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Sensation and Perception

Sensation and Perception. Chapter 3. Sensing the World Around Us. Learning Outcomes Define absolute thresholds Explain the difference threshold and Weber’s law Discuss sensory adaptation. Absolute Thresholds.

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Sensation and Perception

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  1. Sensation and Perception Chapter 3

  2. Sensing the World Around Us • Learning Outcomes • Define absolute thresholds • Explain the difference threshold and Weber’s law • Discuss sensory adaptation

  3. Absolute Thresholds • Absolute threshold: the smallest intensity of a stimulus that must be present for it to be detected

  4. Difference Thresholds • Difference threshold (just noticeable difference) • Weber’s law

  5. Sensory Adaptation • Sensory adaptation: an adjustment to sensory capacity when stimuli in the environment are unchanging; “getting used to” a sensory stimulus so that you no longer have the same reaction to it as you initially did

  6. Vision: Shedding Light on Our Eye • Learning Outcomes • Explain the basic structure of the eye • Compare and contrast color vision with color blindness

  7. The Structure of the Eye • Light passes through the cornea, pupil, and the lens before reaching the retina: converts the energy of the light to electrical impulses for transmission to the brain • Rods • Cones • Optic Nerve • Feature Detection

  8. Figure 2

  9. Color Vision and Color Blindness • Trichromatic theory of color vision: three kinds of cones exist in the retina (one most responsive to blue-violet, one to green, & one to yellow-red)

  10. Figure 5

  11. Color Vision and Color Blindness • Opponent-process theory of color vision: receptor cells are linked in pairs (blue-yellow, red-green, & black-white), working in opposition to each other

  12. Hearing and the Other Senses • Learning Outcomes • Describe how we sense sound • Discuss smell and taste • Distinguish the skin senses

  13. Sensing Sound • Sound: movement of air molecules brought about by vibration (sound waves) • Semicircular canals: movement of fluid here affects our sense of balance

  14. Smell and Taste • Smell (olfaction) • Molecules enter the nasal passages and pass over olfactory cells (receptor neurons); responses sent to brain, where they are combined for recognition of particular smells • Taste (gustation) • Receptor cells (taste buds) respond to four basic stimulus qualities: sweet, sour, salty, and bitter

  15. The Skin Senses • Skin senses: touch, pressure, temperature, and pain; receptor cells in skin distributed unevenly throughout the body • Gate-control theory of pain

  16. Perceptual Organization • Learning Outcomes • Explain the gestalt laws of organization • Identify top-down and bottom-up processing • Define perceptual constancy • Explain depth perception • Relate motion perception to daily life • Determine the importance of perceptual illusions

  17. Perceptual Organization • Figure-ground organization: we usually perceive objects as a figure standing out against a background

  18. The Gestalt Laws of Organization • Principles that describe how we organize pieces of information into meaningful wholes (gestalts = patterns) • Closure • Proximity • Similarity • Simplicity

  19. Figure 2

  20. Top-Down and Bottom-Up • Top-down processing: perception is guided by higher-level knowledge, experience, expectations, and motivations • Bottom-up processing: processing information by progressing from the individual elements of a stimulus and moving up to the perception of the whole

  21. Perceptual Constancy • Physical objects are perceived as unvarying and consistent despite changes in appearance or changes in the physical environment • Ex.: the image on your retina of a person far away from you is very small, but you understand (perceive) her to be of “normal” size

  22. Depth Perception • Depth perception: the ability to view the world in three dimensions and to perceive distance • Binocular disparity

  23. Motion Perception • How do we perceive motion? • Movement of an object across the retina is perceived relative to an unmoving background • If a stimulus is coming toward you, the image on the retina will expand in size, filling more of the visual field, but we assume the stimulus is approaching rather than it’s growing in size • We factor information about our head and eye movements with information about changes in the retinal image

  24. Perceptual Illusions • Visual illusions: physical stimuli that consistently produce errors in perception • Muller-Lyer illusion

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