The processing of inflected and derived words in writing.

We report on an English-speaking, aphasic individual (RB) with a spelling deficit more severely affecting orthographically irregular words for which phonologically plausible errors (PPEs) were produced. PPEs were observed for all word forms, with the exception of inflectional suffixes, despite the irregular sound-print mappings of many inflectional suffixes (e.g., walked → /wɔkt/). RB's pattern replicates that reported in Badecker, Rapp, and Caramazza (Badecker, W., Rapp, B., & Caramazza, A. (1996). Lexical Morphology and the Two Orthographic Routes. Cognitive Neuropsychology, 13, 161-176). We extended their investigation by examining RB's spelling of derived words and found a selective deficit for derived words compared to inflected words in writing. This selective deficit did not appear to reflect differences in morphological transparency or suffix frequencies that exist between inflection and derivation. This is the first evidence that distinct neural mechanisms support inflection and derivation in spelling.

How modality-specific is morphology?

Writing has long been considered to be dependent on speaking. However, modality-specific dissociations between written and spoken word production imply that word production is supported by distinct neural mechanisms in writing, which can be impaired or spared regardless of the intactness of spoken word production. Rapp et al. (2015). Modality and morphology: What we write may not be what we say. Psychological Science, 26, 892-902 documented a double dissociation where problems with regular inflections were selectively restricted to writing or speaking. We report on two English-speaking aphasic individuals who exhibit this same modality-specific dissociation of inflectional processing, replicating the original findings. We expand on Rapp et al.'s study by examining whether the dissociations observed with regular inflections extend to other morphological forms, such as derivation and irregular inflection. Results showed that the dissociation holds for derivation; however, both participants were impaired with irregular inflections in both output modalities. Implications of these findings for morphological processing and the independence of the orthographic system are discussed.

A selective morpho-phonological deficit?

We report on an English-speaking, aphasic individual (TB) who showed a striking dissociation in speaking with the different forms (allomorphs) that an inflection can take. Although very accurate in producing the consonantal inflections (-/s/, -/z/, -/d/, -/t/), TB consistently omitted syllabic inflections (-/əz/, -/əd/), therefore correctly saying "dogs" or "walked," but "bench" for benches or "skate" for skated. Results from control tests ruled out that TB's selective difficulties stemmed from problems in selecting the correct inflection for the syntactic context or problems related to phonological or articulatory mechanisms. TB's selective difficulties appeared instead to concern morpho-phonological mechanisms responsible for adapting morphological elements to word phonology. These mechanisms determine whether the plural inflection surfaces in the noun bench as voiced (-/z/), unvoiced (-/s/) or syllabic (-/əz/). Our results have implications for understanding how morphological elements are encoded in the lexicon and the nature of morpho-phonological mechanisms involved in speech production.