Chapter 3 (Perception) Flashcards
1. Understand the basic structures and processes involved in visual perception 2. Provide an explanation of Gestalt principles of holistic perception 3. Understand how different modalities (e.g., sound, vision) can interact in the formation of perceptions
What is perception
How sensory information forms conscious experiences of the environment
2 ways (levels) in which perception works
- Subliminal (implicit)
- Subjective (conscious)
What is the subjective threshold
A continuum, how much we are affected by subliminal subjective …
at first, information is processed subliminally, and when the information is important enough, or gone far enough through the stages of processing, it comes to awareness (aka subjective perception)
What is functional perception
Neurons are chatty
networks communicate back and forth between different modules adding info and meaning
Steps in the visual system
- Info in through cornea lens hits the retina in back (whole where optic nerve axons out)
- Signals transmitted through optic nerve
- Primary visual cortex = retinotopic area
Perfectly mapped from retina to visual cortex (backward inverted)
- Depth perception from different views
The conscious subjective perception of vision is created by a combo of 2 systems
1) Dorsal pathways go up “where”
2) Ventral pathways go down “what”
What is the “where” pathway
The dorsal pathways going up through the parietal cortex giving spatial meaning to visual stimuli
What is the “what” pathway
The ventral pathways going down through the temporal lobe through language adding meaning to visual stimuli
What does damage to the dorsal pathways do
Harder to find location of objects
What does damage to the ventral pathways do
Know there is an object there but can’t recognize or name it
Perception is always wrong
True
We fill in gaps
Subliminal systems can work with out subjective system (can even be more accurate)
What does patient TN show us about brain damage to the pathways (Does not see but can navigate = blind sight)
Dorsal pathways intact “spatial location” ok
but damage
to Ventral pathways: no “conscious perception = no vision”
Blind sight
Eyes are fine
So is Dorsal pathways to identify spacial location
but visual cortex (ventral pathway) damaged
Primming (subliminal perception)
Manipulation of the cognitive system
= increase probability of a future conscious perception/choice
Does primming require subconscious presentation of stimuli?
No
Just lack of awareness of stimuli
Pandemonium is
An influential theory of perception (both figurative and literal)
3 levels of higher-order perception processing
- Feature
- Cognitive
- Decision
Pandemonium was developed by
Selfrige (1959)
The Pandemonium theory is both figurative and literal
- The basic visual pattern is relayed to the feature demons - who each identify what they’re trained to find
- The cognitive demons look for associations in what the feature demons are saying
- The cognitive demons shout louder the better the features meet their expectations
What is the McGurk Effect from
From Selfridge’s perspective
What does the McGurk Effect result from
result of a visual cognitive demon overruling an auditory cognitive demon
Does it really matter whether we believe demons are involved
Gestalt perception stats that
The whole (conscious) perception is greater than the sum of its part
Gestalt: Whole object perception is
the overarching goal of perceptual processing
and such structures wholes are the primary unit of the mind
The principle of experience implies that
how we’ve seen something before will influence how we see it now
has only weak support in Gestalt psy
We don’t need to have seen the specific thing, but more precisely the situation before
The higher order visual system processes feed backwards into the primary visual cortex and changes what we perceive
What is the principle of closure
items that are grouped together well are perceived as closed figure
What is the principle of similarity
All else being equal, the most similar parts will group together
What is the principle of proximity
Items that are closer to each other will be grouped together
What is the principle of common fate
Items that are moving in the same way are grouped together
What are some limitations to Gestalt perception
The whole (conscious perception) will not always be greater than just the sum of its parts
Perception and complexity
Gestalt principles might agree with the finding that more complex shapes are easier to recognize than simpler ones
But do we really need the Gestalt view to explain this finding?
We take more neurons that will agree with each other, so the more features we see will activate more neurons
Is perceptual processing uni or bi-directional
Bi-Directional
Perceptual processing in the brain
Sensory input begins simple / Sense-specific
Move forward to higher-order modules (what-where)
The higher order modules also communicate backward to adjust lower-order perceptual processes
Interaction between ventral (what) and dorsal (where)
what we can do with an object affects its perception
Ex Witt & Profitt showed that the perceived size of a baseball is affected by how easily we can hit it
Fovea of the eye
Most capable (colour)
Where we direct it (vision) directs attention
Anstis (1974) mapped out
how much visual acuity is lost as you move from foveal to progressively more peripheral vision
What is Achromatopsia
A visual deficit = inability to perceive colour
because of damage to the area of the brain that processes colour information.
What is Akinetopsia
motion blindness, an inability to perceive the motion of objects
What is Feedforward sweep
propagation of visual information from the primary visual cortex down the ‘what’ and ‘where’ pathways
What is the bottom-up influence
The feedforward influence of the external environment on the resulting perceptual experience.
