Perception Exam 3
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88 terms
Terms | Definitions |
|---|---|
 Functions of color | Object recognition Color facilitates object recognition Easier to recognize object in original color than object in different color Signals Natural (bananas getting old) or man-made (traffic light) Evolution Color helps us pick out objects within scenes |
| Visible light | Visible light 400-700 nanometers Electromagnetic spectrum |
| Wavelength | Colors of objects result from the wavelengths reflected from objects into eyes Some wavelengths reflected more than others |
| Selective reflection | Visible light hits an object (like grass) and green is reflected and all other colors are absorbed. |
| Hue | Experience of chromatic color |
| Chromatic color | Some wavelengths reflected more than others Basic colors-Red, yellow, blue, green |
| Achromatic color | All wavelengths reflected equally |
| Saturation | Amount of white in a color (when add white to a color decreases saturation or de-saturated) Intensity -influences perception of brightness Varying hue, saturation, & intensity 1 million discriminable colors |
| Trichromatic Theory | Young-Helmhotz theory (1800s) Color vision depends on 3 different kinds of receptors in the eye Each with different spectral sensitivities Particular wavelength stimulates each of the 3 receptor mechanisms to different degrees Pattern of activation determines color Behavioral Evidence (leads to) Color Matching Presented with color in test field Adjust 3 wavelengths in comparison field until it matches test field Color Matching Results: All colors could be made by using different proportions of 3 wavelengths All of the colors could NOT be made when given only 2 wavelengths People cannot tell the difference between same colors made of 1 wavelength and those made of 3 wavelengths Physiological Evidence Pattern of responding-color perception |
| Monochromats | Colorblind Usually only rods Perceives achromatic colors only Poor visual acuity and sensitive to light |
| Dichromats Protanopia Deuteranopia Tritanopia | Not everyone has 3 types of cones 8% of males 5% of females are color deficient Dichromats-Perceive a range of colors Missing 1 types of cone Protanopia-missing long wavelength cones Difficulty interpreting their perception: Unilateral dichromat Normal vision in 1 eye/dichromatic vision in the other eye Deuteranopia-missing medium wavelength cone Tritanopia-missing short wavelength cones |
| Opponent Process Theory Opponent neuron | Behavioral Evidence -afterimages (red/green, blue/yellow, flag) -describing "pure" colors -visualization of color combos -colorblindness People who have trouble seeing green also have trouble seeing red Certain colors are paired together (opposite on the color wheel) Hering: 3 mechanisms that respond in opposite ways Black vs. White Red vs. Green Blue vs. Yellow Opponent Neuron Responds with an excitatory response to light from one part of the spectrum and an inhibitory response to light from another part of the spectrum Different theories: Trichromatic=receptor Opponent process=neuron With increased exposure: -Neurons on left that respond to GREEN (G+R-) fatigue stop firing. -Neurons on right that respond to RED (R+G-) fatigue stop firing. On white paper: Green (G+R-) on left / Red (R+G-) on right still not firing Red (R+G-) on left & Green (G+R-) on right Fresh from not having fired, fire spontaneously. Relative amount of activation creates afterimages. |
| Color constancy | Perception that chromatic colors remain the same even under changing illumination |
| Chromatic adaptation | Prolonged exposure to a particular wavelength |
| Influence of memory on color | The effect of surroundings Memory for color |
| Lightness constancy | Lightness-perception of the shade of achromatic colors (white, gray, black) Lightness constancy-we see whites, grays, and blacks as staying about the same shade under different illuminations Perceptual system has to account for uneven illumination In the real world, perceptual system must distinguish between: Reflectance edges: differences in the reflectance of two surfaces Illumination edges: differences... |
| Oculomotor cues Accomodation Convergence | Cues based on our ability to sense the position of our eyes and the tension in our eye muscles. Are created by (1) convergence, the inward movement of the eyes that occurs when we look at nearby objects, and (2) accommodation, the change in the shape of the lens that occurs when we focus on objects at var- ious distances. |
| Monocular cues | Monocular cues work with only one eye. They include accommodation, which we have described under oculomotor cues; pictorial cues, which is depth information that can be depicted in a two-dimensional picture; and movement- based cues, which are based on depth information created by movement. |
| Occlusion | Occlusion occurs when one object hides or par- tially hides another from view. |
| Relative height | Objects that are below the horizon and have their bases higher in the field of view are usually seen as being more distant |
| Relative size | When two objects are of equal size, the one that is farther away will take up less of your field of view than the one that is closer. |
