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Mental Imagery. What are mental images? How are mental images used (or are they)?. Mental Imagery. What are mental images? mental representations can be related to any sense. Dual Coding Hypothesis (Paivio, 1965). Two ways of representing information: imagery verbal
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Mental Imagery • What are mental images? • How are mental images used (or are they)?
Mental Imagery • What are mental images? • mental representations • can be related to any sense
Dual Coding Hypothesis (Paivio, 1965) • Two ways of representing information: • imagery • verbal • Easier to remember when you can use both codes: • higher recall for concrete words than for abstract words
Conceptual-Propositional Hypothesis (Anderson & Bower, 1973) • Information is represented by propositions. • Mental images are generated as byproducts (epiphenomena).
Functional Equivalency Hypothesis (Shepard, 1972) • Mental images are used like real images (they are “functionally equivalent”). • Mental images are not the same as real images: second-order isomorphic.
Size of Mental Images(Kosslyn, 1975) • Imagine a rabbit sitting next to an elephant. • Does the elephant have a tail? • Does the rabbit have a tail? • Imagine a huge rabbit next to a tiny elephant. • Does the elephant have a tail? • Does the rabbit have a tail?
Size of Mental Images: Results • Time to answer a question about a mental image depends on size of the image. • Result holds even when a normally large object is imagined to be small and vice-versa.
Indeterminacy Problem(Anderson, 1978) • Both hypotheses can explain the same results. • There is no way to determine which hypothesis is correct without biological evidence.
Biological Evidence On Imagery • Visual and memory areas of the brain are active during mental imagery tasks. • Primary visual cortex • Temporal lobe • The visual areas are MORE active during imagery than when actually seeing! (Kosslyn et al., 1993)
Biological Evidence On Imagery • Imagery neurons in medial temporal lobe – fire whether seeing or imagining a particular object (Kreiman et al., 2000) • Loss of perceptual ability and loss of imagery ability sometimes co-occur (Bisiach & Luzatti, 1978)
Double Dissociation Between Imagery and Perception • R.M. - Loss of imagery with intact perception (Farah et al., 1988) • C.K. – Loss of perceptual ability with intact imagery (Behrmann et al., 1994)
Is Imagery an Epiphenomenon? • Many similarities between imagery and perception • Double dissociation indicates they are not the same processes • Overlap in the processes involved, but not complete overlap
Evolutionary Psychology • How much overlap between imagery and perception is ideal?