Perception 2 Flashcards
Explain why Desirable objects will appear closer/larger than less desirable objects?
Perceptions are subjective
- A water bottle appears closer than crackers when thirsty
- Hills look steeper when you are tired
What is the order of touch processing?
Mechanreceptors -> Spine -> Somatosensory cortex
What is the Cortical homunculus?
Spatially organized map of the body for sensory and motor
* BUT … current evidence suggests an update of motor homunculus to include regions that
control integrative, whole-body actions. Science is a process
What is Olfaction?
Chemicals moving through the air pass through olfactory epithelium to olfactory bulb
- Direct connections to memory and emotion brain regions … other senses go through the thalamus
- Smell has a stronger link to memory and emotion than any of the other senses
- Explains why the smell of cut grass can trigger a memory better than an image of grass
- New research: Sense of smell is also related to brain and
early symptom of dementia
What is the Taste system?
Works with olfaction
* Explains why things do not taste as good when our nose is stuffed
- Taste buds on tongue, palate, pharynx, upper esophagus
- Measure chemicals that have been ingested
- Relay message to thalamus and then the
primary gustatory cortex - Other areas like PFC and reward
areas of the brain
Flavour (taste) is also affected by other senses, including vision
* Reddish colours associated with sweet tastes
* Greenish colours associated with bitter tastes
What is A Constructivist Theory of
Perception?
A top-down theory of perception
- Perception is influenced by stored knowledge and context
- Mental models
- We make unconscious inferences to interpret and to predict sensory data
Sensory Input -> Mental Model -> Perception and action
What are Ambiguous Bistable figures?
Image that can look like two things.
- Bistable figures suggest that we can experience spontaneous subjective change in perception
- Direct us to understand what factors (constraints) are driving this effect
or how we organize perception
What are the Gestalt organizational principles?
Gestalt Psychology: There are fundamental organizational principles to deal with ambiguity in our environment
- These principles are based on knowledge and experience (top-down
processes) and shared among people
Name the Gestalt principles:
The principle of experience
* Figure ground segmentation
Visual grouping principles
* Principle of proximity
* Principle of closed forms
* Principle of good contour
* Principle of similarity
Explain the Principle of experience ?
Image segmentation (figure-ground)
depends on sensory input, detect edges
or shadows
* Bottom-up
Experience and knowledge also drives
figure-ground segmentation
* Regions perceived as the figure are the
ones that are more familiar and more easily
named to the observer
* Top-down
What is the Principle of proximity?
Objects or features that are close to one another in a scene will be judged as belonging together
What is the Principle of closed forms?
We see a shape in terms of closed forms, and we like to see items that enclosed
as whole
What is the Principle of good contour?
We perceive objects as continuous in cases where it is expected that they
continue
What is the Principle of similarity?
We organize objects or features of a scene based on similarity
What are Constructivist theories of visual info and perception?
Visual information is ambiguous, and perception requires top-down processes
What are Direct models for perception?
Against the idea that ‘top-down’ processes are needed for perception
- A passive bottom-up approach to perception
- Sensory information is rich enough for perception
Requires an an ecological approach to understand perception – study it in the real world (JJ Gibson)
- The ambient optical array (AOA) that reaches the retina has enough information to direct perception and movement
- There are cues (computational tricks) in the AOA (not in the mind) that are used to guide perception and action
- These are bottom-up cues
What are Topographical breakages?
Discontinuity helps see edges and define objects
Ex. Wall and floor
What is Scatter reflection?
How widely light scatters off an object’s surface provides cues about the nature of the surface.
(Rough vs smooth surface)
What are Texture gradients?
Near objects are farther apart and far objects are closer together Incremental changes in texture can provide information about your movement and distance
(In paintings)
What are Affordances?
Cues indicate potential function of an object
- Visual cues in our environment
- Perceived directly and immediately
- Provides information on the potential function of an object
- We ‘see’ based on what we can/need to do in the environment
What is Blindsight?
- No conscious awareness (explicit perception) of visual objects in damaged visual field
- Able to implicitly respond to questions about objects presented in the damaged visual field
- Suggests that they can perceive something without ‘consciousness’ or awareness (implicit perception)
- There is a processing division between conscious (explicit) and non-conscious(implicit) perception
How did they test blindsight?
Flashing light on and off, and asked ppl if light was on / off
Patients performed above chance on the
forced-choice responding task for lights in
the blinded area
What does the the dorsal ‘where’ pathway do?
- spatial information
- depth perception
- estimating movement and
direction of objects
What is dmg to dorsal where pathway:
Akinetopsia?
Visual motion blindness: cannot see motion. Instead, perceives motion as a
series of stationary objects
What us Damage to the dorsal where pathway: Optic ataxia
- Inability to reach for objects with the
ability to name objects - Problems reaching for a cup of coffee …
can recognize coffee - Problems pouring milk … can recognize
milk - There might be action specificity in
this pathway - Selective damage leads to problems
with certain types of movement
What is Damage to the ventral what pathway: Visual
agnosia?
- Difficulties recognizing everyday objects
- Often from damage to the Lateral Occipital Cortex
- Difficulties can be selective to visual categories (faces)
- Functional specialization within the ventral pathway
What is Prosopagnosia?
- Fusiform face area (FFA) damage leads to a selective deficit in recognizing faces, keeping intact the ability to visually recognize other objects
Explain the purple “Greebles”
and the FFA:
- Is the FFA special for faces or just
discrimination? - Participants learn to discriminate
between “Greebles” - fMRI data as participants viewed
greebles and other objects - Greebles activated FFA more than
other objects (cats, household objects)
What is Apperceptive agnosia?
Problems perceiving objects (for
prosopagnosia, faces look contorted )
Associative agnosia?
Problems assigning meaning to objects (for
prosopagnosia, can’t recognize familiar famous faces)
What is Apperceptive visual agnosia?
A failure in recognizing objects due to problems with perceiving the elements of the objects as a whole
- Single visual feature perception (e.g., color, motion) are relatively intact
- Problems with perception and discrimination of objects
- Impairment is in grouping visual features to form perceptions that can
interpreted as meaningful
What is Associative visual agnosia?
- An inability to associate visual input with meaning
- Problems on tests that require accessing information from memory
- Drawing objects from memory
- Naming objects
- Indicating the functions objects
- Determining if a visual object is a possible or impossible
What is Feature detection (Theories of visual object recognition)?
- Visual input is broken down into
individual parts (features) - Each feature is processed separately
- The combination of features is used
as a pattern for recognition (probe)
What is the Template matching theory? (Theories of visual object recognition)
- Every object has a ‘template’ in long-term
memory - too simplistic
- computationally demanding
- Cannot explain
- Identification: The ability to recognize
objects with shifts in perspective - Classification: The ability to recognize new
objects as members of a known category
What is Prototype theory?
- A prototype is the average representation of an object concept
- recognition is determined by a ‘good enough’ match (resemblance)
- allows for ‘flexible’ object identification
