perception test 2

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perception test 2
2013-03-10 20:20:53
perception 413 test

ch. 5,6,9,10
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  1. ambiguity
    image on the retina can be caused by an infinite number of objects

    inverse projection problem
  2. challenge of object perception
    people recognize objects that are not in sharp focus
  3. viewpoint invariance
    human have the ability to recognize objects from different viewpoints
  4. structuralism
    perceptions are created by combining elements called sensations
  5. sensation
    the dots on the face are combined to form a face
  6. how does this explain our seeing things that arent really there?
    • illusory contours
    • represent edges of a cube there doesnt really exist
  7. gestalt psychology
    • whole differs from the sum of its parts
    • perceptual organization
  8. gestalt psychology
    what is perceptual organization?
    how small elements are grouped into larger objects by our brain
  9. gestalt laws of perceptual organization
    1. law of simplicity/good figure/pragnanz: stimulus is perceived in such a way that the resulting figure is as simple as possible

    2. law of similarity: similar things appear to be grouped together

    3. law of good continuation: point that results in smoothly curving lines are seem as belonging together and the lines appear to curve in such a way that they follow the smoothest curving path.

    4. law of proximity/nearness: things that are nearer appear to be grouped together of common fate: things that are moving in the same direction appear to be grouped together.

    6. law of meaningfulness/familiarity: things that appear meaningful are grouped together

    7. Law of common region: things that are within the same region appear to be grouped together

    8. Law of uniform connectedness: elements that are connected by properties such as lightness, color, texture, are grouped together.

    9. Law of synchrony: visual events that happen at the same time will be perceived as belonging together
  10. perceptual segregation/figure-ground segregation
    how elements are seperated from the rest of the scene
  11. reversible figure-ground
    when a seperate object usually seen as the figure stands out from its background which is the ground.
  12. what features determine which area is figure?
    figures in the lower part of a display

    for left-right displays, small preferences for left region
  13. ____when the figure area is positioned over the receptive field

    ____ when the ground area is positioned over the receptive field
    • neurons fire
    • neurons hardly fire
  14. problem with neural responses to figure and ground
    neurons have very small receptive fields, they tend to look at only a small portion of the stimulus field
  15. contextual seperation
    neurons still fire in response to figure-ground seperations
  16. top down processing
    neurons receive signals from higher areas of the visual cortex based on context and experience
  17. oblique effect
    people are sensitive to vertical and horizontal lines than to other orientations
  18. structural descriptive model
    individual 3-d volumes can be combined to create the overall shape of the object
  19. RBC
    • recognition by components model
    • we recognize 36 standard geons
  20. accidental property
    sometimes the object is oriented in such a way that they geon becomes unrecognizable
  21. geon
    geometric ion
  22. binocular rivalry
    different images on the two retinas
  23. Divided attention
    • Divided attention
    • – paying attention to a number of different things at the same time – difficult
    • to focus on any one thing
  24. selective attention
    • Selective attention
    • – focusing on specific objects of interest & ignoring others
  25. saccades
    • Eye
    • movements - saccades
  26. Between saccades eye stops momentarily to take in information_____indicate where the person is attending
  27. eye movements, 3 things
    • (1)
    • Characteristics of the scene
    • – bright colors, salience, high visibility

    • (2)
    • Picture meaning & observer
    • knowledge – scene schema (knowledge of
    • what to expect in a typical scene – e.g., office scene)

    • (3)
    • Observer’s task
    • – only fixate on areas where there is task relevant information
  28. Inattentional blindness
    • Inattentional blindness
    • – a stimulus that is not attended will not be perceived, even if a person is
    • looking at it directly!
  29. We tend to ____ based on our past experience with the environment – predict approximately what
    will happen in a particular scene
    fill in the blanks
  30. Is attention necessary for perception?
    • No
    • – if we only want to can perceive the “gist” of a scene without specific
    • details

    • BUT,
    • Yes if we want specific details
    • - only be perceived with focused attention
  31. spreading enhancement
    • When
    • attention is directed to one part of an object, enhancing effect of this
    • attention spreads throughout the object – “spreading
    • enhancement”
  32. binding
    • Binding
    • – features such as color, form, motion & location combine to create our
    • perception of the world
  33. If
    different neurons fire in response to different stimuli (remember FFA, PPA,
    EBA), how do the they combine to present an integrated view of an object?
    the binding problem
  34. feature integration theory
    • Feature integration theory –
    • at the preattentive
    • stage different features of an object
    • are separated – “what” stream & “where” stream
  35. illusory conjunctions
    • In
    • the absence of focused attention,
    • features associated with one object can be incorrectly combined with another – illusory
    • conjunctions
  36. Balints syndrome
    • Caused
    • by damage to the parietal lobe –
    • failure of attention - Balint’s
    • syndrome
  37. Synchrony hypothesis –
    •  when neurons in different
    • parts of the brain are firing in response to the same object their responses
    • will be synchronized
  38. How can we describe color?
    • Intensity
    • – brighter or dimmer

    • Saturation
    • – quantity of white
  39. selective reflection
    • Some
    • wavelengths are reflected more by some objects – chromatic colors, or hues – this property –
  40. When light reflection is flat across the spectrum – no hue
    achromatic colors
  41. Transparent objects
    selective transmission – only some wavelengths pass through
  42. Normal color vision
    • require at least three different
    • wavelengths to create a perfect match
  43. Color deficient
    perceive that they have created a match with just two wavelengths
  44. Additive
    color mixture –
    all the wavelengths stimulate cone receptors
  45. Subtractive color mixture
    • –each
    • paint reflects only one or two colors & absorbs (subtracts) the others –
    • decreases the light reaching the cone receptors
  46. Monochromat –
    • •Monochromat – can match any wavelength in the spectrum by adjusting the intensity
    • of any one other wavelength

