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Sensation & Perception Chapter4. Sensation Def:the stimulation of sensory receptors and the transmission of sensory information to the central nervous.

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Presentation on theme: "Sensation & Perception Chapter4. Sensation Def:the stimulation of sensory receptors and the transmission of sensory information to the central nervous."— Presentation transcript:

1 Sensation & Perception Chapter4

2 Sensation Def:the stimulation of sensory receptors and the transmission of sensory information to the central nervous system (brain and spinal cord)

3 Sensation Stimulation of the senses is mechanical; results from sources of energy like light and sound or from presence of chemicals, as in smell and taste

4 Perception Not mechanical but interpreted Def: the process by which sensations are organized into an inner representation of the world

5 Perception It reflects learning and expectations and the ways in which we organize incoming information about the world. Personal reality relies on: -vision, hearing, smell, taste, touch

6 Absolute Threshold The weakest amount of a stimulus that can be told apart from no stimulus at all Table 4.1 pg.126 Ex: Taste About 1 teaspoon of sugar dissolved in 2 gallons of water

7 Absolute Threshold There are individual differences in absolute thresholds Ex: Pitch -the highness or lowness of a sound, as determined by the frequency of the sound waves

8 Difference Threshold The minimal difference in intensity required between two sources of energy so that they will be perceived as being different (Ex: Weight Lifting-2 lbs needed before noticing a difference) Table 4.2 pg.127 (toothpick ex)

9 Signal-Detection Theory The view that the perception of sensory stimuli involves the interaction of physical, biological, and psychological factors

10 Signal-Detection Theory The degree to which the signal can be distinguished from background noise Ex: easier to hear a friends voice in a quiet room rather than a room filled with people clinking silverware and chatting

11 Signal-Detection Theory Psychological factors include: -motivation, expectations, learning -emphasizes the aspects of detecting and responding to signals Ex: studying and babys cry

12 Sensory Adaptation The process by which we become more sensitive to stimuli of low magnitude and less sensitive to stimuli of relatively constant magnitude Sensitization vs. Desensitization

13 Sensitization The process of becoming more sensitive to stimulation (positive adaptation) Ex: Dark theater we become more sensitive to faces and objects as time elapses

14 Desensitization Becoming less sensitive to ongoing stimulation constant light appears to grow dimmer Live in city, become desensitized to traffic sounds

15 Vision & Dimensions of Color

16 The Eye Pages Know the different parts of the eye and their functions for the test

17 Rods and Cones Photoreceptors in the retina About 125 million rods and 6.5 million cones are distributed across the retina

18 Rods Rod-shaped photoreceptors that are sensitive only to the intensity of light They allow us to see in black and white

19 Cones Cone-shaped photoreceptors that transmit sensations of color Provide color vision

20 Light Adaptation Dark adaptation: adjusting to lower lighting Dark adaptation: adjusting to lower lighting Movie theater: Movie theater: -Cones: permit perception of color, reach maximum adaptation to darkness in 10 minutes -Rods: allow perception of light and dark only, are more sensitive and continue to adapt to darkness for up to about 45 minutes

21 Light Adaptation cont… Adaptation to brighter lighting conditions takes place more rapidly Emerging from dark theater: at first youll be surprised by featureless blaze around you. Within a minute or so, the brightness will have dimmed and objects will have regained their edges

22 Dimensions of Color Wavelength of light determines its color, or hue Brightness of a color is its degree of lightness or darkness The brighter the color, the lighter it is Create your color wheel: red, orange, yellow,green, blue, purple

23 Warm and Cool Colors Warm:red/orange/yellow colors side (burn) » Warm colors seem to advance toward the viewer Cool:green/blue (ocean and sky) » Cool colors seem to recede into the distance

24 Saturation The degree of purity of a color Pure hues have the greatest intensity, or brightness Saturation (brightness) decreases when another hue or black, gray, white is added

25 Saturation Hue: adding black Tint: adding white

26 Complementary The colors across from one another on the color wheel Red-green Blue-yellow

27 Primary Colors Colors that cannot be produced by mixing pigments of other hues Red Blue Yellow

28 Secondary Colors derived by mixing primary colors Orange: mixing (red/yellow) Green: mixing (blue/yellow) Purple: mixing (red/blue)

29 Tertiary Colors derived by mixing primary and adjoining secondary colors Yellow-green Bluish-purple

30 Afterimage The lingering visual impression made by a stimulus that has been removed Look on page 138 Perception of the complementary color after first color is removed

