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Ch 3 sensation perception

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Ch 3 sensation perception

  1. 1. <ul><ul><li>Chapter 3 </li></ul></ul><ul><ul><li>Sensation and Perception </li></ul></ul>
  2. 2. Chapter Preview <ul><li>How We Sense and Perceive the World </li></ul><ul><li>The Visual System </li></ul><ul><li>The Auditory System </li></ul><ul><li>Other Senses </li></ul>
  3. 3. Sensation and Perception <ul><li>Sensation </li></ul><ul><ul><li>Process of receiving stimulus energies from external environment </li></ul></ul><ul><li>Perception </li></ul><ul><ul><li>Process of organizing and interpreting sensory information </li></ul></ul>
  4. 4. Sensation & Perception: Processes <ul><li>Bottom-Up Processing </li></ul><ul><ul><li>Information about external environment </li></ul></ul><ul><ul><li> Sensory receptors  Brain </li></ul></ul><ul><ul><li>Making sense of information </li></ul></ul><ul><li>Top-Down Processing </li></ul><ul><ul><li>Starts with cognitive processing at higher levels of brain </li></ul></ul>
  5. 5. Sensory Receptors and the Brain <ul><li>Sensory Receptors </li></ul><ul><ul><li>Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and brain </li></ul></ul><ul><li>Afferent nerves </li></ul><ul><ul><li>Bring information to brain </li></ul></ul><ul><li>Efferent nerves </li></ul><ul><ul><li>Send messages away from brain to body </li></ul></ul>
  6. 6. The Human Senses
  7. 7. Sensation <ul><li>Photoreception </li></ul><ul><ul><li>Detection of light </li></ul></ul><ul><ul><li>Perceived as sight </li></ul></ul><ul><li>Mechanoreception </li></ul><ul><ul><li>Detection of pressure, vibration, and movement </li></ul></ul><ul><ul><li>Perceived as touch, hearing, and equilibrium </li></ul></ul><ul><li>Chemoreception </li></ul><ul><ul><li>Detection of chemical stimuli </li></ul></ul><ul><ul><li>Perceived as smell and taste </li></ul></ul>
  8. 8. ‘ Confused’ Senses <ul><li>Synaesthesia </li></ul><ul><ul><li>One sense induces experience in another sense </li></ul></ul><ul><li>Phantom Limb Pain </li></ul><ul><ul><li>Reported pain in amputated arm or leg </li></ul></ul>
  9. 9. Thresholds <ul><li>Absolute Threshold </li></ul><ul><ul><li>Minimum amount of detectable stimulus energy </li></ul></ul>
  10. 10. Thresholds <ul><li>Subliminal Perception </li></ul><ul><ul><li>Detection of information below level of conscious awareness </li></ul></ul><ul><li>Difference Threshold (Just Noticeable Difference) </li></ul><ul><ul><li>Degree of difference that must exist between two stimuli before difference is detected </li></ul></ul><ul><li>Weber’s Law </li></ul><ul><ul><li>Principle that two stimuli must differ by a constant minimum percentage to be perceived as different </li></ul></ul>
  11. 11. Signal Detection Theory <ul><li>Theory of perception which focuses on decision-making about stimuli in presence of uncertainty </li></ul><ul><ul><li>Information acquisition </li></ul></ul><ul><ul><li>Criterion </li></ul></ul><ul><li>Possible outcomes: </li></ul><ul><ul><li>Hit </li></ul></ul><ul><ul><li>Miss </li></ul></ul><ul><ul><li>False alarm </li></ul></ul><ul><ul><li>Correct rejection </li></ul></ul>
  12. 12. Signal Detection Theory
  13. 13. Perception of Sensory Stimuli <ul><li>Attention </li></ul><ul><ul><li>Selective </li></ul></ul><ul><ul><ul><li>Cocktail party effect </li></ul></ul></ul><ul><ul><li>Shiftable </li></ul></ul><ul><ul><ul><li>Novelty, size, color, movement </li></ul></ul></ul><ul><ul><ul><li>Stroop effect </li></ul></ul></ul><ul><li>Perceptual Set </li></ul><ul><ul><li>Predisposition or readiness to perceive something a particular way </li></ul></ul>
