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There has been a long-standing debate between symbolicists and connectionists concerning the nature of representation used by human cognizers. In general, symbolicist commitments have allowed them to provide superior models of high-level cognitive function. In contrast, connectionist distributed representations are preferred for providing a description of low-level cognition. The development of Holographic Reduced Representations (HRRs) has opened the possibility of one representational medium unifying both low-level and high-level descriptions of cognition. This paper describes the relative strengths and weaknesses of symbolic and distributed representations. HRRs are shown to capture the important strengths of both types of representation. These properties of HRRs allow a rebuttal of Fodor and McLaughlin's (1990) criticism that distributed representations are not adequately structure sensitive to provide a full account of human cognition.

Introduction There are some exceptions, which we shall see below, but virtually all theories in psychology and cognitive science make use of the notion of representation. Arguably, folk psychology also traffics in representations, or is at least strongly suggestive of their existence. There are many different types of things discussed in the psychological and philosophical literature that are candidates for representation-hood. First, there are the propositional attitudes – beliefs, judgments, desires, hopes etc. (see Chapters 9 and 17 of this volume). If the propositional attitudes are representations, they are person-level representations – the judgment that the sun is bright pertains to John, not a subpersonal part of John. By contrast, the representations of edges in V1 of the cerebral cortex that neuroscientists talk about and David Marr’s symbolic representations of “zero-crossings” in early vision (Marr 1982) are at the “sub-personal” level – they apply to parts or states of a person (e.g. neural parts or computational states of the visual system). Another important distinction is often made among perceptual, cognitive, and action-oriented representations (e.g. motor commands). Another contrast lies between “stored representations” (e.g. memories) and “active representations” (e.g. a current perceptual state). Related to this is the distinction between “dispositional representations” and “occurrent representations.” Beliefs that are not currently being entertained are dispositional, e.g. your belief that the United States is in North America - no doubt you had this belief two minutes ago, but you were not consciously accessing it until you read this sentence. Occurrent representations, by contrast, are active, conscious thoughts or perceptions. Which leads us to another important distinction: 1 between conscious and non-conscious mental representations, once a bizarre-sounding distinction that has become familiar since Freud (see Chapter 4 of this volume). I mention these distinctions at the outset to give you some idea of the range of phenomena we will be considering, and to set the stage for our central “problem of representation”: what is a mental representation, exactly, and how do we go about deciding whether there are any? We know there are public representations of various kinds: words, maps, and pictures, among others..

?Representation? is a concept which occurs both in cognitive science and philosophy. It has common features in both settings in that it concerns the explanation of behaviour in terms of the way the subject categorizes and systematizes responses to its environment. The prevailing model sees representations as causally structured entities correlated on the one hand with elements in a natural language and on the other with clearly identifiable items in the world. This leads to an analysis of representation and cognition in terms of formal symbols and their relations. But human perception and cognition use multiple informational constraints and deal with unsystematic and messy input in a way best explained by Parallel Distributed Processing models. This undermines the claim that a formal representational theory of mind is ?the only game in town?. In particular it suggests a radically different model of brain function and its relation to epistemology from that found in current representational theories.

Existential phenomenologists hold that the two most basic forms of intelligent behavior, learning, and skillful action, can be described and explained without recourse to mind or brain representations. This claim is expressed in two central notions in Merleau-Ponty's Phenomenology of Perception: the intentional arc and the tendency to achieve a maximal grip. The intentional arc names the tight connection between body and world, such that, as the active body acquires skills, those skills are stored, not as representations in the mind, but as dispositions to respond to the solicitations of situations in the world. A phenomenology of skill acquisition confirms that, as one acquires expertise, the acquired know-how is experienced as finer and finer discriminations of situations paired with the appropriate response to each. Maximal grip names the body's tendency to refine its responses so as to bring the current situation closer to an optimal gestalt. Thus, successful learning and action do not require propositional mental representations. They do not require semantically interpretable brain representations either.Simulated neural networks exhibit crucial structural features of the intentional arc, and Walter Freeman's account of the brain dynamics underlying perception and action is structurally isomorphic with Merleau-Ponty's account of the way a skilled agent is led by the situation to move towards obtaining a maximal grip.

