Explore how we see. Discover that our world of perception is not about documenting reality -- it's all about survival. We do not so much "picture" what's out there as we create a world of perception.

1. Perception: How We See
See Yourself Seeing
Copyright ©2012 by Jeffrey Schrank 1
COPYRIGHT 2011 JEFFREY SCHRANK

2. Once upon a time, there was a
talented sculptor who produced
beautiful works of art.
But when it came time to step
back and share his work with the
admiring public, a strange
forgetfulness would take charge.
The sculptor would look at the
statue and “forget” that it was his
creation.
He saw the statue as simply “out
there” rather than as a creative
product.
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3. When it comes to seeing, we all
behave like this sculptor.
We shape our perceptions, then
promptly “forget” our role in
creating them. We consider them
as “stuff” that happens to be out
there, not as something we
create.
We are aware of what we see –
but not of how we see.
Sculpting sandcastles of reality
happens without our permission
or awareness.
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4. The eye is not a camera.
Perception is all about survival; it cares not for documenting
what is “really out there.” Vision is a survival tool, not a
recording device.
It doesn’t matter if we see things “wrong,” as long as we see
what we need to survive.
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5. 1. Seeing Movement
The setting sun is a giant optical illusion. We know the
sun isn’t actually sinking into the ocean, yet that is what
we see. How could we be so wrong about something so
big and so common?

6. To see, we use “shortcuts,” or “best guesses.” When
we’re not sure which object is moving and which is
stationary, we guess the small object is the one moving.
This “guess” is not a conscious decision; it just happens.
We see the small sun moving into the large horizon – it
seems so obvious. The fact that this “guess” is wrong
does not threaten our survival. It’s an “acceptable
error.”
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7. You sit in a parked train or airplane. You look out the window and see
movement. Are you moving or is it the train on the next track or the
plane parked next to you? You feel a twinge of uncertainty because
you have no size comparison on which to base your educated guess.
This brief feeling of uncertainty is a peek into your normally hidden
visual processing -- your subliminal sculpting.
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8. Consider the toad. It also makes
“educated guesses” about
movement. Like humans, its
“guesses” are also meant for survival.
To a toad, food equals movement.
Put a pet toad in a cage and kindly
provide it with dead flies and it might
starve to death. To the toad, if it
doesn’t move, it’s not food. That’s a
perceptual shortcut that works for
the toad’s survival – most of the time.
Let’s take a look at some other
shortcuts we humans use to sculpt
our visual word.
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9. 2. Seeing Colors
We think of color as something “out there,” as a property
in things. We say “the stop sign IS red,” the sunflower IS
yellow.”
But color is not a thing in objects; it’s a visual effect
– a creation of our visual sculpting. Treating color as a
“thing” that objects have is a toad-like shortcut that
works for us – most of the time.
We use context to judge both movement and color.
This context typically remains invisible to the seer.
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10. The colors in the tiles In the two rectangles above are identical – but they
don’t look that way. The yellow and blue backgrounds influence our
process of color creation. Context (an object’s surround) influences our
perception.
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11. The orange and red squares within in the
diamonds to the right are the same red.
The yellowish-green and bluish green
squares within the diamonds to the right
are the same green.
But our eyes do not see them as the
same. We see colors in terms of what
surrounds them.
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12. Next time you look at a nighttime sky, ask yourself, “is
the moon really white?” Or is that whiteness a result
of context and your visual sculpting?
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13. Light reflected off a surface changes constantly. Sunlight, a
fluorescent bulb, or a shadow each changes what a surface
reflects. Yet (within limits) we perceive the color of the object to
be the same. We call this visual shortcut “color constancy.” If
objects kept changing color on us, the world would be quite
confusing. But color constancy sometimes leads to mis-
perceptions.
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14. The squares labeled “A” and “B” above are the same shade of gray. Since
you mistakenly assume your eyes “document the world” you might say “A”
is darker than “B.” This judgment is based on a visual shortcut you use
that usually works, but not here. Your eyes don’t fail you. It’s your
“interpretation” that leads to a false conclusion. You see your
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interpretation.

