AI tell · grade B
Why AI writing is full of em dashes: the em-dash chain
The em-dash tell is about density, not a single mark. One em dash is a century-old piece of punctuation and flags nothing. What reads as machine writing is the chain: several em dashes packed into a short span, each one hinging a clause onto a restatement of the clause before it. Our logs put the density at roughly one dash every 80 to 90 words. The fix is not to ban the dash but to break the chain: keep at most one per few paragraphs and let periods and commas do the rest.
What it is
A run of em dashes used as an all-purpose joint, each one tacking a rephrase or an aside onto the sentence. The individual dash is fine. The pattern is the tell: two, three, four of them within a paragraph, doing the work that varied punctuation should.
How often it shows up
In our logs (emp-008) em dashes appeared at a density of about one per 80 to 90 words, and 9 of 12 models used a dash to pivot out of a validation opener. Because a lone dash is legitimate and only the density is diagnostic, the checklist scores the chain and treats an isolated dash as report-only.
Why readers flag it
A reader does not object to a dash. They notice the drumbeat of them: every sentence hinging the same way, a rhythm that never resolves into a plain full stop. The uniformity is the giveaway, not any single mark.
The fix
Count the dashes in a paragraph. If there is more than one, convert the extras. Some become periods, some become commas, and a few restatements just get deleted because the sentence already said it. Keep one dash where it genuinely earns its place.
Examples
The plan was simple—deceptively so—because the real work—the part nobody sees—happens long before launch—in the quiet weeks of preparation.
The plan looked simple, but the real work happened long before launch, in the quiet weeks of preparation nobody sees.
Questions
Does using an em dash mean my writing looks AI-generated?
No. A single em dash is normal editorial punctuation and has been for over a century. Only a chain of them in a short span reads as a machine tell.
Should I remove every em dash to be safe?
No, and stripping them all can make prose read choppy. Keep one where it works and break up the rest so no paragraph leans on the dash as its only joint.
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