Final: Motion Perception

Question 1

What is vection? Give an example.

Answer 1

Vection is the illusion of motion of one’s entire self as a result of motion in one’s peripheral field.

Example: On the houseboat when the neighbor’s houseboat pulls out of the slip, it feels as if we are going forward.

Question 2

Is vection considered to be a category of illusory visual motion?

Answer 2

No, even though it is caused by visual stimulation.

Question 3

What is Eye/Head motion perception? Where do we get the information about the objects movement?

Answer 3

Eye/Head motion perception is when we follow an object with our head and eyes while keeping the image of the object relatively stationary on the fovea.

The information we receive has to do with muscular, oculomotor control, and vestibular systems.

Question 4

What is retinal motion perception? Where do we get the perceived movement from?

Answer 4

Retinal motion perception is the perceived motion of an object which requires the object’s image to move across the retina. The information about the object’s motion comes within the VISUAL PATHWAY.

Question 5

How can we have retinal image motion?

Answer 5

We can get retinal image motion by a stationary eye and moving target, stationary target and a moving eye, or a combo of both.

Question 6

What is the troxler effect?

Answer 6

Perception of disappearance from a stationary object.

Question 7

The human visual system is sensitive to ________ in light stimulation.

Answer 7

changes

Question 8

What is the retinal motion detection threshold?

Answer 8

Minimum amplitude of perceivable motion(The smallest distance an object can move with it being detected)

The minimum velocity of perceivable motion (the slowest an object can move with it being detected).

Question 9

True or False:

Retinal motion detection threshold changes on different areas of the retina.

Answer 9

True;

• At the fovea, approximately 20 arc seconds of movement or less
• 20 degrees from the fovea, approximately 3 arc minutes of movement
• 40 degrees from the fovea, approximately 5 arc minutes of movement

Question 10

As you get further away from the fovea, the minimum amplitude of perceivable motion ______.

Answer 10

Increases.

Question 11

At the fovea, what is the minimum amplitude of motion to perceive the motion?

Answer 11

Approximately 20 arc seconds or less

Question 12

At 20 degrees eccentricity, what is the minimum amplitude of motion to perceive the motion?

Answer 12

Approximately 3 arc minutes

Question 13

At 40 degrees eccentricity, what is the minimum amplitude of motion to perceive the motion?

Answer 13

Approximately 5 arc minutes

Question 14

Is the minimum velocity of perceivable motion better or worse when there is a stationary target near the object?

Answer 14

Perceivable motion velocity is easier to see when there is a stationary target next to the object.

Meaning the object’s minimum velocity is lower and easier to detect.

Question 15

How much better is our minimum velocity amplitude of perceivable motion when there is a stationary reference next to the object? At approximately what speed can we detect the motion of that object? If there is no stationary reference, what speed do we detect the motion?

Answer 15

10x better.
With reference = approximately 1-2 arc minutes
Without reference = approximately 10-20 arc minutes

Question 16

Can we detect motion better in high or low luminance? Why?

Answer 16

High luminance because we can see the object better.

Question 17

What is the autokinetic effect? Example?

Answer 17

Illusory motion where the background is featureless and there is a small object present. The object appears to move in random directions along a small area.

Example: A small light in a pitch-black room. The light looks like it’s moving.

Question 18

What is induced motion? In what direction is the induced motion? Example.

Answer 18

The illusion of a stationary object moving due to the movement of background objects. The induced motion is always against the movement of the background.

Example: The moon appears to move against the motionless clouds (but the clouds are the ones moving).
Also, Reverse Spoke Illusion

Question 19

What is motion contrast?

Answer 19

Special case of induced motion where it operates across very short distances.

Question 20

What does the induced motion paradox imply?

Answer 20

It implies seperate neural processing of visual information about position (parvocellular) and motion (magnocellular)

Question 21

What is motion adaptation? Give example.

Answer 21

Illusory changes in perception of motion that occur during prolonged viewing of moving objects or contours.

Example: Driving 70 on highway doesnt feel that fast after driving like that for a while.

Question 22

What is motion after-effects. Give example.

