Transcript Modeling mental imagery
Chapter 2: Modeling mental imagery
The ingredients
• Encountered some of the basic ideas feeding into cognitive science • move away from associationist models of learning and behavior • information theory as a tool for exploring the nature and limits of cognitive abilities • development of “boxological” accounts of how cognitive tasks can be performed • theory of computation as a model for information-processing
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Putting them together: 3 case studies • Terry Winograd and SHRDLU [TODAY] • The imagery debate • Marr’s theory of vision [MONDAY] [WEDNESDAY]
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Earlier themes
• The nature of mental representation – Miller and chunking information processing depends on how information is coded – Winograd and procedural semantics representation of “knowledge” in terms of algorithmic routines
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Common assumptions about information
• Information is amodal • Miller’s suggestion that the sensory systems all have the same channel capacity • Information is coded in a digital/propositional format • based on the formal languages used to program computers
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Digital information-coding
• Information is coded in a format that has the basic properties of a language • Basic constituents are individual symbols • Compositionality – complex structures are built up from individual symbols according to formation rules • Arbitrary connections between symbolic structures and what they represent
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Digital information-processing
• The model for thinking about digital information-processing are formal languages (e.g. logical languages and computer programming languages) • Model information-processing on, e.g. • proofs in logical languages • implementation of instructions in a production system
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Imagistic information-coding
• Non-symbolic: images are not built up from basic elements • Not compositional • The parts of images cannot reoccur in other images • No rules for building up images from their parts
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Representation in images
• Representation depends upon systematic correlation between properties of representation and properties of what it represents • pictorial depiction depends upon resemblance • can be schematic resemblance, as in a map
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José Luis Bermúdez / Cambridge University Press 2010
Tricky issues
• Imagistic representations can exploit symbols (e.g. maps) • need to distinguish between the representation and the labeling of the representation • Imagistic representations ≠ analog representations • a representation is analog just if it permits continuous variation • there are examples of analog representartions that are not imagistic and imagistic representations that are not analog
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Imagistic information-processing
• The real issue comes with how information is extracted from imagistic representations • scanning images • manipulating images (e.g. rotation) • Certain types of information are much easier to extract from images than from digital representations
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
The issues for cognitive science
• Is information always encoded in a digital format - or are there cases of imagistically encoded information?
• How can we explore this experimentally?
• By looking at how subjects carry out information-processing tasks involving images • Seeing whether their behavior provides indirect evidence that they are scanning/manipulating images
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Brooks 1968
F • Form a memory image of a capital F • Trace around the image, starting at the bottom left corner and working clockwise • Indicate for each corner whether it is on a top edge of the figure • Performance is impaired when responses are made visually (i.e. by pointing to the word ‘Yes’), rather than by saying ‘yes’
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Cooper 1975
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José Luis Bermúdez / Cambridge University Press 2010
Scanning mental images
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
The strong interpretation
• Subjects perform the task by rotating/scanning mental images in their “mind’s eye” • The process of mental rotation/scanning has is structurally similar to physical processes of rotation/scanning • Seems to match evidence from introspection
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
•
Problems with the strong interpretation
• Dennett’s “Cartesian theatre” Who or what is doing the scanning/rotating?
• • Where is the image projected?
Threat of regress if we take the metaphor of the “mind’s eye” literally • Not clear how these mental images relate to “phenomenal images”
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Kosslyn’s theory •
Develops metaphor of images as spatial displays on cathode ray tube • Mental images are temporarily generated from propositionally encoded information in long-term memory • Mental images “projected” onto visual buffer (which is where perceptual representations also appear)
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Solving a problem
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010
Ambiguity
• • • • Personal-level phenomena phenomenal images conscious experience of the world accessible to introspection (not always reliable) • Subpersonal information-processing personal-level phenomena and abilities explains our
Cognitive Science
José Luis Bermúdez / Cambridge University Press 2010