1.
OPTICAL ILLUSIONS

2.
OPTICAL ILLUSIONS
• An experience of seeming to see something that does not exist
or that is other than it appears.
• Something that deceives one's eyes and causes such an
experience.

3.
OPTICAL ILLUSIONS
• 1915, a cartoonist named W.E. Hill first
published this drawing
• Is it a drawing of a pretty young girl looking
away from us? Or is it an older woman
looking down at the floor?
• Titled, "Mother, Father, and daughter"

4.
OPTICAL ILLUSIONS
• They have been observed even in early history
• ex. moon appearing larger on horizon
• The architecture of ancient Greece reveals a knowledge of certain optical illusions in the efforts to
over come them.
• The study of optical illusions did not engage the attention of scientists until a comparatively recent
period

5.
OPTICAL ILLUSIONS
• Result from information gathered by the eye being processed in
the brain to give a perception that does not tally with a physical
measurement of the stimulus source.
• Literal optical illusions that create images that are different from the objects that make them
• Physiological ones that are the effects on the eyes and brain of excessive stimulation of a
specific type
• Cognitive illusions, the result of unconscious inferences.

6.
PHYSIOLOGICAL ILLUSIONS
• Presumed to be the effects on the eyes or brain of excessive stimulation or interaction with
contextual or competing stimuli of a specific type
• Brightness, color, position, tile, size, movement, etc.
• The theory is that a stimulus follows its individual dedicated neural path in the early stages of visual
processing, and that intense or repetitive activity in that or interaction with active adjoining channels
cause a physiological imbalance that alters perception.

7.
PHYSIOLOGICAL ILLUSIONS
• ex: Mach Bands

8.
COGNITIVE ILLUSIONS
• Assumed to arise by interaction with assumptions about the world, leading to "unconscious
inferences"
• First suggested in the 19th century by Hermann Helmholtz.
• Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox
illusions, or fiction illusions.

9.
COGNITIVE ILLUSIONS

10.
COGNITIVE ILLUSIONS

11.
COGNITIVE ILLUSIONS

12.
COGNITIVE ILLUSIONS

13.
COGNITIVE ILLUSIONS
• Object Consistencies
• The brain has the ability to understand familiar objects as having a consistent shape or size
• Unfamiliar objects, however, do not always follow the rules of shape constancy and may change
when the perspective is changed.

14.
COGNITIVE ILLUSIONS
• Future Perception
• Researcher Mark Changizi has a more imaginative take on optical illusions, saying that they are
due to a neural lag which most humans experience while awake.
• Changizi asserts that the human visual system has evolved to compensate for neural delays by
generating images of what will occur one-tenth of a second into the future
• This foresight enables humans to react to events in the present, enabling humans to perform
reflexive acts like catching a fly ball and to maneuver smoothly through a crowd.
• Illusions occur when our brains attempt to perceive the future, and those perceptions don't
match reality.

15.
ILLUSIONS IN ART
• Illusionscan be used to create space, motion, and perspective
qualities in an art work.
• Well known artists include:
• M. C. Escher, Salvador Dali, Marcel Duchamp, etc.

16.
M. C. ESCHER

17.
M. C. ESCHER

18.
SALVADOR DALI

19.
SALVADOR DALI

20.
MARCEL DUCHAMP

21.
ACTIVITY TIME
• Go find an example of an optical illusion to share with the
class.
• Explainwhat you initially see, and then what you see after
studying the image more.