The Problems of Parallel Processing

The modular model of the mind that is suggested by cognitive neuropsychology research contains a conceptual lacuna. The existence of many special-purpose processing systems, each of which can operate autonomously, would not seem sufficient to produce coherent and effective operation for the whole system. Does this function itself require special-purpose units?

Another aspect of the functional architecture, in addition to modularity, needs to be considered in responding to this question. It has been widely assumed in theorising on cognitive processes that all the routine cognitive and motor skills that we have are controlled by more or less program-like entities, such as ‘productions’ (e.g. Newell & Simon, 1972) or action or thought ‘schemata’ (Schmidt, 1975; Rumelhart & Ortony, 1977). It is presumed that just as the mind contains representations of a finite but large and extensible set of words, so it contains a large but finite set of action or thought schemata. What would any individual thought or action schema control? There would be an enormous variety of operations. Take, for instance, how to use a table knife for cutting, for pushing, or for spreading food; how to subtract one number from another; how to rotate an object mentally; and so on. Moreover, schema control would be on multiple levels; so the schema for making a sandwich could call those for cutting bread and for spreading butter.