What's so special about seven?

There are the Four-Figure Wonders (Nature, Science). There are the Go Ahead and Publish Your Last Eight Years of Work in 16 Figures Plus Three Tables (some society journals).

But the majority of mainstream biology papers I've seen contain seven figures. Why?

It isn't as though research just naturally falls into seven figures. Putting together a paper, we often struggle to rearrange the panels for maximum intellectual impact, of course, but we also aim to put it into the magic seven.

The last paper we sent out contained seven figures. One reviewer pointed out that two figures could be plausibly combined; and then suggested that we accumulate enough more data to produce another figure. We did, and we did. Reshuffle, and bingo--still seven figures.

(Speaking of bingo, I'm playing Palinbingo Thursday evening--who's in?)

It's clearly an accepted convention (and yes, there are 6 and 8 and 9 figure papers. But the mode in my field, for sure, is 7.) What are the pluses and minuses?

On the down side, from the author's perspective, it's silly to shoehorn your Great Ideas into a prefab structure. Maybe your paper would unfold best in 5 very dense figures, or 10 thinner ones. But because of the norms, I would hesitate to send out such a manuscript (of course, I'm a junior postdoc; maybe when I'm a big fancy pants person who gets mentioned on YouTube has her own grant I'll have the confidence to buck convention.)

As a reader, though, I rather appreciate it. Especially if I'm skimming a paper, I like to have a sense of how the scientific argument will build, and how many experiments will be synthesized into a picture.

It's kind of like reading a novel: you know that when your hero is trapped in a perilous situation, but you're still gripping three hundred pages in your right hand, that this will not be the final test. Conversely, when the lovers are separated by cruel fate and the pages have dwindled to a precious few, the resolution is not likely to be happy.

Not that any science papers I've read have involved lovers, or peril, but you get the drift.

Here's what I would like to know: how did we converge on seven? The old papers I've read are idiosyncratic--the four figures, or the sixteen, at authorial whim. Do we gravitate towards 7 because of its mystical qualities? (That'd be embarrassing, for us rational scientists.) Have our psyches been colored by the 7 Dwarves, or the 7 Deadly Sins (all depending on your childhood, I guess)?

I don't know the answers to these questions, but since 7 is so powerful, next time I write a manuscript I'm going to try for 7 subheadings, and 7 sentences in the abstract, and maybe 7 supplementary movies. If the voodoo works as expected, then I'm predicting reviews like, "I don't know why, but this paper exerted a strange and wonderful force over me."