Letter Migrations between Words in Reading Aloud Can Result Either from an Impairment in Orthographic Input or in Phono-Logical Output

Abstract

Letter migrations between words in reading aloud (e.g., reading "cane love" as "lane love" or "lane cove") are known to result from a deficit in the visual-orthographic analysis and characterize attentional dyslexia. In spontaneous speech, individuals with impairment in the phonological output buffer may show migrations of phonemes between words. The purpose of this study was to examine whether migrations between words in reading aloud can also result from a deficit in the phonological output buffer, to explore the characteristics of migrations resulting from orthographic input and from phonological output deficits, and to examine methods to distinguish these two sources. Using tasks of reading aloud of 92-182 word pairs, we identified 18 adults and adolescents with developmental dyslexia who made between-word letter migrations in reading aloud, significantly more than age-matched controls (372 adults and 26 7th-graders). To distinguish between orthographic-input and phonological-output sources for these migrations, we administered a test assessing orthographic-input without spoken-output (written-semantic-decision on 140 migratable word pairs) and a test of repetition of 36 auditorily-presented migratable word pairs, assessing spoken output without orthographic-input (and word span tests). These tests indicated that the migrations of ten of the participants with dyslexia resulted from an orthographic-input deficit, and for the other eight participants, migrations resulted from a phonological-output deficit. We identified several differences between the two types of between-word errors: first, whereas the individuals with attentional dyslexia made omissions of a letter that appeared in the same position in the two words, the phonological output buffer group did not make such omissions. In addition, the groups differed in the origin of migration: orthographic input migrations involve letters that are orthographically adjacent, whereas phonological output migrations involve phonemes that have just been spoken or that are prepared together in the phonological buffer for production. This was manifested in that migrations from the line below and from two lines above occurred only in the orthographic input deficit group, and migrations occurred from a word vertically close to the target in the orthographic input group but from a word that has just been spoken (placed diagonally to the target) in the phonological output group. This study thus indicates that between-word migrations in reading-aloud can result not only from attentional dyslexia, but also from a phonological output buffer deficit, and offers ways to distinguish between the two.