Clinical linguistics involves the study of how language and communication may be impaired. In its narrowest and most applied sense it focuses on the use of linguistics to describe, analyse, assess, diagnose and treat communication disorders (e.g. Crystal 1981). However, it is also commonly taken to include the study of clinical language data in order to throw light on the nature, development and use of normal language and thus to contribute to linguistic theory (Ball et al. 2008). Indeed, it is sometimes only through the analysis of language breakdown that we become aware of hitherto unknown features of language structure and function, and this is part of the reason why the discipline has grown considerably over the last few decades. The scope of clinical linguistics is broad, to say the least. No level of language organisation,
from phonetics to discourse, is immune to impairment, with problems manifested in both the production and comprehension of spoken, written and signed language across the human lifespan. The subject matter of clinical linguistics is thus amenable to study through virtually all branches of linguistics, and various sub-specialisms have been accorded their own distinct labels such as ‘clinical phonology’, ‘clinical pragmatics’ and ‘clinical sociolinguistics’. The fact that communication disorders may be manifested linguistically does not necessarily mean that they will always have a speciﬁcally linguistic cause, and thus if we are interested in explaining them fully we are inevitably drawn beyond linguistics to its interfaces with domains such as physiology, neurology, cognition and social interaction. One might thus deﬁne clinical linguistics as ‘the study of communication disorders, with speciﬁc emphasis on their linguistic aspects (while not forgetting how these interact with other domains)’. This cross-disciplinary perspective is a key feature of clinical linguistics. Such a breadth of focus notwithstanding, establishing a clear causal link between behavioural symptoms and underlying deﬁcits is not always easy. For example, there is disagreement with regard to whether speciﬁc language impairment (SLI) (a condition found in otherwise healthy children who have problems with syntax and/or phonology) is best attributed to underlying deﬁcits in auditory perception, cognitive processing, a dedicated language module or some combination of all of these (see below for further discussion). Nevertheless, it is still possible to characterise the linguistic features of SLI precisely enough to be able to design assessments and remedial programmes. It is this key
grounding in linguistics – and in particular the focus on linguistic behaviour – which distinguishes clinical linguistics from related ﬁelds such as neurolinguistics (see chapter by Ahlsén, this volume) and speech and language pathology, which accord primary importance to the underlying causes of communication disorders. This important distinction was ﬁrst outlined by Crystal (1980) in terms of the ‘behavioural’ as opposed to the ‘medical’ model of language pathology.