Motion perception Flashcards
True or False?
Many animals have very poor depth, shape, colour perception but none lack the ability to perceive movement
True
What are the 6 main functions of motion?
1) Attracts our attention
2) Provides information about an object’s 3-D shape
3) Helps segregate figures from the ground and perceptual organisation (common fate)
4) Breaks camouflage (freeze reflex)
5) Provides information that enables us to actively interact with the environment
6) Informs of your heading and time to collision, your movement as well as other objects
How does movement attract our attention?
Active or Passive
Movement helps with common fate.
What is common fate?
Information that helps segregate figure from the ground and perceptual organisation
Movement helps with freeze reflex.
What is freeze reflex?
Breaking camouflage
What stimulus suggests that we do not need to be able to recognise an object in order to see it move and we do not need to match edges and contours between successive views of an object?
Random dot kinematograms
What do Random dot kinematograms suggest about motion and form perception?
1) We do not need to be able to recognise an object in order to see it move
2) We do not need to match edges and contours between successive views of an object
What problem highlighted by RDKs suggests that motion detection is direct?
Correspondence problem
What does the correspondence problem suggest?
Motion detection is direct
Simply = We cannot imagine a visual system matching point for point over time in these displays
What are the 5 Ways to make a spot of light move?
1) Real movement
2) Apparent movement
3) Induced movement
4) Autokinetic movement
5) Movement aftereffects
What is real movement?
When the light physically moves
i.e. The spot of light is physically displaced from one place to another
When the light physically moves
i.e. The spot of light is physically displaced from one place to another
This is known as…?
Real movement
When and how do we perceive real movement of light?
1) When the eyes are stationary so that the image moves across the retina
2) When an image moves across the retina, it stimulates a series of receptors
3) There are neurons in the visual system that respond best when a stimulus moves in a particular direction
When an image moves across the retina, it stimulates a series of receptors
What are these called?
Movement detectors
How do movement detectors respond to movement?
Excitation and inhibition interact to create a neuron/cell that responds only to movement from right to left
True or False?
Motion detectors and neural circuit detect movements in every direction and speed
False
Motion detectors and neural circuit detect movements of a specified direction and speed
What happens when something moves in the proper direction that the neuron/cell responds to?
Two signals meet at the same time, which induces a strong response from the neuron/cell
What happens when something moves in the wrong direction that the neuron/cell responds to?
There would be no response from the neuron/cell
What happens when something moves at the wrong speed/timing is off?
There would be no response from the neuron/cell
How do we perceive light coming from the other direction that is not right to left?
Change the order of the delay
How do we perceive light coming at different speeds?
Change the spacing of the detectors
Bigger separation/spacing of the detectors allows for the detection of …… motion
a. Slower
b. Faster
b. Faster
Which cells in humans are sensitive to different orientations, speeds and directions of movement?
Cells in the cortex
Cells in the cortex are sensitive to 3 things
What are they?
- Different orientations of movement
- Speed of movement
- Direction of movement
What is the Aperture problem?
Many different motions on the retina could cause the same response in a single motion-sensitive neuron with a small receptive field
Different directions of motion can appear identical when viewed through an aperture
E.g. The aperture problem can be demonstrated by looking at a moving image through a small hole – the aperture. Different directions of motion can appear identical when viewed through an aperture. For example, looking at the three moving lines through an aperture, most people perceive all three lines as moving from the upper left to the lower right. In reality, the lines are moving in different direction.
The output of all detectors must be integrated at some stage (Medial Temporal Area)
This is known as…?
Aperture problem
Many different motions on the retina could cause the same response in a single motion-sensitive neuron with a small receptive field
Different directions of motion can appear identical when viewed through an aperture
This is known as…?
Aperture problem
What does the Aperture problem suggest about the output of all detectors?
They must be integrated at some stage
As the correlated movement of random dots increased, neurons in the medial temporal area fired …?
a. More
b. Less
a. More
Real movement mostly has worked focused on determining factors that influence 2 things
What are they?
1) Threshold for perceiving movement
2) Perception of velocity
What is the threshold for detecting movement?
