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21 Cards in this Set
- Front
- Back
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The Aperture Problem
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The ambiguity present in the response of an individual motion detector, caused by the limited spatial extent of its receptive field; true stimulus direction cannot be determined uniquely.
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What 4 things are true about the Aperture Problem
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- It can be resolved by motion integration
- It can be seen with real and apparent motion - It is caused by the limited receptive field size of motion detecots - It demonstrates that responses in local motion detectors are ambiguous |
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What mechanism of motion integration will account for motion in a rigid planar surface?
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Velocity space model
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What is Velocity Space?
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A graph in which arrows or vectors represent motion signals; the length of each vector specifies the speed of a signal, and angle specifies direction.
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What evidence is there that shows motion integration does involve some form of velocity space computation.
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- Studies of plaid stimuli (made by superimposing two gratings drifting in diff directions.
The apparent direction of the plaid agreed w/ the direction predicted by the velocity space model of integration. |
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Kinetic depth
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Using the motion of an object to derive an impression of its 3D shape from a 2D image.
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What is the most appropriate model for motion integration in rigid 3D objects
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Motion based model
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In motion based theories 3D structure is inferred from what?
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The retinal velocities of points in the image provided by simple motion detectors, rather than from their positions.
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Biological Motion
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The perception of a moving form, either human or non-human, when the body is visible only by means of light points attached to fundamental joints
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What are some things that are true about biological motion
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- It can be seen at exposure durations less than 200ms
- It can be used to determine gender - It can be perceived by cats and infants - It can activate cells in the superior-temporal sulcus |
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Perceptual Inference Theory
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Motion perception can arise from perceptual problem solving
(explains y something appears n disappears in apparent motion) |
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Attention based theory of perception
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When features that have been paid attention to change they cause the perception of motion.
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Random-dot Kinematogram (RDK)
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A two frame sequence containing pseudorandomly arranged dots; some or all dots shift location in one frame relative to the other to offer a signal for motion detection
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What are the possible perceptions of Neuhaus's classical display using a pair of flashing lights
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- Seeing good apparent motion
- Seeing two lights flash simultaneously - Seeing apparent Succession ie. one light flashing after the other. |
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What is Dmax in RDKs
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It is the maximum displacement that supports motion
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What did the empirical dichotomy b/w RDK data and classical apparent motion lead to?
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The proposal that two separate processes mediate the perception of apparent motion, "short range" and "long range" systems - Known as the Two-Process theory.
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What do Random-dot kinematograms and Classical displays originally show evidence for
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RDK -> short range process (involves neural detectors)
Classical displays -> long range process (high-level processing) - However short range appears to extend into the stimulus range for long |
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First order motion detectors
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A motion stimulus containing shapes/patterns defined by variations in luminance.
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Second-order motion display
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A motion stimulus containing shapes/patterns defined by variations in texture, with no corresponding variation in luminance.
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What are some true things bout Second-order motion display
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- They have extra processing before the comparator
- More MT cells than V1 cells respond to this motion - A filter-rectify-filter mechanism would detect texture-defined borders - Their displays have moving texture-defined shapes - Second order motion is not seen by first-order detectors. |
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What are some evidence for the existence of Second-order motion detectors?
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- Second Order RDKs support motion
-Recordings from monkey n cat cortical cells are sensitive to second order motion - Adaptation effects occur w/ second order motion displays. |
