Sensation and Perception Unit 4 1 Sensation 1

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Sensation and Perception Unit 4 1

Sensation and Perception Unit 4 1

Sensation 1. Sensing the World: Some Basic Principles § Thresholds § Sensory Adaptation 2.

Sensation 1. Sensing the World: Some Basic Principles § Thresholds § Sensory Adaptation 2. Vision § The Stimulus Input: Light Energy § The Eye § Visual Information Processing § Color Vision 2

3. Hearing § The Stimulus Input: Sound Waves § The Ear § Hearing Loss

3. Hearing § The Stimulus Input: Sound Waves § The Ear § Hearing Loss and Deaf Culture 4. Other Important Senses § Touch § Pain § Taste § Smell 3

5. Perceptual Organization § Form Perception § Depth Perception § Motion Perception § Perceptual

5. Perceptual Organization § Form Perception § Depth Perception § Motion Perception § Perceptual Constancy 4

6. Perceptual Interpretation § Sensory Deprivation and Restored Vision § Perceptual Adaptation § Perceptual

6. Perceptual Interpretation § Sensory Deprivation and Restored Vision § Perceptual Adaptation § Perceptual Set § Perception and the Human Factor 5

7. Is There Extrasensory Perception? § Claims of ESP § Premonitions or Pretensions? §

7. Is There Extrasensory Perception? § Claims of ESP § Premonitions or Pretensions? § Putting ESP to Experimental Test 6

Sensation & Perception How do we construct our representations of the external world? To

Sensation & Perception How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we select, organize, and interpret our sensations, the process is called perception. 7

Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up

Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A. ” 8

Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing

Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT 9

Making Sense of Complexity Our sensory and perceptual processes work together to help us

Making Sense of Complexity Our sensory and perceptual processes work together to help us sort out complex images. “The Forest Has Eyes, ” Bev Doolittle 10

Sensing the World Senses are nature’s gift that suit an organism’s needs. A frog

Sensing the World Senses are nature’s gift that suit an organism’s needs. A frog feeds on flying insects; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice. 11

Exploring the Senses What stimuli cross our threshold for conscious awareness? 12

Exploring the Senses What stimuli cross our threshold for conscious awareness? 12

Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological

Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World Light Brightness Sound Volume Pressure Weight Sugar Sweet 13

Thresholds Proportion of “Yes” Responses 0. 00 0. 50 1. 00 Absolute Threshold: Minimum

Thresholds Proportion of “Yes” Responses 0. 00 0. 50 1. 00 Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time. 0 5 10 15 20 Stimulus Intensity (lumens) 25 14

Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/

Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock 15

Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a

Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = d. I/I. Stimulus Constant (k) Light 8% Weight 2% Tone 3% 16

Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid

Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. 17

Now you see, now you don’t 18

Now you see, now you don’t 18

Vision 19

Vision 19

Transduction In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses.

Transduction In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses. 20

Both Photos: Thomas Eisner The Stimulus Input: Light Energy Visible Spectrum 21

Both Photos: Thomas Eisner The Stimulus Input: Light Energy Visible Spectrum 21

Physical Characteristics of Light 1. Wavelength (hue/color) 2. Intensity (brightness) 22

Physical Characteristics of Light 1. Wavelength (hue/color) 2. Intensity (brightness) 22

Wavelength (Hue) Hue (color) is the dimension of color determined by the wavelength of

Wavelength (Hue) Hue (color) is the dimension of color determined by the wavelength of the light. Wavelength is the distance from the peak of one wave to the peak of the next. 23

Wavelength (Hue) Violet Indigo 400 nm Short wavelengths Blue Green Yellow Orange Red 700

Wavelength (Hue) Violet Indigo 400 nm Short wavelengths Blue Green Yellow Orange Red 700 nm Long wavelengths Different wavelengths of light result in different colors. 24

Intensity (Brightness) Intensity: Amount of energy in a wave determined by the amplitude. It

Intensity (Brightness) Intensity: Amount of energy in a wave determined by the amplitude. It is related to perceived brightness. 25

Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases,

Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more “washed out” or “darkened. ” 26

The Eye 27

The Eye 27

Parts of the eye 1. Cornea: Transparent tissue where light enters the eye. 2.