Answer 22

Illusory perception of motion of stationary objects OR changes in the perception of speed of moving objects after prolonged viewing of moving objects or contours.

Example: Looking at a school of fish circle the light at night and then looking at the dock. The dock can appear to move in a circular way like the fish.

OR

Going 80 down a highway and then getting on new road going 30. You feel like you are going extremely slow.

Question 23

What is velocity adaption? Give example.

Answer 23

Prolonged viewing of an object moving at constant velocity may cause decrease in the perceived speed of motion.

Example: Not realizing that you are speeding.

Question 24

What is direction-specific adaptation?

Answer 24

Motion detection where contrast detection thresholds increase during prolonged viewing of moving objects or contours but only for objects or contours moving in the same or similar direction.

Question 25

The direction of the motion aftereffects is ________ to the direction of adaption motion

Answer 25

Opposite

Question 26

Motion aftereffects is a ________ phenomenon. What does this mean?

Answer 26

Binocular. If one eye adapts to the motion, the other eye will automatically feel the aftereffects when viewing with only that eye.

Question 27

Describe velocity aftereffects. Give example.

Answer 27

If the field viewed after adaption contains contours moving in the same direction as those previously viewed while adapting, the velocity of those contours will appear slower.

Example: Getting off the highway on a slower road. Contours moving in same direction but feel slower

Question 28

What is 2-D directional aftereffect?

Answer 28

If the field after adaption contains contours that move more than 30 degrees of the adapted motion, the perceived direction of their motion may be altered by the adaption.

Meaning, if it moves more than 30 degrees, we might not perceive the motion aftereffect.

Question 29

Famous examples of the motion aftereffect

Answer 29

Waterfall illusion

Spiral illusion.

Question 30

What is stroboscopic motion? What is it referred to as? Give example.

Answer 30

Referred to as “Apparent Motion”
Illusory motion resulting from presentation of different stimuli close together that give the perception of one stimulus moving.

Example: (Phi motion) Movement of images on Memphis bridge. The lights are all stationary but give the appearance of movement.

Question 31

What are the types of Stroboscopic motion? Explain them.

Answer 31

Alpha Motion- illusory expansion or contraction of an object due to successive presentations of different sizes of the object.

Beta (phi) Motion- illusory motion of an object due to successive presentations at optimally spaced positions along a continuous path.

Gamma Motion- illusory expansion or contraction of an object as its LUMINANCE is increased or decreased on successive presentations.

Delta Motion- illusory (phi) motion of two stimuli in reverse direction when the luminance of one is significantly higher than that of the other. (same explanation as backward masking)

Question 32

What does Korte’s Law describe? Describe what he came up with to maintain the same phi motion.

Answer 32

describe the relationships among various stimulus parameters necessary to maintain optimum phi motion when any one parameter is changed.

If you increase the luminance:

• Increase the spatial seperation
• Decrease the interstimulus interval

If you increase the ISI (interstimulus interval)

• Increase duration
• Increase spatial seperation

Question 33

First order motion stimulus definition. Give example.

Answer 33

Motion defined by movement of areas or contours that are defined by their luminance.

Examples: Most real moving objects, phi motion

Question 34

Second order motion stimulus definition. Give example.

Answer 34

Motion defined by movement of areas whose contours or shapes are defined by texture; and NOT by luminance.

Examples: motion-defined form, coherent motion.

Question 35

Third order motion stimulus definition. Give example.

Answer 35

Motion defined by movement of areas defined as “figure” with neither luminance nor texture boundaries.

Example: motion in isoluminant displays, where the “figure” is defined by a difference in color with NO differences in luminance or luminance variance (texture).

Question 36

What is coherent motion?

Answer 36

motion of elements that all share the same velocity (direction & speed) of motion.

Question 37

What is the Gestalt organizing principal “common fate”.

Answer 37

elements may be perceptually integrated to comprise an “object”

Question 38

What demonstrates “form from motion”.

Answer 38

Identification of an “object” or shape that depends upon the characteristic of coherent motion

Question 39

What is Cyclopean motion?

