Unit IV Sensation Perception

Transcription

1 Unit IV Sensation Perception Module 16: Basic Principles of Sensation and Perception Module 17: Influences of Perception Module 18: Vision Module 19: Visual Organization and Interpretation Module 20: Hearing Module 21: The Other Senses 1

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3 Module 16 Quick Write: If you had to lose one of your senses (either hearing or vision) which would it be? Why? Describe a time you were so caught up in an activity that you missed something obvious in the environment, or when the environment was so distracting you couldn t concentrate. 3

4 Module 16 I.Basic Principles of Sensation and Perception Objectives: Contrast sensation and perception, and explain the difference between bottom-up and top-down processing. Discuss how much information we can consciously attend to at once. Identify the three steps that are basic to all our sensory systems. Distinguish between absolute and difference thresholds, and discuss whether we can sense and be affected by stimuli below the absolute threshold. Explain the function of sensory adaptation. 4

5 Module 16 Sensation Perception Process by which our sensory receptors and nervous systems RECEIVE and represent stimulus energies from our environment. The process of organizing and INTERPRETING sensory information, enabling us to recognize meaningful objects and events. 5

6 Module 16 Bottom-up processing Taking sensory information and works up to higher level processing. Sensation What am I seeing? (eyes see the bowl and contents, nose smells chocolate, pickles, and hot sauce, stomach churns, face grimaces, head turns away) DETECT through SENSES 6

7 Module 16 Is that something I ve seen before? Top-down processing Constructs perceptions from the sensory information by drawing on our OWN experiences and expectations Perception Guided by higher level mental processes INTERPRET what our senses detect 7

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9 Module 16 Is this you? 9

10 Module 16 Attention is POWERFULLY selective! Selective Attention: Focusing of conscious awareness on a particular stimulus Example: Cocktail PartyEffect Ability to attend to only ONE voice, while detecting your own name fmri scans show that multi-tasking distracts from brain s resources Our attention shifts back & forth while multi-tasking 10

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12 Module 16 Selective Inattention Inattentional blindness: Failing to see visible objects when our attention is directed elsewhere Our conscious mind is in one place at a time PIRA Change blindness: Failing to notice change in the environment A form of inattentional blindness Magicians manipulate our selective attention- Out of sight, out of mind Attention is POWERFULLY selective! 12

13 Module 16 What three steps are basic to all our sensory systems? Transduction: conversion of one form of energy so that our brain can use/make sense of it. R.T.D RECEIVE sensory stimulation, often using specialized receptor cells. TRANSFORM that stimulation into neural impulses. DELIVER the neural information to our brain. 13

14 Module 16 Absolute Threshold Faint stimuli The minimum stimulation necessary to detect a particular light, sound, pressure, taste, or odor 50% of the time Can be tested by exposing each ear to varying sound levels Single detection theory A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Detecting a weak signal, depends not only on the signal s strength but also out psychological state (our experience, expectations, motivation, and alertness) Seek to understand why people respond differently to the same stimuli Examples: teachers and cell phones, lonely speed daters being unselective, parents of newborn hearing faint whimper 14

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16 Module 16 Subliminal Stimuli you cannot detect 50% of the time (below your absolute threshold) Under certain conditions, you can be affected by stimuli so weak that you don t consciously notice them Imperceptibly brief stimulus triggers weak response in brain. Only detected by brain scans. Priming The heart has its reasons which reason does not know. The activation, often unconsciously, of certain associations, thus predisposing one s perception, memory, or response Experiment: image or word is quickly flashed, then replaced by a masking stimulus that interrupts the brain s processing before conscious perception Much of our information processing occurs automatically, out of sight, off the radar of our conscious mind. DUAL PROCESSING! 16

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18 Module 16 JND? 18

19 Module 16 Difference Threshold Minimum difference a person can detect between 2 stimuli 50% of the time (just noticeable difference {jnd}) Weber s law The principle that to be perceived as different, two stimuli must differ by a constant minimum percentage; not a constant amount Examples: Quarters, envelopes, & shoes. 19

