(Incidentally, although it was once widely believed that visual imagery in humans was primarily a function of the right hemisphere of the brain (e.g., Ley, 1983), more recent research contradicts this. It now appears that imagery involves structures on both sides of the brain, with, if anything, the left hemisphere playing a slightly more extensive role (Ehrlichman & Barrett, 1983; Farah, 1984, 1995; Sergent, 1990; Tippett, 1992; Trojano & Grossi, 1994; Loverock & Modigliani, 1995; Michimata, 1997).)
Far too many discussions of visual mental imagery fail to draw a clear distinction between the contention that people have quasi-visual experiences and the contention that such experiences areto be explained by the presence of representations, in the mind or brain, that are in some sense picture-like. This picturetheory (or pictorial theory) of imagery experience is deeply entrenched in our language and our folk psychology. The very word ‘image,’ after all, suggests a picture. However, although the majority of both laymen and experts probably continue toaccept some form of picture theory, many 20th century philosophers and psychologists, from a variety of theoretical traditions, have argued strongly against it, and, in several cases they have developedquite detailed alternative, non-pictorial accounts of the nature and causes of imagery experiences (e.g., Dunlap, 1914; Washburn, 1916; Sartre, 1940; Ryle, 1949; Shorter, 1952; Skinner, 1953, 1974; Dennett, 1969; Sarbin & Juhasz, 1970; Sarbin, 1972; Pylyshyn, 1973, 1978, 1981, 2002a, 2003a, 2005; Neisser, 1976; Hinton, 1979; Slezak, 1991, 1995; Thomas, 1999b, 2009). Others, it should be said, have developed and defended picture theory in sophisticated ways in the attempt to meet these critiques (e.g., Hannay, 1971; Kosslyn, 1980, 1983,1994; von Eckardt, 1988, 1993; Tye, 1988, 1991; Cohen, 1996). However, despite these developments, much philosophical and scientific discussion about imagery and the cognitive functions it may or may not serve continues to be based on the often unspoken (and even unexamined) assumption that, if there is mental imagery at all, it must consist in inner pictures.
Mental Imagery (Stanford Encyclopedia of Philosophy)
Clearly Pylyshyn objects, as many philosophers have before him, to the notion of inner mental pictures that are somehow called to mind and reperceived by the “mind's eye”. In his 1973 article he raised a number of objections to this notion, some of which have withstood criticism better than others, but the underlying worry was clearly that the inner-picture theory of imagery inevitably commits the homunculus fallacy: it implicitly relies on the assumption that there is a little man (or rather, something that is the functional equivalent of a full-fledged visual system, including eyes), or, at the very least, something with inexplicable mental powers, inside the head to reperceive, experience, and interpret the image. The broad functional architecture of Kosslyn's theory, in fact, closely parallels that of Descartes' account of imagery (see , and ), and, of course, Descartes notoriously relied upon aconscious homunculus, the immaterial soul, that is placed foreverbeyond the reach of natural science. Modern defenders of thepictorial/analog theory protest that they cannot have committed thehomunculus fallacy (let alone committed themselves to Cartesiandualism) because a computer model of the theory has been implemented,and they have outlined an account of how picture-likerepresentations, formed at an early stage of visual processing in thebrain, are subject to several more stages of neural processing beforethey give rise to visual knowledge and experience (Kosslyn, 1980,1994; Kosslyn, Thompson, & Ganis, 2002, 2006).
Imagery: Basic Relaxation Script | Psych Central
Pylyshyn also argues (1981, 2002a) that most if not all of the experimental evidence that is supposed to show that imagery has inherently spatial properties (such as Kosslyn's work on mental scanning (Kosslyn, Ball, & Reiser, 1978; Kosslyn, 1980)) can be explained away as the result of the interaction of the experimental subject's tacit knowledge of the properties of visual experience and the experimental instructions. For instance, he holds that if subjects are asked to scan their mental gaze from one point toanother on a mental image of a map, what they interpret these instructions to be asking them to do is to behave as if they were actually looking at the relevant map and scanning their gaze between the points. Because they know from their history of ordinary visual experience that it takes longer to scan between points that are further apart, this will be reflected in their performance. Thus, thefact that people instructed to scan across their images take longer to scan longer distances is not evidence of the existence of some inner, mental, image-space. Rather, it is a reflection of people's implicit understanding (which they may not necessarily always be ableto articulate) of the visual properties of the actual space around them (cf, Morgan, 1979).