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Exploring Vision: Sensation & Perception

Dive into the intricate processes of sensation and perception, exploring how the sensory system receives stimuli and organizes information. Understand thresholds, adaptation, transduction, and visual properties like hue and intensity. Learn about sensory receptors, pathways to the brain, and color theories. Enhance knowledge of vision with concepts such as accommodation, retinal reactions, and visual processing. Discover the complexities of color vision, opponent-process theory, and color constancy. Delve into the fascinating world of visual perception and its mechanisms.

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Exploring Vision: Sensation & Perception

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  1. Myers EXPLORING PSYCHOLOGY Module 14 Introduction to Sensation and Perception: Vision James A. McCubbin, PhD Clemson University Worth Publishers

  2. Sensation • Sensation • the process by which our sensory receptors and nervous system receive and represent stimulus energy • Perception • the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

  3. Sensation • Our sensory and perceptual processes work together to help us sort out complex images

  4. Sensation • Bottom-Up Processing • analysis that begins with the sense receptors and works up to the brain’s integration of sensory information • Top-Down Processing • information processing guided by higher-level mental processes • as when we construct perceptions drawing on our experience and expectations

  5. Sensation: Basic Principles • Psychophysics • study of the relationship between physical characteristics of stimuli and our psychological experience of them • Light- brightness • Sound- volume • Pressure- weight • Taste- sweetness

  6. Sensation: Thresholds • Absolute Threshold • minimum stimulation needed to detect a particular stimulus 50% of the time • Difference Threshold • minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND)

  7. 100 Percentage of correct detections 75 50 Subliminal stimuli 25 0 Low Absolute threshold Medium Intensity of stimulus Sensation: Thresholds • Subliminal • when stimuli are below one’s absolute threshold for conscious awareness

  8. Sensation: Thresholds • Weber’s Law • to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount) • light intensity- 8% • weight- 2% • tone frequency- 0.3%

  9. Now you see it, now you don’t! Sensory Adaptation- diminished sensitivity as a consequence of constant stimulation

  10. Vision • Transduction • conversion of one form of energy to another • in sensation, transforming of stimulus energies into neural impulses • Wavelength • the distance from the peak of one wave to the peak of the next

  11. Vision • Hue • dimension of color determined by wavelength of light • Intensity • amount of energy in a wave determined by amplitude • brightness • loudness

  12. The spectrum of electromagnetic energy

  13. Great amplitude (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision: Physical Properties of Waves

  14. Vision

  15. Vision • Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina • Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

  16. Retina’s Reaction to Light- Receptors • Rods • peripheral retina receptors • detect black, white and gray • for peripheral or twilight conditions • Cones • receptors near center of retina • fine detail and color vision • for daylight or well-lit conditions

  17. Retina’s Reaction to Light • Optic nerve • nerve that carries neural impulses from the eye to the brain • Blind Spot • point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there

  18. Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Vision: Receptors

  19. Pathways from the Eyes to the Visual Cortex

  20. Cell’s responses Stimulus Visual Information Processing • Feature Detectors • nerve cells in the brain that respond to specific features • shape • angle • movement

  21. Visual Information Processing • Parallel Processing • simultaneous processing of several aspects of a problem simultaneously

  22. Visual Information Processing • Trichromatic (three color) Theory • Young and Helmholtz • three different retinal color receptors • red • green • blue

  23. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” redgreen greenred blueyellow yellowblue black white white black

  24. Visual Information Processing • Color Constancy • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

  25. Color-Deficient Vision • People who suffer red-green dificiency have trouble perceiving the number within the design

  26. Opponent Process: Afterimage Effect

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