Sleep Like A Dolphin


A dolphin rests with one eye closed. (Photo credit: urosr/Shutterstock)

Has this ever happened to you? You finally arrive at your destination, ready to get a good night’s sleep so you can begin your vacation, and then you find … you simply can’t seem to get a good night’s sleep. It’s not you. It’s a phenomenon sleep researchers have long known about, called the “first-night effect” or FNE.

You simply don’t sleep well the first night in a new, unfamiliar place. The effect is so common that some sleep studies disregard readings from a patient’s initial night, as they are considered unreliable. Recently, a Brown University study may have an answer to why we experience FNE: we’re a lot more like dolphins and birds than we realize.

The study looked at 35 sleepers over several nights in the sleep lab. Using highly-advanced brain imaging technology, researchers observed that the left hemisphere of the brain remained more active during deep sleep (“slow-wave sleep”) than the right hemisphere. In addition, they observed that the greater the difference in activity between the left and right hemispheres, the more difficult it was for a patient to get to sleep. They also found that patients awoke more readily when exposed to soft “beeping” sounds directed toward the right ear than if directed toward the left. The right ear, of course, would activate the left side of the brain. While a curious discovery in humans, it’s not a phenomenon unknown in the animal kingdom. It’s a more moderate version of “unihemispheric slow-wave sleep,” an important survival technique many animals employ to stay continually mentally and physically alert.

Birds, for example, are rather extraordinary in how they sleep. While they have the same cycles of deep and REM sleep as humans do, they sleep with one eye open so they’re on constant alert. Birds can even control how deeply they sleep by how much they open or close an eye. Birds also don’t lose muscle tone when they sleep, so they can stand, perch, hang upside down, and even fly, yes fly, while partially sleeping. On a related note, the design of down jackets came from sleeping birds. While sleeping, birds “fluff” up their feathers in order to maintain body temperature.

Whales, orcas, porpoises, and dolphins also don’t go completely unconscious when they sleep. During a 24-hour period, dolphins, for example, get about four hours of sleep for each brain hemisphere by closing one or the other of its eyes. They keep alert, keep swimming, and, perhaps most importantly, keep from drowning, as dolphins need to surface for air periodically. Unlike birds and humans, however, dolphins don’t show any evidence of REM sleep, the stage of sleep where dreams typically occur.

So, it would seem that what the Brown University study uncovered is something that may be evolutionarily hot-wired into our brains, back from the time our species had to remain alert in unfamiliar conditions. The Brown researchers are not completely sure why we experience FNE only in the left hemisphere of the brain, rather than the right or a combination of the two. They believe it may have something to do with differences in the neural connections between the two sides. Those connections responsible for deep sleep may simply be stronger in the left side, making wakefulness of the left hemisphere more advantageous than in the right, as we can respond more quickly to stimuli.

While the study does appear to indicate that FNE does not last past the first night, the question now is “Is there any way we can turn it off?” It doesn’t seem likely much can be done to stop this phenomenon. The best advice might be to do what you can to make your unfamiliar surroundings more familiar. Bring your pillow, wear a sleep mask, or in some way try to make the room you’re sleeping in appear more like the at home.

More to Explore
How Do Birds Sleep?
Here’s why you don’t sleep well in a new place
How Do Dolphin sleep?
When We Sleep in New Places, Half of Our Brains Stay Awake

What Do You Think?