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Understanding Visual Perception: Power Functions, Sensitivity, and Adaptation in Vision Systems

This overview explores the complexities of human visual perception, emphasizing key concepts such as power functions, adaptation processes, and feature detection. It discusses Steven's Law and differential adaptation in rod and cone systems, detailing how these systems manage sensitivity to light and color with varying acuity. The role of neural interactions and perceptual constancies is examined alongside top-down and bottom-up processing. Visual input analysis is contextualized through various species, highlighting the evolutionary aspects of vision, including notable studies on Limulus and cats.

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Understanding Visual Perception: Power Functions, Sensitivity, and Adaptation in Vision Systems

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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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