Among
the issues that kept me awake that night (as a result of this “diversion”)
were: (1) what is it that we see with
our eyes; (2) why do we see what we see; and (3) why does our brain automatically
accept what it sees as what is really there.
Vision
itself is a complicated process requiring numerous components of the eye and
brain to work together. Light reflects
off objects around us, enters the eye through the cornea, passes through the
pupil, and is imaged onto the retina by the lens. The
retina has light-sensitive cells called rods and cones, and is responsible for
detecting light from images and sending the resulting impulses to the brain via
the optic nerve. Specifically, rods
identify shapes and work best in dim light; cones identify color and work best
in bright light. When those light rays
pass through the pupil, the iris (colored ring) makes the size of the pupil
change depending on the amount of light available. The brain
decodes these images into information that we know as vision.
A
fascinating piece of information discovered along the way: Rene Descartes, who is more known as a
philosopher than anything else, was also a physicist who made many advances
regarding the understanding of sight in the Seventeenth Century. Descartes surgically removed an eye from an
ox and scraped the back of the eye to make it transparent. He then placed the eye on a window ledge as if
the ox were looking out the window. He
looked through the back of the eye and saw an inverted image of the scenery
outside. Descartes postulated that the
image was inverted as a result of being focused onto the retina by the eye's
lens. Kind of makes you appreciate
Descartes even more.
There is also a field called the “psychology of sight” in
which a study by Canadian researchers seemed to provide the first direct evidence
that our mood affects the way we see things by modulating the
activity of the visual cortex. Putting
on the proverbial rose-tinted glasses of a good mood is not so much about color,
but about the broadness of the view. Positive
moods are associated with a tendency to perceive global components, and
negative moods with the local components.
The neural mechanisms of these phenomena are unclear. One possibility is that mood has a “top-down”
effect on vision, such that higher order cognitive processes impinge on the
visual areas of the brain.
On
the other hand, positive emotions broaden the scope of the visual field,
leading to increased breadth of attention.
Positive moods do so by directly modulating the visual system so that we
can gain access to more information. In
psychology, the broaden-and-build theory holds that positive emotions enhance
one’s awareness, and that this global perspective encourages novel thoughts and
actions. This broadened behavioral
repertoire in turn leads to increased creativity and inventiveness.
Remember
though that our eyes do not send images to our brains. Images are constructed in our brains based on
very simple signals sent from our eyes. The
nerve signals from our eyes mostly represent edges, shapes and motion; no
images. The images our brain forms are
based on pattern recognition, which develops from infancy as we learn about the
world around us. I repeat: we do not see
images; our eyes see line and motion, which our brains work to interpret and cause us to perceive whatever that object might be.
So what came
first: the properties of the object we
see (the thing itself), or the perception of that object put together by lines and lights?
Now
that we know about “patterning,” which develops from infancy, and that such patterning
does not reflect what we are actually looking at, we now know also that we are
not actually “seeing” anything we think we are seeing. Since what we see is as a result of this
patterning, what is it that we actually see?
Are we seeing what is really out there or merely a shared reality, a
shared visioning?
And
does it matter?
Until
next time, LLAP!
References:
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