Re: Illiad

From: Grant Callaghan (
Date: Thu 06 Mar 2003 - 16:49:54 GMT

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    Do you see how, even among people that supposedly share a culture (for instance, we could concievably find ourselves talking about the subject at a departmental cocktail party) the meaning of the Illiad is different depending on what other memes are in our *individual* heads?



    The act of "seeing" and thus "reading" begins with the act of taking what we perceive and placing it in a category based on experience within a culture. Everything else we do with what we see or hear begins here. The following excerpt from the archives of the Cogsci department at UCSD explains what they have learned about the process.

    Perceiving a New Category: The Neurobiological Basis of Perceptual Categorization Kara D. Federmeier Department of Cognitive Science University of California, San Diego

    Categorization is a ubiquitous cognitive phenomenon -- ubiquitous in more than one way. The influences of categorization can be seen in nearly every aspect of higher cognition. We categorize to determine what to pay attention to, to talk and understand, to remember, and to reason. However, categorization can also be observed at every level of cognitive processing. From the earliest stages of sensory processing, neurons and groups of neurons respond to some kinds of inputs and not to others, creating perceptual categories that are the roots of all human experience. While current approaches to the study of categorization generally acknowledge the important relationship between categorization and other higher cognitive processes, these approaches have largely failed to acknowledge that the roots of categorization begin in early sensory processing and are thus deeply entrenched in the functioning of the human brain. To understand categorization -- and, thereby, significant portions of all of higher cognition
    -- it is useful to try to understand those roots.

    Current theories and models of categorization have tended to define categorization as a grouping process that operates on perceptual inputs. Perception, defined as the extraction of the perceptual features of a stimulus, is believed to precede categorization and to provide the input for it. Grouping done on the basis of perceptual features is often termed
    “perceptual categorization” while grouping done on the basis of more abstract features has been termed “semantic categorization.” Note that the term “concept” is sometimes conflated with the term “category”. While the line between the two can be fuzzy, in general, a category is defined as a group of items that are treated similarly, while a concept can be defined as a flexible abstraction of a category (often linguistic). If an organism treats a set of perceptually different items similarly by eating all of them, for example, these items could be said to define the category “food” for that organism. If that organism also has a representation in which
    “food” is understood to be anything potentially edible, the organism might then be said to also have a concept of food. Categories, not concepts, will be dealt with in this paper.

    These traditional definitions will be maintained throughout the paper. However, the goal is to demonstrate that categorization happens via rather than on perception and that one cannot be understood without reference to the other. In particular, this paper focuses on the relationship between visual processing and perceptual categorization done on the basis of visual features. First, it is argued that, far from being a phenomenon unique to human higher cognitive processing, categorization is a general solution to a basic conflict that arises for any information processing system. Such systems must be able to recognize and act on important (relevant) differences between stimuli in their environment while still ignoring other, irrelevant differences. A simple, effective solution to this conflict is to divide stimuli into groups -- to categorize. In fact, human categorization is structured in two dimensions to both maintain information and allow for appropriate generalizations.

    Having established categorization as a general solution to an information processing problem, it is then shown that the visual system itself faces this problem and solves it by categorizing. Models of categorization have generally ignored perception, assuming that, prior to categorization, the visual system has acted to extract the features needed for categorization while suppressing information about irrelevant stimulus differences. However, this is exactly the problem that, as this paper argues, entails categorization. Neurobiological evidence suggests that bottom-up visual processing mechanisms, from the earliest levels, sort stimuli into groups according to features known to be important for perceptual categorization. Complex feature maps, with many category-like properties, can be observed in higher visual areas, such as the inferotemporal cortex. At the same time, top-down factors that determine which features are important and used for categorization have been shown to influence visual physiology as well.


    Perceptual categorization is thus an inherent part of visual processing, and it is difficult to even talk about object recognition without reference to categorization.


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