20 Module 16 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation When we are constantly exposed to a stimulus that does not change, we become less aware of it because our nerve cells fire less frequently Influences our perceptions of emotions (see Fig.16.9 p.160) Examples: watch on wrist, smelly moth ball home, stinkies We perceive the world not exactly as it is, but as it is useful for us to perceive it. 20

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22 Module 17 II: Influences on Perception Objectives: Explain how our expectations, contexts, emotions, and motivation influence our perception. List the claims of ESP, and discuss the conclusions of most research psychologists after putting these claims to the test. 22

23 Module 17 What do you see? a. b. 23

24 Module 17 Describe what you saw. Keep in mind, that this is a police investigation and that your testimony can be used in a court of law. 24

25 Module P a st ex p e rie n c e s Star spangled 2. M o o d s, A ttitu d e s, a n d V a lu e s Having a bad day a n d th in g s se e m to sn o w b a ll 3. Needs If y o u re h u n g ry, y o u th in k ab o u t 4. What the group believes W e h a v e a ten d e n c y to, g o a lo n g w ith th e c ro w d. SEEING HEARING TOUCHING TASTING SMELLING 25

26 Module 17 Perceptual Set a mental predisposition to perceive one thing and not the other (top-down processing) Can influence what we hear, taste, feel, and see Through experiences we form concepts, or schemas that organize and allow us to interpret unfamiliar information 26

27 Module 17 Perceptual Set Examples: Pilot: Cheer up Gear Up Vinegar in beer- tastes better. Until.. Stereotypes about gender. Newborn David or Diana? Without color cues blue or pink- difficult identifying gender. 27

28 Module 17 Context Effects a stimulus may trigger radically different perceptions (in others), partly because of our differing perceptual set, but also because of the immediate context. The brain can work backward in time to allow a later stimulus to determine how we perceive an earlier one. (top-down processing) eel is on the wagon perceive the first word as wheel 28

29 Module 17 Emotion and Motivation Our emotional context, as well as our motivation, can create expectations and color our interpretation of events and behaviors 29

30 Module 17 ESP The controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition Parapsychology The study of paranormal phenomena, including ESP and psychokinesis 30

31 Module 17 Testable forms of ESP Telepathy Mind-to-mind communication Clairvoyance Perceiving remote events, such as a house on fire in another state Precognition Perceiving future events, such as a unexpected death in the next month 31

32 Module 17 Premonitions or Pretensions? Can psychics see the future? Can psychics aid police in identifying locations of dead bodies? What about psychic predictions of the famous Nostradamus? The answers to these questions are NO! Nostradamus predictions are retrofitted to events that took place after his predictions. 32

33 Module 17 Putting ESP to Experimental Test In an experiment with 28,000 indivduals, Wiseman attempted to prove whether or not one can psychically influence or predict a coin toss. People were able to correctly influence or predict a coin toss 49.8% of the time. 33

34 Module 17 Claims to ESP Skeptics argue: 1. to believe in ESP you must believe the brain is capable of perceiving with out sensory input 2. researchers have been unable to replicate ESP Phenomena under controlled conditions 34

35 Module 18 III: Vision Objectives: Describe the characteristics of visible light, and explain the process by which the eye transforms light energy into neural. Describe how the eye and the brain process visual information. Discuss the theories that help us understand color vision. 35

36 Module 18 The Wavelengths we see What we see as light is only a tiny slice of a wide spectrum of electromagnetic energy, which ranges from gamma rays as short as the diameter of an atom to radio waves over a mile long. The wavelengths visible to the human eye (below) extend from the shorter waves of blue-violet light to the longer waves of red light. 36

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38 Module 18 Light Energy Two physical characteristics of light help determine our sensory experience of them. Wavelength The distance from one wave peak to the next determines its perceived hue (the color we experience) Intensity (amplitude) The amount of energy in light waves determined by a wave s amplitude (height) influences brightness 38

39 (a) Waves vary in wavelength (the distance between successive peaks). Frequency, the number of complete wavelengths that can pass a point in a given time, depends on the wavelength. The shorter the wavelength, the higher the frequency. Wavelength determines the perceived color of light (and also the pitch of sound). (b) Waves also vary in amplitude (the height from peak to trough). Wave amplitude determines the brightness of colors (and also the loudness of 39 sounds).

