Perception

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What is perception used for?
All organisms must adapt to their environment in order to survive an reproduce
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What is one property of light?
it is one form of electromagnetic radiation - propagation of energy through space
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What is absorbtion of light?
Photons collide with particles of matter
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What is reflection?
When it dtrikes an opaque surface, other wavelengths may be absorbed
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What is diffraction?
It passes through transparent media (blue sky from light of shorter wavelengths being scattered more)
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What did Gibson provide?
The concept of the ambient optic array
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What does this mean?
Light will converge from all directions - the intensity and mixture of wavelengths will vary from one angle to another
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What does this array carry?
information about the nature and position of the surface from which it has been reflected
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What was the movement of the fluctuations in the array?
slow: movement of the sun, fast: other animals
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What does the eye use?
a convex lens to project an image on receptor cells- the retina
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What did the Photoreceptors transduce?
Light into a receptor potential- arranged so that they are furthest away from the lens
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What are the cones for?
fine detail/colour
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What are the rods for?
Movement/coarse detail
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why isn't the eye a camera?
The image on the retina is very poor quality, image is constantly moving this would produce a blur, retinal image is yellowish contains shadows of blood vessels, the optic nerve does not transmit a picture (pattern of light/brain interprets)
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What are the top down processes to perception?
Processes that use knowledge about the structure of the world to influence perception
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What are the bottom up approaches?
Processes that take information coming into the eye and make jusgements about the nature of the visual world solely based on this information
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Why are both types of process important?
Perception is frequently modified by subsequent knowledge, but knowledge cant always overrid perceptions
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What are some theories of visual perception emphasising?
One component more than the other, constructivist theories VS direct theories
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What did HelmHoltz suggest about the top down approach?
inadequate information provided by the sense is argumented by unconscious inference
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What is the contructivist approach?
perception is an active and constructive process, end-product of the presented stimulus and internal factors, as perception is influenced by hypotheses that ill sometimes be incorrect it is prone to error
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What does the bottom up approach suggest?
There are a great variety of cues in the natural world that provide much information about the structure of the environment
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What is the perceiver?
They interact with the environment- this interaction is also the key to picking up useful information
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What is the primary function of Gibson's theory?
facilitate interactions between individual and environment
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What is the starting point?
It is not a stream of photons but a pattern of light extending across space and tme
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What is this called?
An ambient optical array
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What does this provide
unambiguous invariant information about the layout of objects
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What form does this take?
Optic flow pattern, texture gradients, affordances
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What does the perception and utilisation do?
enables interaction with our world - the pattern of outward flow can tell you where you are headed and how to steer around obstacles
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For example, what do you do when you walk through a doorway?
The door stays at the centre of the flow field, objects around it shift radially outward, focus of expansion allows you to steer, youll successfully reach the door if you keep it at the centre of the outward flow
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What do drivers rarely look at?
The focus of expansion and tend to look at the centre lines and road edge
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What did Lee suggest?
Drivers use flow itself-the line that passes from view below the driver is the locomotor flow line
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When on course what happens?
This concides with the road - when negotiating a curve this will change
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When does a texture gradient occur?
viewed at an angle so that the individual elements are packed closer as distance from the observer increases
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What information does this provide?
information about distance and depth
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What else is indicated?
The orientation of surfaces - rapid changes in texture indicate that the surface is oriented at a sleep angle whereas smaller changes suggest that we are looking almost straight on
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What does texture gradient provide?
invariant information because they remain constant during movement of the observer
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What four cues to depth can a beach scene hold?
texture gradient caused by the sand, overlap of the two signs, relative heights of the two signs, relative sizes of the signs
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What is the meaning of affordances?
meaning is not necessary to interact with much of the environment - questions role for long term memory in using objects
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What are all potential uses of an object?
Directly perceivable - animal and environment are directly interlinked
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For example?
A ladder affords climbing
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What is the affordance of a surface?
what it can offer the animal - a log might afford sitting on for a human and hopping on for a frog
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What is hemispatial neglect?
where patients fail to respond to items in the contralesional visual field
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What did Humphreys and Riddoch report?
patient MP showed neglect symptoms when searching for objects defined by name or visual feature but could successfuly locate objects defined by the action they afforded
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What did Gibson propose?
A process of resonance - analogous to the workings of a radio
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For example?
If a radio is turned on it may hiss, but if properly tuned then speech or music can be perceived
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What can animals do?
They pick up on information automatically and effortlessly provided that they are attuned to that information ('hopping' affordances will not be perceived by humans)
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What can gibson's research not do?
account for non-verdical perceptions brought about by illusory stimuli
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For example?
the hollow face illusion and the ames room are not examples of static simple lab based illusions
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What did they depend on?
Movement of the observer or movement of the illusion does not disturb the effect, they depend on the invocation of some kind of memory representation
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What do we perceive according to Gestaltists?
We perceive objects not as combinations of isolated sensations but as gestalten (organised wholes) the whole is greater than the sum of its parts
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What is the law of common fate?
Things that move together are grouped together, for example, birds or fish move as one
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What is good continuation?
Tend to preserve smooth continuity rather than yielding abrupt changes
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therefore, what about dissimilar objects?
May be perceived as belonging together by virtue of a combination of proximity and good continuity
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What is the law of closure?
Of several geometically possible perceptual organisations that one will be seen which produces a closed rather than open figure
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What is figure ground segregation?
other things being equal, the smaller of two areas will be seen as a figure against a larger backdrop
