Basics of Color Vision

Wavelength: determines color – longer=red/shorter= violet

Amplitude: determines brightnessPurity: determines saturation

Theories of Color Vision

• Trichromatic theory – Young and Helmholtz– Receptors for red, green, blue color

mixing

• Opponent Process theory – Hering– Three pairs of antagonistic colors– Red/green, blue/yellow, black/white

Current Perspective

• Both theories are necessary to explain color vision.

Perceiving Forms, Patterns and Objects• Reversible figures• Perceptual sets• Inattentional blindness• Feature detection theory – bottom-up processing• Form perception – top-down processing• Subjective contours• Gestalt psychologists: the whole is more than

the sum of its partsreversible figures and perceptual sets demonstrate that the same visual stimulus can result in bery different perceptions

Principles of Perception• Gestalt principles of form

perception:– Figure-ground, proximity, similarity,

continuity, closure, and simplicity• Recent research:

– Distal (stimuli outside the body) vs. proximal (stimulus energies impinging on sensory receptors) stimuli.

– Perceptual hypotheses• context

Depth and Distance Perception

• Binocular cues – clues from both eyes together– Retinal disparity– Convergence

• Monocular cues – clues from a single eye– Motion parallax– Accommodation– Pictorial depth cues

Stability in the Perceptual World: Perceptual Constancies

• Perceptual constancies – stable perceptions amid changing stimuli– Size– Shape– Brightness– Hue– Location in space

Optical Illusions: the power of misleading cues

• Optical illusions – discrepancy between visual appearance and physical reality

• Famous optical illusions: Muller-Lyer Illusion, Ponzo Illusion, Poggendorf Illusion, Upside-Down T Illusion, Zollner Illusion, the Ames Room, and Impossible Figures

• Cultural differences: perceptual hypotheses at work