31 Afterimage Similar or comparable colors Hues that lie next to one another on the color wheel, forming families of related colors Yellow and orange Orange and red Green and blue Intermarry: blue with violent, violet with red and so on…

32 Visual Perception

33 Color Blindness Trichromat: A person with normal color vision Monochromat:A person who is sensitive to black and white only and hence color blind Dichromat: A person who is sensitive to black and white and either red- green or blue-yellow and hence partially color blind

34 Color Blindness Partial blindness is more common than total color blindness Partial color blindness is a gender or sex-linked trait that strikes mostly males (found on X chromosome)

35 Visual Perception Relies on our knowledge, expectations, and motivations An active process by which we interpret the world around us Meaningless splotches handout

36 Perceptual Organization The tendency to integrate perceptual elements into meaningful patterns

37 Figure-ground Perception When figure-ground relationships are ambiguous (capable of being interpreted in various ways), our perceptions tend to be unstable, to shift back and forth. The Rubin Vase The Necker Cube Gestalt Rules for Organization

38 Gestalt Organization 1)Closure-perceive broken figure as being complete or whole 2)Proximity-nearness, group together objects that are near one another 3)Similarity-group together objects that are similar in appearance

39 Gestalt Organization 4) Continuity-perceive a series of points or lines as having unity 5) Common fate-perceive elements that move together as belonging together

40 Top-Down Processing The use of contextual information or knowledge of a pattern in order to organize parts of the pattern Ex:puzzles Box picture=top Finding pieces=top down process

41 Bottom-up Processing The organization of the parts of a pattern to recognize, or form an image of, the pattern they compose Start with bits and pieces of info and become aware of the pattern formed by the assembled pieces only after you have labored a while Ex: puzzles with the box picture

42 Perception of Movement 1)Autokinetic effect-the tendency to perceive a stationary point of light in a dark room as moving 2) Stroboscopic motion-a visual illusion in which the perception of motion is generated by a series of stationary images presented in rapid succession (flip book, motion pictures)

43 Perception of Movement 3) Phi phenomenon- the perception of movement as a result of sequential presentation of visual stimuli -a row of lights is switched on, then off, then the next row… -the on-off process is perceived as movement (Ex: electronic scoreboard baseball)

44 Depth Perception Monocular cues:cues that can be perceived by one eye, to create an illusion of depth Perspective:a monocular cue for depth based on the convergence (coming together) of parallel lines as they recede into the distance

45 Interposition A monocular cue for depth based on the fact that a nearby object obscures a more distant object behind it Same size but which one seems closer?

46 Shadowing A monocular cue for depth based on the fact that opaque objects block light and produce shadows Shadows give a sense of 3- dimentionality

47 Texture Gradient A monocular cue for depth based on the perception that closer objects appear to have rougher (more detailed) surfaces

48 Motion Parallax A monocular cue for depth based on the perception that nearby objects appear to move more rapidly in relation to our own motion Mountains-move with us (greater distances) Trees, roadside markers-move rapidly

49 Binocular Cues Stimuli suggestive of depth that involve simultaneous perception by both eyes Ex: close one eye and bring fingertips together Ex: roll up paper and you will see a hole in your hand

50 Retinal disparity-difference in the image cast by an object on the retinas of the eyes as the object moves closer or farther away Ex: index finger to nose

51 Constancy 1)Color Constancy- objects retain color even though lighting conditions may alter their appearance 2)Brightness-object just as bright even though lighting conditions changes its intensity 3)Shape- object as being the same shape although the retinal image varies in shape as it rotates

52 Visual illusions Spinning Circle Pg The Hering-Helmholtz The Muller-Lyer illusion Ponzo illusion

53 The Ganzfeld Contours are important Little sensory change can lead to: – Dizziness – Fatigue – snow blindness

54 Vision and Balance Exercise: stand on one foot, then close your eyes, then try after you spin around a few times Maintaining balance depends on visual cues to some extent

55 Hearing

56 Pitch and Loudness The pitch of a sound is determined by its frequency, or the number of cycles per second as expressed in the unit Hertz (Hz). Hz=one cycle per second The greater the number of cycles per second (Hz), the higher the pitch of the sound (women vs. men)

57 Loudness Amplitude:loudness of a sound that is determined by its height of sound waves Decibel (dB): a unit expressing the loudness of a sound (Sound waves of various frequencies and amplitudes)

58 Loudness Tones (musical sounds) Consonant:when a combination of tones are pleasant; in harmony Dissonant:incompatible; not harmonious, discordant

