A well researched technique that bores you to sleep
July 16, 2026·4 min read
Cognitive Shuffle, also known as Serial Diverse Imagining or SDI, is a technique developed by cognitive scientist Luc Beaudoin to help quiet a racing mind at bedtime. The idea is simple to describe and surprisingly effective in practice: instead of trying to force your mind blank, you feed it a slow stream of random, unrelated, concrete words. Picture each one for a few seconds, then let it go and move to the next.
EFFECT SIZE (BEAUDOIN, 2016, N=154) VS. STANDARD BENCHMARKS
Cohen's benchmarks for effect size: small = 0.01, medium = 0.06, large = 0.14. The study's reported effect sizes ranged from 0.43 to 0.71, well past the large-effect threshold.
The mechanism is about denying your mind the raw material for a narrative. Racing thoughts at bedtime are usually a story: tomorrow's meeting, an argument replaying, a worry looping. That story needs continuity to sustain itself.Random, disconnected words can't be woven into a story. Your mind can't build a coherent thread out of "umbrella," then "mountain," then "spoon." Without a thread to hold onto, the looping has nothing to grip, and it tends to loosen.
Evocative, unusual nouns like "lantern," "trellis," or "meringue" might read as more atmospheric, but interesting words keep your mind hooked. That's the same mechanism Instagram, TikTok, and every other engagement-driven app relies on: give the brain something stimulating enough and it stays alert, curious, awake. Exactly the opposite of what you want right before sleep.
We built the word bank around common, everyday nouns instead (apple, chair, river, pillow), words that get pictured instantly and don't ask anything of you. Boring is not a bug in this technique. Boring is the entire mechanism.
apple
Yes. Every word is shown on screen and spoken out loud at the same time, using real recorded audio. You don't pick between seeing the words or hearing them, you get both together.
That also means you don't have to keep watching. Once a session starts, you can turn your screen off and just listen, the audio keeps playing straight through a locked screen, the same way a podcast or music app would.
That's closer to how the technique was actually designed to be used: eyes closed, phone face-down, nothing to look at.mySleepButton, the original app built by the technique's inventor, works this same way for exactly that reason. If you'd rather have no sound at all, the volume slider goes all the way down.
We're actively refining the word sequencing itself. Early testing points toward starting a session with genuinely interesting words and gradually shifting toward plainer, more neutral ones as it goes, keeping the mind engaged early without working against the calming effect later on. We're also introducing slight variation in the timing between words. A perfectly predictable rhythm is something the brain quickly learns to tune out as background noise, and that habituation is exactly what the technique is trying to avoid.
Cognitive Shuffle works by giving your mind boring, unrelated words instead of the story it's trying to build, so the racing thoughts have nothing left to hold onto. Numbscroll takes the same core idea and applies it to scrolling instead of imagining.
Try it for yourself. No app to download, it works instantly in your browser, free, and always will be.
Try Cognitive Shuffle