We report a study of referential choice in discourse production, understood as the choice between various types of referential devices, such as pronouns and full noun phrases. Our goal is to predict referential choice, and to explore to what extent such prediction is possible. Our approach to referential choice includes a cognitively informed theoretical component, corpus analysis, machine learning methods and experimentation with human participants. Machine learning algorithms make use of 25 factors, including referent’s properties (such as animacy and protagonism), the distance between a referential expression and its antecedent, the antecedent’s syntactic role, and so on. Having found the predictions of our algorithm to coincide with the original almost 90% of the time, we hypothesized that fully accurate prediction is not possible because, in many situations, more than one referential option is available. This hypothesis was supported by an experimental study, in which participants answered questions about either the original text in the corpus, or about a text modified in accordance with the algorithm’s prediction. Proportions of correct answers to these questions, as well as participants’ rating of the questions’ difficulty, suggested that divergences between the algorithm’s prediction and the original referential device in the corpus occur overwhelmingly in situations where the referential choice is not categorical.

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.

The lack of standardized language assessment tools in Russian impedes clinical work, evidence-based practice, and research in Russian-speaking clinical populations. To address this gap in assessment of neurogenic language disorders, we developed and standardized a new comprehensive assessment instrument – the Russian Aphasia Test (RAT). The principal novelty of the RAT is that each subtest corresponds to a specific level of linguistic processing (phonological, lexical-semantic, syntactic, and discourse) in different domains: auditory comprehension, repetition, and oral production. In designing the test, we took into consideration various (psycho)linguistic factors known to influence language performance, as well as specific properties of Russian. The current paper describes the development of the RAT and reports its psychometric properties. A tablet-based version of the RAT was administered to 85 patients with different types and severity of aphasia and to 106 age-matched neurologically healthy controls. We established cutoff values for each subtest indicating deficit in a given task and cutoff values for aphasia based on the Receiver Operating Characteristic curve analysis of the composite score. The RAT showed very high sensitivity (> .93) and specificity (> .96) substantiating its validity for determining presence of aphasia. The test’s high construct validity was evidenced by strong correlations between subtests measuring similar linguistic processes. The concurrent validity of the test was also strong as demonstrated by a high correlation with an existing aphasia battery. Overall high inter-rater and test-retest reliability were obtained. The RAT is the first comprehensive aphasia language battery in Russian with properly established psychometric properties. It is sensitive to a wide range of language deficits in aphasia and can reliably characterize individual profiles of language impairments. Notably, the RAT is the first comprehensive aphasia test in any language to be fully automatized for administration on a tablet, maximizing further standardization of presentation and scoring procedures.

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Coherence is a semantic property of the text to make sense to readers or listeners and is crucial for any text. Various coherence measures have been developed for assessment of discourse abilities in different clinical populations. However, the results of decades of research on coherence of speech of individuals with brain damage have yielded contradictive results. We suggest that this might be due to the different sensitivity of the methods.In this study we two measures of global coherence and five measures of local coherence on the same set of texts by healthy speakers of Russian and people with dynamic aphasia in order to find which methods allow to distinguish between the two groups and how these results correlate.The material for the study is texts from the Russian CliPS corpus which is a collection of oral retellings of the pear film by individuals with brain damage and healthy speakers of Russian language.