Parts of the eye 1. Cornea: Transparent tissue where light enters the eye. 2. Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. 3. Lens: Focuses the light rays on the retina. 4. Retina: Contains sensory receptors that process visual information and sends it to the brain. 28

The Lens: Transparent structure behind the pupil that changes shape to focus images on

The Lens: Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina. 29

Retina: The lightsensitive inner surface of the eye, containing receptor rods and cones in

Retina: The lightsensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information. 30

Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye

Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster. http: //www. bergen. org 31

Test your Blind Spot Use your textbook. Close your left eye, and fixate your

Test your Blind Spot Use your textbook. Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At some point the car on the right will disappear due to a blind spot. 32

Photoreceptors E. R. Lewis, Y. Y. Zeevi, F. S Werblin, 1969 33

Photoreceptors E. R. Lewis, Y. Y. Zeevi, F. S Werblin, 1969 33

Bipolar & Ganglion Cells Bipolar cells receive messages from photoreceptors and transmit them to

Bipolar & Ganglion Cells Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which converge to form the optic nerve. 34

Visual Information Processing Optic nerves connect to the thalamus in the middle of the

Visual Information Processing Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex. 35

Feature Detection Ross Kinnaird/ Allsport/ Getty Images Nerve cells in the visual cortex respond

Feature Detection Ross Kinnaird/ Allsport/ Getty Images Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. 36

Shape Detection Ishai, Ungerleider, Martin and Haxby/ NIMH Specific combinations of temporal lobe activity

Shape Detection Ishai, Ungerleider, Martin and Haxby/ NIMH Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses. 37

Visual Information Processing of several aspects of the stimulus simultaneously is called parallel processing.

Visual Information Processing of several aspects of the stimulus simultaneously is called parallel processing. The brain divides a visual scene into subdivisions such as color, depth, form, movement, etc. 38

From Sensation to Recognition 39

From Sensation to Recognition 39

Color Vision Trichromatic theory: Young and von Helmholtz suggested that the eye must contain

Color Vision Trichromatic theory: Young and von Helmholtz suggested that the eye must contain three receptors that are sensitive to red, blue and green colors. Standard stimulus Comparison stimulus Max Medium Low Blue Green Red 40

Color Blindness Genetic disorder in which people are blind to green or red colors.

Color Blindness Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory. Ishihara Test 41

Opponent Colors Gaze at the middle of the flag for about 30 Seconds. When

Opponent Colors Gaze at the middle of the flag for about 30 Seconds. When it disappears, stare at the dot and report whether or not you see Britain's flag. 42

Hearing 43

Hearing 43

Hearing The Stimulus Input: Sound Waves Sound waves are compressing and expanding air molecules.

Hearing The Stimulus Input: Sound Waves Sound waves are compressing and expanding air molecules. 44

Sound Characteristics 1. Frequency (pitch) 2. Intensity (loudness) 45

Sound Characteristics 1. Frequency (pitch) 2. Intensity (loudness) 45

The Ear Dr. Fred Hossler/ Visuals Unlimited 46

The Ear Dr. Fred Hossler/ Visuals Unlimited 46

The Ear Outer Ear: Collects and sends sounds to the eardrum. Middle Ear: Chamber

The Ear Outer Ear: Collects and sends sounds to the eardrum. Middle Ear: Chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window. Inner Ear: Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs. 47

Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to

Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals. 48

Intensity (Loudness): Amount of energy in a wave, determined by the amplitude, relates to

Intensity (Loudness): Amount of energy in a wave, determined by the amplitude, relates to the perceived loudness. 49

Loudness of Sound Richard Kaylin/ Stone/ Getty Images 120 d. B 50 70 d.

