1. Copyright McGraw-Hill, Inc. 2010 1 Chapter 3 Sensation and Perception

2. Copyright McGraw-Hill, Inc. 2010 2 Chapter Preview How We Sense and Perceive the World The Visual System The Auditory System Other Senses

3. Copyright McGraw-Hill, Inc. 2010 3 Sensation and Perception Sensation Process of receiving stimulus energies from external environment Perception Process of organizing and interpreting sensory information

4. Copyright McGraw-Hill, Inc. 2010 4 Sensation & Perception: Processes Bottom-Up Processing Information about external environment  Sensory receptors  Brain Making sense of information Top-Down Processing Starts with cognitive processing at higher levels of brain

5. Copyright McGraw-Hill, Inc. 2010 5 Sensory Receptors and the Brain Sensory Receptors Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and brain Afferent nerves Bring information to brain Efferent nerves Send messages away from brain to body

6. Copyright McGraw-Hill, Inc. 2010 6 The Human Senses

7. Copyright McGraw-Hill, Inc. 2010 7 Sensation Photoreception Detection of light Perceived as sight Mechanoreception Detection of pressure, vibration, and movement Perceived as touch, hearing, and equilibrium Chemoreception Detection of chemical stimuli Perceived as smell and taste

8. Copyright McGraw-Hill, Inc. 2010 8 ‘Confused’ Senses Synaesthesia One sense induces experience in another sense Phantom Limb Pain Reported pain in amputated arm or leg

9. Copyright McGraw-Hill, Inc. 2010 9 Thresholds Absolute Threshold Minimum amount of detectable stimulus energy

10. Copyright McGraw-Hill, Inc. 2010 10 Thresholds Subliminal Perception Detection of information below level of conscious awareness Difference Threshold (Just Noticeable Difference) Degree of difference that must exist between two stimuli before difference is detected Weber’s Law Principle that two stimuli must differ by a constant minimum percentage to be perceived as different

11. Copyright McGraw-Hill, Inc. 2010 11 Signal Detection Theory Theory of perception which focuses on decision- making about stimuli in presence of uncertainty Information acquisition Criterion Possible outcomes: Hit Miss False alarm Correct rejection

12. Copyright McGraw-Hill, Inc. 2010 12 Signal Detection Theory

13. Copyright McGraw-Hill, Inc. 2010 13 Perception of Sensory Stimuli Attention Selective Cocktail party effect Shiftable Novelty, size, color, movement Stroop effect Perceptual Set Predisposition or readiness to perceive something a particular way

14. Copyright McGraw-Hill, Inc. 2010 14 Other Perceptual Phenomena Sensory Adaptation Change in responsiveness of sensory system based on average level of surrounding stimulation Extrasensory Perception (ESP) Perception in absence of concrete sensory input Parapsychology Scientific study of ESP Absence of empirical data for existence of ESP

15. Copyright McGraw-Hill, Inc. 2010 15 The Visual Stimulus Light Form of electromagnetic energy Wavelength  Hue, or color Amplitude  Brightness Purity  Saturation, or richness

16. Copyright McGraw-Hill, Inc. 2010 16 Wavelengths & Color

17. Copyright McGraw-Hill, Inc. 2010 17 Structure of the Eye Sclera White, outer part of eye Helps maintain shape of eye Protects eye from injury Iris Colored part of eye Pupil Opening in center of iris Size controlled by muscles in iris

18. Copyright McGraw-Hill, Inc. 2010 18 Structure of the Eye Cornea Clear membrane just in front of eye Lens Transparent, somewhat flexible, disk-like structure The cornea and the lens both bend light falling on the surface of the eye just enough to focus it on the retina. Retina Multilayered, light-sensitive surface at back of eye Converts visual stimuli to neural impulses

19. Copyright McGraw-Hill, Inc. 2010 19 Structure of the Eye

20. Copyright McGraw-Hill, Inc. 2010 20 Visual Receptor Cells Cells on retina which convert electromagnetic energy into electrochemical impulses Rods Sensitive to light Not very useful for color vision Function well under low illumination Cones Used for color perception Require more light than rods

21. Copyright McGraw-Hill, Inc. 2010 21 Structure of the Eye: Retina Fovea Tiny area in center of retina at which vision is best Contains only cones Rods & cones  Bipolar cells  Ganglion cells  Optic nerve Blind spot Place on retina containing neither rods nor cones Where optic nerve leaves eye

22. Copyright McGraw-Hill, Inc. 2010 22 Structure of the Eye: Retina

23. Copyright McGraw-Hill, Inc. 2010 23 Visual Processing Optic Nerve  Optic Chiasm  Visual Cortex Optic nerve fibers divide at optic chiasm: Left Visual Field  Right Hemisphere Right Visual Field  Left Hemisphere

24. Copyright McGraw-Hill, Inc. 2010 24 Visual Processing

25. Copyright McGraw-Hill, Inc. 2010 25 Visual Processing Feature Detectors Neurons in primary visual cortex that respond to particular features of a stimulus Parallel Processing Simultaneous distribution of information across different neural pathways Binding Integration of what is processed by different pathways or cells

26. Copyright McGraw-Hill, Inc. 2010 26 Color Vision: Trichromatic Theory Three types of cones, sensitive to different (but overlapping) ranges of wavelength Support includes... Color matching Color blindness

27. Copyright McGraw-Hill, Inc. 2010 27 Color Blindness

28. Copyright McGraw-Hill, Inc. 2010 28 Color Vision: Opponent-Process Theory Afterimages Sensations that remain after stimulus is removed Not explained by trichromatic theory Explained by opponent-process theory Visual system treats colors as complementary pairs. Conclusion: Both theories are correct.

