Tense and mood in French and German agrammatism: a morphosemantic analysis of inflectional impairment

Background: Studies on verbal inflection in agrammatism have repeatedly reported an impairment of tense, but it is controversial whether mood is also problematic. It is also unclear whether dissociations occur within inflectional categories. Inconsistent findings have led to several hypotheses for agrammatic impairments of verbal inflection, most of which are rooted in morphosyntactic analysis. Aims: This multiple case study investigated tense and mood in agrammatism in French and German. The aim was to highlight impairments between and within inflectional categories and to compare them with morphosyntax-oriented hypotheses on agrammatism. Methods and procedure: Three French-speaking and four German-speaking people with agrammatism and matched controls participated in the study. Different tenses and moods were assessed through sentence completion, word ordering, and grammaticality judgment. A quantitative analysis and an error type analysis were performed. Outcomes and results: The people with agrammatism in this study had overall difficulties with tense and mood. Within-category dissociations were observed, with indicative perfect and conditional being more problematic in both languages. Substitutions were the main type of error, and several crosslinguistic substitution patterns emerged. This is consistent with previous morphosyntactic approaches to agrammatism, but these fail to account for the reported within-category dissociations. Conclusions: The present study argues for an alternative view anchored in morphosemantics. It suggests that morphosemantic encoding is deficient in agrammatism. Marked semantic values, such as past and hypothetical, are more error-prone and typically substituted by less marked semantic values. External factors, such as frequency and morphological complexity, may also play a role in the agrammatic impairment of verbal inflection.