On the properties of cognitive modules

Summary This paper evaluates the properties of cognitive modules and central systems as defined by Fodor (1983) against a set of empirical data from the domain of language processing. On the basis of results from normal and pathological language behavior the Fodorian dichotomy between domain-specific input systems and general central systems is rejected. Instead a model of cognitive processes is proposed which assumes three qualitative different types of system: a general system similar to that defined by Fodor, a domain-specific system that represents knowledge in procedural form, called input system, and a domain-specific system that respresents knowledge in declarative form and serves as an interface between the input system and the central system. These interface systems represent the same knowledge domain as their corresponding input systems, but in a different format. As the representational format of these interface systems is declarative, it allows for direct communication with the central system whose representational format is propositional by definition.