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Thomas, N. J. T. (1999). Are theories of imagery theories of imagination? An active perception approach to conscious mental content. Cognitive Science 23, 207--245.

  author = 	 {Thomas, Nigel J. T.},
  title = 	 {Are theories of imagery theories of imagination? An
active perception approach to conscious mental content},
  journal = 	 {Cognitive Science},
  year = 	 {1999},
  key = 	 {},
  volume = 	 {23},
  number = 	 {},
  pages = 	 {207--245},
  month = 	 {},
  note = 	 {},
  annote = 	 {}

Author of the summary: Jim Davies, 2006, jim@jimdavies.org

The preprint of the actual paper can be downloaded from http://www.calstatela.edu/faculty/nthomas/im-im/im-im.htm. The page numbers in this summary come from a printout of the preprint version of this at cogprints.org.

Cite this paper for:

There are three approaches to mental imagery: Picture Theory (PT, touted by Kosslyn), Description Theory (DT, touted by Pylyshyn, called "propositional theory" by psychologists) and Perceptual Activity Theory (PA, touted in this paper.) In this paper Thomas tries to show that PT and DT are inadequate and describe how PA might be better. He also tries to discuss the above theories with respect to imagination.

He views these theories actually as reserach programs which cannot be explicitly confirmed or rejected (in the sense of Lakatos 1978), but are chosen based on parsimony and consistency. [3]

Kosslyn says that the "deep representations" used to create the imagery in the visual buffer are not available to consciousness. [5]

Kosslyn and Schwartz (1977) made a model of imagery. ASCII letters filled slots on a grid, and faded over time. Each cell contained qualitative features at that point. Other implementations are Julstrom & Baron 1985; Mel 1986, 1990; Stucki & Pollack 1992; Glasgow & Papadias 1992; Glasgow 1993. [6]

Kosslyn 1980: The cells need not be physically adjacent in the brain, but need to be treated as adjacent by computational routines that inspect the array.

The essence of PA theory is perception occurs by the reasoner requesting particular information for hypothesis-confirming, rather than a more passive interpretation of what's coming in. [9]

Each new question follows from the answers of previous ones.[10] This is best understood with haptics (touch) passive touch is almost useless. [11] This is how it accounts for imagery: "On this view, no end-product of perception, no inner picture or description is ever created. No thing in the brain is the percept or image. Rather, perceptual experience consists in the ongoing activity of schema-guided perceptual exploration of the environment. Imagery is experienced when a schema that is not directly relevant to the exploration of the current environment is allowed at least partial control of the exploratory apparatus. We imagine, say, a cat, by going through (some of) the motions of examining something and finding that it is a cat, even though there is no cat (and perhaps nothing relevant at all) there to be examined. Imagining a cat is seeing nothing-in-particular as a cat (Ishiguro, 1967)." [10]

There are fibers that go from the brain to the retina (about 8% in the optic nerve according to Pribram 1991). Perhaps they are changing the kind of information the retina is getting. another good quote: " The suggestion is that during imagery, the schema is active in much the same way that it is during perception. It still sends out at least some of its "orders" to the perceptual instruments, and selects procedural branches to follow. However, the reciprocal control of the schema's activity by the perceptual instruments is lost, or at least much attenuated. Hypotheses are still being put forward, as it were, giving rise to (potentially) conscious experiences, but they are not subject to testing against reality. This might either be because the instruments themselves (or some of them) are inhibited from carrying out their tests (Marks, 1973; Jacobson, 1932), and so fail to return any meaningful result, or it might be that results that are returned are disregarded, or not given full weight, by the schema. Either or both these processes may well occur in particular cases. However this may be, the processes that do occur will still display the intentionality of perceptual consciousness, being still directed towards an object, albeit a merely intentional ("intentionally inexistent") object rather than a material one (Anscombe, 1965; Ishiguro, 1967). It is important to stress that, on this theory, no thing or state in the mind or brain corresponds to the percept or image. Although the schema may be considered the repository for what we learn about the world through perception, and although it controls our conscious perceptual activity, it should not be identified with that activity. As has been independently argued (Rabb, 1975; Heil, 1982; Tye, 1984), strictly speaking there is no percept or mental image, only the activity of perceiving or imagining, which takes different forms according to what is being perceived or imagined." [14]

The visual buffer is primarily for perception of input, but can be "hi-jacked" for mental imagery. [23]

PA's core committments: [15]

Poor results with re-interpretation through mental imagery: [16] Reed 1974; Palmer 1977; Hinton 1979; Reisberg, Smith, Baxter, and Sonenshine 1989; Reisberg and Chambers 1991) and Slezak 1991, 1995.

But modifications yielded some good results...
Finke, Pinker, Farah 1989; Peterson, Kihlstrom, Rose, Glisky 1992; Brandimonte, Gerbino 1993; Cornoldi, Logie, Brandimonte, Kaufmann, Reisberg 1996.

Mnemonic effects of imagery in congenitally blind: [17]
Craig 1973; Jonides, Kahn, Rozin 1975; Zimler, Keenan 1983; Kerr 1983 (aosl reports mental scannign, and size/inspection time effects.

Bisiach, Berti 1990: Mentalese neurally implausible [18]

Psychologists consider imagery important to imagination: Finke, Ward, Smith 1992; Weisberg 1986

Imagination gets used not only for mental imagery, but also for generally supposing, or entertaining ideas. [22]

One thing that some imgagery theories have trouble doing is augmented reality (summary author's term), or seeing as during real perception, like looking at a book and imagining it falling, or forcing yourself to see letters in the tiles on the floor (example from Kosslyn 1994). This is "seeing as."[23] PT tries to do this by pasting over, but then how come when the lights go out we don't see the residual pasted image section? [24]

Imagery ubiquitous in science: [25]
Shepard 1978; Tweney, Doherty, Mynatt 1981; Miller 1984

Summary author's notes:

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