Development and Functions of the Symbolic Systems
Nonverbal imagery and verbal processes are distinguished here primarily in terms of their functions as symbolic systems, although an assumed relationship between the two processes and visual and auditory sensory modalities has functional implications that are important to later discussions. In the classical approach to imagery, initiated empirically by Galton (1883) and explored by subsequent investigators particularly in relation to individual differences, the term image was used to refer to consciously-experienced mental processes rather generally and distinctions were drawn in terms of the sensory modality (visual, auditory, kinesthetic, and so on) of the image as revealed by introspection. Verbal thought processes were usually regarded as auditory images of words or as proprioceptive sensations from implicit verbal responding, or both, and occasionally as visual images of words. Images of nonverbal objects and events, on the other hand, usually implied visual imagery because of the dominance of visual sense experience, but nonverbal events obviously could involve other modalities as well. Some writers (e.g., Pear, 1927) simply distinguished between verbal and nonverbal imagery, although this terminology confounds distinctions based on modality and those based on symbolic systems, as when reference is made to "visualizers" and "verbalizers" (e.g., Golla, Hutton, & Walter, 1943). Presumably the intended distinction is between nonverbal (visual) and verbal (auditory-motor?) thinking, but this is not clear from the terms. At any rate, some preliminary definitions will help avoid confusions that might arise in subsequent discussions, although appropriate qualification of the terms will still be necessary from time to time. Ultimately, however, we shall rely
primarily on operational rather than verbal definitions of the postulated processes. Moreover, introspective awareness will be viewed simply as one possible behavioral manifestation of those processes, rather than as an essential feature of their definition, contrary to the classical approach and some contemporary approaches to imagery (e.g., Richardson, 1969).