What are Re-entrant (feedback) connections:
Connections between brain areas that allow the propagation of visual information from the endpoints of the “what” and “where” pathways back to the primary visual cortex.
What are top-down influences
The feedback influence of context and the individual’s knowledge, expectations, and high-level goals on perceptual experience.
What is the Höffding function
The process whereby an experience makes contact with a memory trace, resulting in recognition.
What is a memory trace
The trace that an experience leaves behind in memory.
What are photoreceptors
cells that transduce light energy into neural signal
What is the fovea
Region of the retina where photoreceptors are most densely packed
What is the lens
transparent tissue in the eye that refracts light and focuses it on the back of the eye
What is the cornea
Outer tissue of the eye first layer that light passes through on its way to the back of the eye
What does retinotopic mean?
principle of organization of the primary visual cortex where information falling on adjacent areas of the retina is processed in adjectiveacent areas of the cortex
One of central principles of visual processing in the brain
it is highly module
Ex some areas process color others motion etc.
Info bi-directional visual pathways: from primary-visual cortex in a “feedforward sweep” - 100ms influence
Bottom up influences
Feedback influence: high level goals … End of Dorsal and Ventral areas send info back to primary visual cortex: “re-entrant pathways”
Top down influences
Elements of the ventral pathway for object recognition
Faces (fusiform face area inferior templar cortex) propopagnosia
Places (temporal pharahipocampal place area)
Pattern recognition (memory and recognition)
What is the Huffing function
the process where an emerging perception (experience) makes contact with a memory trace = recognition
what is contrast energy
the relative ease with which a stimulus can be distinguished for the background against which it is displayed
what is pandemonium
a model of pattern recognition
3 levels
1.Data
2.Cognitive demons
3.Decision demons
What is squelching
The tendency of the nervous system to inhibit the processing of unclear features
Recognition by components
The theory that we recognize objects by breaiking them down into their fundamental geometric shapes.
Geons
A set of 36 basic 3D shapes from which all real-world objects can be constructed
What is template matching theory
hypothesis that the process of pattern recognition relies on the use of templates or prototypes
Multiple trace memory model (Hintzman)
Traces of each individual experience are recorded in memory. No matter how many times it is experienced.
Primary - what we are actively aware of (can generalize from probe - from primary to secondary - eco)
Secondary - can be activated by probe from primary memory
context effect is
The change in perception of a visual component of a scene based on the surrounding information in the scene and the observer’s prior knowledge
- Perception is influenced by its neiboughs
- contextual info can influence perception of a visual component through feedback connections eg moon illusion
Gestalt - visual principles of organization
Principle of experience: we organize components in whole objects depending on our prior experience (inferior temporal cortex)
Principle of similarity
Principle of parallelism
Principle of proximity
Principle of symmetry
figure– ground segmentation (segregation)
The separation of a scene such that one component of the scene becomes a figural object and the other component(s) become(s)
the backdrop
Small - Figure
Large - Backdrop
The jumbled word effect
ability to read words in sentences even when some of the letters are mixed up
The word superiority effect
Letter easier to spot if in a word than alone
empirical theory of colour vision
The theory that colour perception is influenced by prior experience with the way different illuminations affect colour
- prior experience of the way objects look when illuminated
- the inferences that the visual system makes as a result
Dorsal pathway (where) perception of action
Eg visual agnosia can match the orientation but can’t identify objects
optic ataxia
inability to properly reach for objects,
Especially in periphery vision
Able to identify objects visually
JJ Gibson ecological optics, (not completely correct) thinks that the primary role of perception is … and that perception is accomplished by the sensory organs themselves so he is … but still …
Action … wrong … influential
Gibson’s notions of perception vs visual stimuli
Ambient optical array
Transformation
Optic flow field
topological breakage
intentional binding effect
that “intentional actions elicit perceptual attraction,” which “binds together awareness of the voluntary action with awareness of its sensory consequences, bringing them closer in perceived time.”
Multimodal perception (lack of research except last 2decades)
Most of the time at least 2 of our senses are actively processing information
Modality appropriateness hypothesis
The hypothesis that different senses are better at processing different
stimuli, and therefore that different sensory modalities dominate at
different times, depending on circumstances.
visual prepotency effect
The hypothesis that the visual system dominates the other senses when
it comes to perceptual processing.
McGurk effect (vision & audition)
Perceptual systems creating an experience of something in between visual and auditory stimuli
Eg. The auditory experience of the syllable “da” when seeing a mouth silently saying “ga” while at the same time hearing a voice say “ba.”3
Vision and touch (proprioception)
When arms are crossed accuracy goes down (hard to judge the temporal order of the stimuli)
Perception and taste
Influence = multi-sensory.
