Spatial Knowledge, Imagery, Visual Memory

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15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Visuospatial Representation

Spatial Knowledge, Imagery,
Visual Memory

Representation


What is a representation?


Four aspects of representation


The represented world


The representing world


Set of informational relations on how the
two correspond


Set of processes that extract and use
information from the representation

Meaning


Mental representations are carriers of
meaning


In order to interact appropriately with the
environment we represent info from it and
manipulate those representations


Correspondence


Meaning derived from how representation stands
in consistent relation to the represented world


Conceptual


Meaning determined by relations to other
representations

Spatial Knowledge


How we represent and use spatial
information


Separate from strictly verbal knowledge


Semantic propositions


Dependent on the linear dimension of
space.

Spatial Cognition


How is the representing world like the
represented world?


The represented world is a space


The representing world is a space


What kinds of processes might be
involved?


Space as a representation


Spatial representation


Representing world is a space. What is a space?


Geometric entity in which locations are specified relative to a
set of axes


Dimensionality defined by the number of axes that can point
in independent directions


Of interest is the distance between items, which can be
measured in different ways


Euclidian


Straight line


Non
-
independent dimensions


Saturation and brightness


City
-
block


Distinct dimensions


Color and size

Space as a representation


Physical world experienced (at least
perceptually) has three dimensions (+ time)


However, the representing world is not
confined to any number of dimensions


Represented world does not need to be
spatial


Conceptual info can be represented spatially


More on that later


Spatial Representation


Analog representation


Representation mimics the structure of the
represented world


Multidimensional scaling


Propositional


Abstract assertions regarding the state of
the represented world


Not tied to a particular sensory modality

Multidimensional Scaling (MDS)


MDS


Mathematical technique for taking a set of distances and finding
the best
-
fitting spatial configuration that corresponds to those
distances


Input: a distance or proximity matrix that describes
how close every object in a set is to every other
object


N objects are represented by N(N
-
1)/2 numbers (distances)


Output: a geometric representation where every
object is represented as a point in D
-
dimensional
space


Each object is represented as a point in space


N objects are represented by ND numbers (coordinates)


Purposes of MDS


Give psychological interpretations to the dimensions


Reveal the dimensionality of a data set

Difficult to get a sense of relative distance by means of this information

MDS


MDS recovers absolute original locations for the objects from the
distances


Flipping on horizontal axis would give us a rough approximation of
NSEW


Analog representation

MDS

Propositional Representation


(A,B) 10 miles east


(E,C) 20 miles
south, 10 miles east


(F,D) 10 miles
south, 10 miles west

Analog vs. Propositional


Analog


Good for configural info


Easy incorporation of new info


Propositional


Time
-
consuming


Lots of info must be represented


E.g. one point added may require many propositions


Allows for communication of spatial knowledge
and incorporation of additional information not
related to distance


Going south on I35, one must pass through Denton to
get to either Fort Worth or Dallas

Cognitive Maps


Where is Seattle?


Where is Terrill Hall?



Large vs. small
-
scale space


Hierarchical representation


Small vs. Large
-
scale space


Maps of small
-
scale (navigable space)


Cognitive geography


Maps of large
-
scale space


What is our sense of the locations of items
in the world?


Small scale space


Survey knowledge


Bird’s eye view (map knowledge)


Good for global spatial relations


Easy acquisition


Not so great for orientation


Route knowledge


Gained from navigating through the environment


Locate landmarks and routes within a general frame of
reference


Landmark knowledge


Salient points of reference in the environment


More difficult to acquire but better for navigation in irregular
environments


May lead to survey knowledge


Perhaps a different type


Cognitive collage vs. orientation free

Large scale space


Which is farther north:


Denton, TX or Chicago, IL?


Portland, OR or Portland, ME?


Hierarchical representation of locations

Hierarchical representations


Relative locations of smaller regions are determined
with respect to larger regions.


