6 - Form Perception Flashcards
What is the gestalt philosophy/principle meaning
the whole is other than the sum of its part
principles: laws that describe how we organize visual input
What are the gestalt principles
Figure ground
proximity
closure
similarity
continuity
common fate
What is figure ground
the ability to distinguish an object from its backgroun id a visual scene
What is proximity
the tendency to group elements that are close together in space
What is closure
the tendency to fill in gaps in a contour to perceive a whole object
What is similarity
the tendency to group togehter elements that are physcically similar
What is continuity
the ability to perceive a simple continous form rather than a combination of awkward forms
What is common fate
the tendency to group together elements that change in the same way
What are methods of object recognition
bottom up processing
top down processing
bi-directional activation
What is bottom up processing
object recognition guided by features that are present in stimulus
knowing cow because four legs, spots…
What is top down processing
object recognitino guided by your own beliefs or expectations
What is priming in top down processing
telling a category before the word
What is bidirectional activation
using both top and bottom processing
- features and experiences
What is the geon theory
we have 36 simple geons (geometrical forms) stored in our memory
- can recognize 150 million objects
What are the cons to the geon theory
difficult to imagine complex images if geon theory were true (faces), we still can
doesn’t explain brain injuries where we can’t recognize fruit but can still recognize tools
What is the template theory
we compare objects to templates in memory
(requries exact match – would need a lot of storage)
What is prototype theory
we compare objects to internal best
- doesnt have to be exact match
What are the cons to prototype theory
too many different stimuli, slwoer to identify
we can still categorize unique/specfic objects (my dog)
What is perceptual constancy
our ability to percieve an object as unchanging even though the visual image produced by the object is constantly changing
What is shape constancy
an object is percieved to have a constant shape despite the shape of its retinal image changing with shifts in POV or change in object position
- seeing door open
What is location constnacy
an object is perceived to be stationary despite changing location on our retina due to body movements
- seeing things when in a moving car
What is size constancy
an object is perceived to be the same size despite the size of its retinal image varying with distance
person walking away (size is smaller with distance)
What is brightness constancy
an object is percieved to be the same brightness despite reflecting more or less light onto our retina
mug is the same outside in the sun and inside in dimly lit room
What is colour constancy
an object is percieved to have a constant colour despite different illumination
know white dog is white under neon sign
What are cues in a scene indicating perpetual constancies
depth cues: knowing someone is far away
colour cues: using info form rest of scene
motion cues: seeing the scene to know if something is coming towards you
What are visual illusions
What are the different illusions
missaplying size constnacy and misinterpretation depth
: ambugities of perception
muller-lyer illusion
ames room
ponzo illusion
What is the muller-lyer illusion
closer line = shorter
further = longer
people accustumed to no right angles don’t have struggles with the room
What is the ames room illusion
gives illusion to height
room celiing tilted, same height person but one looks a lot taller
What is the ponzo illusion
gives illusion to depth
- have lines drawn together, makes top look longer
What did hodgkin and huxley discover
method for recording actiivty in neurons
- giant axons of squid = enhances responses
What did letvinon discover
discrovered neuron in optic neuron of frog that responded only to moving black dots (bug detectors)
What did cubal and weasel discover
recorded neurons in visual cortex as thye moved a bright light against retina
- visual cortex nruson firing was affected by the stimulus location, orinetation, direction of movment
learned what type of stimuli the individual cortical cells responded to
- put microelectrodes on cortex of cat to record electrical activity of individual neurons as the cat was shwon different stimuli
What is a simple cell
responds maximally to a bar of a certain orientation in a particular region of the retina
What is the baseline response in a simple cell
no stimulus
What is elicits a strong excitatory response in simple cells
preffered oritnetation and location
passes through on version only
What elicits a strong inhibitory response in simple cells
not preffered orientation and location
passes through the “off” receptive field
What is a complex cell
responds maximally to a bar of a certain orientation, regardless of location
some respond maximally to a specific direction of movement
What elicits a baseeline response in complex cells
no stimulus
What elicits a strong excitatory response in complex cells
stimulus at 45 degrees
What elicits a weak excitatory response
stimulus at 60 degrees
What is a hypercomplex cell
responds maximally to a bar of particular orientation and direction of movement, ending at specific points with receptive field
What elicits a baseline response in hypercomplex cells
no stimulus
what elicits a strong excitatory response in hypercomplex cells
stimulus moving up horizontally
across ON region only
what elicits a weak excitatory respones in hypercomplex cells
stimulus moving up horizantally
across ON and half of OFF region
what elicits a weak inhibitory response
stimulus moving up horizantally
across ON and OFF region (in the middle)
how do the inputs work to form our visual percepts
input from all feature detectors combine to create our visual precepts
our brain can optimally balance the fucntion of each while consuming the least possible amount of energy
What is parallel processing
topographic organization in primary visual cortex
neurons can fire maxiamally for orientation, length and movemnet // colour // direction of movmenet
speed is a benefit
where is visual input integrated, what do they do
extrastriate cortex
- contains multiple cell regions that recieve different PVC about visual scene (colour, movment orientation)
ventral and dorsal stream
- ventral (what): arranged in columns - vertical and horizantal)
- dorsal (where)
What are infant preferences of visual information
infants prefer looking at things with patterns and sharp boundaries with light and dark (interest based on complexities)
- depends on infants visual acuity
attraction to certain key features on stimulus, not object as a whole
- whole form perception is an emerging process from the first two months of life
Describe visual development at 3,4,5 months
3: can percieve a partial form as whole forms
- difficulty percieving overlaping objects (can’t use colour or texture to tell objects apart)
- can identify seperate objects if objects move independently of one another
4: develop perceptual competency (brightness, colour, shape)
5: can use colour, texture to distinguish objects
What is an important factor of visual development
critical period
- early visual deprivation prevents proper feature detection
1 month old kitten kept in the dark for 3-4 days experience visual difficulties but regained
1 month old kitten kept in the dark for an entire week or longer experienced sever and permanent visual degeneration
cataracts in humans (disrupts light –> blurry): delay in removal = increase visual impairments
What is object agnosia
the inabilty to percieve objects
- can see all features but cannot name them
What is prospagnosia
inability to recognize faces
- pattern recognition disoder
- damage to right fusiform gyrus (not r/t to memory loss)
- can’t put individual parts together