    • Generally
    • hereditary, occurs in 10 out of 1 million people

    • Vision
    • resembles rod vision
    • in dim & bright lights

    • See
    • everything in shades of lightness/darkness –
    • white, gray, black – color blind

    • Poor
    • visual acuity – sensitive to bright lights & need
    • to wear dark glasses

    • Rod
    • system is not designed to function in bright light – overloaded under strong
    • illumination
  47. Dichromat –
    need only two wavelengths to match any other wavelength

    • Experience
    • some color – lesser range than trichromats

    • Inherited
    • through the X-chromosome – sex-linked

    • More
    • common in males since they have only one X
    • chromosome (XY)

    • Females
    • have two X chromosomes (XX), so even if one if dichromatic, the other normal
    • chromosome compensates

    • Females
    • can carry the passive gene without experiencing dichromatism
    • themselves
  48. Anomalous trichromat
    – needs three wavelengths to match any other wavelength like anynormal trichromat – BUT, will mix these wavelengths in different proportions
  49. Unilateral dichromat
    • •Unilateral dichromat – person with trichromatic vision in one eye & dichromatic vision
    • in the other eye – extremely rare
  50. Types of dichromatism
    • Protanopia
    • – 1% males & .02% females – perceive
    • short wavelengths (blue), as wavelength increases blue become gray
    • – neutral point at around 492nm, above the neutral point they abruptly switch
    • to yellow – missing long-wavelength pigment

    • Deuteranopia
    • – 1% males & .01% females – similar to protanopia,
    • but neutral point at 498 nm – missing medium-wavelength pigment

    • Tritanopia
    • – very rare, .002% males & .001% females – sees blue & red, neutral
    • point at 570nm – missing short-wavelength pigment
  51. Visualization
    & Color Scaling
    • B+Y- = increases firing to 450nm light,
    • inhibits firing to 580nm light

    • G+R- = increases firing to 510nm light,
    • inhibits firing to 660nm light

    • Y+B- and R+G- = increases firing to long wavelengths,
    • inhibits firing to short wavelengths
  52. Color constancy
    • Color constancy
    • – ability to perceive the same color under different levels of illumination –
    • memory color
  53. The Ratio Principle
    • Two
    • areas that reflect different amounts of light look the same if the ratios of
    • their intensities to the intensities of the surrounding areas remain the same
  54. Uneven Illumination
    • Reflectance
    • edge – the point where the reflectance of two
    • edges changes – (a) vs. (b)
  55. Different cues that signal depth in a scene"

    –Oculomotor cues
    –Monocular cues
    –Binocular cues
    • Different
    • cues that signal depth in a scene

    • –Oculomotor cues - based on our ability to sense the
    • position of our eyes & muscle tension

    • –Monocular cues
    • – work with one eye

    • –Binocular cues
    • – depend on two eyes
  56. convergence
    • –cross-eyed” pattern of eyes as they
    • bring the image into focus
  57. Deletion & Accretion
    Deletion & Accretion

    • –Deletion – farther object is covered by a
    • nearer object due to the sideways movement of the observer relative to the
    • object

    • –Accretion – Observer moves in the other
    • direction – object is uncovered
  58. Binocular Disparity
    –Differences in the images on the right eye & left eye
  59. Corresponding retinal points –
    • Corresponding retinal points – places on the retina that would
    • overlap if one retina could be slid on top of the other
  60. Horopter
    – imaginary circle that passesthrough the point of fixation
  61. stereopsis
    Impression of depth resulting from information provided by binocular disparity -
  62. stereoscope – concept used in 3-D movies
    Instrument designed from this principle – camera + two lenses –
  63. How does the visual system match
    the images in the left & right eye?
    correspondence problem
  64. Three different sized circles having the same visual angle
    –View test circles with one eye

    • –View test circles through a
    • peephole

    • –Adding drapes to the hallway to
    • eliminate reflection
  65. Principle of size constancy –
    our perception of an object’s size remains relatively constant even when we view an object from different distances which changes the object’s image on the retina
  66. Constancy scaling mechanism
    • – equation – as a person walksaway from you, the size of the person’s image on the retina (R) gets smaller,but
    • your perception of the person’s distance (D) gets larger. These two
    • changes balance each other – you perceive the person’ size(S) as remaining constant
  67. Afterimage
    – look constantly at a stimulus(bright light) for about a minute, blink & to focus on a blank surface –you will see an “afterimage” of the object
  68. Emmert's Law
    Farther the afterimage, larger the perceived size – Emmert’s Law
  69. veridical perception
    – perception that matches the actual physical world
  70. Mueller-Lyer Illusion
    • Misapplied size constancy scaling – cues that help us perceive 3-D
    • create illusions when applied to objects on a 2-D surface
  71. Mueller-Lyer Illusion

    Conflicting cues theory
    line perception depends on two cues

    –Actual length of lines

    –Overall length of figures

    • –The line on the right appears
    • longer because overall length of the figure is longer
  72. Ponzo Illusion
    The horizontal line on top appears longer–Depth information makes is appear farther away
  73. Ames Room
    Woman on the right appears much larger

    • The actual structure of the room is not visible when you look through a
    • peephole

    • Missing depth information – we judge relative size based on how much of the room the object
    • fills

    • Woman on the left has a much smaller visual angle than the one on the
    • right
  74. Moon Illusion
    Moon on the horizon appears much larger than when it is up in the sky

    • Horizon & elevated moons have same visual angle – but horizon moon appears
    • to be farther away since it is on the horizon (it looks closer when it is in
    • the sky directly above) – we believe the horizon moon is larger – apparent-distance theory

    • –Moon
    • appears smaller when it is surrounded by larger objects – large expanse of sky
    • – angular-contrast theory