Writers’ Lab: The Art of Writing Compelling Figure Captions

When skimming through a paper, you typically read the abstract, glance over the introduction and conclusions and study the figures. 

However, when we write (and subsequently proofread) our papers, the figure captions are an often overlooked element of writing.

By writing compelling figure captions, you can attract the reader to go and read the entire paper. But how do we select figures and write good captions along with them?

1. The right figures

Consider your figures as a graphical representation of what you want to tell your reader. For a traditionally structured paper, this would mean that your visuals go from introducing a concept, then showing your specimens, your results and finally your analysis of these results.

2. Check the guidelines

When preparing a paper, carefully read the instructions. Play the game by the rules and avoid a straight rejection. Make sure your figures use the right font, line thickness and calculate their word equivalent according to the given rules.
If you react to this piece of advice with a “duh” – awesome! But too often authors seem to overlook this essential element of writing.

3. Caption and figure belong together

Your caption should explain your figure without the reader needing to go and dive into the text to figure out what the figure actually means.
When proofreading, give the figures and captions a separate round on a different day, and check if you can understand the figure by simply reading the caption.

4. Give due credit

Another “duh” moment, but again not always correctly done.
If you use an existing figure, make sure you request the right to replicate the figure to avoid copyright infringement.
If you build a figure based on a theory, give due credit to the author of the original idea by adding the correct citation in the caption.

5. Print the page

To check if your font size is correct and your labels clear, print a separate page and check the figure.
I learned this lesson while working on my dissertation. My promotor remarked that my figures had odd font sizes. On my screen, and in Illustrator everything looked fine and I consistently used the same font size – but I had overlooked that fact that figures are rescaled as you implement them into MS Word.

6. Dual approach

A good figure caption contains two parts:
1. A description of what the figure shows, and
2. an explanation of what it means.

7. Subfigures

If a figure consists of different components, give them a name (a), (b), … This rule should be totally obvious as well, but too often authors refer to Figure 2, bottom or Figure 7, right – and when an article is prepared for printing and the layout is arranged by the editors, these spatial references might lose their meaning.

8. The Ranly rules

Don Ranly’s rules [1] are too good not to state here:

• Every picture needs a caption.
• Captions are read five more times than text.
• Complement the image; say what it does not say.
• Give useful information.
• Connect the figures to the text. A good caption says “see story” without saying it.
• Write complete sentences.
• Use active verbs in the present tense.
• Scale the caption to the size of the image: captions should be at least two lines, optimum three lines, maximum four lines.

Do you have a personal style of writing captions? Or have you not paid much attention to them until now?

[1] Don Ranly, “Ranly on Heads,” University Research Magazine Association Annual Conference, Florida State University, May 16–19, 2006.