Study: Believing You’ve Slept Well, Even If You Haven't, Improves Performance

The positive effects of "placebo sleep" 
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Alyssa L. Miller/flickr

Problem:  Who even sleeps anymore? You and everyone you know are probably loading yourselves up with coffee or whatever your stimulant of choice is so you can plod through your day as some semblance of an upright human being. Then you get home and you don’t go to bed early enough because this is the only me-time you get, damn it, and if you want to watch three hours of Netflix, then you will. Or you try to go to sleep but you fail and end up tossing and turning, because sleeping is actually kind of hard, and the more you want it, the more it slips through your grasp.

But maybe the knowledge that you aren’t sleeping enough is part of what’s keeping you trapped in your swamp of lethargy during the day. Maybe if you were sweetly, blithely ignorant of your somnial failings, you’d feel more chipper and work more efficiently. In a recent study published in the Journal of Experimental Psychology, researchers from Colorado College tested the effects of being told you’re getting enough sleep—“placebo sleep,” as they call it.

Methodology: Participating undergrads first reported how deeply they’d slept the night before, on a scale of one to 10. The researchers then gave the participants a quick, five-minute lesson about sleep’s effect on cognitive function, telling them it was just background information for the study. During the lesson, they said that adults normally spend between 20 and 25 percent of their sleep time in REM sleep, and that getting less REM sleep than that tends to cause lower performance on learning tests. They also said that those who spend more than 25 percent of their sleep time in REM sleep usually perform better on such tests.

Then participants were hooked up to equipment that they were told would read their pulse, heartrate, and brainwave frequency, though it actually just measured their brainwave frequency. They were told that these measurements would allow the researchers to tell how much REM sleep they’d gotten the night before. This was not true.

Then one of the experimenters pretended to calculate that each participant got either 16.2 percent REM sleep or 28.7 percent REM sleep the previous evening. After getting their reading, participants took a test that measures “auditory attention and speed of processing, skills most affected by sleep deprivation,” according to the study.

A second experiment repeated these conditions, while controlling for experiment bias.

Results: Participants who were told they had above-average REM sleep performed better on the test, and those who were told their REM sleep was below average performed worse, even when researchers controlled for the subjects’ self-reported sleep quality.

Implications: A great victory was won here for lies, over truth. This study shows that if you’re in the mindset that you’re well-rested, your brain will perform better, regardless of the actual quality of your sleep. Conversely, constantly talking about how tired you are, as so often happens in our culture, might be detrimental to your performance.


The study, "Placebo Sleep Affects Cognitive Functioning," appears in the Journal of Experimental Psychology.

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Julie Beck is a senior associate editor at The Atlantic, where she oversees the Health Channel.

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