| Perspective convergence Vanishing point | When parallel lines extend out from an observer, they are perceived as converging—becoming closer together—as distance increases. |
| Familiar size | When we judge distance based on our prior knowledge of the sizes of objects. |
| Atmospheric perspective | Occurs when more distant objects appear less sharp and often have a slight blue tint. The farther away an object is, the more air and particles (dust, water droplets, airborne pollution) we have to look through, making objects that are farther away look less sharp and bluer than close objects. |
| Texture gradient | Elements that are equally spaced in a scene appear to be more closely packed as distance increases. |
| Motion parallax | Occurs when, as we move, nearby objects appear to glide rapidly past us, but more distant objects appear to move more slowly. Thus, when you look out the side window of a moving car or train, nearby objects appear to speed by in a blur, whereas objects on the horizon may appear to be moving only slightly. |
| Deletion & accretion | Deletion and accretion are related to both motion par- allax and overlap because they occur when overlapping sur- faces appear to move relative to one another. They are espe- cially effective for detecting the differences in the depths of two surfaces. Covering the right hand is deletion. Uncovering is accretion. Close one eye. Position your hands out as shown in Figure 10.9, so your right hand is at arm's length and your left hand at about half that distance, just to the left of the right hand. Then as you look at your right hand, move your head sideways to the left and then back again, keeping your hands still. As you move your left hand will appear to move back and forth, covering and uncovering your right hand. |
| Binocular cues | Cues that depend on two eyes. |
| Binocular disparity | Is the difference in the images in the left and right eyes. The following demonstration illustrates this difference. |
| Corresponding retinal points | The places on each retina that would overlap if one retina could be slid on top of the other. |
| Horopter | Which is an imaginary surface that passes through the point of fixation and indicates the location of objects that fall on corresponding points on the two retinas. |
| Angle of disparity | Carole's image falls on the lifeguard's retinas when he is looking at Frieda. Frieda's image falls on corresponding points F^L and F^R. Carole's images fall on noncorresponding points C^L in the left eye and C^R in the right eye. Note that if you slid the retinas on top of each other, point C^L would not overlap with point C^R. The difference between where Carole's image falls on the right eye (C^R) and the corresponding point is called the angle of disparity. See Figure 10.13 |
| Stereopsis/stereoscope | Stereopsis-the impression of depth that results from information provided by binocular disparity. Stereoscope-An example of stereopsis is provided by the depth effect achieved by the stereoscope, a device introduced by the physicist Charles Wheatstone (1802-1875), which produces a convincing illusion of depth by using two slightly different pictures. Presents two photographs that are made with a camera with two lenses separated by the same distance as the eyes. The result is two slightly different views. The stereoscope presents the left picture to the left eye and the right picture to the right eye. This creates the same binocular disparity that occurs when a person views the scene naturally, so that slightly different images appear in the left and right eyes. The binocular disparity created by two pictures creates a perception of depth. |
| Visual angle | Is the angle of an object relative to the observer's eye. |
| Eclipse | An example of size perception that is determined by visual angle is our perception of the sizes of the sun and the moon, which, due to a cosmic coincidence, have the same visual angle. The fact that they have identical visual angles becomes most obvious during an eclipse of the sun. Although we can see the flaming corona of the sun surrounding the moon, as shown in Figure 10.32, the moon's disk almost exactly covers the disk of the sun. If we calculate the visual angles of the sun and the moon, the result is 0.5 degrees for both. As you can see in Figure 10.32, the moon is small (diameter 2,200 miles) but close (245,000 miles from Earth), whereas the sun is large (diameter 865,400 miles) but far away (93 million miles from Earth). Even though these two celestial bodies are vastly different in size, we perceive them to be the same size because, as we are unable to perceive their distance, we base our judgment on their visual angles. |
| Size constancy | This principle states that our perception of an object's size remains relatively constant, even when we view an object from different distances, which changes the size of the object's image on the retina. |
