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Visual System Characteristics and Perceptual Processes

Explore the power functions of the visual system, including Steven's Law, magnitude estimation, and cross-modality matches. Learn about the retina's distribution, color vision, and adaptation range. Study the duplex theory of vision and the role of top-down and bottom-up perceptual processes in feature detection.

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Visual System Characteristics and Perceptual Processes

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  1. Average: 77; SD: 14.4

  2. Power Functions (vs. Weber)(r)a =(s)b • Magnitude Estimation • Steven’s Law: Power Function • Cross Modality Match

  3. Visual system characteristics • Retina: 120 million rods & 6 mill. Cones • Retinal distribution meaningful

  4. System operating characteristics • Color • Sharpness or acuity: 1 sec. line (1 inch at 3.5 miles) • Sensitivity (range (candle at 10 mi. to noon sun 10,000,000,000,000:1) • Differential course of adaptation

  5. Duplex Theory of Vision • Two systems: • Rod based • Sensitive • Low acuity • Monochromatic • Cone based • High threshold • High acuity • Color

  6. Adaptation • Overall range of light 1013 : 1 • Adaptation range of eye 105 : 1

  7. We’re not from Missouri! • Color Vision ( Perceptual constancies/neural interactions) • Feature Detection--the analysis of visual input • Limulus • Cats • Humans • Top-down perceptual processes and their interactions with bottom-up

  8. Active processing • Sentence • Necker Cube • Gestalt principles

  9. The large black dog was chasing the the pretty little groundhog who was very much afraid of him across the carpet.

  10. Feature Detection: the analysis of visual input Bottom-up perceptual processes (lateral inhibition) • Limulus (Hartline & Ratliff) • Frogs (Matarana, Lettvin, McCullough & Pitts) • Cats (Kuffler, Hubel & Weisal) • Humans • Top-down perceptual processes and their interactions with bottom-up

  11. Top-down processes:Some examples and a mechanism

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