'Water in the road' mirage
Visual illusions have tricked and fascinated humans for thousands
of years. They have influenced history, religion and society,
been studied by scientists and philosophers, used by athletes,
architects, medical doctors, engineers and artists, and have
amused kids and mystery lovers of all ages. Visual illusions
include rare spectacular atmospheric events and mundane everyday
Learning about visual illusions and how they work show us
that reality and human perception of reality are different things.
* * * *
What are Visual Illusions?
A visual illusion is when the viewer misperceives what she
is looking at. What she thinks she sees is different than what
she is looking at.
Visual illusions include misidentifying objects, perceiving
things that don't exist or not perceiving things that do exist.
It also includes significantly misjudging qualities, such as
color, angle, amount, shape, weight, size and distance. Visual
illusions happen to birds, fish, flies, dogs and other animals.
The above are perfect circles
Humans have natural and learned ways of perceiving. These methods
are good, serving our practical day-to-day needs, but are far
from perfect. Mistakes, often minor, are made daily by all humans.
Visual illusions are caused by a wide variety of factors.
The factors differ from illusion to illusion, and there are multiple
causes working together for each illusion. General factors include:
Physiology: As with all animals with eyes, humans have
strengths, weaknesses and limitations in how they detect and
translate light. Humans see better during day than at night,
see a limited range of light and their eyes/mind do not translate
light in an entirely efficient and accurate way. This all effects
our visual perception.
Physical environment: This includes the brightness
and angle of light, along with atmospheric conditions like fog,
smog and air temperature. Many mirages are caused by unusual
atmospheric conditions that distort light. In daily events the
difference between light and dark, clear and cloudy can be the
difference between identification and misidentification.
Biases: Humans have conscious and subconscious, innate
and learned biases that effect how they perceive. These biases
are used to categorize, prioritize, label, translate and judge
information. Biases often cause the viewer to perceive patterns,
shapes, colors and identities that do not objectively exist.
Biases cause us to place undue emphasis on trivial information,
while ignoring what may be important. The proverbial missing
the forest for the trees.
Personal knowledge and background: How a human perceives
something is greatly affected by his knowledge, what he has been
taught and past experiences. You identify a dog by having already
seen animals and learned they are called dogs. Without that experience,
you would be mystified by that strange creature sniffing around
your neighbor's hedges. People new to geography often fall for
visual traps the natives do not. In the crystal clear air of
mountains, long distance objects typically appear much closer
than reality. Newbies to high altitude are accustomed to seeing
through the hazier air of low altitude, with distance of a far
away object being judged in part by its relative haziness-the
further away a building or cliff, the hazier. In an environment
with clearer air, low altitude rules can deceive. In highest
altitudes a mountain can both be far away and crystal clear,
appearing closer than it is to the new climber. As one might
imagine, misjudging distance in the mountains and cliffs can
Humans shape their perceptions and overcome many of their
visual illusions with experience. After walking into a sliding
glass door for the second time, you likely have learned not to
do it again. Humans aren't omniscient and learn by trial and
error, gaining knowledge as they go. In many cases visual illusions
are a natural part of the learning process-- error in judgment
(visual illusion), followed by realizing the error, followed
by having better knowledge.
(c) david rudd cycleback, cycleback.com
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