PSY 2012 Chapter 4 Outline
PSY 2012 Chapter 4 Outline PSY 2012
Popular in General Psychology
Popular in Psychlogy
This 34 page Class Notes was uploaded by Amanda Martinez on Friday February 5, 2016. The Class Notes belongs to PSY 2012 at University of Florida taught by in Fall 2015. Since its upload, it has received 37 views. For similar materials see General Psychology in Psychlogy at University of Florida.
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Date Created: 02/05/16
Chapter 4: Sensation and Perception • Illusion-‐ perception in which the way we perceive a stimulus doesn’t match its physical reality • Sensation-‐ detection of physical energy by sense organs, which then send info to the brain o Sensation first allows us to pick up the signals in our environments • Perception-‐ the brain’s interpretation of raw sensory inputs o Perception allows us to assemble these signals into something meaningful • Naïve realism-‐ Often assume that our sensory systems are infallible and that our perceptions are perfect representations of the world around us o Naive realism is wrong o World isn’t as we see it • Filling-‐in-‐ reconstructing a missing part and putting it in the empty space o Occurs without our awareness o Adaptive o Helps us make sense of our often confusing and chaotic perceptual worlds o Can fool us • We often blend real with the imagined • We simplify our world to make better sense of it in the process Two Sides of the Coin: Sensation and Perception • Our brain picks and chooses among the types of sensory info it uses o Relies on expectations and prior experiences to fill in the gaps and simplify processing Sensation: Our Senses as Detectives • Sense enables us to see majestic scenery, hear music, feel touch, maintain balance as we walk and taste food • All of our senses rely on a mere handful of basic principles • Transduction-‐ the process of converting an external energy or substance into electrical activity within neurons o First step o Converting external energies into a “language” the nervous system understands o Sense receptor-‐ specialized cell responsible for converting external stimuli into neural activity for a specific sensory system § Specialized cells at the back of the eye transduce light § Cells in a spiral-‐shaped organ in the ear transduce sound § Odd-‐looking endings attached to axons embedded in deep layers of the skin transduce pressure § Receptor cells lining the inside of the nose transduce airborne odorants § Taste buds transduce chemicals containing flavor • Sensory adaptation-‐ activation is greatest when we first detect a stimulus o Adaptation takes place at the level of the sense receptor o Strongly at first then dies down to conserve energy and additional resources • Psychophysics-‐ the study of how we perceive sensory stimuli based on their physical characteristics • Absolute threshold-‐ lowest level of a stimulus needed for the nervous system to detect a change 50% of the time o Demonstrate how remarkably sensitive our sensory systems are § Visual systems can detect a single candle from 30 miles away § Smell from as few as 50 airborne odorant molecules • Just noticeable difference (JND)-‐ the smallest change in the intensity of a stimulus that we can detect o Relevant to our ability to distinguish a stronger from a weaker stimulus • Weber’s law-‐ there is a constant proportional relationship between the JND and original stimulus intensity o The stronger the stimulus, the bigger the change needed for a change in stimulus intensity to be noticeable • Signal detection theory-‐ theory regarding how stimuli are detected under different conditions o Trying to figure out what a friend is saying on a cell phone when there’s a lot of static in the connection § High background noise § Need to increase signal by shouting over the static so they can hear us o Signal-‐to-‐noise ratio-‐ harder to detect a signal as background noise increases o Response biases-‐ tendencies to make one type of guess over another when we’re in doubt about whether a weak signal is present or absent under noisy conditions § Developed a clever way to take into account some people’s tendency to say “yes” when they’re uncertain and other people’s tendency to say “no” § Sometimes they presented a sound, sometimes not • True positive-‐ hit; hearing a sound when it was present • False negative-‐ miss; denying hearing a sound when it was present • False positive-‐ false alarm; hearing a sound that wasn’t there • True negative-‐ true negative; deny hearing a sound that wasn’t there • Specific nerve energies-‐ even though there are many stimulus energies, the sensation we experience is determined by the nature of the