54 | New Scientist | 19 March 2022The back pages Almost the last word
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Full terms and conditions at newscientist.com/lw-termsSticking it out
Why does sticking my tongue out
seem to help me concentrate?Gillian Forrester
Birkbeck, University of London, UK
It isn’t so much that sticking
your tongue out helps you to
concentrate, rather it is something
that most people naturally do
when engaging in fine manual
motor actions, such as threading
a needle.
We think this behaviour has a
long evolutionary history. When
humans became bipedal, around
4 million years ago, our hands
became busy with competing
activities like manipulating
tools and communication
gestures. We also think that
the modern human language
system originated from a visually
based gestural communication
system incorporating the hands,
face and posture.
These competing hand actions
created problems if we wanted to
simultaneously communicate and
act, for example when teachingsomeone to make or use a tool.
This may have created a pressure
for our communication system
to move from gestures to another
signalling channel: the voice.
Neuroscientific evidence backs
this up, showing that our hand
behaviour for tool use engages
the same brain regions used in
speech. Behavioural evidence
also shows that these two motor
systems are closely linked and
that the mouth mirrors hand
action when engaging in fine
motor movements.
Experiments show that when
people are asked to pick up large
objects and then smaller ones,
their mouth will open and close
in proportion to the grip sizeJANE^ AYT
Othey are using with their fingers.
Most children stick out their
tongues when making fine motor
hand actions. Adults probably
still make these tongue actions
too, but social pressures teach us
to keep our mouths closed so our
tongues aren’t visibly hanging out.Contee Seely
Berkeley, California, US
Sticking out one’s tongue and
wiggling it seems to stimulate
a part of the brain that can make
a difference in one’s mental state.
Doing this almost unfailingly
clears headaches from the
back of my head.Drew Barlow
Kerikeri, New Zealand
I have noticed a similar
phenomenon with manyprofessional snooker players, who
twitch the middle finger of their
“bridge” hand while concentrating
on lining up a shot. It really stands
out once you notice it.Burn out
Why does a candle make
more smoke just after it
has been extinguished?Philip Bradfield
Edinburgh, UK
The plume visible after
extinguishing a candle flame is a
stream of unburned fuel particles
rather than smoke. It is powered
by the residual heat of the wick.
This can be tested by collecting
the stream on absorbent paper.
There is a delightful poster
of candle combustion in TheChemical Atlas by Edward
Livingston Youmans, which
was published in 1856.David Muir
Edinburgh, UK
When you light a candle, the flame
melts the wax to form a pool at the
base of the wick. This liquid rises
through capillary action up the
wick to the flame, where the wax
is vaporised. The hydrocarbon
wax molecules burn to make
carbon dioxide and water
if enough oxygen is present.
These products are invisible.
When a candle is extinguished,
the smoke comprises wax vapour,
intermediate breakdown products
and unburned carbon, altogether
a very combustible fuel. This can
be demonstrated by snuffing out
a candle, then putting a flame
to the rising smoke and watching
the flame shoot down the smoke
to relight the wick.
During decades of noisy
competitions in science classes,
I have watched pupils make
flames jump down smoke
columns up to 6 centimetres
long, given careful flame-snuffing,
still air and the right wick.David Jackson
Gosport, Hampshire, UK
My preferred way of putting out
a candle is to lick my thumb and
forefinger then pinch out the
flame. This prevents the plume
of white “smoke”, which is actually
condensing paraffin wax.
If a candle wick gets too long in
the flame, some wax gets drawn
up into the cooler part of the
flame where there is insufficient
oxygen for complete combustion.
This results in black carbon
smoke above the flame.
In days gone by, wicks were
regularly trimmed with small
scissors to prevent this, but
they are now specially woven
so that they bend over and
trim themselves by burning
off in the flame edge.This week’s new questions
Lichen this sign Why are the lichens distributed in this
way on this road sign? The surfaces have the same texture,
just different colours. Jane Ayto, Plymouth, UKPlanetary fly-through Would it be possible to fly
a spaceship through the centre of a gas giant planet?
Bob Yelland, Alton, Hampshire, UKWhy has the lichen
grown more in certain
areas of this sign?“ Hand and mouth
actions are closely
linked, and the
mouth mirrors hand
actions during fine
motor activities”