By SETH S. HOROWITZ,
Published November 9, 2012
Here's a trick question. What do
you hear right now? If your
home is like mine, you hear the humming sound of a printer, the low throbbing
of traffic from the nearby highway and the clatter of plastic followed by the
muffled impact of paws landing on linoleum — meaning that the cat has once
again tried to open the catnip container atop the fridge and succeeded only in
knocking it to the kitchen floor.
The slight trick in the question
is that, by asking you what you were hearing, I prompted your brain to take
control of the sensory experience — and made you listen rather than just hear.
That, in effect, is what happens when an event jumps out of the background
enough to be perceived consciously rather than just being part of your auditory
surroundings. The difference between the sense of hearing and the skill of
listening is attention.
Hearing is a vastly underrated
sense. We tend to think of the world as a place that we see, interacting with
things and people based on how they look. Studies have shown that conscious
thought takes place at about the same rate as visual recognition, requiring a
significant fraction of a second per event. But hearing is a quantitatively
faster sense. While it might take you a full second to notice something out of
the corner of your eye, turn your head toward it, recognize it and respond to
it, the same reaction to a new or sudden sound happens at least 10 times as
fast.
This is because hearing has
evolved as our alarm system — it operates out of line of sight and works even
while you are asleep. And because there is no place in the universe that is
totally silent, your auditory system has evolved a complex and automatic
“volume control,” fine-tuned by development and experience, to keep most sounds
off your cognitive radar unless they might be of use as a signal that something
dangerous or wonderful is somewhere within the kilometer or so that your ears
can detect.
This is where attention kicks in.
Attention is not some monolithic
brain process. There are different types of attention, and they use different
parts of the brain. The sudden loud noise that makes you jump activates the
simplest type: the startle. A chain of five neurons from your ears to your
spine takes that noise and converts it into a defensive response in a mere
tenth of a second — elevating your heart rate, hunching your shoulders and
making you cast around to see if whatever you heard is going to pounce and eat
you. This simplest form of attention requires almost no brains at all and has
been observed in every studied vertebrate.
More complex attention kicks in
when you hear your name called from across a room or hear an unexpected
birdcall from inside a subway station. This stimulus-directed attention is
controlled by pathways through the temporoparietal and inferior frontal cortex
regions, mostly in the right hemisphere — areas that process the raw, sensory
input, but don’t concern themselves with what you should make of that sound.
(Neuroscientists call this a “bottom-up” response.)
But when you actually pay
attention to something you’re listening to, whether it is your favorite song or
the cat meowing at dinnertime, a separate “top-down” pathway comes into play.
Here, the signals are conveyed through a dorsal pathway in your cortex, part of
the brain that does more computation, which lets you actively focus on what
you’re hearing and tune out sights and sounds that aren’t as immediately
important.
In this case, your brain works
like a set of noise-suppressing headphones, with the bottom-up pathways acting
as a switch to interrupt if something more urgent — say, an airplane engine
dropping through your bathroom ceiling — grabs your attention.
Hearing, in short, is easy. You
and every other vertebrate that hasn’t suffered some genetic, developmental or
environmental accident have been doing it for hundreds of millions of years.
It’s your life line, your alarm system, your way to escape danger and pass on
your genes. But listening, really listening, is hard when potential
distractions are leaping into your ears every fifty-thousandth of a second —
and pathways in your brain are just waiting to interrupt your focus to warn you
of any potential dangers.
Listening is a skill that we’re
in danger of losing in a world of digital distraction and information overload. Find
the full article here.
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