Visuospatial Representation

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

MDS 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

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.

Inconsistent RT Consistent 0 Elephant Fly True False 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.

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

Inconsistent RT Consistent 0 Picture Words 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

Visuospatial Representation