Are Theories of Imagery Theories of Imagination? An Active Perception Approach to Conscious Mental Content
Nigel J.T. Thomas
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Source: http://cogprints.org/5018/1/im-im-cp.htm
Can theories of mental imagery, conscious mental contents, developed within cognitive science throw light on the obscure (but culturally very significant) concept of imagination? Three extant views of mental imagery are considered: quasi-pictorial, description, and perceptual activity theories. The first two face serious theoretical and empirical difficulties. The third is (for historically contingent reasons) little known, theoretically underdeveloped, and empirically untried, but has real explanatory potential. It rejects the "traditional" symbolic computational view of mental contents, but is compatible with recent situated cognition and active vision approaches in robotics. This theory is developed and elucidated. Three related key aspects of imagination (non-discursiveness, creativity, and seeing as) raise difficulties for the other theories. Perceptual activity theory presents imagery as non-discursive and relates it closely to seeing as. It is thus well placed to be the basis for a general theory of imagination and its role in creative thought.
1 Introduction
Can extant scientific theories of mental imagery (quasi-perceptual experience) account for, or accommodate, the much wider functions of imagination as traditionally conceived? Such functions range from ordinary supposal to the most valued aspects of human insight and creativity (Thomas, 1997a, 1999a), but it is the latter that will be of particular concern here. The issue is raised not only to bring a fresh perspective to the notoriously recalcitrant scientific debate about the nature and cognitive importance of imagery, but also to try to illuminate the obscure topic of imagination itself.Prima facie imagery and imagination are intimately related--certainly "imagination" is often used to name the faculty of image production (or the mental arena in which images appear)--and this fact itself demands explanation. I will argue that neither of the better known theories of imagery, the "quasi-pictorial" theory (Kosslyn, 1980, 1994) and the "description" theory (Pylyshyn, 1973, 1981), are capable of meeting this challenge. I will develop and defend a theory that can, I believe, meet it: a version of the little known "perceptual activity" theory, related to recent "situated" approaches to cognition (Clancey, 1997).
It seems likely that the association between imagery and creative imagination is not unrelated to the unusual passion (Dennett, 1978) surrounding the debates about imagery of the past 30 years or so. Except to the aficionado, mere visualization is surely not obviously, in itself, a terribly exciting matter; "imagination", by contrast is a highly value laden and culturally charged term (Kearney, 1988). If the relationship between imagery and imagination (in the relevant sense) can be clarified, perhaps the constraints which scientific results lay upon theories of imagery may help to bring some discipline to the more extreme claims made on behalf of the imagination.
In particular, the concept of imagination has played a key role in anti-scientific attitudes and ideologies, at least since the writers and artists of the Romantic movement gave it a central place in their ideology (Daston, 1998). Imagination is presented as supremely valuable and forever beyond the reach of scientific understanding; it is the guarantor and the embodiment of the (alleged) fact that science will never be able to illuminate "what really matters" in life. Romanticism was by no means unequivocally hostile to science (Abrams, 1953), but the strong anti-scientific strand of the 1960s "counter culture" movement clearly derived from it (Roszak, 1970), and although Gross and Levitt (1994) try to blame the contemporary prevalence of anti-science on the "academic left", they acknowledge that its intellectual roots are in Romanticism rather than Marx or the labor movement. Furthermore, despite the fact that the vital role of imagination in scientifically thinking has been urged repeatedly and convincingly (e.g. Tyndall, 1872; Van't Hoff, 1878/1967; Brown, 1991; Holton, 1996) the apologists of science have frequently demonstrated a hostility to the claims of imagination that is quite comparable to the hostility to science shown by the ideologues of imagination (Daston, 1998). Nevertheless, the Romantic conception of imagination (which was heir to a long tradition) has had an enormous and ineradicable intellectual influence, and is deeply embedded in our folk psychology (Brann, 1991; Sutherland, 1971). There is every reason to think that it contains genuine and important insights, and that it addresses real socio-cultural, or even spiritual, needs. For science to dismiss the issues it raises would amount to the acceptance of a major limitation on the scope of the scientific approach to reality. In order to address these issues rationally and effectively we need a scientific theory of imagination that pays due respect to the folk/Romantic conception.
In what follows I will first outline the extant scientific theories of the nature and mechanisms of imagery, and will attempt to assess them purely as such. I will then try to delineate the relevant key components of the folk/Romantic conception of imagination, and finally I will try to assess to what degree the respective scientific theories of imagery are capable of throwing light upon them.
2 Imagery and Theories of Imagery in Cognitive Science
Let us provisionally define mental imagery as quasi-perceptual experience, experience that significantly resembles perceptual experience (in any sense mode), but which occurs in the absence of appropriate external stimuli for the relevant perception (for discussion and defence of this definition see Thomas, 1999b). There are normally important experiential differences between imagery and perception--without them imagery may slide into hallucination--but these need not concern us here; it is the similarities which are definitive.
"Experience", of course, implies consciousness, and this may raise a problem because there are reasons to think that imagery can play a role in cognition even when subjects are not consciously aware of it (Paivio, 1971, 1986; Baars, 1996). However, people often are consciously aware of quasi-perceptual experiences, and it is upon this phenomenological fact that the major cognitive research programs into imagery have been built (Thomas, 1987). I submit that we should think of occurrent mental images as, at the least, potential contents of consciousness (in something like the sense of Searle, 1992), even if it is the case that they may sometimes occur without the subject being explicitly aware of them. Imagery may, conceivably, play an important role in cognition even when people deny consciously experiencing it (Thomas, 1989, 1999b).
Notoriously, many psychologists of the behaviorist era did deny if not the experience certainly the psychological significance of imagery. However, from the late 1950s interest in imagery gradually increased (Holt, 1964), and from the later 1960s a number of striking, now classic, experimental effects (for reviews see Morris and Hampson, 1983, and Finke, 1989) convinced many of its cognitive significance (Thomas, 1987). Imagery proved to have powerful mnemonic effects (Paivio, 1971, 1986, 1991), and it appeared that an image could be smoothly rotated (Shepard & Metzler, 1971; Shepard & Cooper, 1982), and scanned across (Kosslyn, 1973, 1980). It also appeared that when inspecting their images, subjects could find subjectively large details more quickly than subjectively small ones (Kosslyn, 1975, 1980), and that imagery and perceptual tasks in the same mode would often mutually interfere with one another (Brooks, 1968; Segal, 1971; Craver-Lemley & Reeves, 1992). A theory of the nature of imagery was clearly needed.
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