3. Perception Flashcards
distal stimulus vs. proximal stimulus vs. percept
distal stimulus: actual stimulus itself
proximal stimulus: the information
consisting of the reception of the distal stimulus
percept: meaningful interpretation of the proximal stimulus
What is one fact that supports distinguishing proximal stimuli from percepts
size constancy
what is form perception (gestalt)
distinguishing of the display into objects and background
what do subjective contours mean in gestalt psychology for perception
when we simplify a complex display into a simple one, by sometimes imagining edges that arent actually there
What some (5) of the Gestalt principles of perceptual organization
Principle of proximity
Principle of similarity
Principle of good continuation
Principle of closure
Principle of common fate
Explain top-down vs bottom-up processes
Top-down: Perceiver’s expectations/theories guide the pattern recognition process
Bottom-up: Perceiver starts with small bits of information and combines it to form a percept
What are 3 bottom-up models of perception
Template matching
Featural analysis
Prototype matching
Describe template matching
Type of bottom up perception model
- we read in patterns and compare them to previously stored patterns (templates)
What does the template matching model fail to explain
- We will need to store an impossibly large number of templates
- How do templates get created and how they are kept track of
- Patterns are recognized to be the same even if their stimulus patterns differ (etc. blurriness)
Describe featural analysis
Bottom up perception model
We conduct perception by searching and recognizing features, and then recognizing the object as a whole
What are some neurophysiological experiments (3) that support featural analysis
Implanting electrodes to the retinas of frogs: noticed that “edge” and “bug” stimuli caused certain cells to fire more frequently
Hubel and Wiesel found evidence of separate horizontal + vertical line detectors in cats and monkeys
Visual search: participants recognize letters by features
What was the finding of Neisser’s ZQ visual search task
Participants took longer picking out Z or Q from a group of letters, depending on how similar the letters around them were
Showed that we identified letters by features (featural analysis model)
What is Selfridge’s Pandemonium model for feature analysis
Think of a neural network, but instead of feature maps you have feature demons on each layer
And instead of weights you have the volume of demon’s screaming as they communicate between layers
What does the feature analysis model fail to explain
What is a feature, and how is this decided?
since an observer would need to have a list before starting perception, and this list can be arbitrarily large, how do we do perception quickly?
Describe prototype matching
We match input to a stored prototype: its idealized representation
What did Cabeza and colleagues find when giving participants of various edited variations of faces (prototype model)
Participants could form prototypes pretty quickly and were more likely to call a face “old” if it was similar to a previous face they saw
What is the context effect in perception processing
For top-down processing
- the speed/accuracy at which we recognize objects can depend on the context
- etc. utensils in a kitchen photo or in a random one
Explain the steps of Marr’s model in incorporating top down and bottom up processes
first, we have different independent “modules” that analyzes different things like colour, motion, etc.
- primal sketch: add light and darkness
- 2 1/2 D sketch: add shading, textures etc. (bottom up)
- 3D: add knowledge on real world + meaning (top down)
What is change blindness
the fact that we often do not detect changes to an object/scene especially when given different views of it
shows top down processing: we only encode the “gist” of the situation
The following experiment by Simons and Levin shows what?
A researcher approaches a person and asks for directions.
Halfway through, two people interrupt between by carrying a door.
You don’t notice that the person you were talking to was then replaced by a completely different person
Change blindness, and specifically the fact that it occurs in real world, not just clips
50% of participants don’t notice
students are more likely to notice than older participants
however, if wearing construction clothing, then less than half of the students noticed
What is the word superiority effect
Letters are easier to perceive in a familiar context (words) than in an unfamiliar context or no context
top down processing
What are phonemes
sounds (makes up a word)
likened to letters when using feature detection for a word
What is the missing letter effect
When trying to find letters, we often miss those used in function words (vs. content words)
function words: for, of, or
What is the connectionist model for word perception and how might it explain the word superiority effect
there are layers (features, letters, words) that get activated
having a word has more of the same activation (vs. just a letter) so maybe that’s why we perceive a letter easier in the context of a word
What regions of the brain showed greater activity under a PET scan when doing word perception for real and pseudo words
Both hemispheres of visual cortex were active
But there was more activity in left hemisphere + regions in visual cortex when viewing words rather than gibberish
(might be related to semantic processing)
what is the constructivist approach to perception
models that assume perception takes place as:
distal -> proximal -> percept
we distort + add to the information of a proximal stimulus to form a percept
in opposition to the direct perception view
what is the direct perception view of perception + who led it
James Gibson, in opposition to the constructivist approach
The world already offers a lot of information, and the perceiver does very little work
experiment: participants can recognize people dancing w/ lights attached to their body in the dark
What is an affordance
Part of direct perception view
acts/behaviours permitted by objects, places, and events
What is Neisser’s perceptual cycle model
attempts to incorporate direct perception + constructivist views
cognitive structures called schemata guide the perceiver to explore. Results of exploration then updates the schemata
What is apperceptive agnosia
- very limited visual information
- can see contours (outlines) of objects
- cannot match objects or categorize them
- cannot recognize object if parts of the lineart is missing
- cannot recognize object if in unusual orientation
What is asociative agnosia
- can match objects + copy drawings but do so very slowly (point by point, not as a whole)
- cannot name objects they have drawn
- cannot access meaning from a visual description alone
What kind of injury causes apperceptive agnosia
bilateral damage to a particular region
What kind of injury causes associative agnosia
injury to to the right side of the brain
What is prosopagnosia and its injury causes
Inability to EXPLICITLY recognize faces
- implicitly some abilities exist: galvanic skin response (GSR) recorder shows different responses to loved ones vs. strangers
- usually damage to region in right hemisphere (sometimes with some left as well)
What is unilateral neglect and what causes it
Caused by damage to one side of parietal cortex, and causes the patient to ignore stimuli that occurs on the opposite side
What is synaesthesia
etc. digit to colour
What is capgras syndrome
explicit face recognition, but not implicity recognition
- sees the person as an imposter