Loudness of Sound Richard Kaylin/ Stone/ Getty Images 120 d. B 50 70 d. B

Frequency (Pitch) Frequency (pitch): The dimension of frequency determined by the wavelength of sound.

Frequency (Pitch) Frequency (pitch): The dimension of frequency determined by the wavelength of sound. Wavelength: The distance from the peak of one wave to the peak of the next. 51

Localization of Sounds Because we have two ears, sounds that reach one ear faster

Localization of Sounds Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. 52

Localization of Sound 1. Intensity differences 2. Time differences as small as 1/100, 000

Localization of Sound 1. Intensity differences 2. Time differences as small as 1/100, 000 of a second can cause us to localize sound. The head acts as a “shadow” or partial sound barrier. 53

Touch Bruce Ayers/ Stone/ Getty Images The sense of touch is a mix of

Touch Bruce Ayers/ Stone/ Getty Images The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain. 54

Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of

Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. Pressure Burning hot Vibration Cold, warmth and pain 55

Pain tells the body that something has gone wrong. Usually pain results from damage

Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in which the afflicted person feels no pain. AP Photo/ Stephen Morton Ashley Blocker (right) feels neither pain nor extreme hot or cold. 56

Biopsychosocial Influences 57

Biopsychosocial Influences 57

Gate-Control Theory Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological

Gate-Control Theory Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gary Comer/ Phototake. USA. com 58

Pain Control Pain can be controlled by a number of therapies including, drugs, surgery,

Pain Control Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction. Todd Richards and Aric Vills, U. W. ©Hunter Hoffman, www. vrpain. com 59

Taste Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors

Taste Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”. Sweet Sour Salty Bitter Umami (Fresh Chicken) 60

Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the

Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor. 61

Smell Like taste, smell is a chemical sense. Odorants enter the nasal cavity to

Smell Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell. 62

Smell and Memories The brain region for smell (in red) is closely connected with

Smell and Memories The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell. 63

Body Position and Movement The sense of our body parts’ position and movement is

Body Position and Movement The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position. Bob Daemmrich/ The Image Works http: //www. heyokamagazine. com Whirling Dervishes Wire Walk 64

Perceptual Organization How do we form meaningful perceptions from sensory information? We organize it.

Perceptual Organization How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that a figure formed a “whole” different than its surroundings. 65

Form Perception Organization of the visual field into objects (figures) that stand out from

Form Perception Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Time Savings Suggestion, © 2003 Roger Sheperd. 66

Grouping After distinguishing the figure from the ground, our perception needs to organize the

Grouping After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules. 67

Grouping & Reality Although grouping principles usually help us construct reality, they may occasionally

Grouping & Reality Although grouping principles usually help us construct reality, they may occasionally lead us astray. Both photos by Walter Wick. Reprinted from GAMES Magazine. . © 1983 PCS Games Limited Partnership 68

Depth Perception Innervisions Depth perception enables us to judge distances. Gibson and Walk (1960)

Depth Perception Innervisions Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. Visual Cliff 69

Binocular Cues Retinal disparity: Images from the two eyes differ. Try looking at your

Binocular Cues Retinal disparity: Images from the two eyes differ. Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset. 70

Monocular Cues Relative Size: If two objects are similar in size, we perceive the

Monocular Cues Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away. 71

Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as

Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer. Rene Magritte, The Blank Signature, oil on canvas, National Gallery of Art, Washington. Collection of Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli. 72

Monocular Cues Relative Height: We perceive objects that are higher in our field of

Monocular Cues Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower. Image courtesy of Shaun P. Vecera, Ph. D. , adapted from stimuli that appered in Vecrera et al. , 2002 73

Monocular Cues Relative motion: Objects closer to a fixation point move faster and in

Monocular Cues Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction. 74

Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in

Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. © The New Yorker Collection, 2002, Jack Ziegler from cartoonbank. com. All rights reserved. 75

Monocular Cues Light and Shadow: Nearby objects reflect more light into our eyes than

Monocular Cues Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away. From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved. 76

Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal images change. 77

Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal images change. 77

Color Constancy Perceiving familiar objects as having consistent color even when changing illumination filters

Color Constancy Perceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object. Color Constancy 78

Size-Distance Relationship The distant monster (below, left) and the top red bar (below, right)

Size-Distance Relationship The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues. Alan Choisnet/ The Image Bank From Shepard, 1990 79

Size-Distance Relationship Both girls in the room are of similar height. However, we perceive

Size-Distance Relationship Both girls in the room are of similar height. However, we perceive them to be of different heights as they stand in the two corners of the room. Both photos from S. Schwartzenberg/ The Exploratorium 80

Ames Room The Ames room is designed to demonstrate the sizedistance illusion. 81

Ames Room The Ames room is designed to demonstrate the sizedistance illusion. 81

Co ur tes y Ed wa rd Ad els on Lightness Constancy The color

Co ur tes y Ed wa rd Ad els on Lightness Constancy The color and brightness of square A and B are the same. 82

Perceptual Interpretation Immanuel Kant (1724 -1804) maintained that knowledge comes from our inborn ways

Perceptual Interpretation Immanuel Kant (1724 -1804) maintained that knowledge comes from our inborn ways of organizing sensory experiences. John Locke (1632 -1704) argued that we learn to perceive the world through our experiences. How important is experience in shaping our perceptual interpretation? 83

Sensory Deprivation & Restored Vision After cataract surgery, blind adults were able to regain

Sensory Deprivation & Restored Vision After cataract surgery, blind adults were able to regain sight. These individuals could differentiate figure and ground relationships, yet they had difficulty distinguishing a circle and a triangle (Von Senden, 1932). 84

Facial Recognition Courtesy of Richard Le. Grand After blind adults regained sight, they were

Facial Recognition Courtesy of Richard Le. Grand After blind adults regained sight, they were able to recognize distinct features, but were unable to recognize faces. Normal observers also show difficulty in facial recognition when the lower half of the pictures are changed. 85

Sensory Deprivation Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal

Sensory Deprivation Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars. Blakemore & Cooper (1970) 86

Perceptual Adaptation Courtesy of Hubert Dolezal Visual ability to adjust to an artificially displaced

Perceptual Adaptation Courtesy of Hubert Dolezal Visual ability to adjust to an artificially displaced visual field, e. g. , prism glasses. 87

Perceptual Set A mental predisposition to perceive one thing and not another. What you

Perceptual Set A mental predisposition to perceive one thing and not another. What you see in the center picture is influenced by flanking pictures. From Shepard, 1990. 88

Perceptual Set Other examples of perceptual set. Dick Ruhl Frank Searle, photo Adams/ Corbis-Sygma

Perceptual Set Other examples of perceptual set. Dick Ruhl Frank Searle, photo Adams/ Corbis-Sygma (a) Loch ness monster or a tree trunk; (b) Flying saucers or clouds? 89

Context Effects Context can radically alter perception. Is the “magician cabinet” on the floor

Context Effects Context can radically alter perception. Is the “magician cabinet” on the floor or hanging from the ceiling? 90

Cultural Context instilled by culture also alters perception. To an East African, the woman

Cultural Context instilled by culture also alters perception. To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree. 91

Perception Revisited Is perception innate or acquired? 92

Perception Revisited Is perception innate or acquired? 92

Is There Extrasensory Perception? Perception without sensory input is called extrasensory perception (ESP). A

Is There Extrasensory Perception? Perception without sensory input is called extrasensory perception (ESP). A large percentage of scientists do not believe in ESP. 93

Claims of ESP 1. Telepathy: Mind-to-mind communication. One person sending thoughts and the other

Claims of ESP 1. Telepathy: Mind-to-mind communication. One person sending thoughts and the other receiving them. 2. Clairvoyance: Perception of remote events, such as sensing a friend’s house on fire. 3. Precognition: Perceiving future events, such as a political leader’s death. 94