Depending on an object and its surroundings
e.g. with the dot and surroundings (add vertical lines in space between A & B, lower threshold)
If a dot has to travel 3 cm and is viewed from 30 cm away, what would be the threshold for detection?
1/6th to 1/3rd of a degree of visual angle per second (14 seconds)
If a dot has to travel 3 cm and is viewed from 30 cm away in front of a vertically-striped background, what would be the threshold for detection?
As low as 1/60th of a degree of visual angle per second (280 seconds)
How do we lower the threshold of movement detection?
Adding more things to the surroundings
e.g. adding vertical lines in the background of a dot
What is the perception of velocity affected by? List 2 things
1) Surroundings
2) The size of both the moving object and the framework through which it moves
e.g. A cat in a large cage must move faster than a mouse in a small cage if they are to appear to move at the same speed
1) Surroundings
2) The size of both the moving object and the framework through which it moves
What do these affect?
Perception of velocity
1) Surroundings only
What do these affect?
The threshold for movement detection
A cat in a large cage must move faster than a mouse in a small cage if they are to appear to move at the same speed
This is an example of…?
Perception of velocity
The bigger the object, the …. you perceive its velocity
a. Slower
b. Faster
a. Slower
The smaller the object, the …. you perceive its velocity
a. Slower
b. Faster
b. Faster
A larger circle has to travel twice as ….. to appear at the same speed as a smaller circle
a. Fast
b. Slow
a. Fast
Movement detectors cannot explain when…? List 2 things
1) There is no movement on the retina
2) When you perceive no movement when there is movement on retina
What does it mean by no movement on the retina?
When you follow a moving object with your eyes, your eye movements keep the object’s image stationary on the fovea
When you follow a moving object with your eyes, your eye movements keep the object’s image stationary on the fovea
This is known as…?
No movement on the retina
What does it mean by perceiving no movement when there is movement on the retina?
When you move your eyes to look at different parts of the scene or as you walk through a scene
When you move your eyes to look at different parts of the scene or as you walk through a scene
This is known as…?
Perceiving no movement when there is movement on the retina
What mechanism does motion perception need?
A mechanism that tells us whether retinal stimulation results from the movement of stimulus, movement of the observer or both
What does the Helmholtz’s outflow theory suggest?
Rather than comparing image motion on the retina with eye muscle movement, the comparison should be made with the signal from the brain that tells the eye muscle to move
Rather than comparing image motion on the retina with eye muscle movement, the comparison should be made with the signal from the brain that tells the eye muscle to move
Which theory suggests this?
Helmholtz’s Outflow theory
Describe how Helmholtz’s Outflow theory works
1) There out an outgoing/efferent signal from the brain to the eye muscles telling them to move
2) There are ingoing/afferent movement signal from the retina
3) The brain comparator decides whether to signal the eye to move or not move
What does the brain comparator do?
Decides whether to perceive movement in the world or no movement
What does the brain comparator do?
Decides whether to perceive movement in the world or no movement
How does the brain comparator decide whether to perceive movement in the world or no movement?
If afferent (ingoing signals from the retina) signals cancels out efferent signals (outgoing signal to eye muscles), the comparator would signal no movement
If there is a mismatch, movement is perceived
If there is a difference between muscle movement command and movement of an image across the retina then we do not perceive movement
True or False?
False
If there is a difference between muscle movement command and movement of an image across the retina then we perceive movement
e.g. when tracking a car, the eyes move but the retinal signal remains stationary, therefore perceive the movement of the car
When tracking a car, the eyes move but the retinal signal remains stationary, therefore perceive the movement of the car
This is an example of …?
Helmholtz’s Outflow theory
In terms of Helmholtz’s Outflow theory, how we perceive movement?
When there is a difference between muscle movement command and movement of an image across the retina
Why do we perceive no movement when we look around the world?
Eye movement command and retinal image movement are equal so we perceive no movement
What are the 3 main convincing evidence for the Helmholtz outflow theory?
- Afterimages move when we move our eyes (eye muscle movement signals no retinal movement).
