Em dashes—heroes, or villains?

Why has a punctuation mark become such a hot topic?

On LinkedIn, the em dash has caused a flurry of debate with two broad camps emerging. Many have pointed out how they are being used more frequently and seem to be the hallmark of AI-generated content. Others have jumped to their defence, pointing to their long-standing use in books and articles.

I've certainly spotted them much more recently, and I've struggled to get AI to create content without them. But at the same time, I find them in many of the books on my bookshelf, most of which pre-date ChatGPT.

It got me thinking, how much has their use actually changed? When should they be used? How do you even type them?

These questions seemed like a great topic for some ChatGPT research.

The research

Like most of my deep research sessions, this started out as a conversation to define the brief. My basic concept was looking at whether em dash usage had increased after ChatGPT launched compared with the two years before, and breaking it down to compare the UK and US to see if there was a geographical difference. The deep research clarification questions prompted me to add a genre breakdown (news, blogs, posts and so on).

After getting the research back, I realised that it might be missing a styling nuance. What if the em dashes were replacing en dashes and hyphens, rather than being purely additional? I also wondered if there were any other reasons AI favoured em dashes, and how easy it is for humans to type them on various devices. So I set off another round of research to build in these questions.

ChatGPT carried out the research, in which it says it compared thousands of UK and US headlines, blogs, academic abstracts, social posts and forum comments before and after ChatGPT, counting every dash per 1,000 words. Of course, even deep research can hallucinate, and there's no way of knowing for sure if it actually did that, and what it found. But assuming that it did, there are some interesting concepts that come out. If you want to see the research, you'll find it in my post about em dash research in the If You're Wondering topic of the Community.

Em dash use has increased, particularly in the UK

Em dashes now appear more often across almost every form of online writing. The increase is most visible in blogs and social posts, which are also the places where AI tools are most likely to be used.

The Deep Research suggests that in UK writing, em dash use has roughly doubled since ChatGPT was released. In the US, where it was already more common, the increase is slightly smaller in percentage terms but still significant. In blogs, for example, usage went from about 1.5 to 3 per thousand words in the UK, and from 3 to 5 in the US. Social media posts show smaller but consistent increases.

In edited writing, such as news and academic work, the difference is minor. The em dash is used occasionally, but not more than before. Presumably this is down to style guides and more rigorous reviews.

My own experience is that em dashes are occurring more in online-only news article titles, but despite wasting a couple more Deep Research credits, I couldn't get any Deep Research that backed that hunch up.

According to the research, hyphen use has remained roughly the same, en dash use has reduced slightly, and double hyphens (--) are reducing a lot. So this would suggest that some of the increase will be down to a switch from one kind of dash to another.

Why does AI favour em dashes

Part of the answer to this feels fairly obvious. Em dashes were already more common in US writing, especially formal writing, so they will have appeared in the training data more often than we are used to seeing them in the UK.

Less obviously, the Deep Research pointed to the flexibility of em dashes. They can be used in the place of a comma or colon, or a set of brackets. So they are effectively a kind of catch-all when trying to calculate how to connect clauses.

How easy are em dashes to type?

There's no key for an em dash on a keyboard. On a Mac, you can get one with Option + Shift + hyphen (which I never knew until doing this research). On Windows it's Alt + 0151. On iPhone and Android, it's holding down on a hyphen and then selecting from a popup.

As humans, we have to go out of our way to use an em dash, even when we want to. But for AI it's just another character, and one that can cover a lot of different uses.

In the end, it's about intent and accountability

We've always had em dashes, and people have taken the extra steps to use them when they were the right choice in prose or formal writing. They have become a signal of AI content because they are now appearing more in informal content.

The issue isn't really em dashes, but in the copy and paste use of AI content. We should be setting our intent clearly when we set out to create content: what style am I using? What sort of punctuation would work?

And we need to take accountability for the end result. And if you're using em dashes because you made the decision to use that style, you've considered whether they are appropriate in the final content, and you're happy to put your name to it, then maybe it's a good thing they are on the rise.

Of course, if you're not a fan, then this is precisely where the HAHAH Method can help.

And, in case you were wondering, that is an intentional use of an em dash in the title. Personally I avoid dashes and only use hyphens for compound words. But, the title just didn't feel right without one.