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 imageryThree 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 ImageryImportant findings:1. Same areas of brain important for imagery and visual perception:

Occipital/temporal visual pathway2. 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