Sensation and Perception Psychology Modules 9 & 10 Mrs. McVey • If its underlined, bolded, italicized you need to know it for the test • Take notes on the provided graphic organizers • Open books to page 157----its important to look at pictures in this chapter What Is Sensation? • It occurs when a stimulus activates a sensory receptor • A stimulus is measured by the following: size, intensity, duration, wavelength Slide # 3 What Is Perception? • The organization of sensory information into meaningful experiences Slide # 4 What is sensation? What is perception? • Perception – Process of organizing and interpreting sensory information • Sensation – The process by which sensory systems (ears, eyes, etc.) and nervous system receive stimulus from the environment S E N S A T IO N Book Definition: The stimulation of sensory receptors and the transmission of sensory information into the central nervous system O u r s e n s e s h a v e p ic k e d u p a m e s s a g e fro m th e e n v iro n m e n t – v e r y s im p ly “ T a k in g it a ll in ” P E R C E P T IO N Book Definition: The process by which sensations are organized into an inner representation of the world In te rp re tin g w h a t w e s e n s e – M a k in g s e n s e o u t o f s e n s a tio n s Making Sense of Complexity Our sensory and perceptual processes work together to help us sort out complex images. “The Forest Has Eyes,” Bev Doolittle 7 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. 8 Processing • Bottom-up processing (sensation) – Focuses on the raw material entering through our eyes, ears, and other organs of sensation • Top-down processing (perception) – Focuses on our expectations and experiences in interpreting incoming sensory information 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.” 10 Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT 11 Thresholds • Absolute – The minimum stimulation needed to detect a particular stimulus • Can’t hear sounds at low level=below absolute threshold • Difference (jnd—just noticeable difference) – Minimum difference that a person can detect between two stimuli Absolute Thresholds • Vision: a flame from a single candle 30 miles away • Hearing: ticking of a watch 20 feet away • Taste: one teaspoon of sugar in two gallons of water • Smell: one drop of perfume in a small house • Touch: the wing of a bee brushing your cheek Slide # 13 Signal-Detection Theory • The study of people’s tendencies to make correct judgments in detecting the presence of stimuli Slide # 14 Signal Detection Theory • Set of formulas and principles that predict when we will detect the presence of a faint stimulus (“signal”) amid background stimulation (“noise”). Detection depends on qualities of the stimulus, the environment, and the person who is detecting. – Stimulus variables – Environmental variables – Organismic variables Sensory adaptation • Sensory Adaptation – Diminished sensitivity as a result of constant stimulation • Wearing socks…do you feel them? Probably not • Failure to realize the bath water is hot at first • Selective Attention – Focusing conscious awareness on a particular stimulus to the exclusion of others • Listening to the teacher-not the gossip around you 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 Selective Attention • Selective Attention – Focusing conscious awareness on a particular stimulus to the exclusion of others • Listening to the teacher-not the gossip around you The Eye 22 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. 23 Both Photos: Thomas Eisner The Stimulus Input: Light Energy Visible Spectrum 24 Physical Characteristics of Light 1. Wavelength (hue/color) 2. Intensity (brightness) 25 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. 26 Intensity (Brightness) Intensity: Amount of energy in a wave determined by the amplitude. It is related to perceived brightness. 27 Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more “washed out” or “darkened.” 28 The Lens 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 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 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 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 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 brain, and the thalamus connects to the visual cortex. 35 Slide # 36 Visual system • The color we perceive light to be is determined by its wavelength • Trichromatic color theory—can’t see the color due to an absence (lack of) cones • Opponent process theory of color vision: every color has an opposite color (afterimage) 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 38 VISUAL PROBLEMS Color Blindness Color Blind – sensitive to only black & white Dichromat – only sensitive to certain colors – partially color blind Trichromat – normal color vision Link Jay and Maureen Neitz Color Vision Page Hearing • Depends on sound waves or vibrations • Sound waves pass through various bones in the inner ear • Thin, hair-like cells move back and forth Slide # 45 The Path of Sound • Sound waves are funneled by the outer ear to the eardrum, causing it to vibrate • Ossicles and oval window, cochlea • Basilar membranes, Organ of Corti, hair-cell receptors Slide # 46 Hearing • The vibrations of the eardrum are transmitted to the oval window by three tiny bones located in the middle ear. • Cochlea is fluid-filled tube in which sound waves trigger nerve impulses • Hearing loss: damage to your cochlea • A time lag between the time sound reaches your left and right ears is important for accurately locating sounds. • Semicircular canals are for balance Loudness of Sound Richard Kaylin/ Stone/ Getty Images 120dB 48 70dB The Ear Dr. Fred Hossler/ Visuals Unlimited 49 Cochlea Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals. 50 Localization of Sounds Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. 51 Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. The four basic sensation are pain, pressure, warmth, and cold Pressure Burning hot Vibration Vibration Cold, warmth and pain 52 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. Gatecontrol theory: other touch sensations close the gate on pain sensations Gary Comer/ PhototakeUSA.com 53 Taste Taste is a chemical sense! Sweet Sour Salty Bitter Umami (Fresh Chicken) 54 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 55 Kinesthetic • The sense of movement and one’s body is vestibular sense • Receptors in muscles, tendons, joints • Semicircular canals Slide # 56 Perceptual Organization You NEED a book. Open to page 183 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. 