Narrative and conversational discourse of adults with closed head injuries and non-brain-injured adults: A discriminant analysis

Background: Although there is general agreement regarding the clinical utility of discourse analyses for detecting the often subtle communicative impairments following closed head injuries (CHI), there is little consensus regarding discourse elicitation or analysis procedures. Consequently it has been difficult to compare findings across studies. Aims: In an effort to facilitate a movement towards the adoption of a more consistent methodology for the assessment of discourse abilities, the current study examined several commonly used measures of discourse performance and the accuracy with which these measures were able to distinguish individuals with CHI from non-brain-injured (NBI) controls. Previous studies have suggested that conversation is less demanding than narrative discourse because such narratives require greater manipulation of extended units of language while conversational discourse can be maintained with minimal responses (Chapman, 1997; Galski, Tompkins, & Johnston, 1998). On the basis of these reports it was hypothesised that the measures of narrative story performance would more accurately discriminate the participant groups than conversational measures. Methods & Procedures: Discourse samples were elicited from 32 adults with CHI and 43 NBI adults. Discourse samples included two story narratives, generation and retelling, and 15 minutes of conversation. A variety of discourse analyses were performed including story narrative measures of grammatical complexity, cohesive adequacy, and story grammar. Measures of conversation included appropriateness and topic initiation. Discriminant function analyses (DFA) were then employed to determine the accuracy of the selected measures in classifying the participants into their respective groups. Outcomes & Results: Results of the DFA with only the story narrative measures indicated that 70% of the cases, 64.5% of the CHI group, and 74.4% of the NBI group were accurately classified. This finding was not significant, suggesting that the story narrative measures did not reliably discriminate the CHI from the NBI participants. The DFA with the conversational measures correctly classified over 77% of the cases, 78.1% of the CHI participants, and 72.1% of the NBI group. This finding was significant, which suggests that the measures of conversational discourse were better able to discriminate the participant groups. A third DFA was performed, with all of the story narrative and conversational discourse measures included, which revealed that the conversational measures, comments and adequate plus responses, and the story narrative measure, T-units within episode structure in the generation task, made the greatest contributions to discriminating between the groups. Overall, group membership was correctly classified by the DFA in 81% of the cases, 84.4% of the CHI group, and 77.5% of the NBI participants. This finding was significant, suggesting that these three discourse measures discriminated the two participant groups with the highest degree of reliability. Conclusions: These findings did not support the hypothesis that the narrative discourse measures would more accurately predict group membership of the CHI and NBI participants than the conversational measures. A variety of factors may account for these findings including the interactive nature of conversation as well as social factors which appear to make this genre more difficult for individuals with CHI and a more sensitive index of their cognitive-communicative impairments.