The aim of the proposed work is to determine whether perceptual representations enter significantly into conceptual processing. Subjects will perform conceptual tasks that have traditionally been explained with propositional, non-perceptual theories of knowledge, e.g., feature listing (what features are typically true of a chair) and property verification (e.g., does a chair have a seat). Of interest will be whether subjects use perceptual representations in these tasks, even though the task contexts do not require or demand that they do. The use of perceptual representations will be detected in two ways: instructional equivalence and perceptual work. Instructional equivalence occurs when subjects who receive no imagery instructions (`neutral subjects`) perform similarly to subjects explicitly asked to use imagery (`imagery subjects`). Perceptual work occurs when performance of both neutral and imagery subjects is affected by perceptual variables. Initial experiments on feature listing and property verification provide strong evidence for both instructional equivalence and perceptual work, indicating that neutral subjects use perceptual representations. Further studies will replicate and extend these findings. For feature listing, various experiments examine the roles of perceptual representations in conceptual combination, event concepts, abstract concepts, gesture, and production modes. For property verification, various experiments use distractor relatedness, preparation time, part expectancy, and perspective to examine the role of perceptual representations. In an additional project on modality-specific interference, several experiments test the prediction that perceptual representations of conceptual knowledge should produce specific patterns of attentional interference. Should these projects provide evidence that perceptual representations play central roles in conceptual processing, theories of cognition and intelligence would require significant reformulation. Most existing theories assume that intelligent behavior reflects the processing of an abstract, amodal, and arbitrary language of thought, much like the symbolic computer languages used widely in electronic computation. According to existing theories, perceptual experience is transduced into a set of conceptual symbols that bear no perceptual resemblance to their referential origins. An alternative, and much less explored view, is that conceptual symbols are fragments of perceptual states, extracted directly from these states via selective attention. The resulting conceptual representations are not static holistic 'pictures in the head,' but instead are systems of perceptual symbols that combine productively to produce infinite conceptual structures. Additionally, these perceptual symbols are analytic, schematic, multimodal, and dynamic, offering a rich expressive system for representing a wide variety of concepts, not just those for concrete objects. Intuitively, such perceptual symbol systems resemble modern multimedia computing much more than traditional non-analogue computing. Evidence continuing to indicate the presence of a perceptual symbolic system in humans, has strong implications for understanding and applying intelligence as well as theories of the brain's operation and visions of artificial intelligence. Rather than viewing intelligence as the manipulation of arbitrary amodal symbols, it would come to be viewed as arising from a productive system of perceptual symbols.
