Lecture 9 Motion Perception

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Lecture 9 - Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Conditions for Motion Perception

• is retinal image motion enough to see motion?

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Conditions for Motion Perception

• (1) fixating a point in a static environment
• no eye movements, no target motion
• (no retinal image motion --gt no motion perceived)
• (2) fixating a point while a target passes
• no eye movements, moving target
• (retinal image motion --gt motion perceived)

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Conditions for Motion Perception

• (3) moving eyes in static environment
• eye movements, no target motion
• (retinal image motion --gt no motion perceived)
• (4) tracking a moving target
• eye movements, target motion
• (no retinal image motion of target --gt motion
  perceived) 

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Conditions for Motion Perception

• (5) passive eye movements - no command from brain
• eye movements, no target motion
• (retinal image motion --gt motion perceived)
• (because this is normally whats seen in a static
  environment - see 2, above)
•  

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Conditions for Motion Perception

• (6) paralysis of e.o. muscles - command from the
  brain
• no eye movements, no target motion
• (no retinal image motion --gt motion perceived) 
• (command to look left results in leftward motion
  percept, because normally this would cause an
  expectation of RW motion)

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Conditions for Motion Perception

• is retinal image motion enough to see motion?
• No - we need to know whether eyes moved as well
• See Table 9.1

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Physiological Basis for Motion Perception

• directionally-selective cells
• selective adaptation
• motion aftereffect
• MT cells

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Wiring Diagram for motion-sensitive cell

• Slide 11

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• Slide 12 - individual neural responses

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Selective Adaptation

• motion aftereffect
• populations of directionally-selective neurons
  (neural pools)
• MT
• MST

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Selective Adaptation

• motion aftereffect
• Demo here
• www.visionscience.com/demonstrations/
• Motion Perception
• MAE

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• Slide 15 - neural pools

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• Slide 16

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• Slide 18

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• Slide 20

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Object Motion

• motion perception thresholds
• aperture problem

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Minimum Motion Threshold

• for change in position over time, (assume no eye
  movements)
• for spots of light
• lowest thresholds (ignore cognitive inference of
  movement - e.g. hands of a clock or sun's shadow)
• 1-2 min arc/sec (with landmarks)
• 10-20 min arc/sec (with no landmarks - i.e. gt 3
  deg away)

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Maximum Motion Threshold

• highest threshold (before fusion into a streak)
• 30 deg/sec

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Aperture Problem

• Demo here
• www.visionscience.com/demonstrations/
• Motion Integration
• Aperture Problem
• Barberpole illusion
• Occluded Terminators

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Vector Averaging

• Demos here
• www.visionscience.com/demonstrations/
• Motion Perception
• Plaid

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Structure From Motion

• organization of components into a meaningful
  whole
• biological motion
• random dot patterns (again)
• relative motion

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Biological Motion

• recognition of living forms
• good example of top-down influence in
  perception
• i.e. human form is very familiar

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• Slide 34

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• Slide 35

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Biological Motion

• Demo here
• www.visionscience.com/demonstrations/
• Motion Perception
• Biological Motion

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Structure from Motion

• Slide 37

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Random Dot Kinematograms

• Slide 38

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Structure from Motion

• Demo here
• www.visionscience.com/demonstrations/
• Motion Perception
• Kinetic Depth

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Apparent Motion

• correspondence problem
• animation

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Apparent Motion

• Exners spark experiment
• Demo here
• www.visionscience.com/demonstrations/
• Magni-phi
• Custom simpli-phi

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• Slide 43

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• Slide 44

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Animation

• critical flicker frequency (CFF)
• 60 Hz
• (i.e. below 60 Hz, we can detect flicker)
• 30 Hz is usually adequate min. for foveal vision

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• Slide 46

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Animation

• Demo here
• www.visionscience.com/demonstrations/
• Motion Perception
• Four-Stroke Apparent Motion

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Motion In Depth

• self motion
• optic flow field
• expansion as motion in depth (looming)
• neural basis

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Self Motion

• Slide 50

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Optic Flow Field

• Slide 51

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Object Motion

• Slide 52

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• Slide 53

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• Slide 54

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Eye Movements

• disjunctive - for fixation in depth
• convergence, divergence
• conjunctive (conjugate)
• smooth pursuit eye movements
• saccades
• saccadic suppresion
• microsaccades

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Monitoring Saccades for Suppresion

• Slide 57 - see textbook Fig. 8.8

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Why do we Move our Eyes?

• 1) shifts in attention
• 2) because of fovea
• functional fovea
• drift during fixation 2.5 arc min over 60 sec
  time period
• dead zone 5 - 15 min.

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Physiology

• 2 visual pathways
• dorsal more reflexive
• coarse, practical spatial encoding of location
• ventral more cognitive
• fine, thoughtful spatial encoding of detail

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Measuring Eye Position

• Yarbus
• search coil
• non-contacting methods

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Motion Perception

• Conditions for Motion Perception
• Physiological Basis for Motion Perception
• Object Motion
• Structure from Motion
• Apparent Motion
• Motion-in-Depth
• Eye Movements
• Visual-Vestibular Interactions

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Visual-Vestibular Interactions

• vestibular apparatus
• balance
• motion sickness

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• Slide 63