Object Recognition Flashcards
MIddle Vision
Involves perception of edges and surfaces
determins which regions of an image should be grouped together into objects.
Edge Detection
a sudden change in brightness, color, texture- also called a contour
Which cells are involved in edge detection?
Cells in V1- tuned to detect edges with different orientations and width.
How good is Computer based edge detection
Not as good as humans- sometimes they dont find enough edges or sometimes they find too much
What are illusary Contours?
An edge that we perceive that is not actually present.
What does middle vision find?
- important edges and ignores others & edges that are not physically present
What is Gestalt Grouping?
A set of rules that describe when elements in an image will appear to group together.
What are the Gestalt Grouping Rules?
Good continuation Similarity Proximity Parallelism Symmetry
Common region
Connectedness
Common fate
Synchrony
What is good continuation?
a. Elements group to form smoothly continuing lines.
What is similarity?
a. Objects that are similar to each other, group together.
What is proximity?
a. Objects that are close to each other group together.
What is parallelism?
a. Elements that are parallel group together
What is Symmetry?
a. Elements that are symmetrical to each other group together.
What is Common Region?
a. Elements perceived to be part of a larger region group together.
What is Connectedness?
a. Elements that are connected to each other group together.
What is common fate?
a. Elements that move in the same direction group together.
What is Synchrony?
a. Elements that change at the same time group together.
What is a perceptual committee?
Many different and sometimes competing principles are involved in perception.
What is the Pandemonium Model?
Developed by Oliver Selfridge (1959).
Perceptual committee made up of “demons”
Demons loosely represent neurons.
Each level is a different brain area.
What are ambiguous figures?
A visual stimulus that gives rise to two or more interpretations of its identity or structure.
- Neckar Cube
What are the rules of the perceptual committee?
Honor physics and avoid accidents.
What is an accidental viewpoint?
A viewing position that produces some regularity in the visual image that is not present in the world.
How do the perceptual committees describe accidental viewpoint?
Perceptual committees assume viewpoints are not accidental.
What is figure?
a foreground object.
What is ground?
the background.
What is figure ground assignment?
The process of determining what parts of an image belong to the figure and what parts belong to the ground.
What are the gestalt figure ground assignment rules?
Surroundedness
A surrounding region is likely to be ground.
Size
A smaller region is likely to be figure.
Symmetry
A symmetrical region tends to be seen as figure.
Parallelism
Regions with parallel edges tend to be seen as figure
What is occlusion?
an object blocking another
What does relatability have to do with occlusion?
The degree to which two line segments appear to be part of the same contour
What is the global superiority effect?
The properties of the whole object take precedence over the properties of parts of the object.
What is an non accidental viewpoint?
A feature of an object that is not dependent on the exact (or accidental) viewing position of the observer.
What are some nonaccidental features?
- t-junction
- y junction
- arrow junction
What is the template theory?
The proposal that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same “shape” in the brain.
What are some problems with the template theory?
You can recognize an infinite number of different shapes as the same object
What is a structural description?
A description of an object in terms of the nature of its constituent parts and the relationships between those parts.
What is recognition by components?
Objects are recognized by their parts and how those parts fit together
What are geons?
(“geometric ions”):
3-dimensional primitives.
Any object can be built out of them.
What is viewpoint invariance?
A property of an object that doesn’t change when an observer changes viewpoint.
What are some problems with the RBC?
One is that object recognition is not completely viewpoint-invariant.
Are there multiple recognition comittees?
Perhaps there are several object recognition processes, depending on the category level.
Entry-level category: For an object, the label that comes to mind most quickly.
Subordinate-level category: A more specific term for an object.
Superordinate-level category: A more general term for an object.
What is prosopagnotia?
An inability to recognize faces.
What is agnosia?
A failure to recognize objects despite being able to see them.
What part of the brain is used in object recognition?
Extrastriate cortex
The region of cortex bordering V1.
Includes multiple areas involved in visual processing.
What is the infertomporal pathway?
Part of the cerebral cortex in the lower portion of the brain.
Important for object recognition
Part of the “what” pathway
What happens when the IT pathway is injured?
leads to agnosia
