Middle Ducks Sleep with Both Eyes Closed


Many animals and birds have the ability to sleep with only one hemisphere of the brain going dormant at a time, which affords them some measure of protection from predators while resting. Ducks sleeping in a row actually seem to assign the role of “guard duty” to the ducks on either end of the row. The “end ducks” have been observed with the eye facing toward the group closed in sleep, while the eye facing away from the group was more likely to remain open.  

It was long thought that human beings do NOT engage in single hemisphere sleep. But, sleep researchers have known about something they call the “first night effect” for decades, where the first night of sleep in a new place is predictably poor. In fact, they would often discard the data for the first night in a study. This effect disappears on the second night (for unexplained reasons), and does not appear to be under conscious control.

Recently, researchers studied 11 subjects, looking for clues to the cause for this effect. They observed that the left side of the brain appeared to remain more watchful and alert on that first night in a new place, while the right side was less rousable.

Pity the business traveler who arrives at a location the night before an important presentation and has to cope with “first night effect”. Or the patient going into a hospital for a one night sleep apnea study?

Those of us who work with studies and data will quickly note the small sample size, and indeed, some of the reactions to the study focused on this point. Could this study group adequately account for the effects of gender? Or right brain/right hand dominance?

We might also wonder, what, exactly, triggers this effect? And can we minimize it? Is it tactile, and most influenced by the unfamiliar mattress firmness, pillow softness, sheet scratchiness? Is it olfactory, or auditory, more driven by unfamiliar smells and sounds? Is it the difference in ambient light? Is it worse when crossing time zones? Does it help to bring your spouse along, or does that just result in TWO people with “first night effect?”

And, does each duck get a chance to be the middle duck?


“Sleeping with Half a Brain”, Scientific American (Mind), Sept 1, 2016.

“Half Your Brain Stands Guard When Sleeping in a New Place”, NPR, April 21, 2016.

“Sleeping With One Eye Open”, A Moment of Science, Indiana Public Media, June 5, 2012.

Photo by Roksolana Zasiadko on Unsplash