sense receptor, not the stimulus o Sensation of light when we rub our eyes o Doesn’t matter if light or touch activated the sense receptor o Our brains reacted the same way o Stimulus is touch (rubbing our eyes) but we’re putting pressure on the eye’s receptor • Scientists have found many examples of cross modal processing that produce different perceptual experiences than either modality provides itself o McGurk effect-‐ we integrate visual and auditory info when processing spoken language, and our brains automatically calculate the most probable sound given the info from the 2 sources § Hearing audio track of one syllable (ba) § Seeing a video of a different syllable being spoken (ga) § Produces perceptual experience of a different third sound (da) § Brain’s best guess at integrating the 2 conflicting sources of info o Illusion that shows how our senses of touch and sight interact to create false perceptual experience § Placing a rubber hand on a table with the precise positioning of a participant’s hand if they were to have it one the table § Researcher simultaneously strokes participants hidden hand and the rubber hand gently § Participant feels like the rubber hand becomes their own hand • Cross-‐modal effects may reflect “cross-‐talk” among different brain regions • Single brain region may serve double duty helping to process multiple senses • Synthesia-‐ a condition in which people experience cross-‐modal sensations o Hearing sounds when they see colors o Tasting or smelling colors The Role of Attention • Flexible attention is critical to our survival and well-‐being • Selective attention-‐ process of selecting one sensory channel and ignoring or minimizing others o Filter theory of attention-‐ allows us to pay attention to important stimuli and ignore others o Dichotic listening-‐ hearing 2 different messages § Ignored messages sent to 1 ear § Seemed to know little or nothing about these messages § Could repeat message they attended • Sometimes mixed some info they were supposed to ignore § The info we’ve supposedly filtered out of our attention is still being processed at some level we’re not aware of o Cocktail party effect-‐ ability to pick out an important message, like our name, in a convo that doesn’t involve us o Filter in our brain is more complex than just an “on” and “off” switch • Inattentional blindness-‐ failure to detect stimuli that are in plain sight when our attention is focused elsewhere • Often need to pay close attention to pick out even dramatic changes in our environment • Change blindness-‐ failure to detect changes in one’s environment The Binding Problem: Putting the Pieces Together • Binding problem-‐ brain manages to combine diverse pieces of info into a unified whole o Don’t know how we do it o Apple looks red, feels round/smooth, tastes sweet/tart, smells like an apple o Any characteristic in isolation isn’t an apple, characteristics together make it an apple • Rapid, coordinated activity across multiple cortical areas assist in binding o May explain many aspects of perception and attention o Rely on shape, motion, color and depth cues to see the world o Mind combines everything we receive from different senses to make an image of the world for us Seeing: The Visual System • Building up an image involves many external elements, such as light, biological systems in the eye and brain that process images for us, and our past experiences Light: The Energy of Life • Light is a central player in our perception of the world o A form of electromagnetic energy o Visible light has wavelengths o We only respond to a narrow range of wavelengths of light § Human visible spectrum • When light reaches an object, part gets reflected and part gets absorbed • Brightness-‐ influenced by intensity of reflected light that reaches our eyes o White-‐ reflects all light shone on it and absorbs none; presence of all colors o Black-‐ absorb all light shone on it and reflect none; presence of no colors o Brightness also depends on lighting surrounding object • Hue-‐ color of light • Maximally attuned to 3 primary colors: o Red, green and blue • Additive color mixing-‐ mixing of varying amounts of these 3 colors to produce any color • Subtractive color mixing-‐ mixing of colored pigments in paint or ink The Eye: How We Represent the Visual Realm • Structures towards the front of the eyeball influence how much light enters our eye o Focus the incoming light rays to form an image at the back of the eye • Sclera-‐ white of the eye • Iris-‐ colored part of the eye o Usually blue, brown, green or hazel o Controls how much light enters our eyes by expanding and contracting • Pupil-‐ circular hole through which light