How modality-specific is morphology?

ABSTRACT

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.

KEYWORDS:

• Morphology
• inflection
• derivation
• orthography
• aphasia

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 The small number of errors observed with nouns probably reflects the impoverished morphology of English nouns that only distinguishes number, as in one cat, two cats. It is worth mentioning that in other writing tasks S.D. produced morphological errors with nouns, which involved either the incorrect omission of the plural morpheme (books → book) or its incorrect addition (teacher → teachers).

2 A similar difference appeared for S.D. with the larger set of irregular verbs tested with the original material used for V.B.R.: S.D.’s accuracy was equal to 28% in writing and 64% in speaking, χ²(1) = 57.73, p < .001.