15. The visual shortcut we use is to “guess” that if something is lighter in color
than what surrounds it, it is probably of a light color in absolute terms. In
other words, it’s “light,” not merely “lighter.” Another perceptual shortcut
we use is to assume that something in a shadow is lighter than it appears.
These assumptions work well but they mislead us in this image. Why don’t
you simply avoid these shortcuts? You can’t “not use them” because you’re
not aware that you “do use them.”
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16. The typical human retina has three cones that detect blue, green and red.
So, humans are “trichromats, we see three (tri) colors (chroma). The brain
combines variations of these three colors into about a million different hues.
A small percentage of the world’s women have a genetic mutation giving
them a fourth photoreceptor that enables them to distinguish among colors
that look identical to most of us. To these tetrachromats, most of us must
seem somewhat color blind.
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17. About eight percent of the world's men
are color blind. This does not mean they
see no color. A more accurate term is
“color vision deficiency.” Most of them
inherit two red or two green cones along
with the standard blue cone, making it
impossible for them to distinguish
between red and green peppers, tell how
well-done a steak is, pick out matching
clothes, or see red lines painted on grass
marking a hazard.
Why men? Because color vision deficiency is carried by the X chromosome. Women are carriers of
this defective chromosome, but need two defective x chromosomes to be affected. Only .5% of
women are color blind. So a color blind male will not pass the gene to his children. But a
colorblind woman will pass that trait to all her sons.
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18. Most people who are color blind are not aware they
see differently until they talk to others who speak of
hues they cannot see. If everyone were color blind,
we would never know it.
The inability to see a number in the above circle is part of a typical test for color
blindness.
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19. 3. Seeing in 3-D
Seeing the world in three dimensions is
another of your sculpting creations.
The fact that you have two eyes means
each sees from a slightly different angle
and distance. You knit the two images
together to produce a single “3-D” image.
You might become aware of your 3-D
creation after a blow to the head or too
much alcohol causes you to “see double.”
The alcohol or blow interferes with your
normal image-knitting.
Seeing double is your default vision.
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20. Hold a finger between your eyes and the monitor so it covers the
lighthouse. View the lighthouse with only one eye. Close that eye and
open the other. The lighthouse seems to move as you switch eyes.
Try the same test with a more distant object, and it will appear to move
even more. This “jumping” is caused by the fact that your eyes are
separated horizontally, and present slightly different viewpoints.
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21. One reason movies and TV have been flat for over a hundred years is
that cameras have only one lens. They lack two images that can be
“knitted together” to create depth.
3-D cameras have two lens (to better simulate our binocular visual
system) each taking a slightly different picture so they can be “re-
united” into a single 3-D image.
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22. Your visual sculpting includes a lot of “editing” that you do without
awareness. Consider your nose, for example.
Close one eye. Notice that you see your nose. Now look through the
other eye. The side of your nose is again in your field of vision. So why
doesn’t your nose interfere with your ordinary vision?
Your 3-D creation “edits out” awareness of your nose. You have the
ability to make your nose vanish. Quite a trick.
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23. …it’s merely a drawing -- lines on a surface. You “assemble” these
lines into a three dimensional cube using a visual grammar whose
rules are invisible to you. You can’t help but see a cube.
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24. 4. Size, Shape, Distance, and Height
As objects move into the distance, they appear to become smaller. But
we know the world around us does not grow and shrink as it did for
Alice in Wonderland.
We saw earlier that we possess a sense of color constancy. We also
have a sense of size constancy.
We know that planes don’t get smaller after they take off, even if our
eyes present them that way.
What we finally “see” is not so much “what’s out there” as it is our
interpretation of what’s out there.
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25. You make “guesses” concerning size based on clues about distance. If you don’t know how
far away something is, you cannot determine its actual size visually.
Moviemakers use the lack of distance cues to make you think a small object is large. A film
director can surround a small plastic model of a cruise ship with featureless ocean to make
a believable giant ship. In sci-fi movies , a spaceship model only a few feet long can seem
as large as a building.
