All
6 Bizarre Sleep Habits and the Facts Behind Them
Last updated: September 2026 Human sleep looks odd enough from the outside, but nature and history make it look positively sensible. Dolphins sleep with half a brain at a time, horses doze standing up, and our own ancestors treated the night as two sleeps with an intermission. Here are six of the strangest sleep habits on record, and what the facts behind them say about your own nights. Quick answer: The animal kingdom's strangest sleep habits are real adaptations: dolphins sleep one brain hemisphere at a time so they can keep surfacing to breathe, and horses lock their legs to doze upright while predators prowl. The strangest human habits are mostly history or bad ideas: segmented "first and second sleep" was normal before artificial light, while extreme polyphasic schedules like the Uberman are unsustainable for almost everyone. The common thread is that every species protects deep sleep however it can, and humans do it best in one consolidated night. 1. Dolphin sleep: the art of unihemispheric slumber Dolphins sleep with one half of the brain at a time, keeping the other awake with one eye open so they can keep breathing at the surface and watching for danger. It is called unihemispheric slow-wave sleep, and it means a dolphin is never fully unconscious. Humans have no true equivalent, though the "first night effect", sleeping badly in a new place while part of the brain stays vigilant, is a faint echo of the same instinct. 2. Sleeping upright like horses Horses can doze standing thanks to a stay apparatus, tendons and ligaments that lock the legs without muscular effort, an anti-predator adaptation that lets them bolt from a standing start. Even so, they must lie down for their REM sleep. For humans there is no benefit to upright sleeping, whatever the occasional claim; we get our best sleep, and all of our deep and REM stages, lying down. 3. Segmented sleep: a sleep pattern from the past Before artificial light, many Europeans slept in two shifts: a "first sleep" from early evening, an hour or two awake around midnight for prayer, chores or conversation, then a "second sleep" until dawn. The historian A. Roger Ekirch documented hundreds of references to it. Waking in the small hours is, in that sense, an old human pattern rather than a malfunction, though the modern schedule rewards a consolidated night; if your midnight intermissions are unwanted, our guide on resetting your body clock covers how to close the gap. 4. Sleeping with animals (literally!) Surveys consistently find that most UK pet owners let their animals share the bed. The trade-off is real in both directions: a pet's movement, noise and heat fragment sleep, and pets also add allergens and dander to the very surface you breathe against for eight hours, which our guide to dust mites in your bed puts in context. Against that, many people genuinely sleep more securely with a companion. If the dog stays, wash the bedding more often and give the pet its own blanket zone. 5. Extreme polyphasic sleep: the Uberman schedule The Uberman schedule swaps a night's sleep for six 20 to 30 minute naps spread around the clock, about two to three hours of sleep a day, with da Vinci and Tesla rumoured, on thin evidence, to have lived this way. Sleep scientists are close to unanimous that it does not work: deep sleep and REM need longer consolidated blocks, and chronic restriction of both collects the debts covered in our sleep debt guide. Strategic napping helps; replacing the night does not. 6. Fear-induced "segmented sleep" in Korowai tribes The Korowai people of Indonesian Papua traditionally build treehouses high above the forest floor, and accounts describe light, frequently broken sleep, a pattern shaped by an environment that rewards vigilance. It is a reminder that how safely we sleep has always shaped how deeply we sleep, and that the modern luxury is a bedroom secure enough to switch off in completely. What do the bizarre habits teach the rest of us? One consistent lesson: every species protects its deep sleep with whatever its environment allows, and for humans that means a consolidated night somewhere dark, quiet, cool and comfortable. However ordinary it sounds next to dolphin brains and treehouses, the bed is the human adaptation, and every model in our range of hybrid mattresses is built for exactly that job: tall pocket springs that keep a partner's movement on their side, and open-cell memory foam that stays cool through the night. REM-Fit 3000 Supreme Hybrid Mattress 3000 tall premium pocket springs under open-cell memory foam: the unremarkable habit that outperforms every bizarre one. Shop the 3000 Supreme ✓ 100-night trial (200 with a protector)✓ 15-year guarantee✓ Free UK delivery✓ 0% finance Bizarre sleep habits FAQs Last updated: September 2026 Do dolphins really sleep with one eye open? Yes. Dolphins sleep one brain hemisphere at a time, keeping the opposite eye open, so they can continue surfacing to breathe and stay alert to threats. It is called unihemispheric slow-wave sleep, and it means a dolphin is never fully asleep the way humans are. Is segmented sleep healthy for humans? It was normal before artificial light, so waking in the small hours is not automatically a disorder. But the modern day rewards one consolidated night, and for most people a fixed wake time and a good sleep environment close the midnight gap better than embracing the intermission. Does polyphasic sleep work? Not the extreme versions. Schedules like the Uberman cut total sleep to two or three hours a day, starving the deep sleep and REM that only come in longer blocks, and almost nobody sustains them. A single short afternoon nap is the version of polyphasic sleep that science supports. Should I let my pet sleep in my bed? It is a trade: pets fragment sleep with movement, noise and heat, and add allergens to your bedding, but many owners feel calmer and sleep better with them there. If the pet stays, wash bedding frequently, use a mattress protector, and give them their own blanket at the foot of the bed. Sources: Sleep Foundation, Biphasic Sleep; A. Roger Ekirch, At Day's Close: Night in Times Past; Sleep Foundation, Animals and Sleep.
Read more
The Changing Nature of Sleep: How Our Rest Evolves as We Age
In this blog, we will delve into the intriguing changes that occur in our sleep as we age, shedding light on the intricate relationship between age and the quality of our rest.
Read more