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What can it be influenced?
orientation
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What is a criticism of this law?
laws seem rather vague and too descriptive
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What did Navon investigate?
local processing (parts) and global processing (based on wholes)
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What did Cuthill et al investigate?
moth like targets that were exposed to bird predation in the field with the experimental colour patterns on the wings and a dead meal worm as the edible body
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What does this suggest?
aurvival analysis showed disruptive colouration is an effective means of camoflague, above and beyond background pattern matching
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What did HJA find?
They were unable to distinguish between real or novel objects, drew in plecemeal fashion --> intergrtive agnosia
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What do theories of object recognition suggest?
representations of 3D objects are built from component parts in the image
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What did Marr suggest about his Computational theory?
The ultimate goal of vision is to derive a representation of shape
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What is the Primal sketch?
Makes 2D properties explicit by transforming changes in intensity into primitive representation of local geometry
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What are 21/2 D sketches?
Makes orientation and depth explicit and includes information about things in the world that provide the image - only from the viewpoint of the observer
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What is 3D model representation?
Makes shapes explicit as belonging to particular 3D objects independently of any particular position of orientation of the retina
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What does Biederman's theory suggest?
Allows more compex forms than basic cylinders
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What do objects consist of?
basic shapes or components known as geons
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What can geons be?
combined to represent a great variety of objects, justas 44 english phonemes can be combined to form enormous number of words
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What properties can occur?
Non-accidental properties in the primal sketch are sufficient to define 3D component representations -regularities in the image represent regularities in the world
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What are 5 invariant properties of edges?
Curvature, parallel, cotermination, symmetry,co-linearity
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What are objects defined as?
Relationships between Geons
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what can 36 geons lead to?
30,000 readily discriminable objects
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What does object recognition only require?
edges, not impaired by changes in colour, texture and fine detail
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What can they provide?
concavities of a contour are visible, there are mechanisms allowing the missing parts of a contour to be restored disrupted when these are missing
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What is there normally?
Considerable amount of redundancy in the image - complex objects can still be identified when some geons are missing
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What is the difference between written and graphical representations?
They demonstrate the distinction between propositional and analogical forms
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What are propositional representations?
They occur in an abstract form and capture conceptual content (writing)
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What are analogical representations?
Closer to the world, with a structure that resembles the thing being represented (diagram)
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What are 4 factors of language (Propositions)?
Discrete symbols, explicit - needs symbol for relation, grammatical- clear rules of combination for types of symbol, abstract
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What are 4 factors of pictures?
No discrete symbols, implicit, no clear rules of combination or symbol types, concrete
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What are the properties of mental images?
can understand the basic properties of mental images designing appropriate experiments
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What is mental chronometry ?
Measuring reaction times can be used to make inferences about the nature of the task undertaken
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What do visual images appear to have?
Similar properties to actual perceptual eperiences, they preserve the relationships seen in the real world
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For example?
Mental rotation, mental scanning
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What did Shepard and Metzler do?
They showed two 3D figures and asked participants if they were the same shape? The participants had to either pull the lever left for yes or right for no
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What was the stimuli?
Pair A rotated in picture plane, pair B rotated in depth, Pair C can't be rotated in congruence, for type A and B rotation can vary from 0 to 180 degrees
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with practice what did these participants find easy to do?
this task
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What did matter?
Whether rotation in depth or in 2D plane
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What did these results support?
The subjects' introspections, that the are engaged in a constant rate of mental rotation
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What did Kosslyn, Ball and Reisser ask participants to do?
Learn the map of the island with 7 specific locations, imagine the whole map - look at a particular location, imagine a little black speck zipping in the shortest straight line to a second named location
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What did the participants then have to do?
Press a button when you arrive at the second location,
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What was recordeD?
Reaction times for 21 possible pairs of locations
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What was found?
Reaction times was a linear function of actual distance, as if people were visually scanning the image
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What was found in relation to time taken?
Time taken to scan from place to place depends on the actual distance in the picture, not the number of objects in between
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what support was found?
Support for a depictive rather than a popositional account
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What do the findings of shepard and Metzler and Kosslyn et al suggest?
Images have special spatial properties that are analogous to those objects and activities in the world
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What did Pylyshym argue?
The idea that images are picture like entites
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What did Pylyshm argue?
when we forget parts of an image we forget meaningful bits rather than random parts, you need to postulate some form of propositional code to mediate between verbal and non verbal codes
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What else did he suggest?
Any proposed mechanism could be mimicked by another mechanism (mental rotation could occur through a sequence of propositional codes
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What did Kosslyn's computational model do?
Images are represented in a special, spatial medium
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What does the medium have?
Four properties, a space with limited extent, high central resolution, a grain that obscures small detail, the image fades after generation
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What does the LTM contain?
2 forms of data, image files, propositional files
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What do a variety of processes do?
Used to generate, interpret and transform images
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What have more recent studies shown?
sensory modalities do not operate in isolation in mental imagery
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What can they conceive?
Mental rotation as a form of motor imagery
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What is visual image rotaton disrupted by?
performing, concurrent hand movement in opposite direction
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What can rational stratey affect?
Use of motor structure even when the outcome is identical
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What did Sirgu and Duhamel do?
the pps had to sit with there hands behind their backs and infront of them, they were then asked questions about their hands, they found it easier when their hands were on their laps than behind them
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Other cards in this set

Card 2

Front

What is one property of light?

Back

it is one form of electromagnetic radiation - propagation of energy through space

Card 3

Front

What is absorbtion of light?

Back

Preview of the front of card 3

Card 4

Front

What is reflection?

Back

Preview of the front of card 4

Card 5

Front

What is diffraction?

Back

Preview of the front of card 5
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