perception Flashcards
what is the striate cortex?
the primary visual cortex
where the most basic visual information is processed
what is the extrastriate cortex?
the region of cortex bordering the primary visual cortex and containing multiple areas involved in visual processing
what happens in the visual ventral pathway?
process visual information to work out WHAT something is
what happens in the visual dorsal pathway?
process visual information to work out WHERE things are
what is a receptive field?
particular region of sensory space in which a stimulus will modify the firing of that neurone
what is the inferotemporal cortex?
part of the cerebral cortex in the lower portion of the temporal lobe, important for object recognition
what is agnosia?
when you cannot recognise an object even though you can see it
what are grandmother cells?
cells that have very specific responses to very specific objects (e.g. fire when you see a Ferrari but not other cars)
what role does mid-level vision play in perception?
it organises objects into objects and surfaces
determines which regions of an image should be grouped together into objects
what is illusory contour?
when a contour (edge) is perceived even though nothing changes from one side of the contour to the other
what does gestalt psychology suggest?
that a scene is perceived as an organised whole rather than the constituent parts
give some examples of gestalts grouping rules
good continuation texture similarity proximity parallelism symmetry common region connectedness common fate synchrony
what are perceptual committees?
a metaphor for how perception occurs
perception can be ambiguous so ‘committees’ must work together to integrate conflicting opinion
what is an ambiguous figure?
a visual stimulus that gives rise to two or more interpretations of its identity or structure
what is an accidental view point?
a viewing position that produces some regularity in the visual image that is not present in the world (holding up the leaning tower of Pisa)
what is ‘figure-ground assignment’?
process of determining some regions of an image belong to the object and some to the background
what are the gestalt figure-ground assignment principles? (5)
surroundedness size symmetry parallelism relative motion
what is the principle of ‘surroundedness’
the surrounding region is likely to be the background o fan image
what is the gestalt figure-ground assignment principle of ‘size’?
that the smaller region is likely to be the figure
what is the gestalt figure-ground assignment principle of symmetry?
that a sy,,metrical region tends to be seen as a figure
what is the gestalt figure-ground assignment principle of parallelism?
that regions with parallel contours tend to be seen as a figure
what is the gestalt figure-ground assignment principle of relative motion?
that if one region moves in front of another, then the closer region is the figure
what is occlusion?
when one object partially covers another
what is a non accidental feature?
a feature of an object that is not dependent on the viewing position of the observer
what does T junctions indicate?
that the top of the T is in front and the stem is at the back
what do Y junctions indicate?
corners facing the observer
what do arrow junctions indicate?
corners facing away from the observer
what is the global superiority effect?
the properties of the whole object take precedence over the properties of parts of the object
what are the five principles of middle vision? ***
- it brings together that which should be brought together
- split part that which should be split apart
- use what you know
- avoid accidents
- seek consensus and avoid ambiguity
what is the Bayesian approach to perception?
formal, mathematical system that combines information about the current stimulus with prior knowledge about the world
use knowledge of the world to work out what is the most likely outcome
what is the subtraction method?
comparing brain activity with and without the brain process of interest being used
which brain region responds to places?
the parahippocampal place area
which brain region responds to faces more than other objects?
the fusiform face area
what brain region is specifically involved in the perception of body parts?
the extrastriate body are
what are the two types of ‘demons’ in the pandemonium mode?
feature demons (straight line) cognitive demons (R)
what is Biederman’s adel of object recognition?
objects are recognised by the identities and relationships of their component parts
what are geons?
geometric ions that make up objects
what are the three category levels for naming an object?
entry-level
subordinate-level
superordinate-level
what is a subordinate-level category?
a more specific term for an object
what is a superordinate-level category?
a more general term for an object
what is holistic processing?
processing based on an analysis of the entire object or scene and not on adding together a set of similar parts or features
what is prosopagnosia? **
the inability to recognise faces
broad definition of attention
selection some information over others
name some varieties of attention
external internal overt covert divided sustained
what is external attention?