  14. 14. Other Perceptual Phenomena <ul><li>Sensory Adaptation </li></ul><ul><ul><li>Change in responsiveness of sensory system based on average level of surrounding stimulation </li></ul></ul><ul><li>Extrasensory Perception (ESP) </li></ul><ul><ul><li>Perception in absence of concrete sensory input </li></ul></ul><ul><li>Parapsychology </li></ul><ul><ul><li>Scientific study of ESP </li></ul></ul><ul><ul><li>Absence of empirical data for existence of ESP </li></ul></ul>
  15. 15. The Visual Stimulus <ul><li>Light </li></ul><ul><ul><li>Form of electromagnetic energy </li></ul></ul><ul><li>Wavelength  Hue, or color </li></ul><ul><li>Amplitude  Brightness </li></ul><ul><li>Purity  Saturation, or richness </li></ul>
  16. 16. Wavelengths & Color
  17. 17. Structure of the Eye <ul><li>Sclera </li></ul><ul><ul><li>White, outer part of eye </li></ul></ul><ul><ul><li>Helps maintain shape of eye </li></ul></ul><ul><ul><li>Protects eye from injury </li></ul></ul><ul><li>Iris </li></ul><ul><ul><li>Colored part of eye </li></ul></ul><ul><li>Pupil </li></ul><ul><ul><li>Opening in center of iris </li></ul></ul><ul><ul><li>Size controlled by muscles in iris </li></ul></ul>
  18. 18. Structure of the Eye <ul><li>Cornea </li></ul><ul><ul><li>Clear membrane just in front of eye </li></ul></ul><ul><li>Lens </li></ul><ul><ul><li>Transparent, somewhat flexible, disk-like structure </li></ul></ul><ul><li>The cornea and the lens both bend light falling on the surface of the eye just enough to focus it on the retina. </li></ul><ul><li>Retina </li></ul><ul><ul><li>Multilayered, light-sensitive surface at back of eye </li></ul></ul><ul><ul><li>Converts visual stimuli to neural impulses </li></ul></ul>
  19. 19. Structure of the Eye
  20. 20. Visual Receptor Cells <ul><li>Cells on retina which convert electromagnetic energy into electrochemical impulses </li></ul><ul><li>Rods </li></ul><ul><ul><li>Sensitive to light </li></ul></ul><ul><ul><li>Not very useful for color vision </li></ul></ul><ul><ul><li>Function well under low illumination </li></ul></ul><ul><li>Cones </li></ul><ul><ul><li>Used for color perception </li></ul></ul><ul><ul><li>Require more light than rods </li></ul></ul>
  21. 21. Structure of the Eye: Retina <ul><li>Fovea </li></ul><ul><ul><li>Tiny area in center of retina at which vision is best </li></ul></ul><ul><ul><li>Contains only cones </li></ul></ul><ul><li>Rods & cones  Bipolar cells  Ganglion cells  Optic nerve </li></ul><ul><li>Blind spot </li></ul><ul><ul><li>Place on retina containing neither rods nor cones </li></ul></ul><ul><ul><li>Where optic nerve leaves eye </li></ul></ul>
  22. 22. Structure of the Eye: Retina
  23. 23. Visual Processing <ul><li>Optic Nerve  Optic Chiasm  Visual Cortex </li></ul><ul><li>Optic nerve fibers divide at optic chiasm: </li></ul><ul><ul><li>Left Visual Field  Right Hemisphere </li></ul></ul><ul><ul><li>Right Visual Field  Left Hemisphere </li></ul></ul>
  24. 24. Visual Processing
  25. 25. Visual Processing <ul><li>Feature Detectors </li></ul><ul><ul><li>Neurons in primary visual cortex that respond to particular features of a stimulus </li></ul></ul><ul><li>Parallel Processing </li></ul><ul><ul><li>Simultaneous distribution of information across different neural pathways </li></ul></ul><ul><li>Binding </li></ul><ul><ul><li>Integration of what is processed by different pathways or cells </li></ul></ul>
  26. 26. Color Vision: Trichromatic Theory <ul><li>Three types of cones, sensitive to different (but overlapping) ranges of wavelength </li></ul><ul><li>Support includes . . . </li></ul><ul><ul><li>Color matching </li></ul></ul><ul><ul><li>Color blindness </li></ul></ul>