40 Module 18 Retinal Processing Light rays reflected from a candle pass through the cornea, pupil, and lens. The curvature and thickness of the lens change to bring nearby or distant objects into focus on the retina. Rays from the top of the candle strike the bottom of the retina, and those from the left side of the candle strike the right side of the retina. The candle s image on the retina thus appears upside down and reversed. 40

41 Part of EYE Function Cornea Light enters the eye through the cornea. Protects the eye and bends light to provide focus. Pupil Light then passes through the pupil, a small adjustable opening Iris (very distinctive) Lens A ring of muscle tissue that forms the colored portion of the eye around the pupil and constricts in response to light intensity and even inner emotions The transparent structure behind the pupil that changes shape to help focus images on the retina. The lens focuses the rays by changing its curvature in a process called accommodation. Retina The light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information 41

42 Module 18 The Lens: Accommodation (adjustments) The process by which the eye s lens changes shape to help focus near or far objects on the retina. 42

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44 Module 18 Nearsighted 44

45 Module 18 Farsighted 45

46 RETINA Function Photoreceptors - Rods and Cones - Retina cells that respond to light Rods - Most sensitive to light and dark changes - Retinal receptors that detect black, white, and gray - Rods are more numerous than cones in periphery of retina Cones - Not sensitive to light; most sensitive to (green, red, blue) - Signals from cones sent to brain which then translates these messages into the perception of color - Only works in bright light - Color vision, fine details - Color blind does not have a particular type of cone in the retina or the cone may be weak 46

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48 Optic Nerve Fovea Blind Spot - The nerve that carries neural impulses from the eye to the brain - Central region of retina = most clear vision - No rods; only cones (packed together closer) - Blood vessels and nerve fibers go around fovea providing a direct path to the photoreceptors - This is where the optic nerves come together and exit the eye on the way to the brain - Part of the retina that does not contain photoreceptors - Any image that fills on this region you will not see 48

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50 Receptors in the Human Eye: Rod-Shaped Rods and Cone Shaped Cones Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color Sensitivity High Low Detail sensitivity High Low When you enter a darkened theater or turn off the light at night, your eyes adapt. Your pupils dilate to allow more light to reach your retina, but it takes 20 minutes or more before your eyes fully adapt. 50

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52 Module 18 How do the eye and the brain process visual information? after processing by your retina s nearly 130 million receptor rods and cones info travels to bipolar cells then to ganglion cells through axons making up the optic nerve to thalamus where the axons synapse with neurons that run to the visual cortex in the occipital lobe at the back of your brain 52

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54 Module 18 Feature Detection Nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement Specialized neurons in the occipital lobe s visual cortex receive information form individual ganglion cells in the retina These cells pass this information to other cortical areas, where team of cells (supercell clusters) respond to more complex patterns 54

55 Module 18 Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. 55

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57 Module 18 Parallel Processing Our brain computes multiple things at once; a scene is analyzed the brain divides it into subdimensions motion, form, depth, color -and works on each aspect simultaneously Other neural teams integrate the results, comparing them with stored information and enabling perception 57

58 Module 18 Visual Information Processing Scene Retinal processing: Receptor rods and cones > bipolar cells > ganglion cells Feature Detection: Brain s detector cells respond to specific features edges, lines, and angles Parallel processing: Brain cell teams process combined information about motion, form, depth, color Recognition: Brain interprets the constructed image based on information from stored images 58

59 Module 18 What theories help us understand color vision? Young-Helmholtz trichromatic theory The theory that the retina contains three different color receptors one most sensitive to red, one to green, one to blue, which when stimulated in combination, can produce the perception of any color Most people with color-deficient vision are not actually color blind. They simply lack function red or green sensitive cones or sometimes both. (monochromatic or dichromatic) 59

60 Module 18 Ishihara Test 60

61 Module 18 Opponent-process theory Can be see when we look at after images! The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green If there is a red and green marble competing going through a narrow tube both cannot travel at once (they are opponents) However red and blue travel in separate channels, so we can see a reddish-blue magenta 61

