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When we phone in a night of sleep, we set ourselves up for undereye circles, heavy eyelids and jam-for-brains the next day. Sure, we have tricks to combat the mental and physical side effects of sleep loss: coffee, coffee naps, caffeinated eye-cooling gel and the like. But, can we perk ourselves up without downing pick-me-ups or sneaking in naps? Well, there's some evidence that all we need to feel fresh and think sharp is willful ignorance. People who believed they'd slept well subsequently behaved as though they'd slept well — at least for one day, in one study on "placebo sleep." 

In the short term, it makes sense that next-day functioning could hinge more on someone's state of mind than on their state of unrest. We know from Cognitive Behavioral Therapy (CBT) that changing how we think about and understand sleep can inform our ability to fall and stay asleep, as well as or better than drugs can. It's not crazy, then, that perceptions of sleep could similarly affect waking behavior. Still, research on the sleeping brain suggests that the performance-boosting effects of "placebo sleep" would expire quickly. Fool the mind into running like a well-rested machine after one night of shoddy shuteye? Okay. Two? Maybe. But, at some point, faking it will fail. 

Back in 2014, The Atlantic reported on a then-new study about "placebo sleep," published in the Journal of Experimental Psychology. Compared to the knowingly sleep-deprived, the study suggested, underslept people who believe they're logging enough rest (even though they aren't) may feel less tired and, consequently, perform better on tests of cognitive skills most affected by sleep loss.

In the short term, it makes sense that next-day functioning might hinge more on someone's state of mind than on their state of unrest.

To draw this conclusion, researchers from Colorado College toyed with the minds of college kids (all in the name of science). After undergrad participants rated the depth of their previous night's sleep, "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." The lesson included these nuggets: Getting less-than-average REM (i.e., spending less than 20-to-25-percent of sleep-time in the vivid-dreaming stage) impedes test performance. And, people who log more-than-average REM generally do better on the same tests. 

Then, researchers attached participants to various machines and censors, falsely claiming they'd be able to measure how much time participants had spent in REM the night before. After pretending to analyze their results, researchers told participants they'd either spent 16.2 or 28.7 percent of their night's rest in REM. Participants subsequently took a test that measured auditory attention and processing speed, the cognitive skills "most affected by sleep deprivation." Those who'd been told they spent a long time in REM were more lively. 

The implications, per The Atlantic:

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.

Let's talk about mindsets and sleep. CBT-i, a goal-oriented, drug-free treatment method, helps people beat chronic insomnia through changing their bedtime and sleep habits (the behavioral component) and modifying their "disordered" thoughts about why they can't sleep (the cognitive component). They modify those thoughts, in part, by learning how sleep actually works in the brain, thereby helping them abandon their (wrong) notions about the roots of their sleeplessness. So, people gain Zzzs by replacing one set of beliefs with a different, more rest-conducive set, rather than by altering their brain chemistry. 

How do we know their beliefs are disordered in the first place? We don't, for sure. But, insomniacs are notoriously bad at gauging their sleep. Not infrequently, they report getting only an hour or two of sleep, when objective sleep tests show they actually get four or five. Their misperceptions, well-documented in research and clinical literature, influence their functioning and sleep patterns. To some degree, they become the un-slept creatures they believe they are. And, the "placebo sleep" study basically suggests the opposite is also true. 

But, ultimately, our biological drive for sleep will take over. Without sleep, we don't experience the brain activity necessary to form and lock in memories, or make insightful connections. Brain regions, whose back-and-forth communication helps us think rationally, become less connected, which leaves us prone to thinking with our feelings and processing the world through threat-detection-tinted lenses. These physiological changes, which worsen as sleep loss does, play a considerable role in our ability to think critically and quickly. And it's not clear that believing we're hitting our #hardeights could do much to stave off the ill-effects of restricting our brains from doing what they do when we're dozing. If researchers lied to people about their sleep quality for days on end, we might gain better understanding of how and for how long belief can supercede biology.