  27. 27. Color Blindness
  28. 28. Color Vision: Opponent-Process Theory <ul><li>Afterimages </li></ul><ul><ul><li>Sensations that remain after stimulus is removed </li></ul></ul><ul><ul><li>Not explained by trichromatic theory </li></ul></ul><ul><ul><li>Explained by opponent-process theory </li></ul></ul><ul><li>Visual system treats colors as complementary pairs. </li></ul><ul><li>Conclusion: Both theories are correct. </li></ul>
  29. 29. Negative Afterimage
  30. 30. Perceiving Shape <ul><li>Contour </li></ul><ul><ul><li>Location at which sudden change of brightness occurs </li></ul></ul><ul><li>Figure-Ground Relationship </li></ul><ul><ul><li>Principle by which perceptual field is organized into stimuli that stand out (figure) and those left over (ground) </li></ul></ul><ul><li>Gestalt Psychology </li></ul><ul><ul><li>School of thought interested in how people naturally organize perception according to certain patterns </li></ul></ul><ul><ul><li>‘ Whole is different from sum of its parts.’ </li></ul></ul>
  31. 31. Figure-Ground Relationship
  32. 32. Gestalt Psychology
  33. 33. Perceiving Depth <ul><li>Ability to perceive objects three-dimensionally </li></ul><ul><li>Binocular Cues  combined images from two eyes </li></ul><ul><ul><li>Disparity </li></ul></ul><ul><ul><li>Convergence </li></ul></ul><ul><li>Monocular Cues  available from image in one eye </li></ul><ul><ul><li>Familiar size </li></ul></ul><ul><ul><li>Height in field of view </li></ul></ul><ul><ul><li>Linear perspective and relative size </li></ul></ul><ul><ul><li>Overlap </li></ul></ul><ul><ul><li>Shading </li></ul></ul><ul><ul><li>Texture gradient </li></ul></ul>
  34. 34. Monocular Cues: Linear Perspective
  35. 35. Perceiving Motion <ul><li>Retinas of humans cannot detect movement. </li></ul><ul><li>Neurons specialized to detect motion </li></ul><ul><li>Feedback from body </li></ul><ul><li>Environment rich in cues </li></ul><ul><li>Real movement </li></ul><ul><li>Apparent movement </li></ul><ul><ul><li>Perception of stationary object as moving </li></ul></ul>
  36. 36. Perceiving Constancy <ul><li>Recognition that objects are constant even though sensory input is changing </li></ul><ul><li>Size constancy </li></ul><ul><ul><li>Same size despite retinal image changes </li></ul></ul><ul><li>Shape constancy </li></ul><ul><ul><li>Same shape despite orientation changes </li></ul></ul><ul><li>Color constancy </li></ul><ul><ul><li>Same color despite light changes </li></ul></ul>
  37. 37. Perceiving Constancy Size constancy Shape constancy
  38. 38. The Nature of Sound <ul><li>Sound </li></ul><ul><ul><li>Vibrations in air processed by auditory system </li></ul></ul><ul><li>Wavelength  Frequency  Pitch </li></ul><ul><li>Amplitude  Pressure  Loudness </li></ul><ul><li>Complexity  Saturation  Timbre </li></ul>
  39. 39. The Nature of Sound
  40. 40. Structure of the Ear <ul><li>Outer Ear  Collects and channels sound </li></ul><ul><ul><li>Pinna </li></ul></ul><ul><ul><li>External Auditory Canal </li></ul></ul><ul><li>Middle Ear  Channels sound to inner ear </li></ul><ul><ul><li>Eardrum </li></ul></ul><ul><ul><li>Hammer, Anvil, & Stirrup </li></ul></ul><ul><li>Inner Ear  Converts sound into neural impulses </li></ul><ul><ul><li>Oval Window </li></ul></ul><ul><ul><li>Cochlea </li></ul></ul><ul><ul><li>Basilar Membrane  Hair Cells  Tectorial Membrane </li></ul></ul>
  41. 41. Structure of the Ear