attending to stimuli in the world
what is internal attention?
attending to one line of thought over another, or selecting one response over another
what is overt attention?
directing a sensory organ towards a stimulus
what is covert attention?
attending without giving an outward sign that you are
what is divided attention?
splitting attention between two different stimuli
what is sustained attention?
continuously monitoring some stimulus
define reaction time
a measure of time from the onset of a stimulus to a response
what is a cue?
a stimulus that might indicate where or what the subsequent stimulus is
what is stimulus onset asynchrony?
the time between the onset of one stimulus and the onset of another
what is inhibition of return?
the relative difficulty of getting attention to return to a recently attended to location
once you have fixated on an area, you’re less likely to come back to it
what is the ‘spotlight’ model of attention?
attention is restricted in space and moves from one point to another
what is the ‘zoom lens’ model of attention?
the attended region can grow or shrink depending on the size of the area to be processed
what is a visual search?
looking for a target in a display containing distracting elements
what is a feature search?
search for a target defined by a certain attribute
e.g. colour
what is salience?
the vividness of a stimulus relative to its neighbours
what does parallel mean in visual attention?
processing multiple stimuli at the same time
what is a guided search?
attention is restricted to a subset of items based on information about the item’s basic features (e.g. colour_
what is a conjunction search?
search for a target defined by the presence of two or more attributes
what is scene based guidance?
information in our understanding of scenes that helps us find objects in a scene
what is the binding problem in perception?
the challenge of trying to join different attributes of visual stimuli together that are handled by different brain circuits, to the appropriate object so we perceive a unified object
what is illusory conjunction?
wrong combination of two features in a visual scene
what does RSVP stand for?
rapid serial visual presentation
what is RSVP?
an experimental procedure where stimuli appear in a stream at one location at a rapid rate
what is attentional blink?
the difficulty in perceiving and responding to the second of two target stimuli in RSVP steam of distracting stimuli
what are the three ways a cell could be enhanced by attention?
- response enhancement
- sharper tuning
- altered tuning
what is response enhancement?
attention makes the neurones fire more when seeing the stimulus
what is sharper tuning?
attention stops the cell from responding to stimuli that doesn’t fit as well with the target we are intending to find
what is altered tuning?
when attention changes the preferred stimulus that the neurones responds to
what is ‘visual-field deficit’?
when a portion of the visual field has no vision or abnormal vision
what does ‘neglect’ cause?
the inability to attend to or respond to stimuli in the contralesional visual field
what is the contralesional field?
the visual field on the opposite side to the brain lesion
what is the ipsilesional field?
visual field on the same side as the brain region
name some symptoms of ADHD
impulsivity
hyperactivity
inattentiveness
what are the two pathways to scene perception?
selective
non-selective
what is the selective pathway of perception?
only recognise one or very few objects at once
attend/further process certain objects at the expense of others
what is the non-selective pathway of perception?
we process the general gist of the scene very quickly
what are ‘ensemble statistics’?
the average properties of the objects in the scene. e.g. colour or type of region
what is spatial layout?
the description of the structure of a scene without reference to the identity specific objects
what is change blindnesS?
the failure to notice major changes between two scenes
what is inattentional blindness?
the failure to notice (or report) a stimulus that would be easily reportable if it were attended to
monkey in the brain scan
what did yarbus’ experiment find?
the way people distribute their attention depends on their goal
people who think differently, see differently (gaze of cricket players)
what is the physical definition of sound?
waves of changing pressure travelling through air
amplitude definition
magnitude of displacement of a sound pressure wave
max displacement from equilibrium
frequency definition
number of waves per second
what is amplitude perceived as?
amplitude
what is frequency perceived as
pitch
how much does loudness increase if you increase amplitude by 10x
4x
what is the fundamental frequency?
the lowest frequency component of the sound
what is white noise?
sound made up of all audible frequencies in equal amounts
