Letter Spirit Examiner – Now at Home!
Back in the mid-’90s, an era or two ago, and long before the advent of the transformer model and explosive rise of LLMs that define the modern ML landscape, our own Dr. Gary McGraw (under the guidance of Doug Hofstadter) was exploring a fundamental question of artificial intelligence:
“What are the mechanisms underlying the fluidity of human concepts?”
How is it that we can understand conceptual boundaries, develop categories, and implicitly see the sameness that binds different instances of a concept together? And what might we learn by building a machine that simulates this behavior? Or, rather, what is an A?
The perceptual hypothesis behind the Letter Spirit project is that letter-concepts are composed of constituent roles. That is, letter concepts, in turn, have letter-part concepts.
The Letter Spirit project approached these questions from the angle of letter perception. While easy to take for granted, we literate apes possess the ability to differentiate letters and letter categories displayed a huge variety of fonts, handwriting styles, and artistic styles. Our gut instinct may tell us that the letter “a” is a mere shape made up of a bunch of tiny dots; but just a few examples can reveal a much greater depth to what constitutes our concept of the letter ‘a’.
This role model hypothesis is implemented here as the Letter Spirit Examiner program (a program written in scheme in 1995). It works through emergent computation—by segmenting letters into natural, constituent parts that correspond to the conceptual roles of the very concept of a letter—that is, different conceptual rules that when satisfied lead us to identify a letter. The examiner does this by running hundreds of micro-agents (called codelets) that are instantiations of sixteen codelet types. The asynchronous, parallel, local processing done by the codelets implements a parallel terraced scan of possible structures (as in the role model’s predecessor, Copycat). From these codelets emerges a high-level perception—the categorization of a letter shape into an idea.
To our great pleasure and delight, we recently learned that Paul Geiger has developed a JavaScript implementation of the Letter Spirit Examiner based on the original Scheme code developed originally by McGraw and then adapted by Dr. John Rehling (standard-bearer of Letter Spirit – Part 2). This version is now accessible on the web, for curious people to play with.
Check it out in your very own browser now: Letter Spirit Examiner
An in-depth explanation of the architecture and implementation can be found here.
Big thanks to Paul Geiger: https://github.com/Paul-G2/letter-spirit-examiner-js
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