Objects and scenes part 1 Flashcards
What are the two challenges of object perception? Name them
The inverse projection problem
Viewpoint invariance
What is the inverse projection problem
How to we determine the 3D object in the world from the 2D representation on the retina
Different objects can create the same 2D image
Same objects can create different 2D images
2 examples of the inverse projection problem
Rock circle
Ambiguous cylinder illusion
How does the ambiguous cylinder illusion work?
Blend circle into a square
2 sides arching up and 2 arching down
Looks like square from one angle and circle from the other
What is viewpoint invariance
Ability to recognize object regardless of the viewpoint
What is the principle of perceptual organization
Gestalt approach
What are the three examples we were given for the gestalt approach?
Pacman triangle
Dog
dot woman
What is the Gestalt approach and what are some examples?
The whole is other than the sum of its part –> what we perceive is different than just adding up components
Ex: Apparent motion, subjective color, illusory contours
What causes us to group elements together according to the gestalt approach?
Principles of perceptual grouping
What are the principles of perceptual grouping? (7) just name them
Principle of good continuation
Principle of good figure (simplicity or pragnanz)
Principle of similarity
Principle of proximity
Principle of common fate
Principle of common region
Principle of uniform connectedness
What is the principle of good continuation?
Lines tend to follow the smoothest path
What is the principle of good figure?
Stimulus patterns are seen so the resulting structure is as simple as possible
ex: olympic sign
What is the principle of similarity?
similar things appear grouped together
What is the principle of proximity?
Nearby objects appear grouped together
What is the principle of common fate?
Elements that move together appear grouped together
What is the principle of common region?
Elements that are in the same region of space appear to be grouped together
What is the principle of uniform connectedness?
A connected region with the same visual properties is perceives as a single unit
What causes us to separate elements apart according to the gestalt principle?
Principle of perceputal segregation
What is the principle of perceptual segregation?
Figure-ground segregation
Describe the properties of figure/ground separation?
Figure is more “thing-like” and memorable than ground
Figure is seen as in front of ground
Ground is more uniform and extends behind figure
Contour (border) separating figure from ground belong to figure (border ownership)
Example of figure ground separation
Rubin’s reversible face-vase
Can only see one at a time
What are 2 things that contribute to us seeing figure and ground?
Areas lower in figure are perceived as the figure
Convex shapes are seen as figure
What are the 2 characteristics of the gestalt approach
Holistic and Bottom up
What does it mean that the gestalt approach is holistic?
Characterized by comprehension of the parts of something as intimately interconnected and explicable only by reference to the whole
What does it mean that something is bottom up?
Relying primarily on the stimulus and not on past experience
What is the theory of how we group things together that relies on bottom up processing?
Recognition-by-components theory (RBC)
What is the recognition by components theory?
We perceive objects by perceiving elementary features and putting them together
Uses geons: three-dimentional volumes
When do we recognize objects according to RBC theory?
hen enough information is available to identify its geons
How is the RBC theory different than gestalt
more specific and quantitative
How do we determine the geons (4 characteristics)?
Discriminability
Resistance to visual noise
Distinctiveness
Invariance
What is discriminability?
Geons can be distinguished from other geons from almost all viewpoints
What is resistance to visual noise?
Geons can be percieved even if it is partially blocked
What is invariance?
Recongize no matter the surface markings, illumination direction, and texture
What is distinctiveness?
36 different geons have beeen identified
How do we recognize objects using geons?
By recognizing geons and their relationship –> relationships matter because 2 objects can have the same geons but be different
What does the RBC theory work well for?
Man made objects
Do we need all the geons to recognize an object? Give an example?
We can recognize an object from a subset of geons
Is an airplane is made of 9 geons we can still identify it very well with 6 geons (96%) and 3 geons (78%)
Low error rate
What is a principle related to geon recognition
Principle of componential recovery
What is the principle of componential recovery?
Key to object recognition is not the amount of information, but the ability to indentify components (geons)
What is an example of componential recovery?
You have more error rates when you can’t see geons even if the amount of information available is identical
What is the neural network model of RBC and what are its characteristics?
JIM (jim and Irv’s model)
Neurally inspired
Multi-layered –> deep
Purely bottom up –> no recurrent connections
Builds up from small details to overall object
What does the first layer of JIM represent? What area does this?
Edges
V1 recognizes lines and ends
What does the second layer of JIM represent?
vertices, blobs, and axes
What are vertices?
Connected paths like an arrow or a Y
What happens higher up in the JIM layers?
Determine how pieces relate to eachother and determine geons
Single node at the top activates for a single object
What are the nodes at the top of JIM?
Nodes that activate for a single object
