In Chapters 12,13, and 14 we have discussed a number of disturbances that affect single words: disturbances of lexical semantic representations, of the phonological output from the lexicon, and of accessing the lexicon from the written word. In Chapters 15 and 16, we shall be discussing disturbances that affect the form and meaning of sentences. In this chapter, we shall discuss disturbances of sentence production, and in Chapter 16 disturbances of sentence comprehension. In keeping with the philosophy that we have adopted throughout Part III of this book – that of discussing a few aphasic symptoms in detail in relationship to normal processes, rather than presenting a general survey of a large number of studies dealing with a particular topic – we shall focus here upon the symptom (or syndrome) of agrammatism, and upon a particular type of sentence comprehension disturbance in Chapter 16. As elsewhere in Part III, we begin with studies that describe the normal structures and processes involved in sentence production, and then move to disturbances in this functional domain.

We began our discussion of linguistic structures in Chapter 12 by considering the question of what individual words mean, and we continued our investigation of language by outlining some of the properties of the sound system and of the orthographic representations of words in Chapters 13 and 14. Crucial though words are to language, they are not the only elements of linguistic structure, and the meanings of individual words by no means exhaust the semantic features conveyed by language. As John Hughlings Jackson (1874) pointed out, words are generally grouped together into larger structures which convey meanings above and beyond those inherent in each lexical item.