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How do we perceive objects and backgrounds? (LAW OF GESTALT PSYCHOLOGY…
How do we perceive objects and backgrounds?
Relevant features
= typical features of an object-->
perceptual object
= object we are looking at and therefore perceiving
OBJECTS AND BACKGROUND
Perceptual segregation
= distinction between objects between object and background
Figure-ground segregation
= distinction between
figure
(=object) and
gorund
(=background)
Reversible figure-ground
= when the ground can be the figure and vice versa
Interposition
= figure partially hidden
figures
in front
border ownership
= borders between figure and ground, attributed to figure
more detailed
in lower part of image
symmetrical
smaller than ground
parallelism
dark areas
familiarity
Extrinsic contours
= parts hiding figure
Intrinsic contours
= parts of figure
Subjective contours
= contours not present but appearing to be there because of extrinsic contours
LAW OF GESTALT PSYCHOLOGY
Law of proximity
= close elements --> part of same figure
Principle of common region
= elements in same area grouped together
Principle of synchrony
= events happening together --> grouped together
Law of similarity
= similar objects grouped together
Law of familiarity
= things forming familiar patterns grouped together
Law of good continuation
= objects appearing to go in same direction --> grouped together
Law of common motion
= when objects moving together --> grouped together
Law of closure
= when contours surrounding a space --> perception of figure
Law of Pragnanz
= we want to make the world seem as simple as possible
THEORIES
Computational theory
(Marr)
Object's image on retina
Identification of edges and primitives =
Raw primal sketch
The primitives are grouped and processed =
2 and a half D sketch
Perception of object in 3 dimensions =
3D representation
Warrington's object recognition
Perceptual organization
Semantic categorization
Theory of unconscious inference
to perceive object we use the
likelihood principle
= perceive object that the object in front of us is more likely to be
Identification by components
identify objects by their components (=
geons
)
geons have
non-accidental properties
= properties not changing depending on perspective (like lines etc..)
Accidental viewpoint =
unusual viewpoint of an object
Principle of componential recovery
= when object covered, perceive it as the object that it is because of geons
View-point invariance
= no matter the point of view, we perceive the object for what it is
Pandemonium theory
image demon has info from retina
feature demon identifying features in object
Cognitive demon finding combinations of these features and shouting once they are found.
Decision demon choosing which one is the object depending on the shouts of cognitive demons.
Feature integration theory
1.
Preattentive stage
- unconscious processing of features
2.
Attentive stage
- conscious process. Putting together features to form object thanks to attention
Illusory conjunction
= incorrect combination of feature due to lack of attention
Dependent theory
= perception depending on viewpoint
Model-based identification
= retinal image compared to images stored in brain.
DISORDERS
Apperceptive agnosia
= failure in perception of objects. Lesions in right parietal lobe.
Associative agnosia
= cannot recognize objects but can perceive them. Lesions to left posterior hemisphere
Category specificity agnosia
= like associative agnosia but just for a certain category
Integrative agnosia
= difficulties in integrating parts of objects
Prosopagnosia
= not recognizing face. Lesions in occipital and temporal cortex.
BRAIN
Cells with preference for faces in superior temporal sulcus and inferotemporal gyrus
For face recognition --> FFA (fusiform face area) - mainly in right hemisphere.
Evaluation of face attractiveness in frontal lobe