  42. 42. Theories of Hearing <ul><li>Place Theory </li></ul><ul><ul><li>Each frequency produces vibrations at a particular spot. </li></ul></ul><ul><ul><li>But . . . explains high-frequency, not low-frequency, sounds </li></ul></ul><ul><li>Frequency Theory </li></ul><ul><ul><li>Perception of frequency depends on how often auditory nerve fires. </li></ul></ul><ul><ul><li>But . . . single neurons have maximum firing rates </li></ul></ul><ul><li>Volley Principle </li></ul><ul><ul><li>Modification of frequency theory </li></ul></ul><ul><ul><li>Clusters of nerve cells can fire neural impulses in rapid succession. </li></ul></ul>
  43. 43. Auditory Processing <ul><li>Inner Ear  Auditory Nerve  Temporal Lobe </li></ul><ul><li>Most fibers cross over midline between hemispheres: </li></ul><ul><ul><li>Left Ear  Right Hemisphere </li></ul></ul><ul><ul><li>Right Ear  Left Hemisphere </li></ul></ul><ul><ul><li>Some fibers go directly to same-side hemisphere. </li></ul></ul>
  44. 44. Localizing Sound <ul><li>Each ear receives somewhat different stimuli. </li></ul><ul><li>Distance  Timing </li></ul><ul><li>Sound Shadow  Intensity </li></ul><ul><li>Echolocation </li></ul><ul><ul><li>System based on returning echoes of sounds </li></ul></ul><ul><ul><li>Used by bats; humans less accurate </li></ul></ul>
  45. 45. Other Senses <ul><li>Skin (Cutaneous) </li></ul><ul><ul><li>Touch </li></ul></ul><ul><ul><li>Temperature </li></ul></ul><ul><ul><li>Pain </li></ul></ul><ul><li>Chemical </li></ul><ul><ul><li>Smell </li></ul></ul><ul><ul><li>Taste </li></ul></ul><ul><li>Kinesthetic </li></ul><ul><li>Vestibular </li></ul>
  46. 46. The Skin (Cutaneous) Senses <ul><li>Touch </li></ul><ul><ul><li>Mechanical energy, or pressure, against skin </li></ul></ul><ul><li>Temperature </li></ul><ul><ul><li>Warm and cold sensory nerve endings, or thermoreceptors </li></ul></ul><ul><li>Pain </li></ul><ul><ul><li>Widely-dispersed receptors with much higher thresholds for different types of physical stimuli (e.g., pressure, heat) </li></ul></ul>
  47. 47. Pain <ul><li>Prostaglandins </li></ul><ul><ul><li>Stimulate pain receptors and cause experience of pain </li></ul></ul><ul><li>Neural pathways to brain </li></ul><ul><ul><li>Fast Pathway  Directly to thalamus </li></ul></ul><ul><ul><li>Slow Pathway  Through limbic system </li></ul></ul><ul><li>Endorphins </li></ul><ul><ul><li>Neurotransmitters involved in turning pain signals on/off </li></ul></ul>
  48. 48. Chemical Senses: Taste <ul><li>Detecting chemicals dissolved in saliva </li></ul><ul><li>Papillae </li></ul><ul><ul><li>Bumps on surface of tongue </li></ul></ul><ul><ul><li>Contain taste buds, receptors for taste </li></ul></ul><ul><li>Four taste qualities: sweet, sour, bitter, salty </li></ul><ul><li>Taste fibers respond to range of chemicals spanning multiple taste elements </li></ul><ul><ul><li>Umami </li></ul></ul>
  49. 49. Chemical Senses: Taste
  50. 50. Chemical Senses: Smell <ul><li>Detecting airborne chemicals </li></ul><ul><li>Olfactory epithelium </li></ul><ul><ul><li>Lines roof of nasal cavity </li></ul></ul><ul><ul><li>Contains sheet of receptor cells </li></ul></ul><ul><li>Neural pathway </li></ul><ul><ul><li>Olfactory areas of temporal lobe  Limbic system </li></ul></ul><ul><ul><li>Superhighway to emotion & memory </li></ul></ul><ul><li>Interpersonal attraction & MHC genes </li></ul>
  51. 51. Chemical Senses: Smell
  52. 52. Kinesthetic and Vestibular Senses <ul><li>Kinesthetic Sense </li></ul><ul><ul><li>Information about movement, posture, orientation </li></ul></ul><ul><li>Vestibular Sense </li></ul><ul><ul><li>Information about balance, movement </li></ul></ul><ul><li>Proprioceptive Feedback </li></ul><ul><ul><li>Information about relative position of limbs and body </li></ul></ul><ul><li>Semicircular Canals </li></ul><ul><ul><li>Contain sensory receptors to detect head motion </li></ul></ul>