Why the sentences get shorter

As we fall asleep, we stop thinking about the future.

Speth and colleagues collected reports of hypnagogic mentation — the fragmentary stuff of the minutes before sleep — and ran a linguistic analysis over them. The finding is in the title of the paper: as we fall asleep we forget about the future. Forward-looking language drains away as sleep approaches.

Sleep-onset thought turns to images, too. What people report from those minutes ranges from a fleeting, isolated picture to a full-fledged dream, and much of it is closer to a slideshow with the projector slipping than to a story.

A Sheeps story imitates that decline rather than merely getting quieter. It opens at fourteen to eighteen words a sentence and ends at four to eight. The silences between its scenes grow from two seconds to seven. The grammar simplifies — subordinate clauses thin out and are gone by the last third. The words themselves get plainer. And forward-looking language is gone from the final third.

A story that ends in short sentences which are still forward-looking has decayed on one axis out of four.

All four are measured. They are what the story generator was tuned against, scored on sentence-length decay, syntactic decay, vocabulary decay, and how much forward-looking language survives into the final third — and every story it writes is measured again for shortening sentences, while its pauses are set to grow from two seconds to seven.

The longer answer

The state those sentences are matching has a name, hypnagogia: the stretch between waking and sleep when sentences give way to images and fragments and the mind stops planning ahead. What happens when you fall asleep follows the same minutes in the body and the brain, and how a Sheeps story is made shows the rule in practice — sentences that open at fourteen to eighteen words and end as fragments of four to eight.