Ever wondered why we cry, what earwax is for and if we can
smell other people's emotions? In a fascinating look at what goes
on between our ears, physician and philosopher Raymond Tallis
explores the secret world of the human head
• BIRTHS & BEHEADINGS
The
human head is formed after only eight weeks in the womb
The construction of a human head, one of the most complex
structures in the natural world, takes place astonishingly
quickly.
After only eight weeks in the womb, billions of cells have
already formed themselves into a brain, highly developed eyes and
ears, a recognisable face complete with tongue, mouth and nose, a
skull and organised facial bones.
Once fully developed, the human skull can be remarkably tough -
as was demonstrated in 1997 by strongman John Evans on the BBC's
National Lottery Live show.
He balanced 101 bricks, weighing 416lb, on his head and managed
to keep them there for ten seconds.
Such resilience is not confined to the skull. The muscles and
vertebrae in the neck are also very tough, which makes beheading
someone far from the easiest method of killing.
It took three blows to hack through the neck of Mary, Queen of
Scots when she was executed in Fotheringay Castle in 1587.
An assistant held her hair to prevent her from moving.
The result was, as always, extremely gory, given that large
arteries and veins, providing succour to the head, were
severed.
Once cleaved from the body, a hairless human head weighs an
average 11lb - roughly the same as a ten-pin bowling ball - and
accounts for around 8 per cent of our total body weight.
All
in the mind: Phrenologu uses head shape to determine
personality
• A FUNNY BUSINESS
The real business of breathing is done in the lungs - the head
is only a convenient throughway to let oxygen into the body.
Yet for a structure that has a passing interest in air, the head
does an impressive number of things with it, from sneezing to
speaking.
One of the most mysterious is laughing. This seems to be the
most anarchic of all human activities yet giggles, titters, shrieks
and belly laughs all conform to strict rules.
Each laugh has its own distinct "signature" - made up of
short-vowellike notes, not more than a tenth of a second long.
These are repeated at regular intervals about a fifth of a
second apart.
Once a laugh has started with a particular vowel sound, it tends
to stick to it.
The sound may be "ha-ha-ha" or "ho-ho-ho", but not
"ha-ho-ha-ho".
There seems to be resistance to such acoustic mongrels. Laughter
can be infectious, as was illustrated in 1962, when three girls at
a boarding school in Tanzania were stricken with bouts of
uncontrolled mirth for hours on end.
Soon nearly half of the 159 boarders were affected, laughing for
up to 16 days at a time.
The school was closed and the children sent home, but this
resulted in the condition spreading to entire villages and
towns.
No one died during this two-year outbreak of what appears to
have been mass hysteria, but there was much agitation, exhaustion
and interference with daily life.
Under normal circumstances, we laugh 30 times more frequently
when we are with others than when we are alone.
As to why we laugh, no one knows, but scientists think they have
solved one riddle at least - our inability to tickle ourselves.
Self-tickling doesn't work because the brain tends to suppress
sensations caused by the body's own movements.
"This leaves it free to concentrate on its real job, which is to
deal with unexpected stimuli from the outside world, and means that
those entirely expected sensations of self-tickling are scarcely
registered.
WAXING LYRICAL
While people of European and African origin usually have earwax
which is wet and honey-brown, a genetic mutation thousands of years
ago ago resulted in most Asian people - as well as native Americans
and Inuits who have Asian origins - developing earwax which is dry,
flaky and grey.
Indeed, it has proved possible to track human migratory
patterns, such as those of the Inuit, by looking at earwax
type.
Whatever its colour, this mixture of sweat and secretions from
the sebaceous glands performs many useful functions.
Propelled by our jaw movements, it washes out dirt and dust from
the ear canal.
It also lubricates the skin lining within the canal, preventing
it drying up and getting itchy, plus it has anti-bacterial and
anti-fungal properties.
• NOSING AHEAD
Our
nose plays a bigger part in our lives than we think
Our noses play a greater part in our lives than we realise.
Though we may not register it with our conscious minds, we can
smell, for example, the emotions such as fear, contentment and
another person's state of sexual arousal.
Women are better at this than men. Tests show women discriminate
more reliably between armpit swabs taken from people watching
"happy" and "sad" films.
Our ability to smell depends on the olfactory membrane at the
back of the nasal cavity, which is the size of a postage stamp, but
contains 10 million receptors. (Dogs, for whom smell is much more
than recreational, have a billion or more receptors.)