59 White Noise Discordant sounds of many frequencies, often producing a lulling effect

60 The Ear Diagram: Page )The Outer Ear 2)The Middle Ear 3)The Inner Ear

61 Deafness 28 million Americans have impaired hearing 2 million of them are deaf Conductive Deafness Sensorineural deafness

62 Conductive Deafness The forms of deafness in which there is loss of conductions of sound through the middle ear Have high absolute thresholds for detection of sounds at all frequencies Elderly profit from hearing aids

63 Sensorineural Deafness The forms of deafness that result from damage to hair cells or the auditory nerve So called ringing sensation that follows after exposure to loud sounds means that hair cells are being damaged Ex: Rock concerts, shooting range

64 Smell and Taste

65 Smell Smell and taste are the chemical senses With smell and taste, we sample molecules of the substance being sensed Humans are underprivileged when compared to dogs

66 Smell Smell makes crucial contribution to the flavor of foods Ex: If you did not have a sense of smell, then an onion and an apple would taste the same to you Detect odor of one-millionth of a milligram of vanilla in a liter of air

67 Smell Odor: the characteristic of a substance that makes it perceptible to the sense of smell Odors detected by sites on receptor neurons in the olfactory membrane high in each nostril Olfactory: Having to do with the sense of smell

68 Smell Olfactory nerve: the nerve that transmit information concerning odors from olfactory receptors to the brain

69 Smell Mixtures of smell sensations help produce broad range of odors Sense of smell adapts rapidly to odors even obnoxious ones (locker room, outhouse, second hand smoke, fumes) One odor can be masked by another (air fresheners)

70 Taste Dogs can perceive the taste quality of sweetness, as can pigs, but cats cannot 4 primary taste qualities: -sweet -sour -salty -bitter

71 Taste Flavor of food involves taste but is more complex Apples and onions same taste qualities but their flavors differ greatly

72 Taste Flavor cont… Depends on its odor, texture, temperature as well as its taste

73 Taste Cells Receptor cells that are sensitive to taste Located on taste buds

74 Taste buds the sensory organs for taste. They contain taste cells and are located on the tongue 10,000 taste buds-located near the edges of tongue and the back of tongue

75 Taste Buds Specialized a bit Sweetness: tip of tongue Bitterness: back of tongue Sourness: along sides of the tongue Saltiness: overlaps the areas sensitive to sweetness and sourness

76 Taste buds We all have different taste worlds Strong genetic component By eating hot foods and scraping tongue, you regularly kill off many taste buds, Taste buds reproduce rapidly and completely renew once a week

77 Taste buds Elderly complain their food has little or no taste-more likely to experience a decline in the sense of smell Older people experience the loss of flavor.

78 The Skin Senses Skin discriminates among many kinds of sensations: Touch Pressure Warmth Cool Pain

79 Touch and Pressure Sensory receptors at the roots of hair cells appear to fire in response to touching the surface of the skin get the feel of-touching fabric by running our hands over it. Sensation fade quickly if held still

80 Touch and Pressure Active touching-involves reception of information that concerns not only touch but also pressure, temperature, and feedback from muscles

81 Touch and Pressure Two-point threshold:the least distance by which two rods touching the skin must be separated before the person will report that there are two rods, not one, on 50% of occasions. Assess our sensitivity to pressure (fingertips, lips, noses, and cheeks are much more sensitive than our shoulders, thighs, and calves)

82 Touch and Pressure Differential sensitivity occurs for 2 reasons: 1)Nerve endings are more densely packed in the fingertips and face than in other locations 2)A greater amount of sensory cortex is devoted to the perception of sensations in the fingertips and face -sense of pressure, like the sense of touch, undergoes rather rapid adaptation

83 Temperature Receptors for temperature are neurons beneath the skin When skin temperature increases, receptors for warmth fire (same for cold receptors) Sensations of temperature are relative We adapt to differences in temperature (Ms. Yens classroom freezing classroom, pools, weather outside)

84 Pain Pain is a signal that something is wrong in the body Originates at the point of contact (stubbed toe) Pain message to the brain is initiated by the release of various chemicals: (Prostaglandins, bradykinin, mysterious chemical called P)

85 Phantom Limb Pain The pain occurs in the absence of (present) tissue damage, but the pain itself is real enough (war veterans) Sometimes involves activation of nerves in the stump of missing limb Pain reflect activation of the neural circuits that store memories connected with the missing limb

86 Kinesthesis The sense that informs us about the positions and motion of parts of our bodies

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