chapter 6 Flashcards
four major concepts in object recognition
- use terms precisely
- object perception in unified
- perceptual capabilities are flexible and robust
- the product of perception is interwoven with memory
object constancy
our ability to recognize an object in countless situations
what are the three factors that causes variability in how we see an object?
- viewing position (what angle you see it)
- illuminating conditions (lighting)
- context (why you are seeing it)
Ames Room Illusion
visual illusion that makes you think one person is much larger than the other when it is truly just the distance between the two
- showed how the perceptual system automatically uses many sensory cues and past knowledge to maintain object constancy
computational problems in object recognition
- object recognition must accommodate sources of variability
- system must recognize that changes in perceived shape may reflect actual changes in the object
- object recognition must be general enough to support object constancy and specific enough to distinguish slight differences
fasciculi
two major fiber bundles that contain output from V1, involved in object recognition
ventral stream
- occipitotemporal stream
- what stream
- inferior
dorsal stream
- occipitoparietal stream
- where pathway
- posterior/superior
if you have damage to your parietal lobe, which stream is damaged and how does that affect you?
Dorsal stream; damaged spatial perception, or cannot tell where an object is
Cat experiment for what and where pathways
- cats performed two tasks: locate a sound and distinguish between two different sounds
what did the cat experiment show?
- inhibit anterior auditory (ventral stream) region caused deficits in the pattern discrimination task but not in the localization task
- inhibited posterior auditory region (dorsal stream) caused deficit in the localization task but not in the pattern discrimination task
What are the symptoms of a patient with damage to the ventral stream
cannot name objects, recognize faces, or distinguish a rectangle from a square
- but can use vision to guide actions
What are the symptoms of a patient with damage to the dorsal stream
-cant integrate their vision with their movements
- cannot accurately reach out to grasp an object
- while walking they can describe what they see, but they bump into objects, oblivious to their location
agnosia
inability to process sensory information even though the sense organs and memory are not defective
visual agnosia
-difficulty recognizing objects that are presented visually
- recognition using touch/hearing are usually fine
3 types of visual agnosia
apperceptive
integrative
associative
apperceptive agnosia
difficulty recognizing objects or perceive their correct form
what tests are used for apperceptive visual agnosia?
unusual views object test, the shadows test
integrative visual agnosia
perceive parts of an object but are unable to integrate them as a whole
- ie can see corners and curves of shapes, but cannot tell that it is two squares and a circle
associative visual agnosia
inability to link a percept with its semantic info, such as its names, properties, and function
- can perceive objects, but cannot understand them
- they can copy an image down easily, but cannot say what they just drew
tests for associative visual agnosia
matching by function test
- participants are shown three pictures and are asked to point to the two that are functionally similar
prosopagnosia
inability to recognize faces
-damage is in ventral pathway and the FFA
- many cases lesions are bilateral
two types of prosopagnosia
- acquired (abrupt loss due to an accident) and congenital CP (lifetime impairment from birth)
monozygotic vs dizygotic twins in facial recognition
monozygotic twins are more similar in ability to recognize faces than dizygotic
ASD and face recognition
ASD is linked to abnormal face recognition due to the hypoactivity (less) in the FFA
how could CP arise?
from impaired info transmission between FFA and other face processing regions
what supports the hypothesis that the brain has functionally different systems for face and object recognition
double dissociations
- prosopagnosia vs patient C.K
holistic processing
How we accomplish holistic processing
- we recognize an individual but the sum of their parts
- people with prosopagnosia are unable to form a holistic representation necessary for face perception
prosopagnosia experiment
- participants were asked to recognize line drawings of faces and houses
- they were better at identifying an individual facial feature of a person when that feature was showed next to other parts of tjhat persons face
Thatcher Illusion
You are unable to recognize when certain features are wrong when a picture is upside down
