Letter recognition thesis

[Gary McGraw]

Announcing the availability of my thesis on the web...

		      Letter Spirit (part one):
    Emergent High-level Perception of Letters Using Fluid Concepts

			     Gary McGraw
	    Center for Research on Concepts and Cognition
			510 North Fess Street
			  Indiana University
			Bloomington, IN  47405

This thesis presents initial work on the Letter Spirit project, with a
cognitive model of letter perception as its centerpiece.  The Letter
Spirit project is an attempt 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 important and
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 program will attempt to
create the rest of the alphabet in such a way that all 26 letters
share the same style, or spirit.  Letters in the domain are formed
exclusively from straight segments on a 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 character of concepts.

The overall architecture of the Letter Spirit project, based on the
principles of emergent computation and flexible context-sensitive
concepts, has been carefully developed and is presented in Part I.
Creating a gridfont is an iterative process of guesswork and
evaluation --- the ``central feedback loop of creativity''.  The
notion of evaluation and its necessary foundation in perception have
been largely overlooked in many cognitive models of creativity.

In order to be truly creative, a program must do its own evaluating
and perceiving.  To this end, we have focused initial Letter Spirit
work on a high-level perceptual task --- letter perception.  We have
developed an emergent model of letter perception based on the
hypothesis that letter categories are made up of conceptual
constituents, called roles}, which exert clear top-down influence on
the segmentation of letterforms into structural components.  Part II
introduces the role hypothesis, presents experimental psychological
evidence supporting it, and then introduces a complex cognitive model
of letter perception that is consistent with the empirical results.
Because we are interested ultimately in the design of letters (and the
creative process as whole) an effort was made to develop a model rich
enough to be able to recognize and conceptualize a large range of
letters including letters at the fringes of their categories.

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The ~400 page thesis is available on the web at URL:
<http://www.cogsci.indiana.edu/farg/mcgrawg/thesis.html>

It may also be retrieved through ftp to ftp.cogsci.indiana.edu
as the file pub/mcgraw.thesis.ps.gz

Hardcopy is generally not available due to prohibitive costs. However,
if you are having trouble retrieving the text, send me e-mail
(gem at cogsci.indiana.edu). 

Comments and questions are welcome.

				Gary McGraw
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|   Gary McGraw           gem at cogsci.indiana.edu   |              (__)      |
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|  Center for Research on Concepts and Cognition   |       /-------\/       |
|  Department of Computer Science                  |      / |     ||        |
|  Indiana University             (812) 855-6966   |     *  ||----||        |
|  <http://www.cogsci.indiana.edu/farg/gem.html>   |        ^^    ^^        |
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