Optical Illusions
Christopher Landauer
Science of Art
March 9, 2000
What is an Illusion?
il·lu·sion (-lzhen) noun
1. a. An erroneous perception of reality.
b. An erroneous concept or belief.
2. The condition of being deceived by a false perception or belief.
3. Something, such as a fantastic plan or desire, that causes an
erroneous belief or perception.
4. Illusionism in art.
• Latin root of illusion is illudere which means “to mock”
• Optical illusions mock our trust in our senses
• Suggest that the eye is not a passive camera; rather,
perception is an active process that takes place in the
brain and is not directly predictable from simple
knowledge of physical relationships
What’s the big deal?
• Human reliance on
correspondence between
conscious experience and
physical reality
• Continual verification of
our senses
• Cultural Heritage
– “Seeing is Believing”
– “See it with my own
two eyes”
History of Illusions
Prehistory:
• Afterimage caused by
glancing at the sun
• A stick half in and half out
of water
History of Illusions
500 B.C. - Height of the Greek Period
“The eyes and ears are bad witnesses when they are at the service of minds
that do not understand their language”
-Parmenides
Two Viewpoints on Perception:
1.
Sensory inputs are inaccurate. Mind corrects these inaccuracies to
provide an accurate representation of the environment.
Illusions: Senses are relied on more than the Mind
2.
Senses are inherently accurate and produce a true picture of the
environment. Mind is limited.
Illusions: Mind interferes with the Senses
History of Illusions
c. 450 B.C.
“The mind sees and the mind hears. The rest is blind and deaf.”
-Epicharmus
“Man is nothing but a bundle of sensations”
-Protagoras
c. 300 B.C.
“We must perceive objects through the senses but with the mind”
-Plato
384 - 322 B.C.
“Each sense has one kind of object which it discerns, and never errs
in reporting that what is before it is color or sound; Although, it
may err as to what it is that is colored or where it is, or what it is
that is sounding, or where it is.”
-Aristotle
History of Illusions
A. Ideal Parthenon
B. Architrave Illusion
(Jastrow-Lipps)
C. Illusionary Distortion
D. Alterations made to
offset illusion
History of Illusions
“For the sight follows gracious contours; and unless
we flatter its pleasure by proportionate alterations of
the modules--so that by adjustment there is added the
amount to which suffers illusion--an uncouth and
ungracious aspect will be presented to the spectators.”
-Vitruvius
History of Illusions
Entasis:
Convexing of column to overcome
parallel lines appearing concave
Irradiation Illusion:
Bright objects appear larger
History of Illusions
Conclusion:
“More of an Art than a Science”
Early Preparadaigmatic Science
-Trial and error
-Aesthetic, not scientific
-No factual understanding
-No treatsies
-No schools of thought
History of Illusions
1596 - 1650
Descartes:
There is both a registration stage and an interpretation stage
in the perceptual process. Perceptual error or illusion may intrude at
either of these two steps along the road to consciousness.
1700 - 1800
Given at Birth vs. Learned through Experience
Reid & Kant:
All knowledge of the external world comes directly
through the senses and is interpreted by innate
mechanisms
Berkeley & Hume:
All perceptual qualities are learned through
experience with the environment
History of Illusions
1800 - 1870
Experimental Foundations
Mueller, E.H. Weber, Helmholtz, Baldwin, Hering use Physics,
Physiology, Philosophy to form treatises
Specialist and Non-specialist working in area of visual geometric
illusions carrys on to the present
1922 - Luckiesh: lighting engineer
1964 - Tolansky: physicist
1972 - Robinson: psychologist
1900s Revolution and Rebirth
• Behaviorists vs. Gestalt
• Methodology vs. Theoretical
• Percepual response & Brain wave patterns
Current State of
Illisions
Conclusion:
Paradigmatic Science (Psychology)
1900s
Normal Sciences => Anomoly => Crisis => Revolution
Current status: Normal Science
- mopping up
- puzzle solving
- guidelines for research
Ambiguous Figures
Face or Vase?
Ambiguous Figures
RetroActive
Nels Isralson
L'Amour de Pierrot
c.1905
Gossip and Satan
Geo. A. Wotherspoon
Ambiguous Figures
Bust of Voltaire
- Houdon, 1781
Slave Market With the Disappearing Bust of Voltaire
- Salvadore Dali, 1940
Ambiguous Figures
The Great Panoramic
- Salvadore Dali, 1936
Ambiguous Figures
Multiple Figures
2
3
2
2
Ambiguous Figures
Mask Concavity
Ambiguous Figures
Mach’s Figure
Ambiguous Figures
Schroder’s Staircase
Ambiguous Figures
Oscillating Cubes
Ambiguous Figures
Necker Cube
Ambiguous Figures
Ambiguous Figures
Cube looks like a cube.
“Equal sides and right
angles.”
Eye: Perspetive projection
Reverse: Topless pyramid
change of shape
Cube looks distorted, on
face smaller than the
other.
Depth is paradoxical
Reverse: No Change
Ambiguous Figures
Cube does not look like a
cube.
Eye:
Near face is same
size as far face
Reverse: Topless pyramid
further face always looks
larger
Necker Cube. No face is
front or back by
perspective
Depth is paradoxical
Reverse: No change
Ambiguous Figures
Possible views:
• Cube with corner missing
• Box in corner of room
• Small cube infront of large
cube
3 in 1 Illusion
Ambiguous Figures
Cube / Room
Possible views:
• 3D Cube
• Corner of Room