It may be hard to take on board, if you're reading this exhausted from yet another night of bad sleep, but a new study by scientists has revealed that the perception of good sleep is half the battle.
Researchers at Colorado College asked study participants to rate how deeply they had slept the night before, on a scale of 1-10.
They were then told that a new technique "could measure their sleep quality from the night before using sensors which they were told would measure their pulse, heart rate, and brainwave frequency."
The new technique didn't exist - what researchers were hoping to discover was whether the placebo effect could work when it comes to sleep.
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Participants were then split into two groups. One group was told that their sleep had been higher than average at 28.7% REM sleep. REM stands for rapid eye movement and is the deepest stage of sleep.
This group were also told that this was a sign that they were mentally alert.
The second group were told their sleep had been below average, at 16.2% REM sleep.
They were all then told that the average adult spends between 20 - 25% of their time in REM sleep and those that didn't performed worse in tests on memory and it affected their ability to learn.
All of the participants were then tested again, and those who were told they'd had below average REM sleep performed worse, regardless of how well they had slept.
The Telegraph reported study leaders Christina Draganich and Kristi Erdal as saying: "In these experiments, cognitive functioning appeared to be mediated by placebo information, as it was dependent on the assigned sleep quality told to the participants as opposed to their actual self-reported sleep quality".Suggest a correction