Just believing that you’ve slept better than you really have is enough to boost cognitive performance the next day, a recent study finds.
The research, published in the Journal of Experimental Psychology: Learning, Memory and Cognition, divided 164 people into two groups (Draganich & Erdal, 2014).
Both were given a lecture on the importance of sleep quality and dangers of lack of sleep.
They were also told that the average amount of REM (Rapid Eye Movement) sleep that people get each night is 20%.
Their ‘brainwave frequency’ was then measured and they were shown formulas and spreadsheets.
All these measurements were a sham.
- One group was told they’d got ‘above average’ sleep quality, spending 28.7% in REM sleep.
- The other group was told they’d got ‘below average’ sleep, spending just 16.2% in REM sleep.
These numbers had no relationship to any lack of sleep or the REM phase of sleep and were just made up to try and convince one group they’d slept better than the other.
Afterwards, all the participants were given a battery of cognitive tests.
Those told they’d slept better scored higher on tests of attention and memory than those told they’d slept poorly.
Interestingly, the researchers also collected self-reported data on how people thought they had slept the previous night.
There was no association between the self-report measures and how people did on the tests of attention and memory.
Lack of sleep
This experiment is another great example of the placebo effect.
People know that sleep deprivation has all sorts of deleterious effects and good sleep has all sorts of benefits, and so their performance conforms to that belief.
The placebo effect is still somewhat of a mystery, but the study’s authors think the effect is likely due to both our expectations and how we automatically link stimuli and responses, à la Pavlov’s dog:
“It may be that expectancy directly creates the cognitive effects from perceived sleep quality or that they are mediated by increased anxiety or decreased motivation following information about poor sleep quality (or following actual sleep deprivation) or by increased motivation following information about high-quality sleep…” (Draganich & Erdal, 2014).
Whatever the explanation, remember that how you slept last night isn’t just about how you actually slept, it’s also about how you think you slept.
This study suggests that tweaking your mindset a little could be enough to boost your performance.
→ Related: 10 Sleep Deprivation Effects.
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