[Paleopsych] The Times: Caution! Mind under construction
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Caution! Mind under construction
Body&Soul teen special
November 05, 2005
It?s not just the hormones, says Vivienne Parry. During puberty teenagers?
brains are undergoing a radical readjustment
When the hormones start to arrive by the truckload at puberty, something very
strange happens to children. They can turn overnight from sweet, adorable
creatures into an unpredictable and combustible blend of know-it-all arrogance
and furious leave-me-alone vulnerability. They are spotty, moody, truculent and
can?t concentrate for more than two minutes at a time. They also become hugely
self-conscious, suddenly finding everything, including their parents ?sooo
And there is a darker side too. Soaring rates of death, three quarters of which
result from accidents or ?misadventure?, illicit use of drugs or alcohol, risky
sexual behaviours and the first signs of emotional disorders which may be
lifelong. Hormones have a lot to answer for ? or have they? Puberty is
undoubtedly an extraordinary hormonal event and humans are lucky that they on
have to go through it only once, unlike most animals which go through this
hormonal onslaught with every breeding season.
The first hormone event takes place, unseen, between age 6 and 8 and involves
the adrenal glands, which sit atop each kidney. They step up production of male
hormones, particularly one called DHEA, which the body uses as construction
material for other hormones. These androgens prime follicles for pubic hair
growth and make the skin greasy.
The next big step is when the brain begins production of a key hormone called
GnRH (gonadotrophin releasing hormone). This is the true onset of puberty,
although what triggers it is unknown. It?s not just age because age at puberty
varies worldwide. Nutritional status is important, with percentage body fat
especially so for girls. Pulses of GnRH then make the pituitary gland produce
the hormones which will act on ovary and testes to produce sperm and eggs.
The effect is dramatic. In boys, up to 50 times more testosterone is available
than before puberty. It sculpts their bodies and jawlines, increases their
muscles and makes them think about sex every other minute (as little as that?
is the reaction of most 13-year-old boys). In girls, oestrogen rearranges body
fat, and stimulates the growth of womb and breast. They begin to have periods
and to ovulate, although very irregularly at first. In both sexes, body-hair
growth is promoted.
A range of teen traits is directly influenced by hormones. Spots, for instance,
are caused by skin sensitivity to testosterone. Fridge-raiding is caused by
higher levels of the hormone cortisol, which sharpens the appetite and makes
adolescents seek the food that they need for growth. Not getting up until
lunchtime is caused by alterations in the secretion of melatonin (see page 11).
We can see what surges of reproductive hormones do to rutting stags or nesting
birds in the mating season, so there?s no doubt that these hormones can affect
behaviour, but they have never seemed adequately to explain the complexities of
human teenage behaviour. Neither has anyone managed to correlate degree of
teenage angst with hormone levels. But recently a whole new explanation has
It was always thought that the brain stopped developing within a couple of
years of birth. During pregnancy and early life, a huge number of nerve
connections (synapses) are formed, but these are then pruned radically. ?It?s a
way of making the brain more efficient,? says Dr Sarah-Jayne Blakemore, a
research fellow at the Institute of Cognitive Neuroscience at University
College London and an expert on the adolescent brain. She gives the example
that, worldwide, all babies can distinguish the difference between the sound of
the letters R and L. In the Japanese language however there is no difference
and, after about a year, Japanese babies lose the ability to distinguish these
sounds. They don?t need it.
This example relates to the sensory areas of the brain and was long assumed to
be true of the entire brain ? that ?plasticity? as it is called, was lost by
about 3 years old. But post-mortem work in the Eighties on adolescent brains
suggested something very different. It wasn?t confirmed until just a few years
ago, when MRI scans of adolescent brains revealed the stunning truth. Not only
is there major reorganisation in the teenage brain but it continues to develop
until the early twenties.
