PSYC 256 Lecture Notes - Lecture 8: Zenon Pylyshyn, Epiphenomenon, Stimulus Modality
13 Jun 2018
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VISUAL IMAGERY
Definition of Imagery
• Mental representation
o Of things not currently sensed by the sense organs
o OR of things never observed by our senses
o In any sensory modality
Imagery as Knowledge
• Question is NOT about the experience of having a mental image
• Question is what form does that representation take in the mind & brain
o Is it propositional (abstract) or pictoral (analog)?
• Imagery is an epiphenomenon:
o A phenomenon that is not related to the function of the system
• The sensation of seeing an image is real, but that doesn’t mean that the sensation
has anything to do with the actual cognitive task being performed
)mages are epiphenomenal -Zenon Pylyshyn
• Reasoning with mental images involves the same form of representations and the
same processes as that of reasoning in general
• However, the content or subject matter of thoughts experienced as images includes
information about how the things would look
• Images, though real, are epiphenomenal and do not serve any useful function
Propositional Theory
• Libet et al. 1983
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o If you have electrodes, can detect the brain activity leading to motor
movement that occurs before participant subjectively decides to move
• Although the intention to act precedes an action, there is neural activity associated
with action that precedes the intention
• Therefore, conscious awareness is not necessarily functional
• We do not store mental representations in form of images
o Storing image of every scene/object violates cognitive economy
• Mental representations stored as propositions
Alternative Representations
• Is knowledge of math same as knowing what an apple looks like?
• All knowledge is the same
• The apple here is analogous to a real apple
Anti-Propositional View
• Images
o Preserve the structure of original information in quasi-direct manner
o Resemble what they stand for (analog code)
o Implication is that imagery is functionally-equivalent to perception
▪ You use the knowledge the same way regardless if distal stimulus is
present
Functional-Equivalency (Kosslyn)
• Images are functionally equivalent to percepts
• Analogous to the physical percepts they represent
• Therefore, images should obey the same rules as percepts
Functional Equivalency (Kosslyn, Ball, & Reiser 1978)
• Memorize map
• Later ask to scan image
• Manipulate distance between items in scan
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Document Summary
Definition of imagery: mental representation, of things not currently sensed by the sense organs, or of things never observed by our senses. Imagery as knowledge: question is not about the experience of having a mental image, question is what form does that representation take in the mind & brain. Images, though real, are epiphenomenal and do not serve any useful function. Is knowledge of math same as knowing what an apple looks like: all knowledge is the same, the apple here is analogous to a real apple. Images: preserve the structure of original information in quasi-direct manner, resemble what they stand for (analog code) Implication is that imagery is functionally-equivalent to perception: you use the knowledge the same way regardless if distal stimulus is present. Images are functionally equivalent to percepts: analogous to the physical percepts they represent, therefore, images should obey the same rules as percepts. )mages are picture like color, details, viewing angle, texture, perceptual.
