IV: Visual Organization and Interpretation

Transcription

1 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 1

2 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 2

3 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. 3

4 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. 4

5 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 5

6 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 6

7 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 7

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9 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. 9

10 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. 10

11 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. 11

12 Module 19 Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer. 12

13 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. 13

14 Module 19 Monocular Cues Light & shadow: Shadows and highlights can provide clues to an object s depth and dimensions. 14

15 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. 15

16 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 16

17 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. 17

18 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 18

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

20 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. 20

21 Module 20 V: Hearing Objectives Describe the characteristics of air pressure waves, and explain the process by which the ear transforms sound energy into neural messages. Discuss the theories that help us understand pitch perception. Describe how we locate sound. 21

22 Module 20 Audition A world without sounds? the sense or act of hearing Sounds that we hear best are those sounds with frequencies in a range corresponding to that of the human voice Those with normal hearing are acutely sensitive to faint sounds, an obvious necessity for our ancestors survival 22

23 Module 20 The Stimulus Input: Sound Waves Both light and sound travel in waves. Amplitude of sound waves = loudness Measured in decibels (db) 0 = absolute threshold for hearing The length, or frequency = the pitch (a tone) Measured in hertz (Hz); # of waves/sec short waves = high frequency/high pitch (violin) long waves = low frequency/low pitch (cello) Example: violin sound waves are shorter and faster than those produced by a cello or bass guitar 23

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25 The outer ear funnels sound waves to the eardrum. The bones of the middle ear (hammer, anvil, and stirrup) amplify and relay the eardrum s vibrations through the oval window into the fluid-filled cochlea. 25

26 Middle Ear 3 tiny bones (hammer, anvil, and stirrup) pick up vibrations and transmit them to the cochlea Cochlea {KOHK-lee-uh} a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses Inner Ear the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs Outer Ear Pinna, collects sound 26

27 Vibrating air to fluid waves to electrical impulses to the thalamus to the brain s temporal lobe 27

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29 Module 20 Hearing Loss A socially isolated world Damaged cochlea: Sensorineural hearing loss (nerve deafness) Hearing loss caused by damage to the cochlea s receptor cells or to the auditory nerves Cochlear implant: device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea. Undamaged cochlea: Conduction hearing loss (less common form) Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Examples: impacted ear wax, ear infections, perforated ear drums, etc. 29

30 Audiogram 30

31 Translates sounds into electrical signals that, wired into the cochlea s nerves, convey information about sound to the brain. Plasticity? Who would benefit more? Children or adults? 31

32 Module 20 Perceiving pitch Two theories Place theory Links the pitch we hear with the place where the cochlea s membrane is stimulated High frequencies- large vibrations near beginning of cochlea Low frequencies- vibrate MORE of the membrane, including near the end. Frequency theory The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch 32

33 Module 21 VI:The Other Senses Objectives Describe the sense of touch. Discuss how we best understand and control pain. Describe the senses of taste and smell. Explain how we sense our body s position and movement. Describe how our senses interact. 33

34 Module 21 How do we sense touch? Touch is vital and essential to our development Our sense of touch is a mix of distinct skin senses for pressure, warmth, cold, and pain (basic four). Some areas are more sensitives than others. stroking adjacent pressure spots creates a tickle repeated gentle stroking of a pain spot creates an itching sensation touching adjacent cold and pressure spot triggers a sense of wetness, which you can experience by touching dry, cold metal stimulating nearby cold and warm spots produces the sensation of hot 34

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37 Module 21 Controlling PAIN Pain is where body meets mind therefore both should be treated drugs surgery acupuncture electrical stimulation functional MRI (fmri) scans show that playing in the virtual reality reduces the brain s pain-related activity (computer generated 3-D world for burn victims) 37

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39 Module 21 TASTE Evolutionary psychologists believe that taste enabled our survival and not just for pleasure. Taste is a chemical sense (200 or more taste buds inside each bump on tongue, taste receptors in the bud) Taste receptors reproduce every week or two 5 taste sensations: sweet, sour, salty bitter, umami 39

40 Module 21 SMELL Experiences in smell are trickling intimate nursing infant and their mothers quickly learn to recognize each other s scents The receptor cells instantly alert the brain through their axon fibers Buck and Axel stated that odors trigger a combination of receptors that are interpreted by the olfactory cortex For humans, attractiveness of smells depends on learned associations 40

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44 Module 21 Body Position and Movement Kinesthesia The system for sensing the position and movement of individual body parts Vestibular sense The sense of body movement and position, including the sense of balance 44

45 Module 21 Sensory Interaction Sensory interaction The principle that one sense may influence another, as when the smell of food influences its taste Embodied cognition Brain circuits processing our bodily sensations connect with brain circuits responsible for cognition 45

46 Sensory System Source Receptors Vision Light waves striking the eye RODS and CONES in the retina Hearing Touch Taste Smell Body Positionkinesthesia Body Movementvestibular sense Sound waves striking the outer ear Pressure, warmth, cold, pain on the skin Chemical molecules in the mouth Chemical molecules breathed in through the nose Any change in position of a body part, interacting with vision Movement of fluids in the inner ear caused by head/body movement COCHLEAR hair cells in the inner ear Skin receptors detect pressure, warmth, cold, and pain Basic tongue receptors for sweet, sour, salty, bitter, and umami Millions of receptors at top of nasal cavity Kinesthetic sensors all over the body Hairlike receptors in the semicircular canals and vestibular sacs 46