Optical Illusions

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Optical Illusions
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What are optical illusions?

• They are images that appear to be something other
  than what they really are.
• We tend to see what we expect rather than
  whats actually there.

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There are different types of optical illusions.
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Some Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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Which circle is bigger?
Theyre both the same size! WOW! What a surprise!
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Relative Size

• An object surrounded by smaller objects seems
  larger than it actually is.

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Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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Which line is longer?
Theyre both the same?No, its the red one...
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Which line is longer?
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Which line is longer?
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Which line is longer?
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Size constancy

• Some people think that we are taught to see
  outward pointing arrows as far from us, and
  inward as close.

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The lines are the same.
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Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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What is this?
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A native American?
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Or an Eskimo?
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What is this?
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Perception

• When shown a blurred picture, we tend to make
  hunches about it. When we have that hunch, its
  hard to let it go.

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So what is this then?
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A rabbit?
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Or a duck?
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Hmmn...
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Last one...
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Liar?
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Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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Whats pictured here?
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A cup?
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Or two people?
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Foreground/Background

• When looking at pictures, we have to decide
  whats the object, and whats the background.

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M.C. Escher, birds fish.
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Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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How does this work?
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Closure

• If a figure has gaps, the mind tends to complete
  it, filling in the gaps.

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How many legs?
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Different Types

• Relative shape and size
• Size and shape constancies
• Perception
• Foreground/Background
• Closure
• Words and color

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What does this say?
Are you sure?
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How many colors?
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Conclusion

• Miscommunication between the brain and eyes
• Uses assumptions
• Not always carefully designed
• Exists in everyday life