Inspired by Kant, Merleau-Ponty and Sellars, I illustrate and identify certain kinds of unity which are typical (if not universal) features of our conscious experience, and argue that Kant was right to claim that such unities are produced by unconscious processes of synthesis: A perceptual experience of succession is not reducible to a succession of perceptual experiences. The experience of perceiving one object as having several features is not reducible to a conjunction of perceptual experiences of those features. A cross-modal perceptual experience is not reducible to a conjunction of single-modality perceptual experiences. Incoming perceptual information is synthesized into a single scene-a representation of the world as perceived from a spatio-temporal point of view. Any two of the simultaneous features of the experience of a subject S can be thought of together by S. Many of the experiences of a subject S can be thought of by S at a later time as part of his or her history of experience. These can be summarized in the general principle: An experience of a complex is not a complex of experiences. This is consistent with Sellars' principle that: A sense-impression of a complex is a complex of impressions because the latter applies at the sub-personal, unconceptualized level, and the former at the conscious level of conceptualized experiences.

Hubert Dreyfus argues that the traditional and currently dominant conception of an action, as an event initiated or governed by a mental representation of a possible state of affairs that the agent is trying to realise, is inadequate. If Dreyfus is right, then we need a new conception of action. I argue, however, that the considerations that Dreyfus adduces show only that an action need not be initiated or governed by a conceptual representation, but since a representation need not be conceptually structured, do not show that we need a conception of action that does not involve representation.

I examine the following question: Do actions require representations that are intrinsic to the action itself? Recent work by Mark Rowlands, Michael Wheeler, and Andy Clark suggests that actions may require a minimal form of representation. I argue that the various concepts of minimal representation on offer do not apply to action per se and that a non-representationalist account that focuses on dynamic systems of self-organizing continuous reciprocal causation at the sub-personal level is superior. I further recommend a scientific pragmatism regarding the concept of representation.

Human self-consciousness operates at different levels of complexity and at least comprises five different levels of representational processes. These five levels are nonconceptual representation, conceptual representation, sentential representation, meta-representation, and iterative meta-representation. These different levels of representation can be operationalized by taking a first-person-perspective that is involved in representational processes on different levels of complexity. We refer to experiments that operationalize a first-person-perspective on the level of conceptual and meta-representational self-consciousness. Interestingly, these experiments show converging evidence for a recruitment of medial cortical and parietal regions during taking a first-person-perspective, even when operating on different degrees of complexity. These data lend support for the speculative hypothesis, that there exist a neural signature for human self-consciousness that is recruited independent from the degree of representational complexity to be performed.

Husserl and Searle agree that, for a bodily movement to be an action, it must be caused by a propositional representation. Husserl's representation is a mental state whose intentional content is what the agent is trying to do; Searle thinks of the representation as a logical structure expressing the action's conditions of satisfaction. Merleau-Ponty criticises both views by introducing a kind of activity he calls motor intentionality, in which the agent, rather than aiming at success, feels drawn to reduce a felt tension. I argue that Searle can account for Merleau-Ponty's kind of coping only by broadening his notion of propositional representation to include indexicals, but that, in so doing, he covers up the way representational intentionality depends upon motor intentionality.

Is intentionality possible without representation? This paper considers the conditions under which intentionality without representation could occur and what sort of perceptual content such intentionality would have. In addition, it considers the constraints on non-representational intentional content in organisms that have representation. The paper is divided into three parts. The first section compares and contrasts two opposed positions on non-representational intentionality, those of Herbert Dreyfus and John Searle. The second section reviews a neurobiological model that accommodates the possibility of non-representational perceptual content. The final section provides a puzzle for theories of non-representational perceptual content, specifically in connection with the perception of representations. The puzzle of representation and perception illustrates a further need for all theories of perception, both philosophical and scientific: to provide a more finely developed definition of the notion of representation.