- The world moves when we passively wobble our eyes (retinal movement, no eye muscle movement signal)
- Immobilizing eye-ball results in attempted eye movement leading to the apparent movement of the world in the opposite direction (eye movement signal, no retinal movement)
Afterimages move when we move our eyes when there is…?
a. Retinal movement and eye muscle movement signal
b. Eye muscle movement signal and no retinal movement
c. Retinal movement and no eye muscle movement signal
d. No eye muscle movement signal and no retinal movement
b. Eye muscle movement signal and no retinal movement
Immobilizing eyeball results in attempted eye- movement leading to the apparent movement of the world in the opposite direction when there is…?
a. Retinal movement and eye muscle movement signal
b. Eye muscle movement signal and no retinal movement
c. Retinal movement and no eye muscle movement signal
d. No eye muscle movement signal and no retinal movement
b. Eye muscle movement signal and no retinal movement
The world moves when we passively wobble our eyes when there is…?
a. Retinal movement and eye muscle movement signal
b. Eye muscle movement signal and no retinal movement
c. Retinal movement and no eye muscle movement signal
d. No eye muscle movement signal and no retinal movement
c. Retinal movement and no eye muscle movement signal
What is apparent movement?
Stroboscopic movement
The illusion of movement between two lights by flashing one light on and off, waiting for between 40 & 200 msec, then flashing the other light on and off
The illusion of movement between two lights by flashing one light on and off, waiting for between 40 & 200 msec, then flashing the other light on and off
This is known as…?
Apparent movement
Apparent movement is also known as…?
Stroboscopic movement
What happens when one light flashes on and off less than 30 msec from a second light?
a. No movement perceived
b. Partial movement
c. Optimum movement
d. Beta and phi movement
a. No movement perceived
What happens when one light flashes on and off 30-60 msec from a second light?
a. No movement perceived
b. Partial movement
c. Optimum movement
d. Beta and phi movement
b. Partial movement
What happens when one light flashes on and off 60 msec from a second light?
a. No movement perceived
b. Partial movement
c. Optimum movement
d. Beta and phi movement
c. Optimum movement
What happens when one light flashes on and off 60-200 msec from a second light?
a. No movement perceived
b. Partial movement
c. Optimum movement
d. Beta and phi movement
d. Beta and phi movement
What is beta movement?
When you perceive consecutive blinking dots/lights from one side of the screen to another as a continuous movement of one dot
While movement appears to occur between the two lights, it is difficult to actually perceive an object moving across the space between them
This is known as…?
Beta movement
What is phi movement?
When you perceive the consecutive blinking of lights/spots from one side of the screen to the other as “objectless movement”; there is perceived movement but the dot appears to blink out, thus the objectless of objectless motion.
What happens when one light flashes on and off above 200 msec from a second light?
a. No movement perceived
b. Partial movement
c. Optimum movement
d. Beta and phi movement
a. No movement perceived
What happens when one light flashes on and off less than 30 msec from a second light?
a. No movement perceived, simultaneous
b. No movement perceived, successive
a. No movement perceived, simultaneous
What happens when one light flashes on and off above 200 msec from a second light?
a. No movement perceived, simultaneous
b. No movement perceived, successive
b. No movement perceived, successive
True or False?
Slow apparent motion is specified
False
Slow apparent motion can be ambiguous
Apart from the interval between the flashing of one light to another, what other factor affects the perception of apparent movement?
Distance between two lights
In terms of apparent movement, as the distance between two light increase, what 2 things must be increased to maintain the same perception of movement?
1) Time interval
2) Intensity of the flashes
What is induced movement?
Surround a spot of light with another object and then move this object
Simply = An illusion of movement that occurs when a small stationary stimulus is surrounded by a large moving stimulus
Simply = When moving object may cause another object to look like it is moving
Surround a spot of light with another object and then move this object
Simply = An illusion of movement that occurs when a small stationary stimulus is surrounded by a large moving stimulus
Simply = When moving object may cause another object to look like it is moving
This is known as…?
Induced movement
The small object appears to move, while the large object appears to be still
This is an example of…?
Induced movement
The appearance of real motion from a sequence of still images
This is known as…?
