Abstract

We explored morphological decomposition in reading, the locus in the reading process in which it takes place and its nature, comparing different types of morphemes. We assessed these questions through the analysis of letter position errors in readers with letter position dyslexia (LPD). LPD is a selective impairment to letter position encoding in the early stage of word reading, which results in letter migrations (such as reading “cloud” for “could”). We used the fact that migrations in LPD occur mainly in word-interior letters, whereas exterior letters rarely migrate. The rationale was that if morphological decomposition occurs prior to letter position encoding and strips off affixes, word-interior letters adjacent to an affix (e.g., signs-signs) would become exterior following affix-stripping and hence exhibit fewer migrations. We tested 11 Hebrew readers with developmental LPD and 1 with acquired LPD in 6 experiments of reading aloud, lexical decision, and comprehension, at the single word and sentence levels (compared with 25 age-matched control participants). The LPD participants read a total of 12,496 migratable words. We examined migrations next to inflectional, derivational, or bound function morphemes compared with migrations of exterior letters. The results were that root letters adjacent to inflectional and derivational morphemes were treated like middle letters, and migrated frequently, whereas root letters adjacent to bound function morphemes patterned with exterior letters, and almost never migrated. Given that LPD is a pre-lexical deficit, these results indicate that morphological decomposition takes place in an early, pre-lexical stage. The finding that morphologically complex nonwords showed the same patterns indicates that this decomposition is structurally, rather than lexically, driven. We suggest that letter position encoding takes place before morphological analysis, but in some cases, as with bound function morphemes, the complex word is re-analyzed as two separate words. In this reanalysis, letter positions in each constituent word are encoded separately, and hence the exterior letters of the root are treated as exterior and do not migrate.

Highlights

  • Major questions in the study of morphological processing are whether and when morphological decomposition takes place during reading

  • The pattern that the letter position dyslexia (LPD) participants demonstrated was consistent across the six tasks: they made very few migrations adjacent to bound function morphemes, at a rate that was similar to the low rate of exterior letter migrations, indicating they treated letters adjacent to bound function morphemes practically as exterior letters

  • This study examined the nature of early morphological decomposition in reading via testing letter position errors that individuals with LPD make in words of various morphological structures

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Summary

Introduction

Major questions in the study of morphological processing are whether and when morphological decomposition takes place during reading. A different way to look at morphological decomposition through transpositions was created by Beyersmann et al (2011; see Beyersmann et al, 2013) Their idea was to examine priming from a morphologically complex nonword created from a transposed stem and a suffix to the stem. In a recent study, Taft and Nillsen (2013), who used priming in normal reading, took advantage of the fact that primes in which the exterior letters transposed provide a smaller priming effect primes with middle transposition They compared transpositions at the exterior letters of the stem (which would be exterior letters following decomposition) to transpositions in the middle of the stem: comparing, for example, disrpove, and disporve, respectively. No difference was found in the priming of exterior and middle transpositions, which the authors explained by saying that the reduced effect of initial letters is purely perceptual and this was not observed once the initial letters of the stem were not perceptually initial

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