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Week 6 Perception

Week 6 Perception. Sensation & Perception. Sensation Light bounces off people Light forms image on retina Image generates electrical signals in receptors Signals travel along nerve fibers to the brain. Perception Signals are processed and you “ perceive ” people.

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Week 6 Perception

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  1. Week 6 Perception

  2. Sensation & Perception Sensation • Light bounces off people • Light forms image on retina • Image generates electrical signals in receptors • Signals travel along nerve fibers to the brain... Perception Signals are processed and you “perceive” people

  3. How Do We Study Sensation? Psychophysics • Study of the relationship between a physical stimulus and your perception of it. • Concerned mostly with physical attributes of the stimulus (e.g., amp & loudness). Gustav Fechner Father of Psychophysics (Richarson, 1999)

  4. â • á • â • á • â Intensity 105 104 103 102 101 100 99 98 97 96 Y Y Y Y Y Y N Y Y Y Y Y Y N Y Y Y Y Y Y N Y Y N N N N Y N N N N N 99.5 99.5 98.5 100.5 99.5 Crossover Values Absolute Thresholds or How Low Can We Go? • What is the minimum stimulation necessary to detect a stimulus 50% of the time? Vision On a clear, dark night you can see a candle from 30 miles away (Richarson, 1999)

  5. Signal Detection Detecting a weak signal dependson: 1. Signal’s strength 2. Our internal psychological states (experience, motivation & fatigue) Do “absolute” thresholds really exist? (Richarson, 1999)

  6. (Kohn & Kohn, 1998)

  7. (Kohn & Kohn, 1998)

  8. Subliminal Stimulation Can we process information without being aware of it? (Richardson, 1999)

  9. Subliminal Stimulation Self-Help Tape Memory Self-Esteem M-M M-SE Memory Subject Request SE-M SE-SE Self-Esteem Result? No Differences! (Richardson, 1999)

  10. Difference Thresholds (JND) What is the minimum difference between two stimuli that a person can detect 50% of the time? (Richardson, 1999)

  11. Difference Thresholds (JND) What is the minimum difference between two stimuli that a person can detect 50% of the time? (Ernst) Weber’s Law “Regardless of magnitude, two stimuli must differ by a constant proportion for the difference to be noticeable.” (Richardson, 1999)

  12. Vision Transduction - the process by which stimulus energy (e.g., light) is converted into neural energy. Electromagnetic Spectrum (Kohn & Kohn, 1998)

  13. Longer Wavelength Lower Frequency Shorter Wavelength Higher Frequency Properties of...LIGHT (Richardson, 1999)

  14. Smaller Amplitude Dull Colors Higher Amplitude Bright Colors Properties of...LIGHT (Richardson, 1999)

  15. The Eye Lens (Kohn & Kohn, 1998)

  16. Retina (Rods & Cones) Retina Cones Rods Number6 million 125 million Location in RetinaCenter Periphery Sensitivity to LightLow High Color SensitiveYes No (Richardson, 1999)

  17. Dark & Light Adaptation Adaptation - process by which the eye becomes more or less sensitive to light (Kohn & Kohn, 1998)

  18. Processing Info in the Visual Cortex Three Major Types of Visual Cells in Cortex Simple Cells - line of correct width & angle, in the right position in receptive field Complex Cells - same as Simple, plus line must be moving in a particular direction Hypercomplex Cells - same as Complex but line must be a certain length (Richardson, 1999)

  19. (Kohn & Kohn, 1998)

  20. Visual Information Processing Retinal Processing Rods & Cones èBipolar Cells èGanglion Cells Feature Detection Detector cells respond to elementary features Abstraction High-level cells respond to combined info from feature-detector cells Recognition Brain matches the constructed image with stored images (Richardson, 1999)

  21. Helmholtz 1852 Trichromatic Theory of Color Vision Human eye has 3 types of cone receptors sensitive to different wavelengths of light. Short Medium Long People see colors because the eye does its own “color mixing” by varying ratio of cone neural activity (Richardson, 1999)

  22. (Kohn & Kohn, 1998)

  23. Cones and Color (Kohn & Kohn, 1998)

  24. R G B Y B W Opponent Process Theory Ewald Hering - Eye contains 3 mechanisms that produce antagonistic responses to three pairs of colors Why? Afterimages & Color Deficiency (Richardson, 1999)

  25. Hearing What is Sound? Compression & Rarefaction of air molecules. (Richardson, 1999)

  26. Sound Waves Amplitude (Loudness) Strength or height of the wave Frequency (Pitch) Distance twixt consecutive peaks Mix (Timbre) Interaction of different waves 1 Hertz = 1 Cycle/Sec Human Hearing 20 - 20k Hz (Richardson, 1999)

  27. (Kohn & Kohn, 1998)

  28. (Kohn & Kohn, 1998)

  29. (Kohn & Kohn, 1998)

  30. (Kohn & Kohn, 1998)

  31. (Kohn & Kohn, 1998)

  32. Auditory Pathway (Kohn & Kohn, 1998)

  33. Georg von Békésy 1899-1972 Perceiving Pitch Place Theory - pitch determined by point of maximal vibration on basilar membrane Traveling Wave Theory 1957 Frequency Theory - pitch determined by the rate at which the hair cells fire (i.e., 1KHz tone cause hair cells to fire 1k times/sec) Volley Principle (Richardson, 1999)

  34. (Kohn & Kohn, 1998)

  35. Smell (Kohn & Kohn, 1998)

  36. Taste (Kohn & Kohn, 1998)

  37. References • Feldman, M. (1999). McGraw Hill Company. Retrieved May 2002 from World Wide Web at: http://www.mcgrawhill.com. • Kohn, A. J. & Kohn, W. (1998). The Integrator 2.0. CD-Rom. Brooks/Cole Thomson Learning. • Richardson, K. (1999). Retrieved May 2002 from the World Wide Web at: http://www.monmouth.edu.

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