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.
Both were given a lecture on how important sleep quality is
and that they would be given a new test of how well they had slept the previous
night.
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.
Despite the measurements being 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 how they had actually
slept 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.
Magic
mindset
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…” .
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