enters the eye o Closing is a reflex response to light or objects coming towards us § Occurs in both eyes simultaneously o Dilation-‐ expansion of the pupil § Dilate when we’re trying to process complex info, when we view someone attractive and reflect sexual interest • Cornea-‐ part of the eye containing transparent cells that focus light on the retina o Curved layer covering the iris and pupil o Bends incoming light to focus the incoming visual image at the back of the eye • Lens-‐ part of the eye that changes curvature to keep images in focus o Also bends light o Allows us to fine-‐tune visual images o Consists of some of the most unusual cells in the body § Completely transparent, allowing light to pass through them o Accommodation-‐ changing the shape of the lens to focus on objects near or far § Changes shape to focus light on the back of the eyes § Adapt to different perceived distances of objects § Flat-‐ lens becomes long and skinny, allowing us to see distant objects § Fat-‐ lens becomes short and wide, allowing us to focus on nearby objects • How much our eyes need to bend the path of light to focus depends on the curve of our corneas and overall shape of our eyes • Myopia-‐ nearsightedness o Images are focused in front of the rear of the eye o See close objects well; can’t see far objects • Hyperopia-‐ farsightedness o Cornea is too flat or our eyes are too short o See far objects well; inability to see close objects • Vision worsens with age o Eyes lose flexibility due to aging • Retina-‐ membrane at the back of the eye responsible for converting light into neural activity o Many scholars believe it is technically part of the brain o Can think of retina as a movie screen where light from the world is projected • Fovea-‐ central portion of the retina o Responsible for acuity-‐ sharpness of vision • Rods-‐ receptor cells in the retina allowing us to see in low levels of light o More plentiful o Long and narrow o Enable us to see basic shapes and forms o Dark adaptation-‐ time in dark before rods regain maximum light sensitivity § Rods-‐ going from light to dark • Cones-‐ receptor cells in the retina allowing us to see in color o Shaped like small cones o Sensitive to detail o Require more light o Activate when moving from dark to light • Photopigments-‐ chemicals that change following exposure to light o Rods-‐ rhodopsin • Ganglion cells-‐ cells in the retinal circuit that contain axons, bundle all their axons together and depart the eye to reach the brain • Optic nerve-‐ nerve that travels from the retina to the brain o Contains the axons of the ganglion cells o Comes to a fork called the optic chiasm § Half of the axons cross the chiasm and the other half stay on the same side o Optic nerves enter the brain, turning into optic tracts § Send most of their axons to the visual part of the thalamus and the primary visual cortex § Remaining axons go to midbrain, specifically superior colliculus • Play key role in reflexes o Blind spot-‐ part of the visual field we can’t see because of an absence of rods and cones § Axons of ganglion cells push everything else aside § Experience it every moment of our lives § Brain fills in gaps created by the blind spot • Many cells in the primary visual cortex (V1) respond to slits of light of a specific orientation o Vertical, horizontal, oblique lines or edges • Simple cells-‐ cells in the visual cortex that display “yes-‐no” responses to slits of a specific orientation o Slits need to be in a specific location • Complex cells-‐ orientation-‐specific, but their responses are less restricted to one location o Much more advanced than simple cells • Feature detection-‐ ability to use certain minimal patterns to identify objects • Feature detector cells-‐ cell that detects lines and edges • Visual info travels from V1 to higher visual areas o Association cortexes (V2) o One travels up to upper parietal o Other travels down to temporal lobe • Higher cortical regions process more and more complex shapes • Use lower visual pathway leading to temporal lobe to process color • Trichromatic theory-‐ idea that color vision is based on our sensitivity to 3 primary colors o 3 kinds of cones § Each is sensitive to different wavelengths, therefore each detects a different color o Examined colors color blind individuals could see to determine 3 primary colors o Color blindness-‐ inability to see some or all colors § Absence or reduced # of one or more types of cones stemming from genetic abnormalities or damage to a brain area § Monochromats-‐ only have 1 type of cone and lose all color vision § Dichromats-‐ have 2 cones and are missing only 1 • Red-‐green dichromats-‐ can see all colors but can’t