| Size-distance scaling/equation | The link between size constancy and depth perception has led to the proposal that size constancy is based on a mechanism called size-distance scaling that takes an object's distance into account. Size-distance scaling operates according to the equation S=K(R*D), where S is the object's perceived size, K is a constant, R is the size of the retinal image, and D is the perceived distance of the object. (Since we are mainly interested in R and D, and K is a scal- ing factor that is always the same, we will omit K in the rest of our discussion). According to the size-distance equation, as a person walks away from you, the size of the person's image on your retina (R) gets smaller, but your perception of the person's distance (D) gets larger. These two changes balance each other, and the net result is that you perceive the person's size (S) as remaining constant. |
| Muller-Lyer illusion | The right vertical line in Figure 10.36 appears to be longer than the left vertical line, even though they are both exactly the same length. Size constancy normally helps us maintain a stable perception of objects by taking distance into account. Gregory proposes, however, that the very mechanisms that help us maintain stable perceptions in the three-dimensional world sometimes create illusions when applied to objects drawn on a two-dimensional surface. We can see how misapplied size constancy scaling works by comparing the left and right lines in Figure 10.36 to the left and right lines that have been superimposed on the cor- ners in Figure 10.37. Gregory suggests that the fins on the right line in Figure 10.37 make this line look like part of an inside corner, and that the fins on the left line make this line look like part of an outside corner. Because inside cor- ners appear to "recede" and outside corners "jut out," our size-distance scaling mechanism treats the inside corner as if it is farther away, so the term D in the equation S=R*D is larger and this line therefore appears longer. (Remember that the retinal sizes, R, of the two lines are the same, so per- ceived size, S, is determined by the perceived distance, D.) |
| Conflicting cues theory | Which states that our perception of line length depends on two cues: (1) the actual length of the vertical lines, and (2) the overall length of the figure. |
| Ponzo illusion | In the Ponzo (or railroad track) illusion, shown in Figure 10.41, both animals are the same size on the page, and so have the same visual angle, but the one on top appears longer. According to Gregory's misapplied scaling explanation, the top animal appears larger because of depth information provided by the converging railroad tracks that make the top animal appear farther away. Thus, just as in the Müller-Lyer illusion, the scaling mechanism corrects for this apparently increased depth (even though there really isn't any, because the illusion is on a flat page), and we perceive the top animal to be larger. |
| Ames room | Causes two people of equal size to appear very different in size. In Figure 10.42, you can see that the woman on the right looks much taller than the woman on the left. This perception occurs even though both women are actually about the same height. The reason for this erroneous perception of size lies in the construction of the room. The shapes of the wall and the windows at the rear of the room make it look like a normal rectangular room when viewed from a particular observation point;actually shaped so that the left corner of the room is almost twice as far from the observer as the right corner. The construction of the room causes the woman on the left to have a much smaller visual angle than the one on the right. |
| Moon illusion Apparent distance theory Angular-size contrast | Moon Illusion-when the moon is on the horizon,it appears much larger than when it is higher in the sky. This enlargement of the horizon moon compared to the elevated moon. Apparent Distance Theory-the moon on the horizon appears more distant because it is viewed across the filled space of the terrain, which contains depth information; but when the moon is higher in the sky, it appears less distant because it is viewed through empty space, which contains little depth information. Angular-Size Contrast-states that the moon appears smaller when it is surrounded by larger objects. |
| Sound wave | Pattern of air pressure changes spreading out through the air (or other medium) Physical-pressure changes in the air or other medium Perceptual-experience of hearing Functions: Survival Communication Pressure changes move Air molecules stay in about the same place Pure Tone-Pressure change corresponding to mathematical sine wave |
| Amplitude | Size of pressure change Loudness Measured in decibels |
| Frequency | Number of times per second that pressure changes repeat Pitch Measured in Hertz (Hz) 1 Hertz=1 cycle per second Most sounds=combination of frequencies NOT pure tones |
| Range of hearing (for humans) | 20Hz-20,000Hz Sensitivity to frequency varies |
| Parts of the ear | Outer Ear: Pinna Auditory canal Tympanic membrane Middle Ear: Ossicles Malleus Incus Stapes Oval window Inner Ear: Cochlea Scala vestibule Scala tympani Cochlear partition Organ of Corti Hair cells Cilia Basilar membrane Tectorial membrane Auditory nerve |
| Pinna | Part we can see |
| Auditory canal | Acts like a funnel, redirecting sound waves (hollow tube) |
| Tympanic membrane | Ear drum: Transmits vibrations Keeps middle ear at constant temp Protects middle/inner ear structures |
| Ossicles | 3 bones in middle ear 3 smallest bones in body Amplify vibration: Concentrate vibration onto smaller area |
