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: 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: Same areas of brain important for imagery and visual perception: Occipital/temporal visual pathway Damage to occip/temp visual pathway leads to visual not spatial deficits (case of LH) Occipital parietal pathway important for spatial tasks – see below.

Combination of conceptual and imagery system 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