Production of German -n plurals in Aphasia: Effects of dominance and predictability

Abstract

Background: In picture naming, both unimpaired and impaired speakers are usually better in naming singular than plural forms of the same noun, such as cat/cats. This singular-advantage is especially present in the case of singular-dominant nouns (e.g., table has higher surface frequency compared to its corresponding plural tables). However, for plural-dominant items (e.g., eyes has a higher surface frequency compared to eye) such singular advantage disappears. Thus, the lexical representation/processing of singular-dominant and plural-dominant nouns seem to differ but the exact underlying source for this dominance effect is still a matter of debate. While most of the available data stem from English experiments, less data are available from German. Aims: This study examines the effect of plural dominance for the German – n plural, a plural form, which can be predictable or non-predictable on the basis of the ending of the singular word form and its grammatical gender. Hence, this study examines the role of dominance and predictability of plural production in aphasia. Our data will enrich the development of materials for the assessment of morpho-lexical impairments in aphasia. Methods & Procedures: In a case-series design, five people with aphasia with severe word-finding difficulties participated in two picture naming tasks with single- and multiple-depictions of objects. Materials included nouns of the German –n plural type. Exp. 1 tested for effects of number and plural dominance in naming fully predictable –n plurals and their corresponding singulars. Exp. 2 tested for effects of number and predictability, using subsets of fully predictable and non-predictable –n plurals, and their corresponding singulars. Outcomes & Results: Exp. 1 revealed a significant plural dominance effect in spoken picture naming across five German speakers with aphasia: a singular advantage was observed for singular-dominant nouns, but plural-dominant singular and plural nouns did not differ. Further, in Exp. 2, no effect of predictability for the German plural affix –n was found, but an overall singular advantage across both groups. Conclusions: We interpret the dominance pattern of Exp.1 as manifestation in the links between concept and lemma level for singular- and plural-dominant nouns. Exp. 2, confirmed the singular advantage for singular-dominant nouns for both –n plural groups, indicating that both –n plural groups follow one plural production mechanism, however, we cannot be confident about the type of mechanism.