5-Form Perception Flashcards
Gestalt Principles
of visual processing
- Figure-Ground: distinguish objects from their background
- Proximity: elements that are close together tend to belong together
- Closure: tendency to fill in gaps to percieve a whole object
- Similarity: tendency to group similar objects
- Continuity: interpret forms in the simplest possible way
- Common Fate: group elements that change in the same way
see figure 5.1 for examples
Bottom-up processing
object recognition is guided by individual features we percieve
Top-down processing
object recognition is guided by beliefs or expectations
study recorded reading time of participants after priming with related or unrelated words
describe methods and results
flashed a word like “animal” followed by a related word (dog) or unrelated word (log)
- participants read the related word faster
- shows that our expectations can affect our reaction time and perception
Geon theory
description + key problem
we have 36 different geons (simple geometric forms) in our memory which we use for object recognition
(eg: ice cream cone = cone + sphere)
largely disproved as certain brain injuries can lead to recognition of some objects (eg: tools) and not others (eg: fruits) even though they are both made up of ‘geons’
Template theory
description + key problem
we compare objects to templates in memory
- if an object does not exactly match a template, it is stored as a new object
not enough storage in the brain for every template (eg: we can still recognize faces despite not having seen them at every angle)
Prototype theory
description
we compare objects to our ideal prototype
Perceptual Constancy
description + example
despite differences in the visual image produced by an object, we can still identify it as unchanging
eg: you understand a dog hasn’t changed colour when a red light is shining on it’s fur
Types of perceptual constancies
list + basic description
- shape constancy: open vs closed door is still a rectangle
- location constancy: objects still percieved as stationary even while we’re moving
- size constancy: objects further away are not smaller
- brightness constancy: objects have the same brightness regardless of the shading on them
- colour constancy: objects do not change colour despite different lighting conditions
Müller-Lyer Illusion
description + which constancy it targets
same two lines with inward pointing arrows or outward pointing arrows –> view lines as different lengths
takes advantage of our size constancy perception, we misinterpret the arrows as depth cues
- people without exposure to right angles are less susceptible to this illusion
see image for visual explanation
Ames room illusion
description + which constancy it targets
trapezoidal shaped room –> percieved as a rectangular room
takes advantage of size constancy perception
see image for visual explanation
Ponzo illusion
description + which constancy it targets
slanted lines around two horizontal lines –> lines percieved as different lengths
manipulates depth cues to trick size constancy
What did Hodgkin & Huxley do?
feature detector cell research: recorded electrical activity in the giant axon of squids
What are certain neurons in the optic nerve of frogs only responsive to?
Who researched this?
moving black dots - bug detectors
Lettvin et al.
Hubel & Wiesel research
description + findings
flashed a line of light onto the retina
neuron firing changed with ___ of line on the retina:
- location
- orientation
- direction of movement
- shape + size
discovered feature detection cells
simple cell
in retina, what does it do?
responds maximally to a bar of certain orientation in a particular region of the retina
complex cell
in retina, what does it do?
responds maximally to a bar of certain orientation regardless of location
some respond maximally to a specific direction of movement
hypercomplex cell
in retina, what does it do?
responds maximally to a bar of particular orientation and direction of movement and length
ventral stream
for visual processing, location + purpose
DOWN from occipital to temporal lobe
what stream
- form
- colour
dorsal stream
for visual processing, location + purpose
UP from occipital to parietal lobe
where stream
- location
- movement
what to the columns vs layers of the temporal cortex respond to? (in terms of visual stimuli)
answer + example
columns: categories of objects
layers: types of objects within a category
eg: column for apples, layer for red apples
what type of stimuli do infants prefer?
the most complex stimuli they are able to perceive
see visual example
Timeline for infants learning to perceive objects
age + what features they can percieve
when perceiving objects, infants will focus on and attribute the following features to one object:
- 2 weeks: key features (angles, edges…)
- 2 months: wider areas of objects
- 3 months: whole forms + gestalt theory of closure + movement
- 4 months: some perceptual constancy brightness + color + shape + some size constancy
- 5 months: color + texture
what type of object do infants prefer? which qualities of this object do they prefer?
prefer faces even at 4 hours of age
prefer attractive faces and mother’s face at 2 months
when can infants begin to detect emotions in faces?
around 5 months
evidence against infant preference for faces
- infants will fixate on stimuli with equal complexity to faces just as much as real faces
- infants only start to fixate on facial features (eyes + mouth) later in development (2 months)
what happened when kittens were kept in a room with only vertical lines?
they did not develop the ability to perceive horizontal lines
what happens when 1 month old kittens are kept in the dark for 3-4 days?
what about a week or more?
3-4 days: experience visual degeneration
1 week+: severe and permanent degeneration
what happens to the visual development for infants with cataracts?
the longer it takes to remove the cataracts, the worse the childs vision later in life
effects of different damage to the occipital lobe
region + effects
Primary visual cortex damage: can only perceive objects in limited field of vision corresponding to undamaged areas
Extrastriate cortex damage: cannot recognize objects despite fully intact field of vision
Visual agnosia
types + cause + effects
Object agnosia: unable to identify objects through sight, can identify them through touch
Prosopagnosia: unable to recognize faces, can still tell they are looking at a face, just can’t tell who’s face