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26. “Sensation itself has no ‘markers’ for size and distance; these have to be learned on the basis
of experience. Thus, it has been reported that if people who have lived their entire lives in
dense rain forest, with a far point no more than a few feet away, are brought into a wide,
empty landscape, they may reach out and try to touch the mountaintops with their hands;
they have no concept of how far the mountains are.” --Oliver Sacks in An Anthropologist
on Mars
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27. A sunset again illustrates how we use context to judge size.
At noon the sun appears a small disk -- there are no objects
near it to help us judge size. But the setting sun turns the
horizon into context. Only when the sun sets or rises do we
see it as a gigantic ball of fire.
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28. Look at the two shapes below. The left is clearly longer and narrower than
the nearly square figure on the right.
The two are actually identical, but your visual system does not present them
to you that way. The part of your visual system that misleads you is not under
your conscious control. You “see” your interpretation.
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29. The red and blues lines are the same length.
The illusion has been well studied since it was described by German
psychiatrist Franz Carl Muller-Lyer in 1889. However, there is no
universally accepted explanation for the apparent difference in the
lengths of the two line segments.
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30. Muller-Lyer attempted to explain the illusion he had discovered as
follows: "the judgment not only takes the lines themselves, but
also, unintentionally, some part of the space on either side.“ In
other words, (a) context shapes perception, and (b) we are not
aware of the influence of context.
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31. The two long horizontal lines above are perfectly straight. They
don’t bend in the middle one little bit.
The visual habits that confuse us in optical illusions serve us well
in everyday life. Optical illusions are not merely “neat tricks”
that confuse the eye. They are illustrations that use unusual
contexts to help us understand how we see.
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32. A whiteout can cause a pilot, or people in a snowstorm t to lose track of
apparent sizes and even confuse up from down. Whiteout is a visual
lack of context – it illustrates how much our everyday vision depends on
context. A helicopter pilot in whiteout might not be able to determine
if these people are doll-sized figures in front of him or real people far
away.
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33. In scuba diving, the term
“blue water dive” refers to a
dive without a reef, floor or
any other visual reference.
An inexperienced diver can
easily be caught in a “blue
out” with no idea of up or
down. He could be sinking
straight down but assume
he is going up.
The ropes here help provide
visual and tactile cues.
Whiteouts and blue water
dives are rare situations, like
those clever optical
illusions.
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34. We seem to have a “built in” tendency to overestimate
heights. When you look at the figure below the vertical line
appears longer than the horizontal even though both are
identical.
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35. The Gateway Arch in St. Louis is as wide as it is tall. It stands 630 feet tall and
630 feet wide at its base. Most observers would report the arch is taller than
it is wide. We give greater visual weight to verticals.
630 feet tall
630 feet wide
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36. The visual shortcut of giving more “visual
weight” to height might cause us to drink
more.
Prof. Brian Wansink at Cornell’s Food and
Brand Lab asked bartenders to pour a
drink into 10 oz. glasses that were either
short, wide tumblers or tall, thin highball
glasses. Even these experienced
bartenders served 20% more liquid in the
short wide glasses.
He also found people who pour their
own drinks from a self-serve machine
will pour about 6% more liquid when
given short, wide glasses than with a tall
tumbler. But, those who poured more
believed they had poured less, and those
who poured less believed they had taken
more.
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37. Why do we over estimate height? Possibly because
in our past, overestimating heights helped us
survive. It is an “error” in our visual processing that
proved useful. After all, to underestimate a height
could prove fatal. Seeing is about survival.
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38. 5. Filling in the Blanks
If I “see it with my own eyes” it must be true. Part of our trust in
the visual comes from the fact that seeing operates almost entirely
below our level of conscious awareness.
Since we are not aware of our role in creating what we see, we
treat it as the gold standard to judge reality. “I saw it with my own
eyes,” it must be true.
We are unaware that what we see is shaped by our expectations
and beliefs.
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39. Some images confuse our visual processing. Stare at the
pattern on this page. The image appears to move. But this is
a still image. You interpret the image as having motion. You
create the movement you see.
