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Mental Imagery

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					                         Mental Imagery
Mental imagery: representation of nonpresent
object or event that is subjectively experienced as
the object or event itself. Note: visual imagery is just
one form of mental imagery
Three hypotheses:
1.Dual code: (Allan Paivio) – info can be encoded into
two possible system: verbal system or imagery
system. Recall is best if represented in both rather
than single system.
Empirical evidence:
Words high in imagery value (tornado) better
recalled than words low in imagery value (reciprocal)
Brooks study – selective interference – verbal task
not affected if paired with spatial response; affected
in paired with verbal response.
*Important point – image systems seen as
independent form of representation; but is this so?
                        Mental Imagery

• Hypo 2: Conceptual/propositional hypo: all info is stored as
  conceptual/propositional information. When propositional info is
  especially elaborate it may be experienced as ‘image’ but this is
  illusion, does not reflect true nature of representation.
• Pylyshyn’s arguments against imagery:
• Pictures in head
• Mind’s eye
• Tacit knowledge
• Epiphenomenalism: Images as ‘dependent’ on more basic form of
  representation
• Empirical evidence
• Mental rotation studies – shoes rotated more slowly than feathers?
• Ambiguous figures: reversal as stimulus not as image
         Image switching: perception vs. imagery




• Subjects report image
  switching in perception,
  not imagery
                Mental Imagery
• Hypo 3: Functional equivalency – images
  formed in STM based on more basic
  (propositional) LTM representation, but
  posses independent features.
• Kosslyn – mental scanning, mental image size
  studies; Shepard – mental rotation
• Kosslyn – fMRI studies showing visual
  system/imagery system equivalency
• Mental rotation and mental scanning studies
                  Neuroscience of Imagery
Important findings:
1.   Same areas of brain important for imagery and visual perception:
     Occipital/temporal visual pathway
2.   Damage to occip/temp visual pathway leads to visual not spatial deficits
     (case of LH)
3.   Occipital parietal pathway important for spatial tasks – see below.
                 Mental imagery

• Cognitive mapping: mental representation of
  spatial layout of navigatable space.
• Combination of conceptual and imagery
  system
• Route vs. Survey knowledge
• Conceptual distortions of spatial
  representations (ex: which is farther west San
  Diego, CA or Reno, NV?)
Conceptual distortions of survey knowledge

				
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posted:9/1/2012
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