Section 2: The Visual System Chapter 3 Lesson 2 Section 2: The Visual System

2. The Visual System

Properties of Light Wavelength: distance between peaks perceived as hue Some wavelengths beyond human sensation Amplitude: height of wave perceived as brightness Purity: mixture of wavelengths Perceived as saturation (c) McGraw-Hill Education Permission required for reproduction or display

A. The Visual Stimulus and the Eye The Structure of the Eye Sclera Iris Pupil Lens Recording Images on the Retina The Lens Rods Cones The Fovea The Optic Nerve

B. Visual Processing in the Brain Visual Cortex and Feature Detectors Parallel Processing Binding

Visual Processing Pathway of Visual Information Left Hemisphere Left Visual Field Right Visual Field Pathway of Visual Information Retina Optic Nerve Optic Chiasm: optic nerve fibers divide Left Hemisphere Right Hemisphere Thalamus Visual Cortex (c) McGraw-Hill Education Permission required for reproduction or display Photo credit: © RubberBall Productions/Getty Images RF

Opponent-Process Theory C. Color Vision Trichromatic Theory Opponent-Process Theory

D. Perceiving Shape, Depth, Motion, and Constancy The Figure–Ground Relationship Gestalt Psychology Depth Perception Binocular Cues Convergence Monocular Cues Motion Perception Apparent Motion Perceptual Constancy Size Constancy Shape Constancy Color Constancy

Visual Perception: Shape Gestalt Psychology perceptions are naturally organized according to certain patterns whole is different from the sum of the parts Gestalt Principles figure-ground relationship closure proximity similarity Photo credit: (c) Brand X Pictures/PunchStock (c) McGraw-Hill Education Permission required for reproduction or display

Figure-Ground Relationship (c) McGraw-Hill Education Permission required for reproduction or display

Gestalt Principles Closure Proximity Similarity Note the rows and columns being different in Similarity. Similarity (c) McGraw-Hill Education Permission required for reproduction or display

Visual Perception: Depth The brain constructs perception of 3D from 2D images processed by the retina Binocular cues disparity convergence (c) McGraw-Hill Education Permission required for reproduction or display Photo credit: (c) Comstock/PunchStock

Monocular Cues: Familiar Size, Overlap Note: Instructors should feel free to replace this figure with any picture or pictures illustrating the various monocular cues of depth perception Photo credit: © Paul Bradbury / age fotostock (c) McGraw-Hill Education Permission required for reproduction or display

Monocular Cues: Height in Field, Linear Perspective Note: Instructors should feel free to replace this figure with any picture or pictures illustrating the various monocular cues of depth perception. (c) McGraw-Hill Education Permission required for reproduction or display Photo credit: Image courtesy National Gallery of Art

Monocular Cues: Shading Note: Instructors should feel free to replace this figure with any picture or pictures illustrating the various monocular cues of depth perception Image: (c) Pixtal/age Fotostock (c) McGraw-Hill Education Permission required for reproduction or display

Monocular Cues: Texture Gradients Note: Instructors should feel free to replace this figure with any picture or pictures illustrating the various monocular cues of depth perception (c) McGraw-Hill Education Permission required for reproduction or display

Visual Perception: Motion Humans have specialized motion detectors Apparent movement Note: As with most visual illusions, there are a number of excellent demonstrations of movement aftereffects available online. (c) McGraw-Hill Education Permission required for reproduction or display

Visual Perception: Constancy Perceptual Constancies recognition that objects do not physically change despite changes in vantage point and viewing conditions sensory information (retinal image) changes, but perceptual interpretation does not size, shape, and color constancies Activity/Demonstration: If in a face-to-face course, you can easily demonstrate shape and size constancy by walking around the classroom and asking students if you are growing larger or smaller as you move closer to them, and hold up and rotate a book and ask students if the shape of the book changes. Of course, you should point out that the resulting retinal image does change in both cases. (c) McGraw-Hill Education Permission required for reproduction or display Photo credit: Purestock/SuperStock