Temporal Vision: Motion Perception Flashcards
What is motion?
A continuous change in an object’s location as a function of time.
How is motion experienced on a retinal level?
Motion is the change in retinal illuminance for that area of the retina that occurs at a rate which depends on the speed at which an object moves, and its spatial frequency composition.
What is temporal frequency experienced by the retina equal to?
Temporal frequency (cycles / sec or Hz) experienced by area of retina = velocity (deg / sec) x spatial frequency (cycles /deg)
True or False- Ability to detect motion is dependent on temporal resolution of visual system.
True
When is temporal resolution at its highest?
At medium flicker frequency at high contrast.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/588/976/a_image_thumb.png?1614590082)
What are the benefits of motion perception/ purposes of motion perception?
Motion perception evolved early.
Associated with survival: detection of predators and prey in periphery (stops predators being able to sneak up on you.
Helps determine 3D shapes as we look around them.
Allows us to interact with environment and to co-ordinate our movement with that of moving objects.
What are the 5 types of motion?
Real Motion
Apparent Motion
Induced Motion
Motion After Effect
Optic Flow
Describe real motion
The physical stimulus is moving against its background e.g. a car is moving across a street.
We will still see this object as moving even if we fixate on the car (so that the image of the car is stationary on our retina) (because the background changing indicates it is moving).
What is apparent motion?
What is an example of the use of apparent motion?
The illusion of motion produced by looking at a rapid succession of static images.
Basis of films, cartoons, TV, advertising.
What are the two types of apparent motion?
Beta and Phi
What is beta motion?
The illusion of smooth movement from one location to the other due to steady stimulus pace e.g. if you had two lights next to eachother and switched one on and off after each other it would appear as if the light jumps from right to left.
What is phi motion?
The perception of flickering lights but no smooth movement between the two because of the rapid pace at which the lights flash e.g. it would be like having two lights next to eachother that you turn on and off one after the other but because you switch them on and off so fast the lights don’t appear to jump from one location to the other , rather they are just perceived as two flickering lights.
What is induced motion?
Movement of one object (usually larger one) induces perception of motion of another object.
e.g. Trains on platform (feeling that your train is moving when it’s actually the neighbouring one)
Clouds against moon on windy night (these can make the moon also look like it is moving)
What is the motion after effect?
If one stares consistently at movement in a particular direction, subsequently viewed stationary scenes briefly appear to move in the opposite direction.
[It is also called the ‘waterfall’ effect]
What is optic flow?
As an observer moves through the world there is a gradual shift in the pattern of light (optic array) around them.
As we walk down the street optic array elements (light from environment) flow past on all sides.
This is Optic Flow. It is caused by relative movement between observer and environment.