57 A Changing Picture Slide # 58 Defining Perception • An active process • The brain pieces together bits of sensory information in order to form orderly impressions or pictures • Gestalt Slide # 59 Gestalt • The “whole” or the organizational patterns, that we tend to perceive. The Gestalt psychologists emphasized that the whole is greater than the sum of its parts – The “Big Picture” Figure-ground relationships • The organization of the visual field into objects (figures) that stand out from their surroundings (ground) – Airplane=figure……sky=ground – Island=figure……..ocean=ground Form Perception Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Time Savings Suggestion, © 2003 Roger Sheperd. 62 Grouping Principles • Grouping: placing items into understandable sets – Similarity • Items that resemble each other as part of the same group • Basketball teams wear two different colors of uniforms, two different groups – Proximity • Objects close together belong in a group – Closure • Fill in gaps in order to perceive disconnected parts as a whole object – Continuity Grouping After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules. 66 Gestalt Principle: Similarity • When similar and dissimilar objects are mingled together, we see the similar objects as groups Slide # 67 Gestalt Principle: Continuity • We tend to see continuous patterns, not disrupted ones Slide # 68 Gestalt Principle: Closure • Occurs when people see a familiar pattern or shape with some missing parts Slide # 69 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 70 Depth Perception • Ability to see in three dimensions & judge distance • Binocular – Require the use of both eyes • Monocular – Require the use of only one eye Retinal Disparity: A binocular depth cue resulting from slightly different images produced by the separation of the retinas in the left and right eyes “somewhat different images are two eyes see of the same subject” Camera one, camera two 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 72 Monocular Cues p. 189 • Relative size • Relative motion • Interposition – Object blocks another object is perceived as closer • • • • Relative height Texture gradient Relative clarity Linear perspective – Parallel rows of corn 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. 74 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. 75 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. 76 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 77 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. 78 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. 79 http://www.eyetricks.com/pinwheel.htm DEPTH PERCEPTION MONOCULAR CUES FOR DEPTH PERSPECTIVE TEXTURE GRADIENT MONOCULAR CUES FOR DEPTH • If two objects make the same size image on the retina, we will perceive the object that appears to be closer as larger than the object that appears to be more distant. PERCEPTION OF MOVEMENT • Stroboscopic Motion – rapid sequencing of visual images • Phi Phenomenon – rapid sequencing of lights Phi Phenomenon Motion Perception • Stroboscopic motion – Perceive motion when there is none—series of varying still images • Flip book • Animation • Phi phenomenon – Movement when lights are turned on and off in sequence • Christmas lights Perceptual Constancy • Perceptual constancy is perceiving the size, shape, and lightness of an object as unchanging, even as the retinal image of the object changes – Size Constancy • Horse galloping towards you is not growing in size – Shape Constancy • Know books are rectangular not trapezoid – Lightness Constancy PERCEPTUAL CONSTANCIES SIZE CONSTANCY PERCEPTUAL CONSTANCIES SHAPE CONSTANCY PERCEPTUAL CONSTANCIES COLOR CONSTANCY PERCEPTUAL CONSTANCIES BRIGHTNESS CONSTANCY Perceptual set, Context, Illusions • Perceptual set: mental predisposition to perceive something one way & not the other • Context: setting or environment in which we interpret sensory stimuli • Illusions “tricks” on schemas (mental frameworks that organize and interpret information) Extrasensory Perception (ESP) • The ability to gain information by some means other than the normal senses • Paranormal phenomena and parapsychology Slide # 93 The “Sixth Sense” • The major focus includes the following: Telepathy, clairvoyance, precognition, and psychokinesis Slide # 94 Telepathy • Communication of thoughts from one mind to another that occurs without the use of our known senses Slide # 95 Clairvoyance • The ability to perceive objects and events without using the senses Slide # 96 Precognition and Psychokinesis • Precognition: the ability to foretell the future • Psychokinesis: the ability to move objects through mental effort alone Slide # 97 ESP • Psychologists are skeptical about the existence of ESP because there is case study evidence that seems to support claims of ESP, but no experimental evidence. Is There Extrasensory Perception? Perception without sensory input is called extrasensory perception (ESP). A large percentage of scientists do not believe in ESP. 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. 99 http://www.garyfisk.com/anim/index.html 100 • http://www.garyfisk.com/anim/index.html • http://psych.hanover.edu/Krantz/sen_tut.html 101 http://dogfeathers.com/java/necker.html 102 Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal images change. 103 Color Constancy Perceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object. Color Constancy 104 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 105 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 106 Ames Room The Ames room is designed to demonstrate the sizedistance illusion. 107 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? 108 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. 109 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? 110 http://dragon.uml.edu/psych/illusion.html 111 Claim: In the film Aladdin, the hero whispers, "Good teenagers, take off your clothes." http://www.snopes.com/disney/films/aladdin.htm 1) The Pepsi Cool Can In 1990, Pepsi actually withdrew one of its “Cool Can” designs after someone protested that Pepsi was subliminally manipulating people by designing the cans such that when six-packs were stacked at grocery stores, the word SEX would emerge from the seemingly random design. Critics alleged that the red and blue lines on the “Cool Can” design were far from random <27>.