The writer is author of ‘Fallen Idols: Twelve Statues That Made History’

Can you be sure that what you’re reading isn’t generated by artificial intelligence? It’s often easy if you read for content — large language models, or LLMs, are famous for advising you to stick toppings to your pizza with glue, advocating eating rocks and insisting that there are only two Rs in the word “strawberry”. But is there also something in the style?

For the last few months, a theory has been circulating on developer forums that one tell-tale sign is a surfeit of em dashes — the longest and proudest dash, the length of a lower-case m, rather than the modest en dash, the length of an n, or the puny hyphen. ChatGPT is apparently so addicted to em dashes that some users claim it’s impossible to prevent it from — sprinkling — them — through — all of its output, as if Emily Dickinson herself is breathlessly circulating your quarterly report.