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40. A similar perceptual illusion
happens with the chemicals
capsaicin and menthol. Capsaicin
is the chemical that makes
peppers hot. Menthol gives
coolness to many skin creams.
We perceive heat and cold, yet a
thermometer will not register
meaningful changes in skin
temperature. The heat or coolness
are in your interpretation of
sensory data, not in the substance
itself; much like the movement in
the previous image was in your
perception rather than the grid
itself.
We see, feel, hear, and taste All these pain relievers contain menthol as an active ingredient.
interpretations, expectations, and
beliefs. 40

41. An optic nerve contains about a million neural “wires” (called axons)
connecting each retina to your brain. Each axon represents one “pixel” of
your visual image. Each eye “sees” with the resolution of a one-megapixel
camera. So your vision is less detailed than a cheap camera or cell phone.
The picture here is a simulation of an actual image on your retina.
But you perceive the world as rich and detailed. The richness of your visual
experience is created by your “fill-in-the blanks “ interpretations.
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42. We see a richly detailed reality even when our eyes capture very limited
data. When viewed up close, the face on the left clearly has more detail,
(more pixels) than the face on the right. But step back ten or more feet
from the screen. Now both appear clear and undistorted. You fill in the
missing detail.
This “filling in” helps explain why you might not see a difference in
snapshots taken by a 3 megapixel camera compared to one with 7
megapixel resolution….or why 720 HDTV looks much like 1080.
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43. A flipbook is a primitive form of movie. It is made of a series
of drawings that, when flipped through rapidly, appear to
move. The drawings show the same scene with only a minor
change in each drawing.
The reason we see movement in a flipbook or a movie is
that we fill-in what we expect to happen between the still
pictures. The movement is our own creation.
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44. Perception is an ongoing process of fill-in-the-
blanks. We are not aware we play ” fill-in-the-
blanks. In fact, we are not even aware the blanks
exist.
Perception requires energy – seeing requires a
steady supply of calories. To conserve energy we
use selective attention – a perceptual shortcut that
works most of the time. We are surprisingly blind
to what we do not pay attention to.
You’ve played card games and looked at the
picture cards thousands of time. So you know
which of the four playing card kings shows only
one eye – don’t you?
Which suit of cards shows the one-eyed king?
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45. If you could not identify the king of diamonds as the one-eyed king,
it’s because you did not need to know. You look at playing cards just
enough to see the suit and rank – that’s all you need to play cards.
Remember, perception is not about documenting what’s there, its
about using it for your own interests.
Speaking of playing cards….here’s another illustration of perception.
This one involves a bit of mind reading.
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46. Above are six playing cards. Select one by staring at it
for eight or more seconds to establish a solid visual
image. Keep it clearly in your mind.
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47. Don’t allow this screen to distract you. We use it to “read”
your mind. Keep the visual image of the card in your mind.
We have now “read your mind” and removed the card
you chose. Look at the next screen and see if the card we
discarded was indeed the one you selected. 47

48. Did we get it right? If so, what does this
teach about how you see?
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49. It illustrates selective seeing. What counts is
not so much what you see, as what you are
aware of. We are aware only of what we pay
attention to, while we ignore much of the
visual data captured by our eyes.
Like the one-eyed king, we see what we need
and ignore the rest. If you wish, go back and
try the experiment again. See if it works twice.
Maybe it was a lucky guess.
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50. Here are the cards presented in both screens. Note
that the face cards in the second screen contain none
of the same cards as in the first. Chances are you
concentrated so hard on the card that you DID pick
you never “attended to” the cards you didn’t pick.
This visual shortcut is called attentional blindness.
The “selection cards” The “answer cards”
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51. An experiment observed
students walking across a
campus square. Some
walked in pairs, some alone,
while others talked on a cell
phone. Each was observed
while a clown on a unicycle
approached and circled them.
Students walking in pairs
were most likely to see the
clown. Surprisingly, half the
students talking on cell
phones missed the clown
completely. The researchers
concluded that cell phones
contribute to attentional
blindness.
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52. In another experiment, volunteers
were asked to follow a jogger at a
fixed distance and count how many
times the jogger touched his hat.