62 Module 18 Opponent-process theory Cones Retinal Ganglion Cells 62

63 Module 18 Opponent Process- Afterimage Effect They are caused by fatigued cells in the retina responding to light. 63

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66 Module 19 IV: Visual Organization and Interpretation Describe Gestalt psychologists understanding of perceptual organization, and explain how figure-ground and grouping principles contribute to our perceptions Explain how we use binocular and monocular cues to perceive the world in three dimensions and perceive motion Explain how perceptual constancies help us organize our sensations into meaningful perceptions Describe what research on restored vision, sensory restriction, and perceptual adaption reveals about the effects of experience on perception 66

67 Module 19 Gestalt An organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes. Filtering incoming information and we construct perceptions Mind matters In perception, the whole may exceed the sum of its parts 67

68 Module 19 Form Perception How do we recognize things? Figure-ground The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground) Example: say face/vase Grouping Our minds bring order and form to stimuli by following certain rules We need to make things meaningful. 68

69 Module 19 Examples of Grouping We group nearby figures together. We fill in gaps to create a complete, whole object. We perceive smooth, continuous patterns rather than discontinuous ones. 69

70 Module 19 Depth Perception How do we perceive depth? The ability to see objects in three dimensions although the images that strike the retina are two-dimensional allows us to judge distance Depth perception is partly innate (discovered by Eleanor Gibson & Richard Walk) Created visual cliff experiments 70

71 Module 19 Visual Cliff A lab device for testing depth perception in infants and young animals 6-14 month old infants were coaxed by their mothers to crawl over the glass Most infants refused, indicating they could perceive depth 71

72 Module 19 Binocular Cues Two eyes are better than one Depth cues, such as retinal disparity, that depend on the use of two eyes Retinal disparity A binocular cue for perceiving depth: by comparing images from the retinas in the two eyes, the brain computes distance the greater the disparity (difference) between the two images, the closer the object 72

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74 Module 19 Monocular Cues Needed to judge greater distances Depth cues, such as interposition and linear perspective, available to either eye alone - Judging how far away an object is by using just one eye. 74

75 Module 19 Monocular Cues Motion Perception What would life be like without motion? Brain computes motion based partly on its assumption that shrinking objects are retreating and enlarging objects are approaching. Sometimes I wonder: Why is that Frisbee getting bigger? And then it hits me! - Anonymous Phi Phenomenon: Illusion of movement created when two or more adjacent lights blink on and off in quick succession. 75

76 Module 19 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. 76

77 Module 19 Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer. 77

78 Module 19 Monocular Cues Relative height: We perceive objects higher in our field of vision as farther away. We assume the lower part of a figure-ground illustration is closer, we perceive it as a figure. 78

79 Module 19 Monocular Cues Light & shadow: Shadows and highlights can provide clues to an object s depth and dimensions. 79

80 Module 19 Monocular Cues Monocular movement parallax (Relative Motion): When our heads move from side to side, objects at different distances move at different speeds, or relative velocity. Closer objects move in the opposite direction of the head movement, and farther objects move with our heads. 80

81 Module 19 Perceptual constancies How to recognize objects without being deceived How do Perceptual constancies help us organize our sensations into meaningful perceptions? Perceptual Constancy (Top down processing) Perceiving objects as unchanging (having constant shapes, size, brightness, and color) even as illumination and retinal images change 81

82 Module 19 Perceptual Constancy Color Constancy perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object. Example: apple in a bowl surrounded by other fruits. 82

83 Module 19 Perceptual Constancy Shape Constancy shape seems to change shape with the angle of our view we perceive the shape as constant, even while our retinas receive changing images to them Example: Rotating plate 83

84 Module 19 Perceptual Constancy Size Constancy Perceive objects as having a constant size, even while our distance from them varies. Example: Moon illusion 84

85 Module 19 Perceptual Adaptation Visual ability to adjust to an artificially displaced visual field (prism glasses) Visual Interpretation: Immanuel Kant: knowledge comes from inborn ways of sensory processing. John Locke: through our experiences we learn to perceive. 85