Within this membrane, there are 1,000 different types of
receptor cells which can respond to more than one smell, enabling
us to recognise more than 10,000 odours, scents, fragrance and
pongs.
• LIFE'S ONE BIG YAWN
Yawning
is just as contagious as laughing
THE unborn child begins yawning after just 11 weeks in the
womb.
Once born, each of us will yawn an average 250,000 times before
we breathe our last.
The most plausible explanation is that this endless
jaw-stretching is a protective reflex that maintains lung
inflation.
It prevents the bubbles in the lung sponge - the so-called
alveoli, where the exchange of oxygen and carbon dioxide takes
place - from collapsing.
Yawning is as contagious as laughing. Research suggests that
within five minutes of seeing someone yawn, 50 per cent of people
will do the same.
Even reading about the subject can provoke an involuntary yawn.
Can you feel one coming?
• RED FACES ALL ROUND
ONE facial feature over which we have no control is
blushing.
We might ask why this is limited to the face - for example, why
do our bottoms not blush when we are embarrassed?
The answer is that the blood vessels of the face are denser,
wider and closer to the surface than those in other parts of the
body.
As to why some people blush far more readily than others, this
has proved much harder to investigate because of the difficulty of
prompting cheek-reddening under experimental conditions.
One research project involved showing suggestive material to a
series of young females.
There was not a blush in sight. Yet when they were thanked for
their help at the end of the abandoned session, they apologised for
their unco-operative cheeks and blushed scarlet.
A possible explanation for blushing is that it is a non-verbal
means of saving face - admitting we are in the wrong before others
criticise us.
This is backed by studies showing that people react less harshly
to mistakes when the perpetrators blush.
• BREAKING A SWEAT
The forehead is one of only a few places on the body - along
with the armpits, palms of the hands and soles of the feet - where
we experience "emotional" sweating.
Unlike thermal sweating, which regulates our temperature and
occurs over most of the skin, this is a reaction to fear, anger or
stress.
Its mechanism is not well understood, though we are so familiar
with it that the phrase "breaking out in a cold sweat" is commonly
used to describe acute anxiety.
One theory suggests that cooling the body in this way allows it
to burn more energy - as one might need to do in a frightening
situation - without getting over-heated.
This is fine if the appropriate response is fight or flight, but
perspiring profusely only adds to our embarrassment when we find
ourselves rooted to the spot with horror at some gaffe.
• FACING THE FACTS
The
human face can produce up to 3,000 expressions
Drawing on 43 muscles, we are capable of producing more than
10,000 facial expressions.
Up to 3,000 have a recognisable meaning to other people, but
seven basic emotions are shown on the face in the same way in every
culture: sadness, anger, surprise, fear, enjoyment, disgust and
contempt.
These are innate, not learned; which explains why people who are
born blind use the same facial expressions for each of these seven
emotions as sighted people.
• SEEING IS BELIEVING
When our ancestors began walking upright four to eight million
years ago, the elevation of the head gave an advantage to two of
the senses - which worked over a long distance: vision and
hearing.
It increased their importance over touch, taste and smell, which
work only when we are close to what we are sensing.
As a result, vision today accounts for about 90 per cent of the
information we acquire about the world through our senses.
Given the importance of our eyes, it makes sense that we produce
tears to keep them moist, grit-free and uninfected.
But what about the tears which flow when we are feeling
emotional - whether it's very sad or extremely happy?
Such tears are clearly central to humanity's understanding of
itself, but still we understand little about their purpose.
Some researchers have pointed to the fact that emotional tears
are different to ordinary tears in their chemical composition,
being richer in substances such as manganese and protein.
But the idea that they may somehow help us get rid of
stress-related toxins is unconvincing.
The kidneys seem better equipped for that job and emotional
crying seems designed to deal with toxins of the soul rather than
those of the body.
Whatever its hidden benefits, crying is not always valued in
this country.
We expect the statesman to wipe away a single tear with a
leather-gloved finger as he places the wreath at the Cenotaph
rather than work his way through box after box of Kleenex.
Other cultures are more Spartan still: the Minangkabau people of
Indonesia forbid crying altogether.
But instead of being ashamed of our tears, we should celebrate
them because the human is the only animal that weeps in this
way.
Just like speaking, journeying to the Moon and the many other
activities that set us apart from other creatures, our tears are
special, making us realise what a mysterious and wonderful
structure we have in the human head.
• The Kingdom Of Infinite Space: A Fantastical Journey
Around Your Head by Raymond Tallis.
Source: Daily Mail, UK. Mar. 25, 2008