object recognition Flashcards
The dorsal pathway is..
spatial
The ventral pathway is predominantly used to..
identify objects
3 stage model of object recognition
stage 1: local features (edge detection, contrast, etc)
stage 2: shape representation (‘blocks’, gestalt principles/feature integration)
stage 3: object representation (stored representations/knowledge)
Gestalt principles
- the whole visual percept is more than the sum of its parts
- perceptual system constantly trying to organise input
- components of an image are grouped together based upon certain visual properties, proximity & similarity
- (law of perceptual organisation)
law of perceptual organisation
“good continuation” and “closure” give rise to “illusory contours”
good continuation
we decide where each line ends due to assumptions based upon the natural world
closure
where bisecting circles end and begin are assumed based off of what we usually experience
illusionary contours
we create shapes, lines and contrast (illusions) due to assumptions
bi-stable stimulus
an image has 2 interpretations that we cannot see simultaneosly
binocular rivalry
when shown different images to each eye - we see one for a while and then the other for a while (not both simultaneously)
Template matching
template = internal representation
memory is matched against visual input
Feature analysis
low level features are analysed first
perceptual system searches for simple but characteristic features of an object
‘feature detectors’
recognition by components
uses geons
geons are viewpoint invariant and easily recoverable from a 2D image
invariant properties include cotermination and parallelism
object recognition is impaired when geons are made non-recoverable by removing termination points