About a minute into the run, three
students stage a fight slightly off to
the side of the jogging path.
Researcher Chris Chabris explains,
“we had two students beating up a
third, punching him and kicking him
and throwing him to the ground."
Only forty percent of the subjects
noticed the fight, even in broad
daylight. At night the figure dropped
to one-third. The subjects were
attending to the task of counting hat
touches, so the nearby mayhem was
invisible.
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53. You imagine your eyes gliding around, soaking in detailed images. In reality, your
eyes jump around and fix on what attracts you. During the jump (called a saccade,
which is French for “jerk"), the eyes move so rapidly that you are unconscious of
any eye movement. Seeing consists of eyes “jumping” in rapid succession from one
focus to another. Your brain edits out the jumps and presents only the information
gained from each “jump target.” You sense a detail-rich, stable-seeming picture of
the world “out there.” Eyesight is jumpy. Awareness is smooth.
Start
Moving your eyes keeps the world stable. To see this for yourself, try
looking into a mirror…… 53

54. Look in a mirror. Move your eyes back and forth, looking
first at your left eye, then at your right eye, then at your
left eye again. Someone watching you can see your eyes
move – they shift from left to right.
But surprise, you don’t see your
own eyes move. You see yourself
staring straight ahead.
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55. We call peripheral vision “seeing out of the corner of the eye,” but no such
“corner” exists. Peripheral vision is created by eye movements. To
experience this, focus on the red dot below. The surrounding circle will
vanish -- it might take 20 seconds or more.
Visual awareness works a bit like a refrigerator light. When you see something
“out of the corner of your eye” you quickly turn your attention to it and see it
clearly. So you assume you see everything clearly. You assume the light in the
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refrigerator is always on.

56. 6. Seeing Me: Self-Blindness
You can sense a difference between how you imagine
yourself and how you look to others. You sense this
difference when you see video of yourself or hear a
recording of your voice. We think “is that really how I
look or sound?” We are designed to be a bit “self-blind.”
We devote far less visual attention to ourselves than to
others. This makes sense in terms of seeing as survival.
We judge others based on what we see, but ourselves
based on what we think and feel. We have a built-in
perceptual double standard.
Being somewhat “self-blind” is part of our nature. The
only problem is we are not aware of our self-blindness,
so we keep bumping into ourselves.
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57. We see ourselves, “through a glass darkly.”
To help understand how we see, consider that we
cannot see our own faces. For 99.99% of human
history, not one single human ever saw his or her own
face.
Our ancestors saw reflections, first in ponds then
much later in the amazing invention called a mirror.
But a reflection is not a face. Reflections are reversed
right to left. The image you see in the mirror is not
the way you appear to others.
This very basic fact of human existence teaches us
something about how we see.
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58. Our ability to see and “read” the faces of others is critical to our humanness.
When a baby looks in a mirror, does it recognize the image as “self” or is it simply
another baby in some untouchable space?
At around six months, babies interact with the mirror image but treat the
reflection as a plaything. At around age one they think of searching behind the
mirror for the playmate. In one research study, 65% of babies demonstrated
recognition of their mirror images by age two. Research suggests that babies
realize they are seeing themselves sometime during the second year.
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59. Someone asks you to
smile for a photo. You
can’t see yourself smile,
so you say “cheese” or
try to imitate what you
think a smile looks like.
It invariably comes off
looking “fake” because it
is not driven by emotion,
and because you have so
little experience in
seeing yourself smile –
you can’t see your face.
A genuine smile is nearly
impossible to fake. You
need to feel an emotion
that “makes you” smile.
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60. When you open your eyes tomorrow
morning, realize you are seeing a world
you spent a lifetime learning to see. It is a
world you create through constant,
demanding, yet invisible work.
You see with your brain. That brain sits in
total darkness. It can’t see anything. It
receives electrical signals, but that’s all. No
pictures. No light. No colors. It has no
screen to serve as a viewfinder. You the
sculptor create colors, dimensions,
brightness, and all the awesome beauty of
the visual world.
Take time to enjoy your amazing creation.
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