States are superodinate to cities, countries superordinate to
states


USA is south of Canada


Maine is just south of Canada


Oregon is well south of Canada


Oregon must be south of Maine


Cities in Oregon must be south of cities in Maine


In this case such cognitive economy works against us


Portland OR is north of Portland ME

Hierarchical representations


Judge relative position
of cities (Stevens and
Coupe)


When superordinate
info congruent with
question, performance
better


Is x north of y when one
of right side maps
presented

Hierarchical coding


Huttenlocher & Hedges


Category
-
adjustment model


Combine info across hierarchical levels


If info at subordinate is known with near certainty, there is
no appeal to categorical info


If info at subordinate (fine
-
grained) levels is at all uncertain,
people use categorical info in estimation


Bias toward center of category


Bayesian approach utilizing prior knowledge


Gist: errors in estimation are due to categorization
rather than nonmetric spatial relations

How are maps learned


From descriptions


Taylor & Tversky: People learned maps from
survey and route descriptions


From navigation


People can assess distance and direction traveled


Integration of information


Visual information


Vestibular information


Maps formed from video games are less accurate
than maps in which people really move


Rotation is particularly important

Using spatial cognition


Adaptive context


Locating and way finding


Tool Use


Mental rotation vs. mental movement


Symbolic representations of space


Drawings, maps, models


Language


Thinking

Adaptive context


Locating and way finding


Consider


Hatchling sea turtles finding the sea


Salmon finding way back home


However these are more behavioral instinct and
imprinting than pure navigation


Desert ant finding direct route home after
meandering paths in featureless environment


Marsh tit stores seeds in holes in a hundred
various places for later retrieval

Locating and way finding


Ego
-
centered systems


Environment
-
centered systems


Hierarchical coding


Locating and way finding


Ego
-
centered system


Location of objects coded relative to self


Updated as we move through the world


Nonconscious


Rieser, Guth, Hill (1986)


Participants asked to point out previously learned
locations in unfamiliar room after blindfolded and led
along path


Did not matter whether previously told which location
they’d be asked about, suggesting attentional focus did
not assist in the process


Problem: may not always be accurate over larger
distances without detailed environmental
information

Locating and way finding


Environment
-
centered system


Object location coded in relation to stable features
of the environment


Requires feature
-
rich environment providing info
to dominate sense used by organism


If conditions met, then superior to ego
-
centered


Allows for rechecking of position (no drift from
accumulation of small errors)


Works better for retaining info over long periods of time

Cognitive maps


Both humans and animals display errors in
judgment that cast doubt in positing a true
‘cognitive map’


Animal studies suggest approximation of
distance from a single landmark


Humans make many errors in spatial
judgments that suggest no real metric
representation


Distance from A to B judged different from B to A


Though again this sort of distortion may be
related to categorization (hierarchy)

Tool use


Making, using and designing tools for
interaction with the environment
involves cognitive processes such as
mental rotation and imagery for success

Shephard & Metzler (1971)

Mental rotation vs. Mental Movement


Logically equivalent


However evidence suggests that mental rotation and
perspective
-
taking/mental movement are
psychologically distinct


Selection task


Which these arrays/models would be the correct view from
over there?


Item question


What object would be nearest to you if you were over there?


Specify frame of reference of relative to the observer

Mental rotation vs. Mental Movement


Selection task


Piaget


Kids (< 10) not so hot at such a task


Usually pick egocentric view


Huttenlocher & Presson


They do much better when asked to do mentally rotate


Can also physically move to new location that matches a
particular array


Suggests conflict between current physically present
perspective and the new (imagined) one they are
trying to obtain


MR allows them to stay put in the physically present room


Physical movement physically transforms that perspective

Mental rotation vs. Mental Movement


Item questions


If kids do not move item questions help (even as
young as 3)


Again, this helps them maintain that egocentric perspective


If asked to mentally rotate, item questions can
actually hurt performance compared to selection
tasks