distinguish reds well § Trichromats-‐ possess 3 different types of cones • Afterimages-‐ occur when we’ve stared at one color for a long time and then look away o Often see a different colored replica of the same image o Arise from visual cortex’s processing of info from our rods and cones o Opponent process theory-‐ theory that we perceive colors in terms of 3 pairs of opponent colors; either red or green, blue or yellow, black or white o Afterimages appear in complementary colors • Nervous system uses trichromatic and opponent processing during color vision o Different neurons rely on one principle more than the other When We Can’t See or Perceive Visually • Blindness-‐ inability to see • Majority of cases from cataracts and glaucoma are treatable • Blind rely more on other senses o Especially touch o Can devote somatosensory and visual cortexes to touch senses § Illustrates brain plasticity • Blindsight-‐ ability of blind people with damage to their cortex to make correct guesses about the appearance of things around them o Some people believe it to be ESP • Echolocation-‐ emitting sounds and listening to their echoes to determine their distance from a wall or barrier o Same parts of the brain associated with visual images in sighted people become highly active • Visual agnosia-‐ deficit in perceiving objects o Can tell the shape and color of an object, but can’t recognize or name it Hearing: The Auditory System • Audition-‐ our sense of hearing • Probably the sensory modality we rely on most to acquire info about our world Sound: Mechanical Vibration • Sound is vibration-‐ mechanical energy traveling through a medium, usually air • Disturbance created by vibration of molecules of air produces sound waves o Can travel through any gas, liquid or solid, but we hear them best when they travel through air o Can’t be sound in a vacuum • Pitch-‐ corresponds with the frequency of the waves o Higher frequency-‐ higher pitch o Lower frequency-‐ lower pitch o Frequency is measured in Hertz (Hz) • Loudness-‐ amplitude, or height, of the sound wave corresponds to loudness o Measured in decibels (dB) o Loud-‐ more mechanical disturbance (more vibrating) of airborne molecules • Timbre-‐ complexity or quality of sound that makes musical instruments, human voices or other sources sound unique Structure and Function of the Ear • 3 parts: outer, middle and inner • Outer ear-‐ o Pinna-‐ part of the ear we see o Ear canal-‐ funnels sounds to the ear drum • Middle ear-‐ o Ossicles-‐ 3 tiniest bones in the body § Hammer, anvil and stirrup § Vibrate at the frequency of the sound wave transmitting it from the eardrum to the inner ear • Inner ear-‐ o Cochlea-‐ bony, spiral-‐shaped sense organ used for hearing § Converts vibration into neural activity § Outer part is bony, inner cavity is filled with a thick fluid § Vibrations disturb this fluid and travel to the base of the cochlea, where pressure is released and transduction occurs o Organ of Corti-‐ tissue containing the hair cells necessary for hearing o Basilar membrane-‐ membrane supporting the organ of Corti and hair cells in the cochlea § Hair cells-‐ where transduction of auditory info takes place • Converts acoustic info into action potentials • Auditory perception becomes increasingly complex like visual perception • Primary auditory cortex processes different tones in different places o Each place receives info from a specific place in the basilar membrane o Hair cells located at the base of the basilar membrane are most excited by high pitched tones o Hairs at the top are excited by low pitched tones o Place theory-‐ specific place along the basilar membrane matches a tone with a specific pitch • Frequency theory-‐ rate at which neurons fire the action potential reproduces the pitch o Volley theory-‐ works for tones between 100-‐5000 Hz, sets of neurons fire at their highest rate slightly out of sync to reach overall rates up to 5000 Hz When We Can’t Hear • 1/1000 people are deaf • Deafness is caused by genetics, disease, injury or exposure to loud noises • Conductive deafness-‐ due to malfunctioning of the ear o Especially a failure of the eardrum or the ossicles • Nerve deafness-‐ damage to the auditory nerve • Loud sounds can damage our hair cells and lead to noise induced hearing loss o Accompanied by tinnitus-‐ ringing, roaring, hissing or buzzing sound in the ear • Hearing loss can also result to hearing one loud sound i.e. an explosion • Most lose hearing ability as we age Smell and Taste: The Sensual Senses • Olfaction-‐ sense of smell • Gustation-‐ sense of taste o Work hand in hand enhancing our linking of some foods and disliking of others • Chemical senses because we