ABSTRACT
In this chapter, we attempt to explore the modularity hypothesis particularly with respect to the speech processing system. Results from the study of aphasia suggest that the speech processing system operates in terms of a specialized vocabulary and set of operations tied specifically to language processing. This vocabulary involves the transformation of a continuous acoustic signal into discrete phonetic segments and ultimately into phonetic features. Further, the speech processing system seems to be separate from general auditory processing mechanisms and in this sense forms a sub-module of the language system. Nevertheless, the speech processing system seems to be interactive rather than autonomous with respect to the language module. That is, speech perception deficits do not seem to occur independent of deficits in higher levels of language and further, these deficits seem to be tied directly to and interact with deficits in lexical access.
