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Krasnow Institute > Monday Seminars > Abstracts Emergent Letter Perception in Letter Spirit Gary McGraw Reliable Software Technologies Corp, Sterling, VA In this talk, I will present initial work on the Letter Spirit project, with a fully-implemented cognitive model of letter perception as its centerpiece. The Letter Spirit project aims to model central aspects of human high-level perception and creativity on a computer, focusing on the creative act of artistic letter-design. The aim is to model the process of rendering the 26 lowercase letters of the roman alphabet in many different, internally coherent styles. Two orthogonal aspects of letterforms are basic to the project: the categorical sameness possessed by instances of a single letter in various styles (e.g., the letter `a' in Times, Palatino, and Helvetica), and the stylistic sameness possessed by instances of various letters in a single style, or spirit (e.g., the letters `a', `k', and `q' in Times alone). Starting with one or more seed letters representing the beginnings of a style, the full Letter Spirit program will attempt to create the rest of the alphabet in such a way that all 26 letters share the same style. Letters in the domain are formed exclusively from straight segments defined by a sparse grid in order to make decisions smaller in number and more discrete. This restriction allows much of low-level vision to be bypassed and forces concentration on higher-level cognitive processing, particularly the abstract and context-dependent nature of letter concepts. This talk will have two major parts. The overall architecture of Letter Spirit, based on the principles of emergent computation and fluid concepts, has been carefully developed and will be presented in Part I. Creating a gridfont is an interwoven process of guesswork and evaluation --- the ``central feedback loop of creativity''. The notion of continual evaluation of a creative product throughout the design process, and its necessary foundation in perception, have been largely overlooked in cognitive models of creativity. In Letter Spirit, we address this issue head-on. In order to be truly and autonomously creative, a program must do its own assessment and adjustment of any large-scale work-in-progress throughout the course of design. To this end, we have focused initial Letter Spirit work on a sophisticated and subtle model of gridletter perception. Our emergent model of letter perception is based on the hypothesis that letter categories are made up of conceptual constituents called roles. Roles exert clear top-down influence on the segmentation of letterforms into structural components. In Part II of the talk I will flesh out the role hypothesis, discuss a model of letter recognition implementing it, and present psychological evidence supporting the existence of roles in human perception of letters. Empirical results support the applicability of our emergent, cognitive architecture to the task of letter recognition. Because we are ultimately interested in the design of letters (and the creative process as a whole), an effort has been made to develop a model rich enough to recognize and understand in terms of constituent roles a large range of letterforms, including letters that push at the fringes of their categories. For more information about Letter Spirit, see the web: http://www.cogsci.indiana.edu/farg/mcgrawg/lspirit.html
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