Optical Illusions

OpticalOptical IllusionsIllusions

Seeing Is Seeing Is

DeceivingDeceiving

Christopher LandauerScience of ArtMarch 9, 2000

What is an Illusion?What is an Illusion?

il·lu·sion (-lzhn) noun1. 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?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 IllusionsHistory of Illusions

Prehistory:

• Afterimage caused by glancing at the sun

• A stick half in and half out of water


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


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


A. Ideal Parthenon

B. Architrave Illusion(Jastrow-Lipps)

C. Illusionary Distortion

D. Alterations made to offset illusion


“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


Entasis:Convexing of column to overcome parallel lines appearing concave

Irradiation Illusion:Bright objects appear larger


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


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


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 engineer1964 - Tolansky: physicist1972 - Robinson: psychologist

1900s Revolution and Rebirth• Behaviorists vs. Gestalt • Methodology vs. Theoretical• Percepual response & Brain wave patterns

Current State of Current State of Illisions Illisions

Conclusion:Paradigmatic Science (Psychology)

1900s Normal Sciences => Anomoly => Crisis => Revolution

Current status: Normal Science- mopping up- puzzle solving- guidelines for research

Ambiguous FiguresAmbiguous Figures

Face or Vase?Face or Vase?


L'Amour de PierrotL'Amour de Pierrot c.1905c.1905

Gossip and SatanGossip and Satan

Geo. A. WotherspoonGeo. A. Wotherspoon

RetroActiveRetroActive

Nels IsralsonNels Isralson


Slave Market With the Disappearing Bust of Voltaire - Salvadore Dali, 1940

Bust of VoltaireBust of Voltaire- Houdon, 1781- Houdon, 1781


The Great Panoramic - Salvadore Dali, 1936


22

2 2

22

33

Multiple FiguresMultiple Figures


Mask ConcavityMask Concavity


Mach’s FigureMach’s Figure


Schroder’s StaircaseSchroder’s Staircase

Ambiguous FiguresAmbiguous FiguresOscillating CubesOscillating Cubes


Necker CubeNecker Cube



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


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


Possible views:

• Cube with corner missing

• Box in corner of room

• Small cube infront of large cube

3 in 1 Illusion3 in 1 Illusion

Ambiguous FiguresAmbiguous FiguresCube / RoomCube / Room

Possible views:

• 3D Cube

• Corner of Room

Optical Illusions

Documents

concaveirradiation illusion

false perception

erroneous belief

latin root of illusion

illusion lzhen noun1

perceptual error

perceptual process

erroneous concept