A Creepy Robotic Cradle Worked Wonders on Sleep in a Weird Study

What works for babies may also work for adults.

sleeping bed

A typical adult rocking bed — yes, they exist — costs a couple of thousand dollars. But the combined power of two recent studies indicates that it might be worth the investment. The research suggests that a gentle rocking motion, calibrated at one particular exact frequency, not only improves sleep quality but can also have an impact on memory the next day.

Since at least 2011, scientists have been showing that rocking can help improve sleep in humans. The two new Current Biology studies, one on humans and one on mice, build upon those findings, showing that being rocked all night at a constant rate by a creepy robotic cradle, shown in the video above, actually promotes deeper sleep and keeps people from waking up in the middle of the night.

In the paper on on humans, Univesity of Geneva biologist Laurence Bayer, Ph.D., tested how being gently rocked at a rate of 0.25 Hz (that’s approximately once every four seconds and is called the “optimal rate”) impacted the sleep cycles of 18 “good sleepers.” The good sleepers spent three days in her lab: one day to get used to the lab, one day in a stationary bed.

rocking hammock
Being rocked to sleep improved memory and sleep quality in adults when they were rocked at a steady rate (so a hammock probably won't work.) 

Bayer and her co-authors found that the participants who were rocked all evening spent significantly more time in the N3 stage of sleep, also called slow-wave sleep. They also woke up less frequently during the unrocked sleepers and even performed better on memory tasks in which they learned random word pairs before bed and were asked to recall them in the morning.

“Here too, rocking proved beneficial,” said co-author Aurore Perrault, Ph.D., to the BBC. the test results were much better after a night in motion than after a still night.”

memory task sleep
Being rocked to sleep improved performance on a memory task the next day. 

Meanwhile, the mouse study led by Konstantinos Kompotis, Ph.D., a postdoctoral researcher at the University of Lausanne, gave detailed insight into what makes sleep rocking effective.

Kompotis found that mice preferred to be rocked to sleep at a rate four times faster than humans’ preferred rocking rate. He was testing an early theory about sleep rocking suggesting that the action triggers a response in the brain’s vestibular system — the organs in the inner ear that help provide a sense of balance.

As it turns out, mice who lacked one particle in their inner ear, called an otolith, didn’t experience the benefits of being rocked to sleep. Otoliths, the team writes, help the brain “encode linear acceleration” and might help the brain process the “rocking signal.” The discovery gives them an idea of how we might be able to hack the vestibular system to improve sleep in a “non-pharmacological, non-invasive” manner.

For now, we’re left to contemplate whether it’s really worth shelling out thousands of dollars for a rocking bed. These studies, taken together, seem to indicate that you really need to be rocked at a constant rate to get the full range of effects. That means a cheaper option, like a hammock, probably won’t do the job, as Bayer told the BBC when she was asked about it point-blank. “A hammock would probably not be as efficient, although people often report a sense of relaxation when rocked in a hammock,” she said.