CLPS 0020- Lectures - Vision Flashcards
How does the visual system resolve ambiguities?
makes assumptiosn about the way the world usually looks: perception is a constructive process based on these assumptions
What do caricatures say about visual perception?
Do not need all features to be accurate to perceive something: certain features stand out more prominently
What are neurons’ receptive fields?
the specific stimuli that the neuron fires to: the pattern in light that causes the cell to fire
Wht happened in Hubel and Wiesel’s one-neuron electrode experiment?
neurons’ responses can be graded: not just all-or-nothing: depending on the pattern, neurons fired a lot or even just partially if the stimuli required that
How fast is the search time for a popout task, in general terms?
Very fast: easy to identify which is different
Why does it tak longer to identify a red t in a field of blue ts and read ls?
You need to itnegrate the double processing of color and shape
When identifying boundary lines, which makes the boundary more salient, change in angle or change in letter?
Change in angle
What is an illusory conjunction?
when you perceive and report both features, but pair them incorrectly: example: mismatching colors to letters in the five letter-color experiment
During the early parsing of visual info, is the info mediated by separate properties, or by combinations, such as color and shape?
Separate properties: that’s why it takes longer to identfy a red t in a field of blue ts and red ls
What are features?
basic units, building blocks present ina ll cognition
What happened in the Takana neuron tiger experiment?
there is no tiger cell, but cells that fire in response to a tiger image may be part of a larger population of cells that can detect tigers in the end, and this one cell contributes to the interpretation of the tiger as a whole
What researcher performed the tiger neuron experiment?
Takana
Is the simple feature approach enough to perceive and process images?
Nope: also depends on context, hence the top-down approach as well
What information is used in priming?
influence of prior or later information
What is the object-constancy problem?
How do we perceive the same object despite variability in viewing conditions?
What is the object-centered view?
objects are defined by invariant features that remain stable across variability, such as Biederman’s geons: color, shape, etc.; very economical
What is the viewpoint-centered view?
object define by viewer’s experience: multiple viewpoints stored in memory, many to one mapping onto a known object
What are some advantages to the object-centered view?
economical, efficient coding because object broken into elemental parts, Occam’s Razor (simplest solution is probably the most correct)
What are some disadvantages to the object-centered view?
neglects the level of detail we see objects at, not all the world is geometric, more than shape contributes to object recognition, we store more tha visual info when recognizing objects
What are some advantages to the viewer-centered view?
world perceived in terms of experience with it; canonical shape recognized faster than not: “most common viewpoint”; many to one mapping for same objects: Shepard and Metzler’s mental rotation exercise
Shepard and Metzler
object rotation exercise
What are some disadvantages to the viewer-centered viewpoint?
not economical: and how do multiple viewpoints map onto a single representation?
What does Moshe Bar propose about time difference in identifying “house” vs “upside-down house?”
For upside-down house, still maps onto house representation, but through a different pathway: partial activation of neurons, graded reactions/response time
What is the visual “what” system?
temporal lobe stream: ventral
What is the visual “where” ssystem?
parietal lobe stream: dorsal
Temporal lobe stream
What: enduring object characteristics, long-term perceptual representations, represents our knowledge base of the world, object-based: constancies of size, shape, color, etc.
Parietal lobe stream
Where: moment to moment info about the location and disposition of an object with respect to the effector
What happens to monkeys in object discrimination tasks with ventral lesions?
Can’t find the food under the new object: temporal lobe stream disrupted; what system
What happens to monkey in object location tasks with dorsal legions?
Can’t find the food near the landmarl: parietal lobe stream system disrupted: where system
What happens to carbon monoxide poisoning victims with damage to the occipital-temporal lobes?
“What” system damaged: can’t recognize faces, differentiate geometric figures, recognize names of objects from shape/form, name/match slot orientation; can recognize voices and objects placed in hand: visual (but NOT representational disorder)
In patients with carbon monoxide poisoning and damage to the occipital/temporal lobes, is it a visual or a representational disorder?
Visual: can still identify voices and objects placed in hands
Which visual processing stream is focused more on perceptions vs action?
Perception for what (temporal) and action for where (parietal)
Which visual processing stream supports long-term vs online/temporary representations?
Long-term is temporal (what) and online/temporary is parietal (where)
Does the dorsal stream care about the object or just the orientation?
orientation: parietal “where”
Does the ventral stream care about the object, or just the orientation?
object: temporal “what”
What is neglect syndrome due to?
damage to the right parietal lobe: ignores input from left side of space: eats food from only one side of plate, fails to locate objects on neglected face, reads pigpen as pen
What happens during neglect syndrome?
ignores input from left side of space of the object (but if given two flowers, will draw right halves of both, not just the flower on the right)
Do people with right parietal damage (neglect syndrome for left visual field) see the whole image, or are they really blind to the left side?
See the whole image: still show priming when stimulus is presented to either damaged or whole visual field-hemisphere combo
What is the binding problem?
how to connect the what and the where of vision: temporal and parietal
What does Roskies say about the binding problem?
Temporal solution? What and where are bound because they are perceived at the same time
What did Kosslyn’s fictional maps experiment show?
That mental images are similar to pictures in how they represent positions and distances: takes longer to “arrive” at a further destination on a mental map
What did Kosslyn’s neuroimaging study show about visual imagery and visual perception?
Similar neural areas activated: can extend that to other areas, so supposed similar activation between sensory imagery and sensory perception: like coma patientes with motor area activation when imagining running
What is prosopagnosia?
selective deficit in visuallt recognizing faces
Why is prosopagnosia considered only a visual deficit rather than a naming deficit?
Can still identify faces based on touch and verbal descriptions
What is the difference in perception of houses and faces?
Faces: whole > parts; fewer errors upright, but more errors inverted than houses; Houses: parts > whole, more errors upright, fewer errors inverted than faces
Would prosopagnosia patients show the inversion effect for inverted faces? (ie. not recognize as accurately)
Nope: treat faces, inverted or no, as objects; TDs treat faces differently, inverted or no
What does the processing of faces by infants as they develop suggest?
prefer faces to objects, can discriminate upright faces from the same face inverted at 16-18 weeks, but not at 22 weeks; developmental trajectory towards seeing faces holistically instead of as separate objects
Based on Greebles, is the face module really just for faces?
Not really: used in tiny identifying discriminations, being experts at identifying
What does the Other Race Effect suggest about face identification?
That it’s also based off of experience
What is suggested by the fact that infants can discriminate small differences in both human and monkey faces, but adults cannot discriminate between novel/familiar monkeys?
If you don’t use it, you lose it.
