Motion perception Flashcards
What is motion in the retina defined as?
A change in retinal illumination at the speed of the moving object and it’s spatial frequency
What is the temporal frequency equation?
Temporal frequency (cycles/sec) = spatial frequency (cycles/degree) x velocity (degrees/sec)
Why is motion perception needed?
Detection of predators/prey
Detection of peripheral moving objects/draw our attention to them
Interact with the environment and coordinate movement
Determine 3D shape and depth
What are the types of motion?
Real
Apparent
Induced
What is real motion?
Motion detected by movement of a stimulus against a background
Can be perceived when:
Eyes and head are still but object moves across VF
Eyes and head are still but you move past a stationary object
Object is moving and eyes/head move to follow it, keeping the image still on the retina.
What is apparent motion?
Motion is perceived from a series of still images that recorded real motion at regular intervals - e.g. videos
What is apparent motion dependent on?
Temporal resolution
What is the temporal modulation transfer function?
Temporal contrast and frequency determine the smoothness of apparent motion (i.e. if you can see flicker or not)
What is induced motion?
Feeling of motion induced by motion of another object - e.g. feeling of movement on a stationary train due to another train moving
What are the types of apparent motion?
Beta
Phi
What is Beta apparent motion?
Movement of the stimulus at a steady pace - gives perception of object itself moving
What is Phi apparent motion?
Movement of the stimulus at a rapid pace - gives perception of movement around stimulus
Why does the wagon wheel effect occur?
The rate at which the wheel is moving exceeds the temporal frequency of the eye or camera (vision is made to be or display is discontinous), and visual system fills in missing info to create continuous movement