It may be that in item questions, whole array must be
rotated to determine object relations vs a simple ‘rotation’ of
the person or single object in selection task


Gist: mental rotation and mental movement can be
differentially affected depending on the nature of the
question asked, suggesting there may be different
underlying processes involved

Drawings maps and models


Spatial learning from maps differs from learning by
means of navigation


Map learning may aid configural knowledge and allow for
better estimates of distance between points while
navigational learning allows for better route distance
estimation and location of unseen points


Recall survey vs. route knowledge


Orientation
-
specific vs. orientation
-
free learning


Studies show evidence that navigational learning is more a
collection of multiple views than orientation
-
free, though
may lead to a sort of orientation
-
free type of knowledge


Sholl & Friedman

Spatial Language


Contrasting experience with communication


Experience spatial relations continuously, but
language is usually discrete (e.g. near vs. far)


Spatial terms function much like other categories
(e.g. fuzzy boundaries, prototypes)


Experience multiple spatial relations
simultaneously, but speak of one relation at a
time


A frame of reference must be agreed upon in
order to communicate spatial relations

Spatial Language


Despite the difficulties in communicating spatial
knowledge, ambiguities are generally overcome and
information encoded (survey, route knowledge)


However it does seem that spatial language may bias
or constrain spatial representation, and may even
affect the development of spatial concepts and
categories


Even so, the actual link between spatial language
and spatial representation is not entirely clear


Impaired sight individuals may have difficulties with a
variety of spatial tasks but have intact spatial language

Thinking


Spatial cognition also contributes to logical
reasoning, metaphor, and creativity


Transitive reasoning


A > B, B > C


A ? C


Metaphor


The future stretched in front of them


My heart is a flame turned upside down


Structural alignment of spatial and temporal
concepts


Diagrams as aids to understanding


Show conceptual similarity of items, connections
amongst various concepts etc.


Creativity


E.g. visualization for problem solving


Taking someone else’s point of view?

Imagery



Some information in memory is purely verbal


Who wrote the Gettysburg address?


Other memories seem to involve mental
images


Trying to recall a procedure


Making novel comparisons of visual items


What is a mental image?


How are mental images represented and
processed?


Are mental images like visual images?

Evidence for use of visual imagery


Selective interference


Segal & Fusella


Imagery interferes with detection of stimuli
(sensitivity decreased)


Auditory imagery interfered with auditory
detection, visual imagery with visual stimuli


Manipulation of images


Mental rotation studies

Evidence for use of visual imagery


Kosslyn


Learn a map


Mentally travel from
one point to another


Measure time to
make this mental trip


Results


Time to make trip
increases with
distance


Times increase with
imagined size of the
map.

Evidence for use of visual imagery


Moyer 1973



Subjects were given the
names of two common
animals and asked to judge
which was larger


Which is larger, a moose or
a roach?


Wolf or Lion?


The time delays as a
function of size difference
were similar to those usually
found for perceptual
judgments.

Kosslyn


Kosslyn 1975


Scenario I: Imagine an elephant
standing next to a rabbit. Does a
rabbit have a beak?


Scenario II: Imagine a fly standing
next to a rabbit. Does a rabbit have
an eyebrow?


People made faster judgments when
relying on a larger mental image
(such as the rabbit next to the fly)
than when using a smaller mental
image (such as the rabbit next to an
elephant)


Kosslyn suggested that the size of
an image is an important factor in
determining how fast we can make
judgments about it.


RT

0

Elephant

Fly

True

False

Inconsistent

Consistent

Paivio's Dual
-
Coding Theory


Information is mentally represented either
in a verbal system (propositional) or a
nonverbal (analogical) system (or both).


Each system contains different kinds of
information.


Each concept is connected to other
related concepts in the same system and
the other system.


Activating any one concept also leads to
activation of closely related concepts.


Paivio


The hypothesis of multiple codes
(verbal and spatial) is based on the
demonstration of independence of
effects.


