Linguistic mechanisms of coherence in aphasic and non-aphasic discourse

ABSTRACT

Background

Coherence is the quality that distinguishes discourse from a random collection of sentences. People with aphasia have been reported to produce less-coherent discourse than non-language-impaired speakers. It is largely unclear how coherence is established in natural language and what leads to its impairment in aphasia.

Aims

This paper presents a cross-methodological investigation on coherence in the discourse of Russian native speakers with and without aphasia. The purpose of this study was to examine the connection between language impairments in aphasia and different aspects of discourse coherence in order to determine the linguistic mechanisms that could be involved in establishing and maintaining it.

Methods & Procedures

Coherence was operationalised as a combination of four aspects: informativeness, clarity, connectedness, and understandability. Twenty participants were asked to retell the content of a short movie. The retellings were annotated using Rhetorical Structure Theory (RST), a formalistic framework for discourse-structure analysis. Next, they were evaluated for coherence on a four-point scale by trained raters. The ratings were compared between groups. A classification analysis was performed to determine whether the ratings could be predicted based on the macrolinguistic variables collected from the RST annotations and several microlinguistic variables previously linked to coherence.

Result

Retellings produced by speakers with aphasia received lower ratings than those of control participants on all aspects of coherence. The results indicate that different combinations of microlinguistic and discourse-structure variables play a role in establishing each of the coherence aspects.

Conclusions

Our results provided supporting evidence on coherence impairment in aphasia. Perception of a discourse as more or less coherent was associated with both microlinguistic and macrolinguistic variables, with different combinations of variables relevant for each of the aspects. Furthermore, we found that discourse structure plays an important role, especially for understandability. We speculate that pragmatic knowledge shared by interlocutors may boost the coherence of aphasic discourse.

KEYWORDS:

• Aphasia
• coherence
• discourse production
• discourse structure
• rhetorical structure theory

Acknowledgments

This work was supported within the framework of a subsidy by the Russian Academic Excellence Project ‘5-100ʹ; Erasmus Mundus International Doctorate for Experimental Approaches to Language and Brain (IDEALAB) under grant number 2012-1713, Framework Partnership Agreement number 2012-0025.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded within the framework of a subsidy by the Russian Academic Excellence Project '5-100' and by the Erasmus Mundus Joint Doctorate (EMJD) program IDEALAB (International Doctorate for Experimental Approaches to Language And Brain; Macquarie University, Newcastle University, University of Groningen, University of Trento and University of Potsdam, FPA 2012-0025, grant nr. 2012-1713).