Online research in philosophy

The origin of features from nonfeatural information is a problem that should concern all theories of object categorization and recognition, not just the flexible feature approach. In contrast to the idea that new features must originate from combinations of simpler fixed features, we argue that holistic features can be created from a direct imprinting on the visual medium. Furthermore, featural descriptions can emerge from processes that by themselves do not operate on feature detectors. Once acquired, features can be decomposed into component features if required by other categorizations. We therefore argue that it is not necessary to separate holistic and componential approaches to representations, because the latter is a development of the former. The requirements for representational flexibility outstrip the performance of any existing computational models, but specific mechanisms of feature creation are discussed and evaluated. Challenges for feature creation mechanisms are discussed together with the constraints (perceptual, statistical, functional, and task) they will need to satisfy.

The theory of event coding by Hommel et al. proposes that feature binding is a central component of action planning. To evaluate the binding hypothesis, we consider findings from studies of action-perception interference and bimanual movements. We argue that although binding of action features may be a valuable concept, interference from partial feature overlap does not provide a parsimonious account for the observed phenomena.

Does feature evolution stop once we have acquired sufficient features to perform a recognition task? With extended practice, novices may develop a more sophisticated feature space that allows them to perform more accurately or quickly. Our work on perceptual expertise indicates that feature learning and reorganization can continue even after an initial set of features is available to represent a novel class of objects.

This paper contrasts three different schemes of reference relevant to understanding systems of perceptual representation: a location-based system dubbed "feature-placing", a system of "visual indices" referring to things called "proto-objects", and the full sortal-based individuation allowed by a natural language. The first three sections summarize some of the key arguments (in Clark, 2000) to the effect that the early, parallel, and pre-attentive registration of sensory features itself constitutes a simple system of nonconceptual mental representation. In particular, feature integration--perceiving something as being both F and G, where F and G are sensible properties registered in distinct parallel streams--requires a referential apparatus. Section V. reviews some grounds for thinking that at these earliest levels this apparatus is location-based: that it has a direct and nonconceptual means of picking out places. Feature-placing is contrasted with a somewhat more sophisticated system that can identify and track four or five "perceptual objects" or "proto-objects", independently of their location, for as long as they remain perceptible. Such a system is found in Zenon Pylyshyn's fascinating work on "visual indices", in Dana Ballard's notion of deictic codes, and in Kahneman, Treisman, and Wolfe's accounts of systems of evanescent representations they call "object files". Perceptual representation is a layered affair, and I argue that it probably includes both feature-placing and proto-objects. Finally, both nonconceptual systems are contrasted with the full-blooded individuation allowed in a natural language.

Three different ways to understand the representational content of the feature maps employed in early vision are compared. First is Stephen Kosslyn's claim, entered as part of the debate over mental imagery, that such areas support "depictive" representation, and that visual perception uses them as depictive representations. Reasons are given to doubt this view. Second, an improved version of what I call "feature-placing" is described and advanced. Third, feature-placing is contrasted with the notion that the representational content of those feature maps could be conveyed in a list of sentences about visual objects. Some problems with this last alternative are described.

Our perception of external features comprises, among others, functional and phenomenological levels. At the functional level, the perceiver’s mind processes external features according to its own causal- functional organization. At the phenomenological level, the perceiver has consciousness of external features. The question of this paper is: How do the functional and the phenomenological levels of perception relate to each other? The answer I propose is that functional states of specifically perceptual attention constitute the necessary basis for the arising of consciousness in a perceiver.

Widely studied within cognitive psychology, perceptual attention is still awaiting a thoroughgoing philosophical treatment. The paper presents and draws upon Anne Treisman’s feature-integration theory of attention (cf. A. Treisman & G. Gelade, “A Feature-Integration Theory of Attention,” Cognitive Psychology, 12, 1980. Pp. 97-136). According to this theory, attentional mechanisms are responsible for the binding of perceptual features into coherent and stable objects of perception. By itself, I will claim, the theory of feature integration does not allow a straightforward reduction of consciousness to the functional processing underlying it. However, on the basis of Treisman’s theory we can produce a methodological argument for endorsing the non-reductivist thesis that attentional states constitute the necessary basis for the arising of consciousness in a perceiver. The paper closes by presenting this argument, according to which the thesis is implied by a unified account of the common representational natures of attentional and conscious states.

Pylyshyn is willing to assume that attention can influence feature integration. We argue that he concedes too much. Feature integration occurs preattentively, except in the case of certain “perverse” displays, such as those used in feature-conjunction searches.