Apparent motion
Beta (apparent) motion involves an object appearing to move …
a. Continuously
b. Objectless motion
a. Continuously
Phi (apparent) motion involves an object appearing to move…?
a. Continuously
b. Objectless motion
b. Objectless motion (due to blinking)
Apparent motion is the basis of our sense of motion in watching …?
Videography and animation
Sitting on a train and feeling it move backwards when you’re actually sitting still and the train next to you is moving forward is an example of what type of movement?
Induced movement
When moving object may cause another object to look like it is moving
This is known as…?
Induced movement
What is autokinetic movement?
When a stationary, small point of light in an otherwise dark or featureless environment appears to move
When a stationary, small point of light in an otherwise dark or featureless environment appears to move
This is known as…?
Autokinetic movement
Turn out all room lights. When the surrounding framework of the room is not visible, the small stationary light appears to move, usually in an erratic path
This is known as…?
Autokinetic movement
In a study by Sherif, when presenting an individual with a small point of light in a dark room, how far did the individual report the light moving?
0.8 - 7.4 inches
In a study by Sherif, when presenting a group of Ps with a small point of light in a dark room, how far did the group report the light moving?
4 inches
True or False?
The autokinetic effect is open to suggestion
True
Why does the autokinetic movement/illusion occur?
Our control of eye muscles may not be completely stable in dark (knowing where our eyes are and how stable they are may be difficult in dark)
What are movement after-effects?
When the visual image caused by prior exposure moves in the opposite direction
e.g. when one looks at the rocks beside a waterfall they may appear to drift upwards after one has viewed the flowing water for a short period
When the visual image caused by prior exposure moves in the opposite direction
e.g. when one looks at the rocks beside a waterfall they may appear to drift upwards after one has viewed the flowing water for a short period
This is known as…?
Movement after-effects
If an observer first views a pattern moving in one direction and then views the spot of light, the spot (and surroundings) will appear to move in the opposite direction
This is known as…?
Movement after-effects
Based on movement after-effects, if an observer first views a pattern moving in one direction, and then views the spot of light, the spot (and surroundings) will appear to move ….?
a. In the same direction
b. In the opposite direction
b. In the opposite direction
The waterfall illusion is an example of…?
Movement after-effects
In an experiment by Anstis & Gregory, what did the results support
Supports the idea of movement detectors, which respond only to the movement across the retina
What did Hubel and Wiesel identify in relation to the ratio hypothesis of motion after-effects perception?
Identified directionally specific motion detectors
What did Sutherland argue in relation to the ratio hypothesis of motion after-effects perception?
Motion after-effects arose from an imbalance in the ratio of activities from two sets of directionally-tuned receptors, each sensitive to the opposite directions of motion
Simply = In the visual cortex of the brain, there are motion detectors or direction-selective cells. They fire action potentials in response to motion in their preferred direction. When you observe motion in a specific direction for an extended period, these cells become adapted or fatigued, reducing their level of firing.
After adaptation, when you are presented with a stationary image, the cells that were previously stimulated by the adapted motion show reduced firing compared to the cells that were not as strongly stimulated. This imbalance in firing rates leads to a perception of motion in the opposite direction to the previously adapted motion. It is as if the brain overcompensates for the reduced firing in one set of cells by perceiving motion in the opposite direction.
What does Sutherland’s ratio hypothesis imply?
It states that motion is coded by taking the ratio between the outputs of detectors tuned to opposite directions
What are the 3 types of event perception?
- Movement provides information about 3-D shapes
- Movement helps us segregate figures from the ground
- Movement interacts with the environment
When a global moving pattern surrounds a high-contrast stationery or slowly moving target stimulus, the target disappears and reappears alternately for durations of several seconds
This is known as…?
Motion induced blindness
What is motion-induced blindness?
- When a global moving pattern surrounds a high-contrast stationary or slowly moving target stimulus
- The target disappears and reappears alternately for durations of several seconds
If you are driving at a high speed on a highway and if you fix your gaze on the road straight ahead, you may not be able to see a car, a scooter, a buggy, a bicycle, a buffalo or even a human being approaching from the side
This is known as…?
Motion induced blindness
