The imagery debate: Analogue media versus tacit knowledge.

The debate over the nature of mental imagery, especially with respect to the interpretation of recent findings on the transformation of images.” has failed to focus on the crucial differences between the so-called “analogue” and “propositional” approaches. In this paper I attempt to clarify the disagreements by focusing on the alleged spatial nature of images and on recent findings concerned with “rotation” and “scanning” of mental images. It is argued that the main point of disagreement concerns whether certain aspects of the way in which images are transformed should be attributed to intrinsic knowledge-independent properties of the medium in which images are instantiated or the mechanisms by which they are processed, or whether images are typically transformed in certain ways because subjects take their task to be the simulation of the act of witnessing certain real events taking place and therefore use their tacit knowledge of the imaged situation to cause the transformation to proceed as they believe it would have proceeded in reality. The fundamental difference between these t o modes of processing is examined, and certain general difficulties inherent in the analogue account are discussed. It is argued that the tacit knowledge a count is more plausible, at least in the cases examined, because it is a more general account and also because certain empirical results demonstrate that both “mental scanning” and “mental rotation” transformations can be critically influenced by varying the instructions given to subjects and the precise form of the task used and that the form of the influence is explainable in terms of the semantic content of subjects' beliefs and goals—that is, that these operations are cognitively penetrable by subjects' beliefs and goals. Functions that are cognitively penetrable in this sense, it is argued, must be explained, at least in part, by reference to computational cognitive processes whose behavior is governed by goals, beliefs, and tacit knowledge rather than by properties of analogue mechanism.