Puberty coincides with two brain events. A process called myelination, which
massively increases brain activity. There is also a pruning exercise among
synapses which have proliferated during childhood as the brain is fine-tuned in
response to the environment: strengthening synapses used frequently, ditching
the rest. The pruning takes place mainly in the pre-frontal cortex. This part
of the brain is responsible for executive action ? a shopping list of the
things that teenagers struggle with: priority setting, impulse inhibition,
planning and organisation.
The changes in the adolescent brain primarily affect motivation and emotion,
which manifest themselves as mood swings and conflict with authority. The
combination of a hormone such as testosterone, which drives bravado, with an
impaired ability to reason, is an explosive one.
The pre-frontal cortex is also responsible for our self-identity and for
socialisation and empathy. Research has already shown that one effect of this
brain reorganisation is a 20 per cent dip at puberty in the ability to gauge
emotions from faces. This is likely to make teenagers less able to read social
situations or recognise when they are treading on dangerously thin ice with
Dr Blakemore is currently researching empathy in teenagers, and her work
suggests that this also seems to dip at puberty. ?It would mean they are less
able to put themselves in other people?s shoes and imagine how they feel.?
One aspect of teenage brains is that they get a bigger reward from nicotine and
alcohol than adults. As a result, those who begin drinking before the age of 15
are four times more likely to develop alcohol dependence than than those who
begin drinking later.
Teenagers are by turns maddening and glorious. But, as they are caught in limbo
between adult and child, we should treasure and understand them. Blame their
brains, not them.
If your child is between the age of 10 and 16 and would like to volunteer for a
brain scan (in Central London) please contact Dr Sarah-Jayne Blakemore by
e-mail at s.blakemore at ucl.ac.uk.
The Truth about Hormones by Vivienne Parry (Atlantic Books, ?9.99) is available
from Times Books First at ?9.49, p&p is free: 0870 1608080:
King of chemistry
ALEXANDER MAYALL: ?I like science because it has a proper right or wrong
answer. Chemistry is my favourite because it?s about what everything in the
universe is made from and you get to look at the way it all fits together. I
also find it quite easy.
In my last project, for my Standard Assessment Tasks, I got a level 7 (the
national average is 5 to 6). I found that memorising the symbols for all the
different chemicals is the hardest thing ? it?s best to approach that like
having to learn spellings.
Experiments are fun. Something always happens and you?re never sure what. We
did quite a good one with magnesium and steam; it made hydrogen. You can set
that alight and then watch it burn. You learn the reaction that the metals have
towards the steam. The teacher told us that the test tube might break ? and it
I know that there are some moral issues involved in science. One of them is
playing God ? now that reseachers are able to create life in an unnatural
environment. Some people are taken aback at the idea of duplicating people.
I haven?t made up my mind completely on this yet ? but if it helps keep people
alive, I?m all for it.
I think that science plays a big role in the world today. Especially in the
discovery of new medicines. If a scientist creates a new medicine then that?s
something that they deserved to be praised for.?
The fact that teenagers? brains are busy re-organising connections gives them a
brilliant advantage over adults. Their thinking is unconventional, they are
more open to ideas and change.
It?s no accident that teenagers are behind some of the world?s great
discoveries, particularly in technology:
# Take Ada, Countess of Lovelace, the daughter of Lord Byron. She was just 17
when she met Charles Babbage, the inventor of the difference engine, an
elaborate calculating machine and forerunner of modern computers. It was Ada,
not Babbage, who saw that his machine could be used to manipulate symbols. Her
contribution to computing has been recognised by Microsoft ? her image is on
their product-authenticity hologram stickers.
# Bill Gates, of Microsoft, began to program computers at 13. He started up his
company when he was just 19.
# Aidan Macfarlane is co-author of the book series based on questions sent to
the TeenageHealthFreak.org website and is a cheerleader for teens: ?Teenagers
see the world in a different way. Their brain is still plastic and
disconnecting, so they question everything. They?re wonderful.?
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