The Context-Sensitive Cognitive Architecture DUAL

Context-sensitivity is an important characteristic feature of every cognitive process and therefore should be reflected in every architecture pretending to explain human cognition. In this paper some experimental facts demonstrating context effects on various cognitive processes are reviewed and an attempt at context modeling is described. A hybrid (symbolic/connectionist) cognitive architecture, DUAL, is proposed. It consists of a multitude of agents having both a symbolic and a connectionist part. The symbolic part represents some knowledge structure, while the connectionist part represents its relevance to the current context. The performance of the cognitive system emerges as result of the work and interaction of the currently active agents, where the set of active agents is not predefined for a specific task but is dynamic and reflects the specific context. So particular symbolic operations and data structures may be supported or suppressed depending on the particular activation pattern of the connectionist parts which represent the context-dependent relevance of the operations and structures. In this way a context-sensitive computation emerges. An example of context-sensitive deductive reasoning is described. 1. Context-Sensitivity of Human Cognition There are two phenomena well studied in perception and language understanding: context effects and priming effects. Context effect is the change in human response caused by changes in the environment (the external context) of the target stimulus, e.g. the change in the success/failure ratio or in the reaction time of recognizing the same letter presented within different words or strings, or without context. Priming effect is the change in human response to a target task caused by changes in the subjects’ preliminary setting (i.e. their internal state), e.g. the change in the success / failure ratio or in the reaction time of recognizing the same target word (e.g. “bread”) presented immediately after different “priming” words (e.g. “butter”, “knife”, or “car”). A common explanation of both effects is proposed in this paper. Both of them are actually due to changes in the context either in the “external” context or in the “internal” one. The context-sensitivity of human perception and language processing is a well-known and widely accepted fact and every cognitive model of those processes is trying somehow to explain it. However, typically researchers tend to regard higher-level cognitive processes, such as memory, decision making, and especially reasoning, as encapsulated and context-independent. This is, however, not true. There are a lot of experimental results that provide evidence for the context-sensitive character of human high-level cognition.