A construction-based approach to spoken language in aphasia

Linguistic research into aphasia, like other areas of language research, has mainly been approached from the perspective of rule-based, generative theory (Chomsky, 1957 onwards). In turn, this has impacted on clinical practice, underpinning both aphasia assessment and therapy. However, this theory is now being widely questioned (e.g. Tomasello, 2003), and other approaches are emerging, such as the constructivist, usage-based perspective, influenced by cognitive and construction grammars (e.g. Langacker, 1987; Goldberg, 1995). This approach has yielded important results in, for example, child language (e.g. Ambridge, Noble, & Lieven, 2014), but it remains largely unapplied to language in aphasia. This thesis begins to address this by conducting an exploratory examination of spoken language in aphasia from a constructivist, usage-based perspective. Two central features of usage-based theory, the nature of constructions and the role of frequency, form the basis of the studies reported in the thesis. Reliable methods of transcription and speech segmentation appropriate for an analysis that employs this approach are developed and then applied to the examination of spoken narratives of the Cinderella story by twelve people with a range of aphasia types and severities. Beginning at the single word level, the effects of general versus ‘context-specific’ frequencies on participants’ nouns are examined, demonstrating that most participants’ noun production appears to be more influenced by context-specific frequency, that is, the frequency of nouns in the context of the Cinderella story. This is followed by an analysis of errors in marking these nouns for grammatical number. A main finding here was that error production seems to be affected by general frequency: the noun form used erroneously was always more frequent than that expected. Finally, beyond the single word level, an in-depth analysis is provided of the participants’ verbs and the strings these were produced in. This focuses on the number and productivity of constructions apparently available to the participants and shows that these speakers can be placed along a continuum largely corresponding to their expressive language capabilities. The productions of the more impaired speakers were mainly limited to a small number of high-frequency words and lexically-specific or item-based constructions. In contrast, those with greater expressive language capabilities used a larger number and variety of constructions, including more lengthy schematic patterns. They seemed much more able to use their constructions productively in creating novel utterances. In addition, an analysis of the errors in participants’ verb strings was conducted. This revealed some differences in the types of errors produced across the participant group, with the more impaired speakers making more omission and inflection errors, whilst the participants with greater expressive language capabilities produced more blending errors. The analysis demonstrates how these seemingly different error types could all be explained within a constructivist, usage-based approach, by problems with retrieval. In showing how the results of these studies can be accounted for by constructivist, usage-based theory, the thesis demonstrates how this view could help to elucidate language in aphasia and, equally, how aphasia offers new ground for testing this approach.