LECTURE 4- OBJECT RECOGNITION Flashcards
What is object recognition?
The process of identifying objects that surround us.
What is perception?
The process of discovering what is present in the world and where it is, based on sensory input.
Why is perceptual organization necessary?
Retinal images are disorganized, like a mosaic, and need to be structured for object recognition.
What are the key components of perceptual organization?
Figure-ground segregation and grouping elements into patterns or objects.
What is figure-ground segregation?
Identifying one object as the figure while the rest forms the background.
What are bottom-up processes?
Stimulus-driven processes independent of cognitive factors.
What are top-down processes?
Cognition-driven processes influenced by prior knowledge.
What is Gestalt psychology?
A school of thought emphasizing perception as a whole, rather than as individual components.
What are the “laws” of perceptual organization?
Principles like similarity, proximity, closure, and continuity, guiding how elements are grouped.
What is the principle of similarity?
Similar elements are grouped together perceptually.
What is the principle of proximity?
Elements close to one another are grouped together.
What is the principle of closure?
The mind completes incomplete shapes to form a whole.
What is the principle of continuity?
Smooth curves or continuous patterns are grouped together.
What is the vase-face illusion?
A classic example of figure-ground segregation where the figure alternates between a vase and two faces.
What are natural scene statistics?
Physical regularities in the environment, like edges being vertical or horizontal, aiding perceptual processing.
What is the “light from above” assumption?
The brain assumes light sources come from above, influencing perception of depth and shadows.
What is Marr’s theory of object recognition?
A computational model involving stages like primal sketch, 2.5D sketch, and 3D model to recognize objects.
What is a primal sketch?
A 2D description of light intensity changes, such as edges and boundaries.
What is a 2.5D sketch?
A representation of surfaces with depth and orientation based on texture, motion, and binocular disparity.
What is a 3D sketch?
A view-independent description of an object’s structure used for recognition.
What are generalized cones?
Basic shapes that objects can be decomposed into, forming the foundation of Marr’s structuralist approach.
What is Biederman’s theory of object recognition?
It extends Marr’s model by introducing geons, or 3D components, as building blocks of objects.
What are geons?
Simple, non-accidental features that are invariant across views and form the basis of object recognition.
What is the difference between recoverable and non-recoverable degraded objects?
Objects can be recognized if their non-accidental features are preserved.
What is viewpoint independence?
The ability to recognize objects regardless of the angle of view, as proposed by structuralist theories.
What is viewpoint dependence?
Recognition performance varies with changes in the object’s orientation or angle.
What is agnosia?
A neurological condition where object recognition is impaired despite intact vision.
What are the two types of agnosia?
Apperceptive agnosia (perceptual deficit) and associative agnosia (interpretation deficit).
What brain area is affected in apperceptive agnosia?
The posterior right hemisphere.
What brain area is affected in associative agnosia?
The bilateral occipitotemporal junction.
What is prosopagnosia?
The inability to recognize faces, often due to damage in the fusiform gyrus.
What is the Thatcher illusion?
A phenomenon where inverted faces appear normal, highlighting the brain’s specialization for upright faces.
What did Kanwisher et al. (1997) discover?
Specialized brain areas, like the fusiform gyrus, are activated by faces.
What is visual imagery?
“Seeing with the mind’s eye,” or forming mental images without direct sensory input.
What happens in mental rotation tasks?
Response times increase with the angular disparity between objects, indicating mental simulation of rotation.
How are visual perception and visual imagery related?
They rely on similar brain mechanisms, as shown by cases like cerebral achromatopsia.
What are the key stages in object recognition discussed in the lecture?
Perceptual organization, object recognition, brain systems, face recognition, and visual imagery.
What is the significance of structuralist theories in object recognition?
They provide a framework for understanding how objects are broken down and reconstructed for recognition.
What is the main challenge in object recognition?
Structuring disorganized retinal images into recognizable objects through perceptual processes.
