1. Color, Form and Depth Perception
Vision Perception
Color, Form and Depth Perception

2. Color Perception Types of Color Mixing (p. 134 fig. 4.17)
Subtractive: remove wavelength of color resulting in less light
Yellow + Blue = Green
How TVs create color
Additive: putting more light in the mixture than exists in one light by itself
How the human eye sees color

3. Theories of Color Vision
Trichromatic Theory
Color vision based on three receptors (Cones: red, green and blue)
We see diverse colors by mixing these three colors
TVs display color by mixing RGB
Occurs in the eye by sending the brain a mixture of RGB

4. Opponent Process Theory
Explains complimentary colors (p. 134 fig. 4.18) that produce afterimages and a gray tone when mixed
Each of the 3 cone types responds to two different wavelengths
Activity in one set of cells in the hypothalamus inhibit activity of “opposite” cells
Green v. red
Blue v. yellow
Black v. white
No colors such as “greenish-red” or “bluish-yellow”

5. Combination of theories
Studies support both theories
Trichromatic theory explains responses of three cone types that absorb wavelengths differently
Carry out 1st stage of color processing
Opponent Process Theory explains responses of ganglion cells
Carry out the last stages of processing
Both theories are needed to explain perception of color

6. Form Perception Top-down processing Bottom-up processing
Sensory info is interpreted in light of existing knowledge, concepts, ideas, & expectations (HM 4-4)
We perceive words before individual letters
Bottom-up processing
System takes in individual elements of a stimulus and then combines them into a unified perception (HM 4-5)
Feature analysis: focus on individual elements and assemble into more complex form

7. Gestalt Principles: viewing the whole
Focuses on top-down processing
Perceptual organization (p. 139 fig. 4.26)
Phi phenomenon
Figure and ground (reversible figures)
Proximity
Closure
Similarity
Simplicity (law of good form)
Continuity

8. Depth & Distance Perception
Monocular Cues: clues about distance based on the image in one eye alone
Pictorial cues (p. 143 fig. 4.34)
Cues from the active use of the eyes (accommodation as things come closer and motion parallax where closer objects appear to move faster)

9. Binocular Cues: clues about distance based on the differing views of the eyes (ex. viewmaster)
Retinal disparity
Convergence

10. Perceptual Constancies
Tendency to experience stable perception in the face of continually changing sensory input
Visual illusions: discrepancy between the appearance of visual stimulus and its physical reality
Muller-Lyer illusion (p. 146 fig. 4.37)
Geometric illusions