Effects of morphological complexity on phonological output deficits in fluent and nonfluent aphasia.

This study examined the effects of morphological complexity on aphasic speakers with lexical-phonological output deficits. Subjects were two fluent and two nonfluent aphasic speakers who repeated morphologically simple words at the same level of accuracy and whose errors were virtually all phonological in nature. They were asked to repeat a variety of morphologically complex (i.e., affixed) words. Results were interpreted within our two-stage model of lexical-phonological production (Kohn & Smith, 1994, 1995), which we expand to include a distinction between derivational and inflectional morphology. When comparing overall performance levels between morphologically simple and complex words, only three subjects exhibited more difficulty repeating the morphologically complex targets. Nevertheless, when comparing repetition accuracy between different types of morphologically complex words (e.g., derived vs. inflected), all four subjects displayed similar patterns. These findings suggested that while morphological complexity has different effects on the two stages within the lexical-phonological output system, the relative effects of different morphological structures are constant. At the level of error analysis, patterns of affix errors distinguished the nonfluent from the fluent subjects in ways that are reminiscent of the affix errors associated with agrammatic and paragrammatic speech. This finding raised questions concerning the relationship between morphosyntactic and morphophonological deficits.

Consonant harmony as a compensatory mechanism in fluent aphasic speech.

This study addresses how fluent aphasics construct complete phonological representations, given the premise that their phonological speech errors result from faulty information about stored lexical representations. We explored whether consonant harmony, a common rule-governed process of feature copying, operates as a compensatory device for completing phonological representations in fluent aphasia. This was examined in a corpus of phonemic paraphasias (n = 543) produced by 8 fluent aphasics during picture naming. Consonant substitutions due to a single feature change (n = 143) were analyzed for the properties of consonant harmony predicted by the phonological principles embodied in a Universal Markedness version of Underspecification Theory (e.g., Chomsky and Halle, 1968). Results indicated that harmony constrained the feature substitution errors involving the feature class of voice (e.g., calendar-->/[symbol: see text]/), but not place of articulation (e.g., igloo-->/idlu/); substitutions due to an error in manner were rare. These findings were used to argue that for English-speaking fluent aphasics a consonant harmony rule for the feature voice is incorporated into a compensatory output mechanism that is used to complete faulty lexical-phonological representations.