Object Perception Flashcards
Set 7 Wk5 L2
Object perception
involves obtaining a description of
shape, size, material composition, etc. from light
information
Object recognition
the matching of some description obtained by perception with something previously stored in memory
“Basic level” recognition
categorization, such as “chair”
Grouping / Unit Formation
the brain must group different parts of the retinal image in order to identify an object
Segmentation
how the brain separates the visible world into separate objects
*problem: we don’t know how the brain does it, even before perception occurs
Object perception
extracting a description of shape, color, size, material composition, etc. from sensory/light information
–> traditionally thought of as lower level processing
Object recognition
the comparison of some description obtained by perception with something previously stored in memory
- previously stored information can be a category, such as “chair” …or an instance, such as “my favorite lounge chair with the big cushions.”
- most research on object recognition involves categorization (so-called “basic level” recognition)
*all recognition research presupposes some description
obtained from perception.
–> traditionally thought of as higher level processing b/c it involves memory
Basic Level Recognititon
Most research on object recognition involves categorization (so-called “basic level” recognition)
e.g. “chair”
Specialized Categorization/Recognition
subordinate level under a basic categorization
e.g. office chair instead of just chair
Important edges are given by differences in…
- luminance
- color
- motion
- depth
- texture
*the brain must rely on statistics, educated guesses
Junction detection and classification (T, X, L, Y)
Occluding edges usually have “T” junctions
Transparency signaled by “X” junctions
Object corners have “L” junctions
Corners of 3D Objects hav “Y” junctions
Gestalt principles
Classical approach to explaining brain’s process for Segmentation and Grouping in Object Perception Tasks
- -> Gestalt = overall form (put together, organized structure)
- -> Perception of a WHOLE thing( e.g., object, scene, etc) is more than the sum of its parts
Gestalt Principles
- Good continuation
- Similarity
- Proximity
- Common fate
- Closure
- Symmetry
- Simplicity or good figure
Gestalt Principle of Good Continuation
continuous forms are favored over discontinuous ones
Gestalt Principle of Similarity
similarity can group things together (e.g. size, shape, orientation, etc)
Gestalt Principle of Proximity
being close to each other can help group
Gestalt Principles of Common Fate
things that move together tend to be grouped together
Gestalt Principles of Closure
the perceptual system favors things that are closed rather than all over the place
*perceiving a connection or continuity between elements
which do not touch each other
*the tendency to complete figures even when part of the information is missing
Gestalt Principles of Symmetry
symmetrical shapes are perceived collectively.
Gestalt Principles of Simplicity or Good form
interpretations that consist of simple objects are preferred over interpretations that consist of complex objects
Gestalt Principles of Figure-ground
some objects are perceived as figure and some as
ground, but never both at the same time
(jazz musician vs face example)
RSVP
rapid serial visual presentation
firing of images in a series, participant is given a task of pressing a button when they see a specific image
rate: 50/100 milliseconds is enough time to perform this task (shocking) –> object perception is fast!
Why is the speed of object perception considered controversial?
The rate of processing through the pipeline may be fast, but the time needed to process an object might be slower (estimated to be about 500 milliseconds/half a second)
Problem of Occlusion
There are different fragments in the visual field that belong to an object, but are occluded by another object
- -> the brain must know which fragments belong to which object (grouping)
- -> we don’t know how the brain does grouping