29. Copyright McGraw-Hill, Inc. 2010 29 Negative Afterimage

30. Copyright McGraw-Hill, Inc. 2010 30 Perceiving Shape Contour Location at which sudden change of brightness occurs Figure-Ground Relationship Principle by which perceptual field is organized into stimuli that stand out (figure) and those left over (ground) Gestalt Psychology School of thought interested in how people naturally organize perception according to certain patterns ‘Whole is different from sum of its parts.’

31. Copyright McGraw-Hill, Inc. 2010 31 Figure-Ground Relationship

32. Copyright McGraw-Hill, Inc. 2010 32 Gestalt Psychology

33. Copyright McGraw-Hill, Inc. 2010 33 Perceiving Depth Ability to perceive objects three-dimensionally Binocular Cues  combined images from two eyes Disparity Convergence Monocular Cues  available from image in one eye Familiar size Height in field of view Linear perspective and relative size Overlap Shading Texture gradient

34. Copyright McGraw-Hill, Inc. 2010 34 Monocular Cues: Linear Perspective

35. Copyright McGraw-Hill, Inc. 2010 35 Perceiving Motion Retinas of humans cannot detect movement. Neurons specialized to detect motion Feedback from body Environment rich in cues Real movement Apparent movement Perception of stationary object as moving

36. Copyright McGraw-Hill, Inc. 2010 36 Perceiving Constancy Recognition that objects are constant even though sensory input is changing Size constancy Same size despite retinal image changes Shape constancy Same shape despite orientation changes Color constancy Same color despite light changes

37. Copyright McGraw-Hill, Inc. 2010 37 Perceiving Constancy Size constancy Shape constancy

38. Copyright McGraw-Hill, Inc. 2010 38 The Nature of Sound Sound Vibrations in air processed by auditory system Wavelength  Frequency  Pitch Amplitude  Pressure  Loudness Complexity  Saturation  Timbre

39. Copyright McGraw-Hill, Inc. 2010 39 The Nature of Sound

40. Copyright McGraw-Hill, Inc. 2010 40 Structure of the Ear Outer Ear  Collects and channels sound Pinna External Auditory Canal Middle Ear  Channels sound to inner ear Eardrum Hammer, Anvil, & Stirrup Inner Ear  Converts sound into neural impulses Oval Window Cochlea Basilar Membrane  Hair Cells  Tectorial Membrane

41. Copyright McGraw-Hill, Inc. 2010 41 Structure of the Ear

42. Copyright McGraw-Hill, Inc. 2010 42 Theories of Hearing Place Theory Each frequency produces vibrations at a particular spot. But... explains high-frequency, not low-frequency, sounds Frequency Theory Perception of frequency depends on how often auditory nerve fires. But... single neurons have maximum firing rates Volley Principle Modification of frequency theory Clusters of nerve cells can fire neural impulses in rapid succession.

43. Copyright McGraw-Hill, Inc. 2010 43 Auditory Processing Inner Ear  Auditory Nerve  Temporal Lobe Most fibers cross over midline between hemispheres: Left Ear  Right Hemisphere Right Ear  Left Hemisphere Some fibers go directly to same-side hemisphere.

44. Copyright McGraw-Hill, Inc. 2010 44 Localizing Sound Each ear receives somewhat different stimuli. Distance  Timing Sound Shadow  Intensity Echolocation System based on returning echoes of sounds Used by bats; humans less accurate

45. Copyright McGraw-Hill, Inc. 2010 45 Other Senses Skin (Cutaneous) Touch Temperature Pain Chemical Smell Taste Kinesthetic Vestibular

46. Copyright McGraw-Hill, Inc. 2010 46 The Skin (Cutaneous) Senses Touch Mechanical energy, or pressure, against skin Temperature Warm and cold sensory nerve endings, or thermoreceptors Pain Widely-dispersed receptors with much higher thresholds for different types of physical stimuli (e.g., pressure, heat)

47. Copyright McGraw-Hill, Inc. 2010 47 Pain Prostaglandins Stimulate pain receptors and cause experience of pain Neural pathways to brain Fast Pathway  Directly to thalamus Slow Pathway  Through limbic system Endorphins Neurotransmitters involved in turning pain signals on/off

48. Copyright McGraw-Hill, Inc. 2010 48 Chemical Senses: Taste Detecting chemicals dissolved in saliva Papillae Bumps on surface of tongue Contain taste buds, receptors for taste Four taste qualities: sweet, sour, bitter, salty Taste fibers respond to range of chemicals spanning multiple taste elements Umami

49. Copyright McGraw-Hill, Inc. 2010 49 Chemical Senses: Taste

50. Copyright McGraw-Hill, Inc. 2010 50 Chemical Senses: Smell Detecting airborne chemicals Olfactory epithelium Lines roof of nasal cavity Contains sheet of receptor cells Neural pathway Olfactory areas of temporal lobe  Limbic system Superhighway to emotion & memory Interpersonal attraction & MHC genes

51. Copyright McGraw-Hill, Inc. 2010 51 Chemical Senses: Smell

52. Copyright McGraw-Hill, Inc. 2010 52 Kinesthetic and Vestibular Senses Kinesthetic Sense Information about movement, posture, orientation Vestibular Sense Information about balance, movement Proprioceptive Feedback Information about relative position of limbs and body Semicircular Canals Contain sensory receptors to detect head motion