Sensation, Vision, and Hearing Part I PDF

¨ Chapter 5 Sensation and Perception There are 9 people in this picture. 1 SENSATION AND PERCEPTION How many legs does this elephant have? 2 1  Chapter Outline I....

¨ Chapter 5 Sensation and Perception There are 9 people in this picture. 1 SENSATION AND PERCEPTION How many legs does this elephant have? 2 1  Chapter Outline I. Sensation versus Perception II. Vision III. Hearing IV. The Other Senses V. Gestalt Principles of Perception 3 Defining Sensation and Perception ¨ Sensation ¤ The detection of physical energy emitted or reflected by physical objects. ¤ It occurs when energy in the external environment or the body stimulates receptors in the sense organs. ¨ Perception ¤ The process by which the brain organizes and interprets sensory information. 4 2  Sensation & Perception Processes 5 Senses and Sensation ¨ Each sense has its own sense organ and sensory receptors ¨ Smell, pressure, pain and temperature ¤ Receptors are extensions of sensory neurons ¨ Vision, hearing and taste ¤ Specific receptors (specialized cells) separated from sensory neurons by synapses 6 3  Sense Signals ¨ Various stimuli (light, mechanical pressure, chemical molecules are converted to electrical impulses (neural- action potential) ¨ Nervous system encodes messages ¨ Doctrine of Specific Nerve energies ¤ Different sense modalities exist because signals received by the same sense organs stimulate different nerve pathways leading to different areas of the brain 7 Sensation ¨ Bottom-Up Processing ¤ Analysis that begins with the sense receptors and works up to the brain’s integration of sensory information ¨ Top-Down Processing ¤ Information processing guided by higher-level mental processes ¤ As when we construct perceptions drawing on our experience and expectations 8 4  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.” 9 Top-Down Processing !"#$%"! 10 5  Sensation- Basic Principles ¨ Psychophysics ¤ Study of the relationship between physical characteristics of stimuli and our psychological experience of them ¤ Light- brightness ¤ Sound- volume ¤ Pressure- weight ¤ Taste- sweetness 11 Measuring the Senses Absolute Thresholds ¨ How sensitive are senses? ¨ Detection of a signal 50% of the time. Our senses can be very sharp! 12 6  Measuring the Senses Difference Thresholds ¨ The smallest difference a person can detect reliably ¨ “Just noticeable difference” or ‘jnd’ 13 Just Noticeable Differences (jnd) Weber’s Law: The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different Weber’s Fraction DI =c I 14 7  Example: Weber’s Fraction Equation: DI Example 1: =c I JND=5g Example 1: 5 = 5% 100 g 100 + 5 g 100 Example 2: Example 2: 10 JND=10g = 5% 200 200 g 200 + 10 g 15 Sensation- Thresholds ¨ Weber’s Law ¤ To be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount) n Light intensity- 8% n Weight- 2% n Tone frequency- 0.3% 16 8  Measuring the Senses Absolute and jnd measurements – Bias, moods, alertness Signal Detection Theory Separate the detection task into sensory process (stimulus intensity) and decision processes (observer’s response bias) 17 Sensation- Thresholds 100 ¨ Subliminal Percentage of correct ¤ When stimuli are 75 detections below one’s absolute threshold 50 for conscious Subliminal awareness 25 stimuli 0 Low Absolute Medium threshold Intensity of stimulus 18 9  Sensation- Subliminal ¨ Subliminal ¤ Unconsciously sense subliminal stimuli ¤ Suggestive powers ¨ Backmasking and Reverse Speech I love you, said the Marijuana… the law will devil banish us. Soon I’ll beat the law 19 Sensory Adaptation Sensation often fades if stimuli remain unchanged or repetitious 20 10  Chapter Outline I. Sensation versus Perception II. Vision III. Hearing IV. The Other Senses V. Gestalt Principles of Perception 21 Sensation and Perception 22 11  The spectrum of electromagnetic energy 23 Visible Spectrum We see only a small part of the electromagnetic spectrum Visible light 400-700 nm 24 12  Physical Properties of Waves Short wavelength=high frequency Great amplitude (bluish colors, high-pitched sounds) (bright colors, loud sounds) Long wavelength=low frequency Small amplitude (reddish colors, low-pitched sounds) (dull colors, soft sounds) 25 The Eye 26 13  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. 27 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. 