Processing Symbols at Variable Speed in DUAL: Connectionist Activation as Power Supply

Abstract

This article explores the advantages and one potential implementation of a new style of com-putation in which multiple lines of symbolic processing are pursued at different speeds within a hybrid multi-agent system. The cognitive architecture DUAL consists of small hybrid computational entities called DUAL agents. Each agent has a symbolic processor capable of simple symbol manipulations. There is also an activation level associated with each agent. Acti-vation spreads according to connectionist rules. The speed of each symbolic processor is propor-tional to the activation level of the correspond-ing DUAL agent and varies dynamically. Thus multiple candidate-solutions to a given problem can be explored in parallel. More computational resources are dedicated to the more promising candidates and the degree of 'promise ' is re-evaluated dynamically. This allows for flexible and efficient behavior of the system as a whole. The exact relationship between symbolic speed and connectionist activation is based on an energetic analogy. The symbolic processor is conceptualized as a machine converting connec-tionist activation into symbolic work. A lan-guage for implementing variable-speed symbol manipulations using delayed evaluation is introduced: S-LlSP. A small example from a DUAL-based cognitive model illustrates variable-speed marker passing in a semantic network. 1