. You won’t find an ecology textbook that doesn’t include figures of real data (or at least I haven’t seen one). Depending on the level, I think students are generally familiar with the basics of seeing figures but it is easy to fall into the trap of thinking you understand and missing the whole picture, as I did on that exam ages ago. And although making your own figures gives a perspective of how they work and how to understand the links between data and figures, I find students tend to make much more simplified figures that only show a simple aspect of their data.

With my own experience in mind, I created an exercise specifically addressing figure interpretation. For general ecology students, I simply searched through the recent literature for figures of various types. Many of the figures contained multiple panels, or different comparisons within the same figure. For each figure, I included captions that explain all the different components of the figure (shapes, colour coding, etc) but trimmed out any interpretation of the patterns. The activity included students working in groups and coming up the interpretation of each figure and then we discussed these as a group. The activity works well with reasonably small sections but I could also see this kind of thing working for larger classes using clicker questions or something similar. I think it is especially important to take the figures out of context to allow the students to come up with their own conclusions rather than just read what the authors write. Before setting the students loose on figures, I introduced some of the general concepts about figures and their interpretation. There are some suggestions on how to do that over at TIEE.

If you’re interested in my set of figures, just send me a message and I’m happy to share the file.