28 14  The Eye 29 Myopia and Hyperopia A nearsighted A farsighted person person sees near sees far objects objects clearly. clearly. 30 15  Retinal Image Though the image is upside down, the brain interprets it as being right-side up 31 Sensory Adaptation Our World Upside Down 32 16  Rods and Cones 33 Retina (inside out) ¨ Rods and cones (receptor cells) synapse with bipolar cells ¨ Bipolar cells -> ganglion cells ¨ Axons of ganglion cells form optic nerve 34 17  Rods and Cones ¨ Cones concentrated in the fovea ¨ Rods are not found in the fovea http://www.handprint.com/HP/WCL/IMG/fovea.gif 35 Pathways from the Eyes to the Visual Cortex 37 18  Visual Information Processing Cell’s responses Stimulus ¨ Feature Detectors ¤ Nerve cells in the brain that respond to specific features n Shape n Angle n Movement 38 How the Brain Perceives 39 19  Illusory Contours 40 Visual Information Processing ¨ Parallel Processing ¤ Simultaneous processing of several aspects of a problem simultaneously 41 20 42 43 21  How We See Colours 1) Trichromatic Theory ¨ Young-Helmholtz ¨ First level of processing (cones) ¨ 3 types of cones (blue, green, red) 44 Colour-Deficient Vision ¨ People who suffer red-green deficiency have trouble perceiving the number within the design 45 22  2) Opponent Process ¨ Second stage (ganglion cells, thalamus, VC) + - - + ¨ “Opponent”- ONE cell fires for one colour (excitatory) and is inhibited by the other 46 47 23  Visual Information Processing ¨ Color Constancy ¤ Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object 50 Color Constancy 51 24  Colour and Language Processing: How well do you know your colours? 52 Higher Order Processing 53 25  The Stroop Effect 54 56 26  HEARING (Auditory System) Absolute threshold for humans is 0 dB 57 Properties of Sound Sounds are vibrations of air molecules that stimulate the auditory system. 58 27  PROPERTIES OF SOUND LOUDNESS Related to the intensity of the wave’s pressure The more energy = higher peak (louder) Measured in decibels (dB) 59 PROPERTIES OF SOUND PITCH Frequency How rapidly the sound wave cycles Measured in Hertz (1 oscillation/second=1 Hz) Humans (16 – 20,000 Hz) 60 28  PROPERTIES OF SOUND TIMBRE Quality of sound- related to complexity of wave Rarely have a perfect tone (made of only one frequency) 61 The Intensity of Some Common Sounds 62 29  Anatomy of the Ear Outer ear Middle ear Inner ear Semicircular Pinna Stirrup canals Hammer Anvil Bone Auditory Sound nerve waves Cochlea Auditory Eardrum Canal- (tympanic Membrane) Round window Oval window Where stirrup attaches 63 OUTER EAR ¨ PINNA ¤ Funnels sounds ¨ Ear Canal ¤ Auditory canal ¨ EAR DRUM ¤ Tympanic membrane ¤ Highly sensitive ¤ Vibrates at different speeds 64 30  MIDDLE EAR BONES OF THE MIDDLE EAR 3 tiny bones (smallest bones in the body) 1. Hammer (Malleus) 2. Anvil (Incus) 3. Stirrup (Stapes) Movement of these bones intensifies the signal The stirrup -> oval window 65 INNER EAR ¨ COCHLEA (fluid filled- perilymph) ¨ AUDITORY NERVE ¨ Organ of Corti holds the auditory receptors- Hair Cells (cilia) 66 31  Receptor Cells The Hair Cells Hair cells are embedded in the basilar membrane (16,000). ¨ Pressure reaches cochlea causes fluid (and basilar membrane to move) 67 ¨ INNER EAR Hair cells are physically displaced when they brush against the tectorial membrane Stereocilia } HAIR CELL ¨ They then initiate a signal that is passed on to the auditory nerve and it is sent to higher centres in the brain. 68 32  All the pieces 69 Perceiving Pitch 1. Place Theory ¤ The theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated 70 33  Place Theory ¨ As you move along the basilar membrane the hair cells vary in size. ¨ Each segment of the basilar membrane is sensitive to a different frequency of stimuli. ¨ Depending on what region of the basilar membrane, the cells are activated, determines what frequency we hear. http://www.sissa.it/multidisc/cochlea/images/spirale.gif 71 2. Frequency Theory ¤ The theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch 72 34  HIGHER AUDITORY PROCESSING http://www.sfu.ca/~saunders/l33098/Ear.f/EarImages%20%25C4/brainsound.jpeg 73 How We Locate Sounds 74 35  HEARING LOSS ¨ Conduction Hearing Loss ¤ Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea ¨ Sensorineural Hearing Loss ¤ Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve ¤ Also called nerve deafness 75 36