From Neuropsychology to Mental Structure: The Cognitive Neuropsychology Approach

On Modularity If Lashley's (1929) idea of mass action were valid, then neuropsychology would be of little relevance for understanding normal function. Any form of neurological damage would deplete by a greater or lesser degree the available amount of some general resource, say the mythical g . Knowing which tasks a patient could or could not perform would enable us to partition tasks on a difficulty scale. It would tell us little, if anything, about how the system operated. If one considers the design principles that might underlie cognitive systems, a rough contrast can be drawn between systems based on equipotentiality (e.g., those that follow principles such as mass action) and more modular ones. At a metatheo-retical level, some form of the ‘modularity’ thesis is probably the most widely accepted position in the philosophy of psychology today (e.g. Chomsky, 1980; Morton, 1981; Marr, 1982; Fodor, 1983). Over the past 30 years, the arguments for the position have become increasingly compelling and diverse; they are of a number of different types: computational, linguistic, physiological, and psychological. The most basic argument is the computational one, which we owe to Simon (1969) and Marr (1976). In Marr's words. Any large computation should be split up and implemented as a collection of small sub-parts that are as nearly independent of one another as the overall task allows. […]