Factors affecting the production of verb inflections in Greek aphasia

Abstract

Verb inflection errors are commonly observed in the speech of aphasic individuals, but the errors are selective and not evenly distributed across different functional categories (e.g., Friedman & Grodzinsky, 1997). An investigation of verb inflection errors in seven Greek aphasic individuals showed more errors in aspect and tense than in agreement (Varlokosta et al., 2006). Moreover, the productions revealed a large proportion of repetition and lexical errors in addition to pure inflectional errors. The presence of different types of errors raises the question of the nature of the underlying deficit in the production of the functional categories. An erroneous production of a verb may involve an error in morphological suffixation, preserving the verb stem; an error in lexical selection, preserving the inflection; and a mixed error, involving both the morphological suffixation and the verb stem. Because all verbs in Greek are affixed, a bare stem is not a possibility as it would result in an illegal word. According to Levelt’s (1999) model of word production, morphological suffixation errors indicate a breakdown at the level of diacritical (lexical–semantic) features, whereas lexical and mixed lexical–morphological errors reflect additional difficulty in lexical selection. Repetition errors involve the least amount of computation and thus may indicate a difficulty in affixation during phonological encoding. To address the above question, we re-examined the productions of the Greek speaking aphasic individuals studied by Varlokosta et al. (2006) by re-classifying the errors as morphological, lexical, or mixed. A second aim was to examine the contributions of severity of spoken language impairment, verb familiarity, regularity, and presence of consonant cluster to the performance per functional category.