Sensation and Perception
The Major Senses <ul><li>There are 6 major senses </li></ul><ul><ul><li>vision </li></ul></ul><ul><ul><li>hearing </li></u...
Principles of Sensation <ul><li>Transduction—physical energy to neural signal </li></ul><ul><li>Absolute threshold—smalles...
Vision <ul><li>Purpose of the visual system </li></ul><ul><ul><li>transform light energy into an electro-chemical neural r...
Light: The Visual Stimulus Gamma rays X-rays Ultra- violet rays Infrared rays Radar Broadcast bands AC circuits Visible li...
Light: The Visual Stimulus <ul><li>Light can be described as both a particle  and a wave </li></ul><ul><li>Wavelength of a...
 
Distribution of  Rods and Cones <ul><li>Cones—concentrated in center  of eye (fovea) </li></ul><ul><ul><li>approx. 6 milli...
Differences Between  Rods and Cones <ul><li>Cones </li></ul><ul><ul><li>allow us to see in bright light </li></ul></ul><ul...
Receptive Fields and Rod  vs. Cone Visual Acuity <ul><li>Cones—in the fovea, one cone often synapses onto only a single ga...
Rods Cones
Processing Visual Information <ul><li>Ganglion cells—neurons that connect to the bipolar cells; their axons form the optic...
 
Color Vision <ul><li>Our visual system interprets differences in the wavelength of light as color </li></ul><ul><li>Rods a...
Properties of Color <ul><li>Hue—property of wavelengths of light known as color; different wavelengths correspond to our s...
Additive Color Mixture <ul><li>By combining lights of different wavelengths we can create the perception of new colors </l...
Trichromatic Theory  of Color Vision <ul><li>Researchers found that by mixing only three primary lights (usually red, gree...
Trichromacy and TV <ul><li>All color televisions are based on the fact that normal human color vision is trichromatic </li...
Opponent Process Theory  of Color Vision <ul><li>Some aspects of our color perception are difficult to explain by the tric...
Complementary Afterimages
Opponent-Process Theory <ul><li>To account for phenomena like complementary afterimages, Herring proposed that we have two...
 
 
Hearing: Sound Waves <ul><li>Auditory perception occurs when sound waves interact with the structures of the ear </li></ul...
<ul><li>Frequency of a sound wave is related the pitch of a sound  </li></ul><ul><li>Amplitude of a sound wave is related ...
Frequency of Sound Waves <ul><li>The frequency of a sound wave is measured as the number of cycles  per second (Hertz) </l...
Intensity of Various Sounds Example P (in sound- pressure units) Log  P Decibels Softest detectable sound Soft whisper Qui...
Anatomy of Ear <ul><li>Purpose of the structures in the ear: </li></ul><ul><ul><li>Measure the frequency (pitch) of sound ...
Major Structures of the Ear <ul><li>Outer Ear—acts as a funnel to direct sound waves towards inner structures </li></ul><u...
Anatomy of the Ear Pinna Sound waves Auditory Canal Stirrup Cochlea Auditory nerve Semicircular canals Round window Oval w...
Anatomy of the Ear Outer ear Middle ear Inner ear A sound causes the basilar membrane to wave up and down Basilar membrane...
Transduction of Sounds <ul><li>The structures of the ear transform changes in air pressure (sound waves) into vibrations o...
Chemical and Body Senses <ul><li>Olfaction (smell) </li></ul><ul><li>Gustation (taste) </li></ul><ul><li>Touch and tempera...
 
 
<ul><li>Taste  </li></ul><ul><li>Sweet </li></ul><ul><li>Sour </li></ul><ul><li>Salty </li></ul><ul><li>Bitter </li></ul><...
Skin and Body Senses <ul><li>Pressure—Pacinian corpuscles </li></ul><ul><li>Temperature—receptors reactive to cold or warm...
Movement, Position, and Balance <ul><li>Kinesthetic—sense of location of body parts in relation to each other </li></ul><u...
Perception <ul><li>The process of integrating, organizing, and interpreting sensory information </li></ul>
Perceptual Processing <ul><li>Bottom-up processing—emphasizes the importance of sensory receptors in detecting the basic f...
Perceptual Organization <ul><li>Some of the best examples of perceptual organization were provided by the Gestalt psycholo...
Figure and Ground <ul><li>Gestalt Psychologists also thought that an important part of our perception was the organization...
 
Gestalt Grouping Principles <ul><li>Gestalt theorists argued that our perceptual systems automatically organized sensory i...
 
