perception and visual cognition Flashcards
what is perception
active process - very important puts focus on individual seeking things out in active world
creation of experience
organises raw swnsory data and gives it meaning
Bottom up processing
Individual elements of the stimulus are combined into a unified perception.
putting together small pieces of information to make unified whole
think of reading
not perceiving all little intricate parts of letter you percieve the whole word
top down processing
Sensory input interpreted in light of existing knowledge, concepts, ideas and expectations.
Important route to idiosyncratic, unique perceptual experiences.
much more formalised component
have expectations that pull together the perception that goes beyond stimulus elements
PEOPLE EXPERIENCE THE SAME SENSORY INPUT BU HAVE DIFFERENT EXPERIENCES
idiosyncratic unique visual experiences
everyone has had different presences and therefore different expectations
top down processing: exMPLE
LOOKING AT PHOTO SOMEONE SEES WOMAN SOMEONE SEES MAN PLAINGSAXAPHONE
led zeppelin song
some people hear the secret message some don’t
this is because some expect it and actively go out to seek it
Attention and perceptionL selective attention
attention is crucial in perception
we are exposed to a lot of stimuli at any given time much of which is irrelevant
Selective attention allows us to focus on certain stimuli and filter out other information.
Cherry’s (1953) cocktail party effect
When you hear someone mention your name at a party, you attend to what they say, filtering out other conversations.
can be seen in dichotic listening tasks
inattentional blindness (Mach 2003)
is easily missing striking occurrences due to not paying attention
what happens to that information we received in sensory information
people aren’t ignoring the other information, they’re just attending more to other information
what determines what we pay attention to
external factors
internal more personal factors
external factors
intensity
movement
size
novelty
internal factors
interests
motives
internal v external: example
Two pictures with bottles and alcohol
those who drink were more likely to notice the change to the alsohol bottles than those who didn’t drink but they didn’t notice a control change
Jones etal 2003
potential source
tend to ‘pop out’ at us (Hansen & Hansen 1998)
Threatening faces make it harder to find other faces
Breaks in perception
When perception breaks down
what this tells us about perception
Breaks in perception:The Thatcher illusion
Two faces
both of Barrack Obama
one picture have some adjustments tot he features
hardly noticed when face is upright but when showed upside down and inverted these processes used for facial perception is dirupted and changes can be noticed more easily
figure ground segregation
Separating out the figure and the ground so the background and the foreground
one of the critical first steps in organising raw sensory data
rule of thumb in distinguishing:
the figure is think on top and ground is behind
Figure-ground confusion: examples
inverting colours on map
optical illusions with line drawing of elephant with too many legs
Gastalt principles
similarity proximity closure continuity figure V Ground ...rules of thumb that the perception system uses to help organise raw sensory data
the whole is much greater than the sum of its parts
Gastalt Principles: Similarity
Group similar things together group different things apart Determined by similarity in: colour size shape etc
Gastalt principles: Proximity
Group things together that are close to each other or organised together such as in squares etc despite colour differences
Gastalt principles: Closure
Tendancy to fill in the gaps o create a unified or coherent object
e fill in gaps in a circle or more angular object like rectangle
closure used a lot in graphic design
Gastalt principles: continuity
Tendancy to perceive flowing patterns in lines rather than those that contain sharp angular changes in perception so in an X you view two diagonal lines rather than two arrows
eg concentric circles that due to the pattern were seen as spirals going off into distance
Gastalt principles: Figure V Ground
Tendancy to distinguish figure from the ground
Relative perception
We perceive things relative to other things
Ebinghaus illusion
perceive an object surrounded by smaller objects as bigger than when its presented with identical ones
use of visual landmarks to estimate the relative size of something
monocular cuesv binocular ces
cues to depth perception between that of one eye and those that depend on information from two eyes
monocular and binocular cues are very different
monocular cues to depth
with object: relative sizesize occlusion relative height combinations of all three provides a very obscured view of depth Other cues: linear perspective shadows clarity motion parallax
monocular cues: relative size
in absence of other information there is a tendency to perceive things large as near and small as far away
monocular cues: occlusion
refers to the tendency to perceive the thing in front of something as being nearer
occlusion refers to covering something so photos where people are pushing over th leaning tower of pisa from a distance that obscures the depth cause your not covering the tower
monocular cues :relative height
boats higher up toward horizon are sensed as further away
monocular cues: linear perspective
tendency of lines to converge as they go od ff into the distance
allows artists to create very powerful strong impressions of depth
monocular cues: texture gradient
perceive things that share a continuity in pattern and group them together and sense that the reason that the patterns flow is because they share the same location in space
monocular cues: shadows
false shadows can create misleading impressions of depth
David Blain giving the impression that he’s levitating through exploitation of shadow
monocular cues: clarity
things that are in the foreground tend to be perceived moocher clearly that things in the background
this can be manipulated by making background more clear to card confusion
motion parallax
tendency for things at different difference to move at different speeds
far things wipe across the retina more slowly than near things to us
e.g. the clouds, aeroplanes
Binocular cues
most effective and compelling depth cues:
binocular disparity
convergence
binocular cues: binocular disparity
refers to tendency of getting a slightly different image from each eye
tendency of perceptual system to use difference between both eyes to compute information about depth
binocular cues; convergence
refer to perceptual systems tendency to use information from muscles in eyes to make inferences about depth
since eyes are in different possessions depending onto far something is
perceiving motion
imperitive for survival sensed by image wing across the retina
stroboscopic motion
ability to perceive something as moving although its not
