perception of things is greatly influenced by nearby objects,
qualities and other information. Both consciously and subconsciously
we judge things through comparison. To measure fabric one compares
the cloth to a yard stick. To judge the size of someone's hand,
you might press your palms against hers. To judge someone's speed,
you might race him or watch him race someone else.
In often less exacting comparisons, humans judge the length,
height, angle, shape, color and distance by comparing one object
to others in the scene. Looking at a family snapshot photo, you
might guess the height of a stranger by comparing him to someone
you know. You will guesstimate the distance to a house by comparing
its size to the sizes of closer houses and trees. You will guesstimate
an angle by comparing it to a level line ("Appears to be
about 10-15% off from level."). Often these guesstimates
are accurate within a reasonable degree. You might guess that
stranger in the photo is 6 feet tall, as you know your aunt is
5"5." When you meet him, you may discover he's 5'11."
Not perfect, but a darn good guess-especially as you were unable
to clearly see what shoes they had been wearing.
A problem is that, while comparing to other objects is essential
to making judgments, comparisons often lead to errors. Sometimes
seemingly logical comparisons can produce answers that are completely
wrong. These errors happen when assumptions about an object or
about the overall scene is wrong.
What happens if you incorrectly remembered your aunt as 6 feet
tall instead of 5'5," perhaps as the last time you met her
was when you were five years old and substantially shorter? Your
guess of the height of the man would be similarly off. You might
wrongly guess he was 6'7." What happens if she was wearing
flats in the photo, while he, shy about his height, was wearing
lifts? What happens if due to illness the man couldn't make the
family reunion and a cousin expertly photo-shopped images of
him into some of the photos?
The following pictures show how your perception can be distorted
by surrounding information.
The men are the same size. It is the skewed 'diminishing scale'
lines that cause you to perceive the men as different sizes.
The above circle is perfectly round. It is the surrounding and
overlapping lines that make you perceive it as lopsided.
Circles A and B are the same size. Without the surrounding grey
circles, they would appear the same size.
Which cyclist is going fastest? Most will say the cyclist
on the left is going the fastest and the one on the right the
slowest. There are, however, many unanswered questions and ambiguities
that make it impossible to know for certain who is going the
fastest. For examples: Did they start at the same place? Did
they start at the same time? Are they bicycling moving foreword
or backward? Are they moving? (I've seen race cyclists stand
still during a race). Even if it's a normal 1-2-3 Go! race, it's
very much possible the guy on the right is going the fastest
and the guy on the left is going the slowest at the moment the
image was shot. Catching up, slowing down and switching positions
are a normal parts of all races.
(c) david rudd cycleback, cycleback.com
all rights reserved