| Malleus | (Hammer) 1st bone in Ossicles |
| Incus | (Anvil) 2nd bone |
| Stapes | (Stirrup) 3rd bone |
| Oval window | Membrane that covers inner ear |
| Cochlea | Liquid filled structure (green) 2 havles: Scala vestibuli Scala tympani |
| Scala vestibule | (On top light pink) |
| Scala tympani | (On bottom darker pink) |
| Cochlear partition | Separates Scala V and Scala T From Base (towards middle ear) to Apex (end) |
| Organ of Corti | Hair cells (inner and outer) |
| Hair cells | Receptors for hearing |
| Cilia | Part of the hair cells that bend to produce electrical signals Bending of cilia begins the transduction process Our ability to hear is from the bending of the cilia |
| Basilar membrane | Supports Organ of Corti (on bottom) When cilia bends the BM moves up and down |
| Tectorial membrane | Extends over the top of the hair cells When cilia bends the TM moves side to side |
| Auditory nerve fibers | Axons of neurons, send info to the brain |
| Resonance | Sound waves reflected back from closed end of auditory canal interact w/ sound entering the canal. (Outer Ear) |
| Signaling different frequencies | Place Theory and traveling wave Timing and phase locking |
| Place Theory & traveling wave | Place Theory: Which nerve fibers are firing Frequency indicted by place along Organ of Corti where nerve firing is highest Traveling Wave: Virbration of the basilar membrane where the peak of the vibration travels from the base to the apex Structure of basilar membrane: Narrower and thinker at base Wider and thinner at the apex P.T.-peak of the traveling wave depends on the frequency of sound Low frequency-max vibration at apex High frequency-max vibration at base |
| Timing & phase locking | Frequency also represented by the timing of neural firing Fibers fire in bursts and the timing corresponds to the frequency of the sounds stimulus Phase locking: Neurons always fire at the same point in the sound stimulus (at the peak) Neurons do not fire every single time it's at the peak The auditory nerve fibers fire when the cilia are bent to the right Groups of fibers fire with periods of silent intervals creating a pattern of firing |
| Hearing impairment Factors Prevalence | Cortical Impairment to the ear itself: Noise induced hearing loss Presbycusis (hearing loss due to aging) Prevalence-10 million Americans (6 million under 65 and .5 million children) (Men more likely-60%) High frequency sounds tend to be the first sound range that are lost |
| Hearing aid | Auditory system not effective enough at passing the vibrations to cochlea Amplifies sound |
| Cochlear implant | Required when the hair cells themselves are damaged 1. Microphone-receives sound info, transforms into electrical signals 2. Sound Processor-picks out certain frequencies associated with speech 3. Transmitter 4. Receiver 5. Electrode-shock to signal the appropriate frequencies |
| Auditory localization | Ability to perceive object location based on sound Azimuth-left to right Elevation-up and down Distance-how far away |
| Binaural cues | Based on info that reaches both ears |
| Interaural time difference | Difference in time it takes for sound waves to reach each ear |
| Interaural level difference | Difference in sound pressure (intensity of) reaching each ear fased on location |
| Acoustic shadow | Decrease in intensity caused by head being in the way for high frequency sounds |
| Monaural cue Spectral cue | Monaural cue: Cue that depends on info from only 1 ear Sound waves bounce off pinna and head Differences in how sounds bounce off folds within pinna creat different freq Important for determining ELEVATION Elevation judgements=worse if smoothing ear molds in ear Spectral cue: Locaiton info provided by spectrum (or distribution) of frequencies reaching ear Even with: decreases at 7,000 and 10,000 Hz 40* below: decreases at 6,000, 11,000, and 14,000 Hz |
| Auditory scene | Array of sound sources in environment Auditory scene analysis: Ability to separate the stimuli produced by different sources into separate preceptions |
| Principles of auditory grouping | Location: Sounds from a source come from 1 location Or follow a continuous path Similarity of Pitch: Sounds with similar pitch are grouped together Auditory Stream Segregation: Ability to separate acoustic stimuli into different perceptual streams |
| Proximity in time | If tones are too far apart in time segregation will not occur, even when the tones are similar in pitch. If two sounds start at different times, it is likely that they came from different sources. |
| Good continuation | Sounds that stay constant or that change smoothly are often produced by the same source. Sound stimuli with the same frequency or smoothly changing frequencies are perceived as continuous even when they are interrupted by another stimulus. |
| Direct sound | The sound reaching your ears directly, along path A. |
| Indirect sound | The sound reaching your ears later, along paths like B, C, and D. |
| Precedence effect | We perceive the sound as coming from the source that reaches our ears first. |
| Echo threshold | ... |
| Visual capture | Sound appears to be coming from the apparent visual source of the sound, even if it actually originates from another location. |
| Synesthesia | ... |
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