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How to write excellent figure legend titles

In scientific manuscripts, graphics are called figures. I have no idea why; however, it is tempting to suggest that it is because we always leave readers to “figure them out” for themselves. We should take no comfort in the “that’s the way everybody does it” justification. Neanderthals left no legends to explain their cave paintings, and many modern scientific manuscripts are little better. Many scientists are extraordinarily poor at communicating their results, which is, after all, the entire reason for publishing.

I had been editing for a number of years before it dawned on me that most of the figure legends in the scientific literature are terrible! When this occurred to me, the problem was so obvious that I wondered why nobody had taught me the solution years before. I also wondered why I hadn’t thought of it myself. Hmmm!

As in the figure below, readers generally have to compensate for the failures of the authors and the journal.

This legend identifies every band in the electropherogram and describes the buffer system. The only thing it omits is the most important thing of all. It doesn’t tell the reader what the data mean!

A well-written legend should be an independent description of figure. Readers should not have to consult the text in order to understand it.

Before writing a figure legend, carefully consider the following:

What is the scientific significance of the data. Why did you create the figure? What scientific principle(s) or finding(s) does the figure illustrate? What is the “take-home message”of the figure?

Make the figure legend a short, declarative statement in active voice that tells the reader what the data mean!

Then use the remainder of the legend to report experimental conditions and to describe figure elements and statistical parameters.

If a figure has multiple parts, subfigure legends can also be written the same way.

Of course, some figures, such as maps of field study sites have no scientific principle to relate, so this does not apply.

Here are two hypothetical legend titles for the figure above. The first is written in classical form. It tells the reader what the figure is about, but that is all. The second tells the reader the scientific finding illustrated by the figure, or in other words, the significance of the data.

Poor: “The relationship between EOCZ dose and mean arterial pressure and heart rate.”

Excellent: “Increasing i.v. bolus doses of EOCZ, anethole, and estragole (5, 10 and 20 mg . kg-1) evoked immediate and dose-dependent decreases in mean arterial pressure and heart rate in male Wistar rats (n=6-9, p < 0.001, one-way ANOVA).”

The following is an excellent example of an actual figure legend from Suzuki et al., 2015, Scientific Reports 5:14779.

Figure 6. Both N-terminal and C-terminal regions are required for CNOT3-dependent mRNA decay.

Decay curves of CNOT3 targets in CNOT3loxP/loxP MEFs transduced with retroviruses (mock or CNOT3 constructs) and adenoviruses (Ad-LacZ or Ad-Cre) determined as in Figure 4A. n=3. WT CNOT3 expression in CNOT3KD MEFs (red lines in left middle graphs), but not CNOTdC and CNOTdN expression (red lines in right middle and rightmost graphs) restored MEF half-lives to control levels (blue lines in leftmost graph). CNOT3dN expression in control MEFs stabilized mRNAs (compare blue lines in between leftmost and rightmost graphs). *P<0.05; **P<0.01; ***P<0.001

Human beings are extraordinarily good at understanding patterns. A well designed figure can convey information more effectively than text. Therefore, think about how to present data in most understandable way. Be creative! A picture truly is worth a thousand words. Then craft a legend that is worthy of your figure.

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