is a model
of analogy making
and human cognition
based on the concept of the parallel terraced scan
, developed by Douglas Hofstadter
, Melanie Mitchell
, and others at the at Center for Research on Concepts and Cognition
, Indiana University Bloomington
. The original Copycat was written in a now defunct version of Common Lisp
; however, a modern Java port exists.
Copycat produces answers to such problems as "abc is to abd as xyz is to what?" (abc:abd :: xyz:?). Hofstadter and Mitchell consider analogy making as the core of high-level cognition, or high-level perception
, as Hofstadter calls it, basic to recognition and categorization.
High-level perception emerges
from the spreading activity of many independent processes, called codelets
, running in parallel, competing or cooperating. They create and destroy temporary perceptual constructs, probabilistically trying out variations to eventually produce an answer. The codelets rely on an associative network, slipnet
, built on pre-programmed concepts and their associations (a long-term memory
). The changing activation levels of the concepts make a conceptual overlap with neighboring concepts.
Copycat's architecture is tripartite, consisting of a slipnet, a working area (also called workspace, similar to blackboard systems), and the coderack (with the codelets). The slipnet is a network comprised of nodes, which represent permanent concepts, and links, which are relations, between them. The codelets increase activations in the slipnet, and build structures, based on the associations there, in the working area.
Comparison to other cognitive architectures
Copycat differs considerably in many respects from other cognitive architectures
such as ACT-R
, or subsumption architectures
Copycat is Hofstadter's most popular model. Other models presented by Hofstadter et al. are similar in architecture, but different in the so-called microdomain, their application, e.g. Letter Spirit, etc.
Since the 1995 FARG book, work on Copycat-like models has continued: as of 2007 the latest models are Metacat (a self-watching version) and SeekWell, a music cognition model. The architecture is known as the "FARGitecture" and current implementions use a variety of modern languages including C# and Java. A current FARG project is to build a single generic FARGitecture framework, Magnificat, that can be reused easily.