Perception Flashcards
what is visual perception
the ability to determine the surfaces in the surrounding environment and make interpretations about them
how do we interpret our environment
by receiving light in the visible spectrum reflected by objects in the environment and giving meaning to this information
what is object perception
- quickly determine what is and what is not an object
* finding your way around
what is depth perception
assess the distance object is away
what is motion perception
workout whether object is moving towards you/away from you
what does object perception require
*interpretation of information form the retina
what is perception a form of
problem solving
when id Gestalt psychology begin
in the early 20th centur
what do Gestalt psychologists perceive objects as
well-organised patterns rather than separate and individual components
what is Gestalt psychology based on
the concept of grouping
- organisation of single elements and features into a coherent whole
- the whole is greater than the sum of its part
what does Gestalt Psychologists say about the unified whole
that its different from the sums of the parts
what is Gestalt organisation a tool for
aiding solving item detection
when is Gestalt organisation detected
early in visual processing
*are automatic so difficult to get your head around
what does Gestalt organisation aid
the segmentation of objects in a scene
Infants and Gestalt psychology
infants show tendency to follow some Gestalt organisation principles
- others are acquired during later child hood
- exploration and assimilation
what do we do to stimuli
we impose visual organisation on stimuli
Gestalt principles of visual perception - laws of grouping
gestalt laws of grouping organise the visual scene into units
Gestalt principles of visual perception - goodness of figure
goodness of figure (Law of Pragnanz) creates the simplest most meaningful pattern
Gestalt principles of visual perception - figure/ground relationships
figure/ground relationships define important parts of the scene
Gestalt grouping principle - A-G
A. proximity B. colour C. size D. orientation E. shape F. closure G. symmetry
how do Gestalt features aid segmentation into items?
the proximity principle
*group items/inputs which are spatially close to each other
how else could you group items
lightness, colour, size, orientation, common region, connectedness
*similar motion behaviour (common fate) is also a factor…
what are other Gestalt Features
- information interpretation
- texture segregation
- pop-out and emergence
- perception and top-down influence
what is information interpretation
- constructive perception
- process is quick
- allows fast responses and decisions
- but sometimes contradictory/wrong…
- optical illusions
what are the biological implications of perception
- increased no. of celss in the fovea
- 140,000 cone cells in each square mm
- no rods in the fovea
*cones sensitive to colour
- rods more sensitive to light
- no role in colour
- can respond to a single photon
what is eye movements role in perception
eye movements direct the fovea
- improve vision of particular area of visual field
- constant eye position - fixation
- eye movement - saccade
whats covert attentions role in perception
allows detection of info not in the fovea
*planning of next eye movement
what is attention shifts role in perception
attention shifts always precedes an eye movement
*but not vice versa
what are the two types of factor that affect deployment of attention
- stimulus-driven
- top-down
- they interact to aid object detection
what is a stimulus-driven factor
- flashing light
- on-rushing object/rhino
- bright object
what is a top-down factor
- what you are interested in
* what you are looking for
what is motion perception
out brains can detect changes in patterns of light over time and space
how does our brain perceive motion
though out brain is sensitive to motion it cannot detect all forms - motions can be too slow or too fast for us to perceive
motion perception is relative
- it is v hard to perceive whether a single dot in a dark room is moving or not unless the motion is very fast
- as soon as a second dot is added it is much easier to perceive the motion
when do further complications occur in the relative nature of motion perception
when one has a moving surround within a surround
what is the aperture problem
where viewing of motion is restricted it is impossible to fully determine the direction a motion signal
the kinetic depth effect - Wallach and O’Connell (1953)
- ps observed image of a piece of twisted wire
- when static - appeared to be a 2D form of its shadow
- its £D structure was immediately obvious as the wire was rotated
motion on the retina and £D objects
motion on the retina is a rich source of cues as to the 3D structure of an object as it moves through space
motion
motion is one way we can distinguish living from non-living things from their distinct movement patterns
the brain and motion
the brain is remarkably good at using motion info to identify animals and animal behaviours
what is apparent motion
the (illusory) impression of smooth motion resulting from the rapid alteration of objects appearing in different locations i rapid succession
what is the motion correspondence problem
- working out what went where..
- all logically possible motion trajectories
- the brain uses a set of rules to determine correspondence such as proximity is space and time
how can motion perception sometimes be induced
by eye movements or by fatigue or low-level receptors
what is motion a useful cue for
determining surfaces and grouping and detection and identification of other animals
when is motion perceived
where objects onset in sequence (apparent motion)
what does motion perception require
the brain to impose rules (the correspondence problem)
what are two types of ocular cues - how does the brain work out how far away things are
- accommodation
* convergence
what is accomodation
the lens of the eye contracts when an object is near, to maintain focus
*monocular cue
what is convergence
the eyes turn inwards (or converge) as something is close to us
*binocular cue
where is visual info processed - stereopsis
- in the occipital lobes
- via LGN
- spatial configuration maintain (retinotopic)
- upside down
BUT each side of the visual field projects tp the contralateral hemisphere
-one side of one eye linked to the opposite hemisphere to the other side
two different images from each retina - stereopsis
- 2 different images from each retina
- images projected to separate hemispheres
- eyes are 6cm apart
- 2 images are different
- brain can combine them into a single coherent object - “cyclopian perception”
- comparison process
- differences tell the brain about depth
distance of item calculated - stereopsis
- communication across the corpus callosum
* the greater the convergence, the closer the object is
where is stereopsis used
- 3D cinemas
- different coloured lens
- lens with different polarities
- different images
*stereograms (“magic eye” pictures)
Motion parallax - kinetic cues
- inferred from the difference in information received by both eyes
- closer objects move faster
- relative motion of stationary objects against a background
looking out a train window.. - kinetic cues
- nearby things pass quickly
* far off objects appear stationary
what is optic flow - kinetic cues
the impression of visual information moving towards or away from us as we move through space
- pattern or apparent motion
- perception of movement
what do changes in our position result in - kinetic cues
a displacement in the optic array
objects in motion become smaller or larger… - kinetic cues
- appear to recede into the distance or move farther away
* increase in size as they come closer
kinetic depth perception
*infer 3D structural form
what is Gibson - kinetic cues
- possibilities for action
* unique, unambiguous interpretation of 3D motion and depth
Optic array - kinetic cues
optic array is a 3D bundle of light rays
- all info reaching the retina
- ‘texture’ of this array - distance,speed
what as some kinetic cues
- cues from personal movement
- landing a plane
- getting up
- moving left to right
what are 8 pictoral cues
1 perspectives 2 relative size 3 familiar size 4 aerial perspective 5 superposition/occusion 6 texture gradient 7 elevation 8 lighting and shading
perspective - pictoral cues
- parallel lines converging at infinity
- reconstruct the relative distance of 2 parts of an object
- or of landscape features
relative size - pictoral cues
- same size objects
* those that look larger see closer
familiar size - pictorial cues
- distance of object you see everyday
* relative size of object on retina - distance object away
aerial perspective - pictorial cues
- light scattering by the atmosphere
- objects far away appear more hazy and bluer
- this can be taken as an indication of distance
superposition/occlusion - pictorial cues
- objects are blocked by those in front of them
* not always correct
texture gradient - pictorial cues
*things further away tend to be more ‘densely packed together’
elevation - pictorial cues
objects closer to the horizon are further away
lighting and shading - pictorial cues
shape of objects and position in space
what is required for survival
speedy processing of visual info
