Day Vision

Color Vision Facts

• Color Mixing: “Rule of 3”

http://www.exploratorium.edu/exhibits

The Color Circle

Subtraction

Color Vision Facts

• Color Mixing: “Rule of 3”

• Color Aftereffects: R and G, B and Y

Color Vision Facts

• Color Mixing: “Rule of 3”

• Color Aftereffects: R and G, B and Y

• Color Blindness

Are You Colorblind?

Red-Green

Trichromatic Theory

• Young and Helmholtz

• Blue, green, and red input channels

• True at receptor level

• Explains “Rule of 3”

Opponent-Process Theoryof Color Vision

• Ewald Hering

• Color-sensitive visual pairs.– Red or green, blue or yellow– Explains aftereffects and blindness

R G B Y

Combined

R G B Y (R + G)

Perception

How do sensations become perceptions?

Perceptual Constancy

• Objects maintain their size, shape, color, and other properties despite changes in their retinal image.

• Allows experience where solid objects do not continuously change

Nonconstant World

Shape Constancy

Saul Kassin, Psychology. Copyright © 1995 by Houghton Mifflin Company. Reprinted by permission.

Depth and Distance

• 3-D experience from 2-D information?

• Cues

Monocular (One Eye)

Binocular (Two Eyes)

Monocular Cues

• Relative Size• Height in the Visual

Field• Interposition• Linear Perspective• Reduced Clarity• Textural Gradient• Light and Shadow

Binocular Cues

Convergence

James D. Laird and Nicholas S. Thompson, Psychology. Copyright © 1992 by Houghton Mifflin Company. Reprinted by permission.

Binocular (con’t)

• DisparityClose – Disparity High

Far – Disparity Low

Douglas A. Bernstein, Alison Clarke-Stewart, Louis A. Penner, Edward J. Roy, and Christopher D. Wickens,

Psychology, Fifth Edition. Copyright © 2000 by Houghton Mifflin Company. Reprinted by permission.

Misperceiving Reality

Which Line Is Longer?

Impossible Figures

Magic Eye

Motion

http://www.exploratorium.edu/exhibits

Perception of Motion

• Looming stimulus (rapid expansion)

• Images moves, but eyes and head do not

• Image moves, but can’t be caused by movement of the body, eyes, or head.– Visual flow without appropriate sensations can

result in motion sickness.

• Stroboscopic Motion

http://www.rpi.edu/~brings/PHI/phi3.html

Recognizing the Perceptual World

How do I recognize familiar people?

How Does Recognition Occur?

• Bottom-Up Processing: Basic features of the stimulus are analyzed to create the perceptual experience.

• Top-Down Processing: Reliance on one’s knowledge, especially when sensory information is vague or ambiguous.

What Can InfluenceTop-Down Processing?

• Schemas– Readiness to perceive a stimulus in a certain

way

• Motivation

• Expectancy or prior context

Expectancy

Organizing the Perceptual World

What determines how I perceive my world?

Principles of Perceptual Organization: Figure and Ground

• Figure: The part of the visual field that has meaning.

• Ground: The contourless part of the visual field.

Figure 3.19: Reversible Images

Gestalt Grouping

• Stimuli are grouped together

• “Gestalt” is the German word meaning (roughly) “whole figure.”

Gestalt Principles of Perceptual Grouping

Categorizing Perceptions

What Do You See Here?

Another Version With Line Grouping

Now Do You See It?