derive the sensory experiences from chemicals in substances • Most critical function of chemical senses is to sample food before we swallow it What are Odors and Flavors? • Odors-‐ airborne chemicals that interact with receptors in the lining of our nasal passages • Noses are veritable smell connoisseurs o Capable of detecting between 2,000-‐4,000 different odors • Can detect only few tastes o Sensitive to 5 basic tastes: sweet, salty, sour, bitter and umami (meaty/savory) o Preliminary evidence for a sixth taste for fat Sense Receptors for Smell and Taste • Humans have 1000+ olfactory genes • Each olfactory neuron contains a single type of olfactory receptor that recognizes and odorant o Lock and key concept • When olfactory receptors come in contact with odor molecules, action potentials in olfactory neurons are triggered • Detect taste with taste buds-‐ sense receptor in the tongue that responds to sweet, salty, sour, bitter, umami and perhaps fat o Papillae-‐ bumps on tongue that contain numerous taste buds o Separate taste buds for sweet, salty, sour, bitter and umami • Myth that “tongue taste map” describes a tongue’s sensitivity to different flavors o Weak tendency for individual taste receptors to concentrate in certain locations • Taste is biased strongly by our sense of smell o We find certain foods “delicious” because of their smell • Supertasters-‐ people with a marked overabundance of taste buds o About 25% of people Olfactory and Gustatory Perception • Perception of smell and taste are sensitive • After odors interact with the sense receptors in the nasal passages, info enters the brain, reaching the olfactory cortex and parts of the limbic system • After taste info interacts with taste buds, it enters brain, reaching the gustatory cortex, somatosensory cortex and parts of the limbic system • Region of frontal cortex is a site of convergence for smell and taste • Analyze the intensity of a smell and determine whether it’s pleasing o Amygdala help us distinguish pleasant from disgusting smells • Taste can also be pleasant or disgusting o Tasting disgusting food and seeing faces of disgust activate gustatory cortex o Persons who experience damage to gustatory cortex don’t experience disgust • Emotional disorders can distort taste perception o Serotonin and norepinephrine make us more sensitive to taste o Antidepressants enhance tastes • Smells play a strong role in sexual behavior o Especially in animals o Mice that can’t smell don’t bother to mate o Pheromones-‐ odorless chemical that serves as a social signal to members of one’s species § Alter our sexual behaviors o Vomeronasal organ-‐ located in the bone between the nose and the mouth, to detect pheromones § Doesn’t develop in humans § Causes some to suggest humans are insensitive to pheromones o Nerve zero-‐ enable pheromones to trigger responses in the “hot-‐button sex regions of the brain” When We Can’t Smell or Taste • 2 million Americans suffer from a disorder of taste, smell or both • Gradual loss of taste and smell can be part of normal aging • Losses can also result from disease, such as diabetes and high blood pressure • Damage to olfactory nerve can damage our sense of smell and ability to identify odors • Losing our sense of taste can also produce negative health consequence Our Body Senses: Touch, Body Position and Balance • Somatosensory-‐ sense of touch, temperature and pain • Proprioception-‐ kinesthetic sense, body position sense • Vestibular sense-‐ sense of equilibrium or balance The Somatosensory System: Touch and Pain • Responds to stimuli applied to the skin o Light touch or deep pressure o Hot/cold temp o Chemical or mechanical injury that produces pain • Stimuli can be very specific o Braille • Damage to internal organs sometimes causes “referred pain”-‐ pain in a different location o Pain in left arm during a heart attack • Sense touch with specialized nerve endings located on the ends of sensory nerves in the skin • Free nerve endings-‐ more plentiful than specialized nerve endings o Sense touch, temperature and especially pain • Nerve endings are distributed evenly across the body’s surface o Most are in our fingertips o Then lips, face, hands and feet o Have the fewest in our middle back • Info about touch, temp and pain travel in our somatic nerves before entering the spinal cord • Touch info travels more quickly than pain info • Touch informs us of our immediate surroundings and keys us into urgent matters • Pain alerts us to take care of injuries, can often wait a little while • Touch and pain info activate local spinal reflexes before reaching the brain o After activating spinal reflexes, touch and pain travels upward through