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Visual experience is useful because it creates memories of past stimuli
that can later serve as a context for perceiving new stimuli. Thus, you
can think of experience as a form of context that you carry around with
you.
When you read, you use the context of your prior experience with words
to process the words you are reading. Context may also occur outside of
you, as in the surrounding elements in a visual scene. When you are reading
and you encounter an unusual word, you may be able to determine the meaning
of the word by its context. Similarly, when looking at the world, you
routinely make use of context to interpret stimuli.
Concentric
Circles
You perceive the size of an object by comparing it with its surroundings.
This is true of everything you see: trees, buildings, people. You would
be shocked to find that a person standing next to his house was taller
than the house. You would think it was trick photography if you saw it
in a picture. In real life, you might think he had built a doll house
for his daughter or a tree house (not yet in a tree) für his son.
You would not be inclined to think it was his own house, even if it was
very elaborate and complete in every detail.
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Consider
the three sets of concentric circles. In each of the three drawingsA,
B, and Cthe
inner circle is exactly the same size. Yet the inner circle at A
looks as if it must be larger than the inner circle at B;
the inner circle at B must, it
would seem, be larger than the inner circle at C;
and of course, the inner circle at C
is much smaller than the inner circle at A.
Yet you can measure the diameters of the inner circles and see that
they are all identical. The outer circles are all that you have to
compare for size when imagining how big or small the inner circles
are. There is no doubt that the outer circles become progressively
larger as you go from A to
B to C. These outer
circles distort the way you see the inner ones. |
Another
example of a size-comparison illusion. The inner circle at A
seems larger than the one at B.
You have probably guessed that they are the same size. I had thought
about making the inner circle at B
a little bit larger than the one at A,
to see if I could fool you into saying that they are the same size.
But that would take away from the spirit, as well as the vividness,
of the illusion. |
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