Lecture 1: Theories of Visual Processing Flashcards
What is a bottom-up view of perception?
Perception is ‘direct’, where information hitting the retina was incredibly rich.
Why was Gibson’s ecological approach termed ecological?
Gibson believed perception should only be studied in a natural environment. Computer-generated stimuli don’t produce the rich information that we should get in a natural environment.
What is an ambient optic array?
Input to perception and describes the structure of light that is reflected from textured surfaces. It is composed of angles reflected from surfaces into the eyes. As the observer moves, the ambient optic array changes.
What are invariants
They are contained in the ambient optic array and provide unambiguous information about the environments can be ‘picked up’ or perceived directly.
What is an example of an invariant?
The horizon ratio relation, so how much of an object is above/below the horizon in the optic array will be constant with distance. If there is a change in proportion of object about/below horizon, must indicate change in size
What are texture gradients and what are they an example of?
How the texture changes in an image tells us about how the surface is varying in distance, orientation and curvature. They are an example of invariants, because no matter what the texture is, the elements will be distorted in the same way by the same change in shape of the surface.
Is there empirical support for invariants?
Gibson & Bridgeman documented that ppts could correctly identify objects, state their colour, identify the lighting conditions and the objects spatial orientations just from black and white photos.
What does motion do to static scenes?
Introducing motion to a static scene highlights invariant properties
What are the two types of motion?
Due to observer movements OR due to object movement.
What is motion parallax?
Things far away move slower than things nearby - speed tells us about distance to object.
What type of cue is motion parallax?
Movement-produced - a monocular cue to depth
Who uses motion parallax the most?
Animals, meaning they don’t have much binocular overlap - head bob and orthogonal running.
What is optical flow?
Combination of parallax and retinal size
What are the practical implications of gibson’s optical flow ideas?
Horizontal lines painted on road, closing together as driver approaches junctions. These markings are often seen on the exit roads to create illusion of increasing speed, which causes the driver to slow down.
What is affordance?
All action possibilities with an object based on users’ physical capabilities
