Sleep loss 'worse for extroverts'
November 06 BBC
Outgoing people appear to suffer worse from the effects of lack of
sleep, US army researchers suggest.
They kept 48 volunteers awake for 36 hours, with some allowed to mix
with others, the journal Sleep reports.
Those defined as introverts did better at staying awake and in
reaction tests.
And those extroverts who were denied social contact also did well,
suggesting it is "social stimulation" that tires out the parts of the
extroverts' brains linked to alertness.
The study involved 48 people aged 18 to 39, who were divided into two
roughly equal groups following personality type screening, which defined
whether they were natural extroverts or introverts.
After a good night's sleep, they remained awake for a day and a half,
with various tests each hour to measure the effects of lack of sleep.
Some of the test subjects - both introverts and extroverts - were
allowed to take part in group discussions, and play board games and
puzzles for 12 hours of the 36. The others were not allowed any such
social interaction.
First of all, the test subjects who were "socially enriched" in this
way were tested to see if there was any difference between the natural
extroverts and introverts.
While there was little difference in one of the tests, in which
volunteers had to push a button as soon as possible in response to a
light, introverts fared better in a "maintenance of wakefulness test",
which checks whether sleep-deprived people are able to stay awake over a
set period of time.The extroverts in that group did badly in the test,
but the extroverts in the second group - those denied social contact -
performed markedly better.
Perception. The researchers, from the Walter Reed Army Institute in
Maryland, said the results suggested that personality type might not
only have a bearing on ability to cope with military tasks which
required being awake for long period, but also with shift work.
They reported: "Overall, the present results might also be
interpreted more generally to suggest that waking experiences, along
with their interaction with individual characteristics, influence
vulnerability to subsequent sleep loss." One possibility, they said, was
that intense social interactions might lead to fatigue in brain regions
which also played a role in alertness.
Conversely, they said, it was possible that introverts might always
have a relatively high level of activity in parts of the brain affected
by social situations.
On a day-to-day basis, it is suggested this could mean that social
contact leads to "over-stimulation", explaining why introverts would
withdraw or shy away.
However, the constant activity might also make their brains better
placed to fight the effects of sleep deprivation, they said. One UK
academic said that there might be a simpler explanation for the
different impact of sleep deprivation.
Professor Mark Blagrove, a neuroscientist from the University of
Swansea, has published similar research into effects of sleep
deprivation on the mood of introverts and extroverts.
Again, he found extroverts more vulnerable to mood changes driven by
lack of sleep.He said: "We suggested that extrovert people might be more
heavily influenced by the sleep-deprived appearance of people in the
group around them.
"They found no differences in the objective test of alertness they
used, but did find differences in the wakefulness test, which is a
slightly less objective measure of how someone is feeling.
"This supports a slightly simpler argument - that the extrovert is
more likely to be influenced by a perception of what is going on in the
group." |