Why Thinking You Didn’t Sleep Soundly Can Ruin Your Day

Source: Thinkstock

Source: Thinkstock

According to the Center for Disease Control and Prevention, adults should be getting 7 to 8 hours of sleep each night. We all know that insufficient quality (or quantity) of sleep we get can affect our performance the following day. Sleep deprivation is one of the most common health problems among contemporary adults, with the CDC going so far as to call it an epidemic.

But did you know that even the belief that we didn’t get sufficient sleep can affect our performance as well?

According to the Harvard Business Review, a recent psychological study at Colorado College has proven just that. Colorado College professor Kristi Erdal, along with psychology student Christina Draganich, conducted an experiment in which subjects were tricked into believing that the quality of the previous night’s sleep could be monitored by brain waves.

Slate reports that in this study of 164 students, “Students in the first group were told that their REM sleep the night before had been above average, or 28.7 percent of their total sleep time. Those in the second group were told they had gotten just 16.2 percent REM sleep, well below the average.”

The randomly selected subjects who were told that they had had a below-average percentage of REM sleep the previous night performed markedly worse on a subsequent auditory math test than their counterparts who had been told the opposite. This held true regardless of whether they had actually had a poor sleep cycle the night prior.


Professor Erdal told Slate that Draganich’s inspiration for the study came from a 2007 experiment, in which Harvard researchers discovered that telling hotel maids their job is a good form of exercise ended up legitimately improving their health. After a month, the maids who received this pep talk ended up losing weight and improving their blood pressure, while the other maids remained at standard health.

The Ergal study, in short, demonstrated that the effects of a perceived insufficiency in sleep quality can mirror the effects of genuine sleep deprivation. In defending her research to the Harvard Business Review, Erdal compares these results to experiments using fake alcohol, which have yielded similar results: When subjects believe that they are ingesting something alcoholic, they will begin behaving as though they are drunk — whether or not their drink actually contains alcohol. This is, for all intents and purposes, an example of what scientists call the placebo effect.

While Erdal’s evidence supports the conclusion that the perception of sleep deprivation will negatively affect performance, the same does not hold true for the opposite argument. That is, subjects who believe that they got an especially high-quality sleep the previous night will not outperform the average.

Scientists have already gathered a remarkable amount of evidence in favor of the placebo effect, so it could be argued that Ergal’s results are unsurprising. However, they do hold value. As Slate notes, “It’s worth keeping in mind the next time you’re tempted to dwell dramatically on how exhausted you are. Instead, try being thankful for the sleep you did get—or just shut up, quit worrying, and focus on getting more sleep tonight.” An optimistic philosophy alone could bolster your future performance!

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