Semantic feature knowledge in persons with aphasia: The role of commonality, distinctiveness, and importance

Abstract

Background: Semantic knowledge refers to the information that a person knows about the world. Semantic representations comprise semantic features that may be categorised based on distinctiveness and importance. The expressive and receptive language problems experienced by people with aphasia may relate to deficits in their semantic feature knowledge. Thus understanding impairments in semantic knowledge in persons with aphasia is key to the rehabilitation process. Aims: The purpose of this study was to investigate differences in distinctive feature knowledge across importance levels in people with aphasia grouped according to their ability to distinguish target words from semantically related foils. The relationship of feature knowledge and comprehension and naming abilities was also examined. The primary hypothesis was that participants who had difficulty choosing among semantically related foils would have significantly more difficulty with identification of distinctive features than common features as compared to participants who were able to choose among semantically related foils. Methods & Procedures: A total of 14 adults with aphasia participated in the study. Participants distinguished target words from semantically unrelated and related foils, and sorted common and distinctive semantic features of high and low importance. Participants also completed standardised testing to determine comprehension and naming abilities. Outcomes & Results: A three-way ANOVA was used to investigate the main effects and interactions between groups based on ability to distinguish targets from semantically related foils, distinctiveness of features, and importance of features. Results of the ANOVA showed significant main effects for feature importance, distinctiveness of features, and group. Between-group differences for high- and low-importance common and distinctive feature knowledge were investigated using a series of t-tests. In addition, results showed that feature knowledge correlated with comprehension and naming scores. Findings support that persons with aphasia demonstrate difficulty with identification of low-importance and distinctive features which contributes significantly to the comprehensiveness of their semantic representations as well as impacts their ability to distinguish among semantically related foils. Conclusions: Participants with aphasia who have difficulty identifying target words among semantically related foils have greater deficits with low-importance distinctive feature knowledge than those who are able to choose among semantically related foils. In addition, participants with relatively intact semantic representations in regard to importance and distinctiveness ratings appear to have better comprehension and naming abilities as evidenced by the significant relationships between feature identification measures and tests of naming and comprehension abilities.