 
 
 
Depth Perception <ul><li>One of our more important perceptual abilities involves seeing in three-dimensions </li></ul><ul>...
Depth Perception Cues <ul><li>Cue—stimulus characteristics that influence our perceptions </li></ul><ul><li>We are able to...
Types of Depth Cues <ul><li>Depth cues are usually divided into categories, we will consider two types  of depth cues: </l...
Monocular Depth Cues <ul><li>Relative image size </li></ul><ul><li>Linear perspective </li></ul><ul><li>Texture gradient <...
 
Binocular Depth Cues <ul><li>Our best depth perception occurs if we look through both eyes </li></ul><ul><li>This is becau...
Stereogram <ul><li>Another way to create the illusion of depth through binocular with a stereogram </li></ul><ul><li>A ste...
Stereogram
Perception of Motion <ul><li>Process that is not very well understood </li></ul><ul><li>Usually assume that the figure is ...
Perceptual Constancy <ul><li>When viewing conditions change, the retinal image changes even if the objects being viewed re...
Size Constancy <ul><li>Cylinders at positions A and B are the same size even though their image sizes differ </li></ul><ul...
Shape Constancy <ul><li>It is hard to tell if the figure on the upper right is a trapezoid or a square slanted backward </...
Some Perceptual Illusions
Relationship Between Perceived  Size and Perceived Depth <ul><li>To perceive the size of objects accurately we must also p...
Ames Room <ul><li>The Ames room is designed so that the monocular depth cues give the illusion that  the two people are eq...
Other Size-Distance Illusions <ul><li>In each of these examples, the top and bottom lines are actually the same length </l...
Müller-Lyer Illusion <ul><li>Perceptual psychologists have hypothesized that the top horizontal line looks longer because ...
Ponzo Illusion <ul><li>Converging lines indicate that top line is farther away than bottom line </li></ul>
Perceptual Set <ul><li>The influence of prior assumptions and expectations on perceptual interpretations </li></ul>
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  • Chapter 3 Ppp

