If you’ve read pretty much anything I’ve written, you might have noticed how much I like the em-dash. I try to pay attention to writing styles, and like many people, I find the em-dash—which delivers a pause if used singly or a semi-parenthetical statement if used doubly—to be an essential component of my own writing style. I was therefore very excited when I read this piece in the New York Times last year, which extols the virtues of the em-dash. Author and English professor Ben Yagoda gets it exactly right when he says the following:
“Writers who deploy this mark comfortably and adeptly (rather than haphazardly) are conscious of the rhythm and dynamics of a sentence. A well-placed dash adds energy and voice.”
But then, just one sentence later, Yagoda says:
“[The em-dash] proposes a long pause—slightly longer than a parenthesis, significantly longer than a comma—that in a subtle way calls attention to itself; as the linguist Geoffrey Nunberg has remarked, dashes are primarily found in “genres that permit reference to be made to the act of composition, whether the break indicated by the dash is genuine or artful invention…” (In other words, be wary of using them in an international treaty or a scientific paper.)”
I was really quite dismayed to read that even a strong proponent of the em-dash felt it has no place in scientific writing. But then I realised that Yagoda isn’t a scientist, and perhaps scientists are actually okay with using em-dashes. So I googled “scientific writing em-dash”; distressingly, the two most relevant hits had this to say:
“But note that the em-dash is rather informal and rarely used in scientific writing.”
“Em dash (―) is an even longer dash [than a hyphen or en-dash] that is not used in scientific writing”
This wasn’t too surprising; after all, almost everyone I’ve asked to edit my scientific manuscripts suggests eliminating em-dashes. And these suggestions work—one of my publications has gone from five em-dashes in an intermediate draft to two in the final article. But I remained adamant that em-dashes can be used effectively even in a scientific paper, and set out to find an example.
My first stop was the work of a former labmate, who I knew was a fan of the em-dash as well. In reading Yagoda’s comment above, this labmate had said:
“I think his comment stems from a general misunderstanding of scientific writing – that it should be made intentionally bland. In fact, I think the two top reasons he outlined for using a dash – to be “conscious of the rhythm and dynamics of a sentence” and to add “energy and voice” – are exactly why we need them in scientific writing.”
However, a quick (and certainly incomplete) scan of some of his recent papers revealed no em-dashes, which really goes to show that it can be tough to incorporate them into scientific writing [update: I stand corrected. He did manage to sneak in a few in the papers I looked at, which I missed in my scans]. I then shelved this post for later, and began to hunt for a paper that illustrated the utility of these punctuation marks.
[two weeks later…]
Scott-Phillips et al. (2014) is a remarkable paper in many regards, foremost being their use of a novel format that they call an adversarial collaboration, resulting in a fairly balanced take on a controversial issue in evolutionary biology. But what’s relevant here is how well this paper is written—it’s one of the more readable scientific papers I’ve ever come across. And encouragingly, they have several great examples of em-dashes! This one is my favourite, using the em-dash to make a potentially involved sentence very clear:
“From a conventional perspective, beavers’ dams are ‘extended phenotypes’ (Dawkins, 1982), which evolve in essentially the same way as other aspects of the beaver phenotype—through the differential selection of dam-building alleles.”
And here’s another example. It might be the closest one can come to being funny in a scientific paper, and the punch of the sentence comes from an em-dash:
“For example, parasites sometimes compete with one another to extract as many resources as possible from hosts, and in doing so kill the host more quickly—an obvious reduction in the host’s fitness.”
For the sake of completeness, here’s a rather amusing piece illustrating how, like with anything, one can overuse the em-dash.