'To be' or not 'to be': an analysis of copula production and omission in people with non-fluent aphasia

Background: Agrammatic aphasia has been widely associated with impairments with functional words and complex sentences. Speech errors of people with aphasia (PWA) have been reported to be selective, with patterns of omissions in functional words, most notably in the domain of tense inflection on verbs compared to agreement in morphologically rich languages.Aims: In languages like English, where tense and agreement are hard to disentangle in their inflectional paradigms, investigations of the inflectional domain in PWA are rare. In this study, we introduce a novel approach that allows the disentangling of inflectional errors in English through the patterns of copula omission of the verb to be. The inflectional system of the functional verb to be is richer, and its distribution in the sentence is based on the semantics of its predicate (stage-level vs. individual-level).Methods and procedures: Spontaneous productions of 16 PWA collated from Aphasia Bank transcripts were analysed for violations of tense alongside other patterns of error that could suggest an impairment in the inflectional domain.Outcomes and results: Copula deletion was found to be modulated by the semantics of the predicate, showing a selective pattern of omission in stage-level predicates. Incorrect case assignment (accusative in place of nominative) was also observed as an indicator of impaired tense.Conclusions: The results confirm the effectiveness of copula to be to investigate the English inflectional system and substantiate previous studies on selective errors in the verbal domain in PWA in English.