    1. 1. Sensation and Perception
    2. 2. The Major Senses <ul><li>There are 6 major senses </li></ul><ul><ul><li>vision </li></ul></ul><ul><ul><li>hearing </li></ul></ul><ul><ul><li>touch </li></ul></ul><ul><ul><li>taste </li></ul></ul><ul><ul><li>pain </li></ul></ul><ul><ul><li>smell </li></ul></ul><ul><li>The list can be extended with balance, joint senses, and others </li></ul><ul><li>Vision has been studied most extensively </li></ul>
    3. 3. Principles of Sensation <ul><li>Transduction—physical energy to neural signal </li></ul><ul><li>Absolute threshold—smallest strength of a stimulus that can be detected </li></ul><ul><li>Difference threshold—(jnd) smallest difference that can be detected </li></ul><ul><li>Sensory adaptation </li></ul>
    4. 4. Vision <ul><li>Purpose of the visual system </li></ul><ul><ul><li>transform light energy into an electro-chemical neural response </li></ul></ul><ul><ul><li>represent characteristics of objects in our environment such as size, color, shape, and location </li></ul></ul>
    5. 5. Light: The Visual Stimulus Gamma rays X-rays Ultra- violet rays Infrared rays Radar Broadcast bands AC circuits Visible light Prism White light 400 500 600 700 10 -5 10 -3 10 -1 10 1 10 3 10 5 10 7 10 9 10 11 10 13 10 15 10 17 Wavelength in nanometers (billionths of a meter)
    6. 6. Light: The Visual Stimulus <ul><li>Light can be described as both a particle and a wave </li></ul><ul><li>Wavelength of a light is the distance of one complete cycle of the wave </li></ul><ul><li>Visible light has wavelengths from about 400nm to 700nm </li></ul><ul><li>Wavelength of light is related to its perceived color </li></ul>
    7. 8. Distribution of Rods and Cones <ul><li>Cones—concentrated in center of eye (fovea) </li></ul><ul><ul><li>approx. 6 million </li></ul></ul><ul><li>Rods—concentrated in periphery </li></ul><ul><ul><li>approx. 120 million </li></ul></ul><ul><li>Blind spot—region with no rods or cones </li></ul>
    8. 9. Differences Between Rods and Cones <ul><li>Cones </li></ul><ul><ul><li>allow us to see in bright light </li></ul></ul><ul><ul><li>allow us to see fine spatial detail </li></ul></ul><ul><ul><li>allow us to see different colors </li></ul></ul><ul><li>Rods </li></ul><ul><ul><li>allow us to see in dim light </li></ul></ul><ul><ul><li>can not see fine spatial detail </li></ul></ul><ul><ul><li>can not see different colors </li></ul></ul>
    9. 10. Receptive Fields and Rod vs. Cone Visual Acuity <ul><li>Cones—in the fovea, one cone often synapses onto only a single ganglion cell </li></ul><ul><li>Rods—the axons of many rods synapse onto one ganglion cell </li></ul><ul><li>This allows rods to be more sensitive in dim light, but it also reduces visual acuity </li></ul>
    10. 11. Rods Cones
    11. 12. Processing Visual Information <ul><li>Ganglion cells—neurons that connect to the bipolar cells; their axons form the optic nerve </li></ul><ul><li>Bipolar cells—neurons that connect rods and cones to the ganglion cells </li></ul><ul><li>Optic chiasm—point in the brain where the optic nerves from each eye meet and partly crossover to opposite sides of the brain </li></ul>
    12. 14. Color Vision <ul><li>Our visual system interprets differences in the wavelength of light as color </li></ul><ul><li>Rods are color blind, but with the cones we can see different colors </li></ul><ul><li>This difference occurs because we have only one type of rod but three types of cones </li></ul>
    13. 15. Properties of Color <ul><li>Hue—property of wavelengths of light known as color; different wavelengths correspond to our subjective experience of color (hue) </li></ul><ul><li>Saturation—property of color that corresponds to the purity of the light wave </li></ul><ul><li>Brightness—perceived intensity of a color; corresponds to amplitude of the light wave </li></ul>
    14. 16. Additive Color Mixture <ul><li>By combining lights of different wavelengths we can create the perception of new colors </li></ul><ul><li>Examples: </li></ul><ul><ul><li>red + green = yellow </li></ul></ul><ul><ul><li>red + blue = purple </li></ul></ul><ul><ul><li>green + blue = cyan </li></ul></ul>
    15. 17. Trichromatic Theory of Color Vision <ul><li>Researchers found that by mixing only three primary lights (usually red, green and blue), they could create the perceptual experience of all possible colors </li></ul><ul><li>This lead Young and Helmholtz to propose that we have three different types of photoreceptors, each most sensitive to a different range of wavelengths </li></ul>
    16. 18. Trichromacy and TV <ul><li>All color televisions are based on the fact that normal human color vision is trichromatic </li></ul><ul><li>Although we perceive the whole range of colors from a TV screen, it only has three colored phosphors (red, green, and blue) </li></ul><ul><li>By varying the relative intensity of the three phosphors, we can fool the visual system into thinking it is seeing many different colors </li></ul>
    17. 19. Opponent Process Theory of Color Vision <ul><li>Some aspects of our color perception are difficult to explain by the trichromatic theory alone </li></ul><ul><li>Example: afterimages </li></ul><ul><ul><li>if we view colored stimuli for an extended period of time, we will see an afterimage in a complementary color </li></ul></ul>