parts of the brain stem and thalamus to reach the somatosensory cortex § Additional cortical areas active for touch info are association areas of the parietal lobe • Many types of pain perception relate to the pain-‐causing stimulus o Thermal, chemical or mechanical • Threshold-‐ point at which we perceive it as painful o Each type of pain-‐producing stimulus has a threshold • Pain has an emotional component o Pain info goes to the somatosensory cortex and partly to limbic centers in the brain stem and forebrain o Experience of pain is frequently associated with anxiety, uncertainty and helplessness • Scientists believe we can control pain through our thoughts and emotions o Gate control model-‐ idea that pain is blocked or gated from consciousness by neural mechanisms in spinal cord § Functions as a “gate” controlling the flow of sensory input to the CNS § Account for how pain varies from situation to situation depending on our psychological state • Become so absorbed in an activity that we forget about pain § The stimulation we experience competes with and blocks the pain from consciousness § Pain demands attention o Brain controls activity in the spinal cord, allowing us to turn up, damp down, or ignore pain o Placebo effect exerts strong response on pain § Stimulate the body to produce endorphins-‐ natural pain killers • Phantom limb-‐ pain or discomfort felt in an amputated limb o 50-‐80% of amputees feel phantom limb sensations o Missing limb feels as if its in an uncomfortably distorted position o Mirror box-‐ treatment for phantom limb § Position other limb so it’s reflected in the position the amputated limb would assume § Patient performs “mirror equivalent” of the exercise the amputated limb needs to relieve a cramp or get comfortable § Illusion must be realistic in order to relieve pain/discomfort • Some people can’t feel pain • Pain serves an essential function • Pain insensitivity-‐ unable to detect painful stimuli o Inherited o Extremely rare o Dangerous • Indifference to painful stimuli-‐ identify the type of pain, but experience no discomfort from it Proprioception and Vestibular Sense: Body Position and Balance • Proprioception-‐ our sense of body position o Kinesthietic sense o Helps us keep track of where we are and move efficiently • Vestibular sense-‐ sense of equilibrium and balance o Sense of equilibrium o Sense and maintain our balance as we move about • Sense of body position and balance work together • Proprioceptors-‐ sense muscle stretch and force o We can tell what our bodies are doing, even with our eyes closed o Stretch receptors-‐ embedded in our muscles o Force detectors-‐ embedded in or muscle tendons o Info enters the spinal cord, travels up the brain stem to the thalamus to reach the somatosensory and motor cortexes, then our brains combine info from our muscles and tendons to obtain a sense of our body’s location • Semicircular canals-‐ 3 fluid filled canals in the inner ear responsible for our sense of balance o Located in inner ear o Sense equilibrium and help us maintain our balance o Reaches parts of the brain stem that control eye muscles and triggers reflexes that coordinate eye and head movements o Travels to the cerebellum, which enables us to catch our balance o Vestibular sense-‐ balancing § Not heavily represented in the cerebral cortex § Awareness of this sense is limited § Become aware only when we lose our balance or experience dramatic mismatches between vestibular and visual imputs Ergonomics: Human Engineering • Human factors-‐ optimizes technology to better suit our sensory and perceptual capabilities • Ergonomic-‐ worker-‐friendly • We use our knowledge about human psychology and sensory systems to build ergonomic tools and gadgets of trade Perception: When Our Senses Meet Our Brains • Our brain pieces together what’s in our sensory field, what was just there a moment ago, what we remember from our past • Sacrifice small details in favor of crisp and more meaningful representations Parallel Processing: The Way Our Brain Multitasks • Parallel processing-‐ the ability to attend to many sense modalities simultaneously o Bottom-‐ up processing-‐ processing in which a whole in constructed from parts § Perceiving an object on the basis of its edges § Starts with raw stimuli and ends with synthesizing them into a meaningful concept § Begins with activity in the primary visual cortex, followed by processing in the association cortex o Top-‐down processing-‐ conceptually driven processing influenced by beliefs and expectancies § Starts with our beliefs and expectations, which we then impose on the raw stimuli we perceive § Starts with processing in association cortex, followed