14. perceptual organization Flashcards
Perceptual organization def?
how we make sense of all the stimuli we perceive so we can identify them and understand the world around us
visual system’s process of dealing with complex, overlapping scenes to make object recognition possible
Image clutter?
A characteristic of visual scenes in which many objects are scattered in 3-D space, with partial occlusion of various parts of objects by other objects.
Object familiarity?
we can recognize (almost instantly) many different types of familiar objects by matching the mental representation of an object in front of us with a representation from our memory
ex. we can recognize our own suitcase, or recognize A general suitcase
Object variety?
we have the ability to distinguish between an enormous variety of objects within one category
ex. diff. types of trees
Viewpoint invariance?
We can recognize an object from many different viewpoints
Diff. retinal images can be projected by the same object –> we can still recognize them
5 basic steps of perceptual organization? (**NOT necessarily sequential)
A. Represent edges
B. Uniform regions bound by edges
C. Divide regions into figure/ground, assign border ownership
D. Group regions with similar properties
–> “figure” –> candidate objects
–> “ground” –> background
E. Fill in missing edges & surfaces
Simplicity meaning?
- simplicity = the number and placement of SHAPES composing an image
- visual system is highly BIASED to interpret an image in the simplest way it can
- an image will be perceived as the fewest shapes possible
Assign border ownership meaning? Important for what other step?
- determine what object the border belongs to
- perception that an edge (border) is “owned” by a particular region of the retinal image
- important for figure-ground
Edge extraction* meaning?
- edges = abrupt, elongated changes in brightness and/or color
- The process where the visual system IDENTIFIES / determines the location, orientation, and curvature of edges in the RETINAL IMAGE
–> NOT edges of individual objects (yet)
Uniform connectedness meaning?
- a characteristic of REGIONS of the retinal image that have approximately uniform properties
- represented within edges
Figure-ground organization?
What is figure and what is ground?
- figure is more “thing” like, perceived as part of an object
- ground is perceived as part of background
- SURROUNDED objects are usually seen as figure
- figure is often IN FRONT of ground
Factors that contribute to perception of figure-ground?
- depth (in front of the other thing)
- surrounded-ness
- symmetry
- convexity
- meaningfulness (suggests there is object recognition BEFORE figure-ground identification in this case)
Neural basis for fig/ground? Where?
What 2 images/graphs/studies explain this?
- Cells in V2 respond to info ab border ownership, assignment, and fig-ground
- single cell recording in monkeys shows cells with preferred orientations that are more sensitive to figures when they’re on one side of the receptive field
- fMRI in humans (pinwheel experiment) shows V2 cells got fatigued, but showed more activity when the image changed borders
–> brain perceives the borders differently in V2
Why is V2 important?
- we know info ab fig-ground happens in V2
- V2 is relatively EARLY in the visual processing stream
Perceptual grouping def?
- The process by which the visual system COMBINES (groups) diff. regions of the retinal image that “go together” based on SIMILAR PROPERTIES.
- Combining image regions (parts) into wholes