Answer 39

Brain blends images of two eyes to form one image.

Question 40

What is Random Element Kinematogram (Cinematogram)?

Answer 40

coherent motion against a static random element background.

Question 41

What is Random Element Correlograms 
(Dynamic Random Element Kinematograms)

Answer 41

coherent motion against a dynamic random element background (i.e. a background in which each background element undergoes spatial displacements of random direction and/or magnitude.

Question 42

random element motion displays require solution of a “_______________”.

Answer 42

correspondence problem

Question 43

What is the correspondence problem?

Answer 43

In a random dot stereogram, which dot in one eye’s retinal image “belong with” (corresponds to) any particular dot in the other eye’s retinal image. Similarly, in a random dot correlogram, there must be some way to determine which dot in one frame of the display corresponds to any given dot in the previous frame.

Question 44

What is coherent motion threshold?

Answer 44

The minimum proportion of elements in a dynamic random element display that must undergo the same velocity (direction and speed) of motion for “coherent motion” to be just detected.

Question 45

How do you test coherent motion thresholds?

Answer 45

1) Randomly present different proportions of dots undergoing coherent motion on consecutive presentations in an n-alternative forced-choice paradigm.
2) On each presentation, the subject guesses the direction of coherent motion.
3) Calculate Frequency-of-Seeing curve and threshold proportion of coherence needed for reliable discrimination of the direction of motion.

Question 46

What do coherent motion thresholds evaluate? If there are elvated thresholds, what diseases may the patient have?

Answer 46

Evaluate MAGNOCELLULAR processeing.

Patient may have glaucoma or optic nerve disease.

Question 47

What is the minimum displacement threshold (Dmin) for 2nd order motion?

Answer 47

• minimum spatial displacement of elements necessary for the perception of stroboscopic motion.
• “displacement acuity” (a hyperacuity)
• typically a few (6 – 10) arc seconds

Question 48

What is the maximum displacement threshold (Dmax) for 2nd order motion?

Answer 48

• Typically ~ 15 arc minutes.
• Also known as the “Braddick Limit”.
• maximum spatial displacement of elements that supports the perception of 2nd-order (short-range) motion.
• larger displacements can still support (long-range) motion of 1st-order stimuli: e.g., phi motion.

Question 49

Explain Braddick’s Short-Range motion mechanism.

Answer 49

Supports 2nd-order stroboscopic motion:

• spatial displacements within the Dmin to Dmax range
• probably also supports short ( < 15 arc min) 1st-order motion
• SOA < 100 msec (stimulus onset asynchrony)
• Not perceived with dichoptic stimulation or bright ISI

Question 50

Explain Braddick’s Long-Range motion mechanism.

Answer 50

Supports 1st-order motion (e.g., continuous and phi motion):
- operates with displacement larger than Dmax

• SOA 100 - 500 msec
• works with dichoptic stimuli and with bright ISI

Question 51

Both short range and long range motion mechanisms are belived to rely heavily upon _____________- pathways.

Answer 51

Magnocellular

Question 52

Describe 3rd-order (isoluminant motion)

Answer 52

-The perception of motion for stimuli whose contours are defined only by differences in color without any luminance or texture differences, is very weak when compared with motion of stimuli defined by luminance or texture.
Any remaining (3rd-order) percept of motion in a truly isoluminant display currently is thought to most likely depend upon PARVOCELLULAR processing.

Recently proposed – much active research, many hypotheses, contradictions, and controversy

Question 53

What is motion ambiguity? GIve examples.

Answer 53

the “aperture problem”
Depending on aperature, you can change the perceived motion or direction even though actual motion does not change.

Examples: Barber pole illusion

Question 54

How does brain resolve motion ambiguity?

Answer 54

-Brain tries to average the components of motion.

Question 55

Motion perception is generated when _________ changes over a given point in space.

Answer 55

luminance

Question 56

How does figure-ground segregation resolve motion ambiguity?

Answer 56

If the elements within a figure move synchronously while those in the surround move at a different time, the figure is easily segregated from the surround and thus perceived.