by processing in the primary cortex o Two kinds of processing work together Perceptual Hypotheses: Guessing What’s Out There • We try to get by with as little neural firepower as we can • Perceptual set-‐ set formed when expectations influence perceptions o Example of top-‐down processing o May perceive a letter as an “H” or an “A” depending on the surrounding letters around it o Tend to perceive the world in accord with our preconceptions • Perceptual consistency-‐ process by which we perceive stimuli consistently across varied conditions o Without it we’d be hopelessly confused because we’d be seeing the world as continually changing o Brain allows us to correct from these minor changes o Size consistency-‐ ability to perceive objects as the same size no matter how far they are from us § Friend walking away from us-‐ image becomes smaller § Brains mentally enlarge figures far away from us so they appear more like similar objects in the same scene o Shape consistency-‐ allows us to recognize a stimulus by it’s shape § We can recognize a door whether it’s open, barely open, or closed o Color consistency-‐ ability to perceive a color consistently across different levels of lighting § Firefighter’s jackets look yellow even in low lighting § Base our colors on the surrounding context • Subjective contours-‐ brain providing missing info about outlines • Gestalt principles-‐rules governing how we perceive objects as wholes within their overall context o Help explain why we see much of our world consisting of unified figures or forms rather than confusing jumbles of lines and curves o Provide a roadmap for how we make sense of our perceptual world o Proximity-‐ objects physically close to each other tend to be perceived as unified wholes o Similarity-‐ we see objects as comprising a whole, much more so than dissimilar objects § Lining up red and yellow dots-‐ perceive rows o Continuity-‐ perceive objects as wholes, even if other objects block them o Closure-‐ when partial visual info is present, our brain fills in what’s missing o Symmetry-‐ perceive objects that are symmetrically arranged as wholes more often than those that aren’t o Figure-‐ground-‐ make an instantaneous decision to focus attention on what we believe to be the central figure and ignore the background • Bistable image-‐ an image we can perceive in 2 ways o Vase and 2 faces looking at each other o Emergence-‐ perceptual gestalt that almost jumps out from the page and hits us all at once • We perceive motion by comparing visual frames o Like film in a movie moving at rapid motion to create movement • Can perceive motion when it’s not there • Phi phenomenon-‐ illusory perception of movement produced by the successive flashing of images o Flashing lights that circle around a movie marquee • Motion blindness-‐ disorder where patients can’t seamlessly string still images processed by their brains into the perception of ongoing motion o “frames” of motion are missing o interferes with simple tasks, like crossing the street • Depth perception-‐ ability to judge distance and 3-‐D relations o Enables us to reach for a glass and grasp it rather than knock it over o Need to have some idea of how close or far we are to from objects to navigate around our environments o Monocular depth cues-‐ stimuli that enable us to judge depth using only 1 eye § Relying on pictorial cues to give us a sense of what’s located where in stationary scenes • Relative size-‐ more distant objects look smaller than closer objects • Texture gradient-‐ texture becomes less apparent as objects move away • Interposition-‐ closer object blocks our view of an object behind it • Linear perspective-‐ outlines of rooms or buildings converge as distance increases • Height in plane-‐ distant objects tend to appear higher, nearer objects lower • Light and shadow-‐ objects cast shadows that give us a sense of their 3-‐D form § Motion parallax-‐ ability to judge the distance of moving objects from their speed • Nearby objects seem to move faster than those far away o Binocular depth cues-‐ stimuli that enable us to judge depth using both eyes § Binocular disparity-‐ each eye sees the world a bit differently • Left and right eyes transmit quite different info for near objects • See distant objects similarly • Brains use info to judge depth § Binocular convergence-‐ focusing on objects reflexively using our eye muscles to turn our eyes • Our brains are aware of how much our eyes are converging and use this info to estimate difference • We can judge depth as soon as we learn to crawl o Visual cliff-‐ a table and floor several feet below, both covered by ch
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