    18. 20. Complementary Afterimages
    19. 21. Opponent-Process Theory <ul><li>To account for phenomena like complementary afterimages, Herring proposed that we have two types of color opponent cells </li></ul><ul><ul><li>red-green opponent cells </li></ul></ul><ul><ul><li>blue-yellow opponent cells </li></ul></ul><ul><li>Our current view of color vision is that it is based on both the trichromatic and opponent process theory </li></ul>
    20. 24. Hearing: Sound Waves <ul><li>Auditory perception occurs when sound waves interact with the structures of the ear </li></ul><ul><li>Sound Wave —changes over time in the pressure of an elastic medium (for example, air or water) </li></ul><ul><li>Without air (or another elastic medium) there can be no sound waves, and thus no sound </li></ul>
    21. 25. <ul><li>Frequency of a sound wave is related the pitch of a sound </li></ul><ul><li>Amplitude of a sound wave is related to loudness of a sound </li></ul>
    22. 26. Frequency of Sound Waves <ul><li>The frequency of a sound wave is measured as the number of cycles per second (Hertz) </li></ul><ul><ul><li>20,000 Hz Highest Frequency we can hear </li></ul></ul><ul><ul><li>4,186 Hz Highest note on a piano </li></ul></ul><ul><ul><li>1,000 Hz Highest pitch of human voice </li></ul></ul><ul><ul><li>100 Hz Lowest pitch of human voice </li></ul></ul><ul><ul><li>27 Hz Lowest note on a piano </li></ul></ul>
    23. 27. Intensity of Various Sounds Example P (in sound- pressure units) Log P Decibels Softest detectable sound Soft whisper Quiet neighborhood Average conversation Loud music from a radio Heavy automobile traffic Very loud thunder Jet airplane taking off Loudest rock band on record Spacecraft launch 9 from 150 ft. 1 10 100 1000 10,000 100,000 1,000,000 10,000,000 100,000,000 1,000,000,000 0 1 2 3 4 5 6 7 8 9 0 20 40 60 80 100 120 140 160 180
    24. 28. Anatomy of Ear <ul><li>Purpose of the structures in the ear: </li></ul><ul><ul><li>Measure the frequency (pitch) of sound waves </li></ul></ul><ul><ul><li>Measure the amplitude (loudness) of sound waves </li></ul></ul>
    25. 29. Major Structures of the Ear <ul><li>Outer Ear—acts as a funnel to direct sound waves towards inner structures </li></ul><ul><li>Middle Ear—consists of three small bones (or ossicles) that amplify the sound </li></ul><ul><li>Inner Ear—contains the structures that actually transduce sound into neural response </li></ul>
    26. 30. Anatomy of the Ear Pinna Sound waves Auditory Canal Stirrup Cochlea Auditory nerve Semicircular canals Round window Oval window Where stirrup attaches Eardrum (tympanic Membrane) Bone Hammer Anvil
    27. 31. Anatomy of the Ear Outer ear Middle ear Inner ear A sound causes the basilar membrane to wave up and down Basilar membrane Hair cells Tectorial membrane Round window Eardrum Oval window Cochlea, partially uncoiled Stirrup Anvil Hammer Sound waves Auditory canal
    28. 32. Transduction of Sounds <ul><li>The structures of the ear transform changes in air pressure (sound waves) into vibrations of the Basilar Membrane </li></ul><ul><li>As the Basilar Membrane vibrates it causes the hairs in the Hair Cells to bend </li></ul><ul><li>The bending of the hairs leads to a change in the electrical potential within the cell </li></ul>
    29. 33. Chemical and Body Senses <ul><li>Olfaction (smell) </li></ul><ul><li>Gustation (taste) </li></ul><ul><li>Touch and temperature </li></ul><ul><li>Pain </li></ul><ul><li>Kinesthetic (location of body) </li></ul><ul><li>Vestibular (balance) </li></ul>
    30. 36. <ul><li>Taste </li></ul><ul><li>Sweet </li></ul><ul><li>Sour </li></ul><ul><li>Salty </li></ul><ul><li>Bitter </li></ul><ul><li>Umami </li></ul>
    31. 37. Skin and Body Senses <ul><li>Pressure—Pacinian corpuscles </li></ul><ul><li>Temperature—receptors reactive to cold or warm, simultaneous stimulation produces sensation of hot </li></ul><ul><li>Pain—free nerve endings are receptors that send message to the spinal cord releasing substance P </li></ul><ul><li>Gate control theory of pain is most influential </li></ul>
    32. 38. Movement, Position, and Balance <ul><li>Kinesthetic—sense of location of body parts in relation to each other </li></ul><ul><li>Vestibular—sense of balance, receptors located in the inner ear </li></ul><ul><li>Proprioceptors—receptors in muscles and joints that provide information about body position and movement </li></ul>
    33. 39. Perception <ul><li>The process of integrating, organizing, and interpreting sensory information </li></ul>
    34. 40. Perceptual Processing <ul><li>Bottom-up processing—emphasizes the importance of sensory receptors in detecting the basic features of a stimulus. Moves from part to whole. Also called data-driven processing. </li></ul><ul><li>Top-down processing—emphasizes importance of observer’s cognitive processes in arriving at meaningful perceptions. Moves from whole to part. Also called conceptually driven processing. </li></ul>
    35. 41. Perceptual Organization <ul><li>Some of the best examples of perceptual organization were provided by the Gestalt psychologists </li></ul><ul><li>Gestalt psychologists hypothesized that “the whole is greater than the sum of the parts” </li></ul><ul><li>They were interested in showing the global nature of our perceptions </li></ul>
