In the study of reading, there is a debate about whether letters or graphemes are the primary units of perception. A promising data basis for empirically contributing to this debate can be gained from measuring the perception of single vowel letters compared to vowel digraphs. We used letter detection with masked pseudoword primes on pseudoword targets among skilled native readers in order to test for the existence and time course of vowel digraph effects during reading in deep (English) and shallow (Dutch) orthographies. Selecting these two languages, which are similar in terms of syllabic structure, allowed us to use exactly the same pseudoword stimuli. Results indicate that whereas the Dutch readers show letter effects at short prime durations and digraph effects at longer prime durations, the English readers show only letter effects. These findings are inconsistent with a strong version of the claim that graphemes are perceptual in nature, but consistent with models of reading acquisition and skilled reading that predict that, although letter effects always precede grapheme effects, grapheme activation proceeds faster in relatively shallow orthographies than in relatively deep ones.
A three-time point longitudinal investigation of the arcuate fasciculus throughout reading acquisition in children developing dyslexia