Pictures of objects


Words of objects


Paivio (1975) compared reaction times for
consistent

and
inconsistent

visual stimuli


If the stimuli are processed semantically, there
should be no difference between consistent and
inconsistent presentations.


If stimuli are processed spatially, inconsistent stimuli
should require a mental conversion to appropriate
size.


Which takes time



Consistent


Inconsistent


Results


“Which is larger?”

RT

0

Inconsistent

Consistent

Paivio


Consistent

RABBIT

FLY

Paivio


Inconsistent

RABBIT

ELEPHANT

Paivio


Congruity Effect only for Pictures (not words)


Imagery relies on perceptual detail and semantic does not


Such findings as this and picture superiority effect (pictures are
better recognized than words), and that verbal + imagery
encoding leads to best recall, suggest a Dual Code Theory

RT

0

Picture

Words

Inconsistent

Consistent

Santa 1977


More evidence of dual
coding


Ss presented array of
objects or words


On test presentation
asked whether the
elements were same as
studied


E.g. In geometric
condition first two would
be yes responses

Santa 1977


Results of positive
responses


Spatial configuration is
preserved in geometric
encoding


Compared to verbal
presentation, which was
encoding in typical
English reading style
and benefited from the
linear configuration

Representation of images


What is the relationship between
imagery and perception?


Can imagining interfere or facilitate
detection of stimuli?


Similar processes involved?

Spatial Knowledge


Symbolic Distance Effect (Moyer 1973)


Process of imagery = process of perception


As perceptual distance increases so does
psychological distance (RT).


Items “farther apart” are more quickly distinguished


Which is larger?

Rabbit
-
Elephant

Rabbit
-
Dog

Representation of images


Contrary evidence


Chambers and Reisberg


Images are (committed
to) a particular
interpretation


E.g. The rabbit comes
once drawn but was only
a duck as imaged


Contrast with
perception which
requires interpretation,
images are already
interpretations

Are visual images visual?


Plenty of evidence to suggest a spatial
component to visual imagery, but perhaps
the visual part is represented propositionally


Kerr


Congenitally blind also take longer to imagine
longer map routes like the one in Kosslyn

Are visual images visual?


Images are also not as sharp as real
pictures


Form a mental image of a tiger


Does it have stripes?


How many?


It is hard to examine details of mental
images that would require eye
movements

Making new pictures


Finke, Pinker, Farah


Example


Imagine a capital letter H and a triangle


Rotate the H 90 degrees


Place the triangle on top of it


What is it?


Suggests images can take on new
interpretations

Are visual images visual?


Facilitation and interference (Farah)


Have people imagine a letter (H or T)


Present one of the letters to the screen briefly (20
ms), or present nothing, followed by mask


Asked if they saw a letter


People are more likely to detect the stimulus
if it was the same as what they were
imaging, suggesting that visual and imaginal
representations joined or fed into the same
process

Are visual images visual?


Evidence from neuroscience


Patients with lesions of
visual cortex that lead to
perceptual problems also
have problems with mental
imagery


ERP evidence PET evidence:
Visual imagery leads to
activation of visual cortex.
Auditory imagery does not


In general, results of studies
from mental rotation to brain
imaging support the idea of
both visual and spatial
representation of images

Translating Words to images


Franklin and Tversky


Create a mental image based
on the description


Asked to identify location of
items in that imagined
environment


Results are what one might
expect given an imagined
spatial environment


Up
-
down, front
-
back more relevant
in navigating real world


Left
-
right confusion in real world
and imagined world

Visual memory


Although our visual
memory seems to be
excellent, it turns out
not to be that great in
many respects



In general, our memory
for details is lost, much
like with other types of
memory

Visual memory


Memory for pictures is quite good
generally


Again, don’t get too detailed


Standing


Presented 10000 photos over several days


Old
-
New memory over 80%


Picture superiority effect


Better memory for pictures than words