    36. 42. Figure and Ground <ul><li>Gestalt Psychologists also thought that an important part of our perception was the organization of a scene in to its: </li></ul><ul><li>Figure—the object of interest </li></ul><ul><li>Ground —the background </li></ul>
    37. 44. Gestalt Grouping Principles <ul><li>Gestalt theorists argued that our perceptual systems automatically organized sensory input based on certain rules </li></ul><ul><li>Proximity </li></ul><ul><li>Similarity </li></ul><ul><li>Closure </li></ul><ul><li>Good Continuation </li></ul><ul><li>Common Movement </li></ul><ul><li>Good Form </li></ul>
    38. 49. Depth Perception <ul><li>One of our more important perceptual abilities involves seeing in three-dimensions </li></ul><ul><li>Depth perception is difficult because we only have access to two-dimensional images </li></ul><ul><li>How do we see a 3-D world using only the 2-D retinal images? </li></ul>
    39. 50. Depth Perception Cues <ul><li>Cue—stimulus characteristics that influence our perceptions </li></ul><ul><li>We are able to see in 3-D because the visual system can utilize depth cues that appear in the retinal images </li></ul>
    40. 51. Types of Depth Cues <ul><li>Depth cues are usually divided into categories, we will consider two types of depth cues: </li></ul><ul><li>Monocular—depth cues that appear in the image in either the left or right eye </li></ul><ul><li>Binocular—depth cues that involve comparing the left and right eye images </li></ul>
    41. 52. Monocular Depth Cues <ul><li>Relative image size </li></ul><ul><li>Linear perspective </li></ul><ul><li>Texture gradient </li></ul><ul><li>Overlap </li></ul><ul><li>Aerial perspective </li></ul><ul><li>Motion parallax </li></ul>
    42. 54. Binocular Depth Cues <ul><li>Our best depth perception occurs if we look through both eyes </li></ul><ul><li>This is because our right and left eyes see a slightly different view of the world this is called binocular disparity </li></ul><ul><li>Convergence is the degree to which your eye muscles must rotate to see an object. </li></ul>
    43. 55. Stereogram <ul><li>Another way to create the illusion of depth through binocular with a stereogram </li></ul><ul><li>A stereogram is formed by superimposing two repeating patterns </li></ul><ul><li>The two patterns are slightly offset; when viewed properly, this offset is seen as a binocular disparity </li></ul>
    44. 56. Stereogram
    45. 57. Perception of Motion <ul><li>Process that is not very well understood </li></ul><ul><li>Usually assume that the figure is moving and the ground is stationary </li></ul><ul><li>Stroboscopic motion--perception of motion caused by carefully timed flashing lights </li></ul>
    46. 58. Perceptual Constancy <ul><li>When viewing conditions change, the retinal image changes even if the objects being viewed remain constant </li></ul><ul><li>Example: as a person walks away from you, their retinal image decreases in size </li></ul><ul><li>Important function of the perceptual system is to represent constancy in our environment even when the retinal image varies </li></ul>
    47. 59. Size Constancy <ul><li>Cylinders at positions A and B are the same size even though their image sizes differ </li></ul><ul><li>The depth cues such as linear perspective and texture help the visual system judge the size accurately </li></ul>Point A Point B
    48. 60. Shape Constancy <ul><li>It is hard to tell if the figure on the upper right is a trapezoid or a square slanted backward </li></ul><ul><li>If we add texture, the texture gradient helps us see that it is actually a square </li></ul>
    49. 61. Some Perceptual Illusions
    50. 62. Relationship Between Perceived Size and Perceived Depth <ul><li>To perceive the size of objects accurately we must also perceive their distance accurately </li></ul><ul><li>Thus, many visual illusions occur simply because a particular image lacks sufficient depth cues </li></ul>This figure shows that image size depends upon both object size and distance Retina Pupil Image A B Image A
    51. 63. Ames Room <ul><li>The Ames room is designed so that the monocular depth cues give the illusion that the two people are equally far away </li></ul>
    52. 64. Other Size-Distance Illusions <ul><li>In each of these examples, the top and bottom lines are actually the same length </li></ul><ul><li>In each case the top line looks longer </li></ul><ul><li>Why? </li></ul>(a) Müller-Lyer illusion (b) Ponzo illusion
    53. 65. Müller-Lyer Illusion <ul><li>Perceptual psychologists have hypothesized that the top horizontal line looks longer because it also looks farther away </li></ul><ul><li>Specifically, the inward pointing arrows signify that the horizontal line is closest to you, and the outward pointing arrows signify the opposite case </li></ul>
    54. 66. Ponzo Illusion <ul><li>Converging lines indicate that top line is farther away than bottom line </li></ul>
    55. 67. Perceptual Set <ul><li>The influence of prior assumptions and expectations on perceptual interpretations </li></ul>
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