Lexical diversity for adults with and without aphasia across discourse elicitation tasks

Abstract

Background Differences in lexical diversity (LD) across different discourse elicitation tasks have been found in neurologically intact adults (NIA) (Fergadiotis, Wright, & Capilouto, 2010) but have not been investigated systematically in people with aphasia (PWA). Measuring lexical diversity in PWA may serve as a useful clinical tool for evaluating the impact of word retrieval difficulties at the discourse level. Aims The study aims were (a) to explore the differences between the oral language samples of PWA and NIA in terms of LD as measured by dedicated computer software (voc-D), (b) to determine whether PWA are sensitive to discourse elicitation task in terms of LD, and (c) to identify whether differences between PWA and NIA vary in magnitude as a function of discourse task. Method & Procedures Oral language samples from 25 PWA and 27 NIA were analysed. Participants completed three commonly used discourse elicitation tasks (single pictures, sequential pictures, story telling) and voc-D was used to obtain estimates of their LD. Outcomes & Results A mixed 2 × 3 ANOVA revealed a significant group task interaction that was followed by an investigation of simple main effects and tetrad×comparisons. Different patterns of LD were uncovered for each group. For the NIA group results were consistent with previous findings in the literature according to which LD varies as a function of elicitation technique. However, for PWA sequential pictures and story telling elicited comparable estimates of LD. Conclusions Results indicated that LD is one of the microlinguistic indices that are influenced by elicitation task and the presence of aphasia. These findings have important implications for modelling lexical diversity and selecting and interpreting results from different discourse elicitation tasks.

Discourse: Assessment and Therapy

“…Speakers with aphasia produce discourse that is impaired in terms of syntax [52][53][54][55]. Evidence from retellings of the Cinderella story is a particularly rich source of information about syntactic difficulty for PWA [9,55,56].…”

Verb Production in Aphasia: Testing the Division of Labor between Syntax and Semantics

“…This study used a sample of discourse from each participant elicited by the retelling of the Cinderella story. This particular discourse elicitation task was chosen as it has been demonstrated that during story retell procedures, individuals tend to produce language with significantly higher lexical diversity than during picture description tasks (Fergadiotis & Wright, 2011). This suggests that story retell tasks produce language samples that are more representative of the individual's best semantic abilities than samples elicited by picture description.…”

“…Finally, individuals with syntactic deficits tend to show reduced use of function words, such as auxiliary verbs, articles, and prepositions . With regards to semantic impairment, individuals with semantic access deficits tend to use fewer different types of words (Fergadiotis & Wright, 2011), and may omit words that are important to convey critical information, such as in retelling a story (Ernest-Baron, Brookshire, & Nicholas, 1987), due to reduced capacity to access semantic representations. These individuals may also demonstrate decreased semantic density, using more words than necessary to convey the same amount of information (Bryant et al, 2013).…”

Comparison of different feature sets for identification of variants in progressive aphasia

“…Covington and McFall (2010) proposed a new measure called the moving-average type-token ratio (MATTR), which is independent of text length. This feature was later applied to aphasic speech in a study by Fergadiotis and Wright (2011), and was found to be one of the most unbiased indicators of lexical diversity in impaired speakers.…”