Why Some People Cannot See Hidden Stereogram
Images
by Jason Weekley A.B.O.C., L.D.O.
The basic
principle behind a stereogram depends on the
ability for a person to merge multiple objects
into one. There are many factors that could
inhibit a person's ability to see the object
hidden beneath the initial surface. As an
example....place your thumbs and index fingers
together in the shape of a triangle, and find an
object in the distance to look at through the
triangle. It must be a distant object!
independently close one eye, then the
other....you will notice that you were only able
to see the complete object through one eye
without moving the triangle. This concept is
called eye dominance. Sometimes the brain will
shut off one eye, and rely on the dominant eye,
if the object to be viewed doesn't come in focus.
There are many people who need corrected vision
that don't realize it because of the human
ability to adapt.
Another possible
cause is convergence. At close range (12-18
inches), your eyes converge an average of
3mm...but this is not so for everyone. Just as
you have a dominant eye for distance, you will
also have a dominant eye for near. After years of
depending on one eye to do the majority of the
work, you can depend less on convergence and
adaptability. By allowing your eyes to relax, and
blur....you attempt to overide your brain's
intent, and allow both eyes to be equally
dysfunctional. Thus, images begin to overlap and
the muscles that control your eyes are less
likely to fix at the same point that they
normally would. The same people that have
problems crossing their eyes...even a
little...will have the greatest frustration when
attempting to view stereograms.
Other conditions
such as esophoria and esotropia can cause the eye
to move inwards...(commonly called a lazy eye),
and exophoria and exotropia (a tendency for an
eye to shift toward the temple), will have an
impact. I would suggest that people could adjust
their distance from the stereogram and have a
greater rate of success. A distance that works
for the majority, doesn't always work for
everyone. And last but not least...I would enjoy
the statistics relating the ability of a person
to see stereograms with regard to their
profession. Analytical/Artistic mindset?
©1998, Jason
Weekley
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