Visual Imagery and Consciousness
Nigel J.T. Thomas
Page 3
http://www.imagery-imagination.com/viac.htm
Subjective Individual Differences in Imagery Experience
Since the pioneering work of Francis Galton in the nineteenth century there has been a tradition of research into individual differences in the subjective experience of imagery. Galton prepared a questionnaire in which he asked his subjects to recall their morning breakfast table, and to consider "the picture that rises before your mind's eye." They were then asked to comment on a number of subjective aspects of that image, such as its brightness, its clarity, and the distinctness of the colors. One of the best knowing findings of Galton's study is that some small minority of the questionnaire respondents reported that they were unable to visualize anything whatsoever. Unfortunately, no systematic research has since been done on this phenomenon, and the issue remains very poorly understood (although recent research has directly contradicted Galton's related claim that scientists are particularly likely to be weak or "non-" imagers).
Subsequent researchers have refined Galton's questionnaire technique in various ways, most importantly, perhaps, by introducing numerical scales along which the subjects can rate the strength of the image attribute of interest. Most often, this attribute is "vividness," but there are also questionnaires that attempt to measure such things as how easily someone can transform their mental images (by asking them to form an image and then change it in some specified way, and then rate the difficulty of doing so), or how frequently they use images of one or another sense mode in their thinking. In the early 20th century there was considerable interest in classifying people into "imagery types" according to which sensory mode of imagery (visual, auditory, haptic, etc.) they preferred. It was hoped that these "types" might prove to be correlated with other independently measurable aspects of the person's psychological makeup. However, no clear cut pattern of findings emerged.
Perhaps the most extensively and successfully used imagery questionnaire of recent times is the Vividness of Visual Imagery Questionnaire (VVIQ) devised by David Marks. Taking the VVIQ involves being asked to visualize a series of specified objects and scenes and to rate the vividness of each resulting image on a five-point scale ranging from "no image at all" to "as clear and vivid as normal vision." An average score is then calculated.
Clearly research of this sort deals with imagery as a conscious phenomenon. It relies upon the subjects' verbal, introspective reports of their subjective experience. Furthermore, there has been much effort to find correlations between people's scores on imagery questionnaires and their other psychological traits. The results, however, have generally been disappointing. Even where reproducible correlations have been found, it has often proven difficult to make much theoretical sense out of them. For example, there is some evidence that vivid imagers (as measured by the VVIQ) remember pictures (color photographs) rather better than less vivid imagers; however, surprisingly, it has also been found that the less vivid imagers (by the VVIQ again) actually remember specific shades and hues of color better. Some research suggests that when people form mental images they have elevated levels of activity in the retinotopically mapped visual cortex of their brain, and that this activity is greater for more vivid imagers. However, other researchers fail to find elevated activity in these areas during imagery (they find it elsewhere in the brain). Perhaps most surprisingly and disappointingly, however, virtually no sign of any correlation has been found between people's vividness ratings and their performance (speed or accuracy) in various visuo-spatial thinking and problem solving tasks, even though, subjectively, such tasks seem to depend on imagery.
There are also a number of conceptual concerns about the validity of questionnaires of this type. Most obviously, as the rating is necessarily purely subjective, and as nobody can experience another's image, there is no way to tell whether the scales are being applied in a consistent way. Perhaps an image that one person thinks of as "clear and reasonably vivid" another might rate as "vague and dim," simply because different subjective standards are being applied.
Furthermore, most people will probably agree that the vividness of their imagery can vary markedly from time to time, circumstance to circumstance, and image to image: Some memories may come back to us (often for no very apparent reason) as especially vivid images, whereas others (or even the same ones on other occasions) are recalled only vaguely and dimly. Thus it may be that these tests do not measure a person's true capacity for having vivid images, but only, at best, the vividness that their images tend to have under the circumstances of filling out an imagery questionnaire.
Finally, it is unclear quite what "vividness" truly means; whether it is really a well defined, coherent attribute of experience. Perhaps different subjective image features such as (for example) clarity, apparent brightness, level of discriminable detail, stability of the image (whether it can be held in consciousness for a time, or quickly fades), and so forth, in fact vary independently of one another, but tend to get indiscriminately lumped together as "vividness." Some recent research suggests that introspective ratings of certain more fine grained aspects of subjective imagery experience may be more meaningful than simple vividness ratings.
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