Background: The aim of this study was to examine longitudinally the acquisition of reading fluency in a shallow orthography from the very beginning using eye movement recordings. The development of reading fluency is easier to examine in shallow (such as German, Finnish, or Italian) rather than in opaque (such as English or French) orthographies because the former limit the presence of speed-accuracy trade-offs at early stages of acquisition. To date, only cross-sectional eye movement studies of reading development are available.
Material and Method: One normally developing child was assessed at the very beginning of first grade and at the end of the first, second, and fifth grades. Eye movement parameters during reading, reading speed and accuracy in a standard reading test, and vocal reaction time at onset to single words varying in length were measured.
Results: Reading fluency improved dramatically during the first grade and progressively less thereafter: the word-length effect decreased abruptly by the end of the first grade and then less onwards. The rate of improvement closely followed a power function. This pattern held for standard reading tests, various eye movement parameters during reading, and vocal reaction times to single word onset.
Conclusions: These longitudinal observations indicate the rapid acquisition of reading fluency in a transparent orthography showing that the largest changes occurred within the first year of education.

Keywords: Regression Analysis, Reading, Reaction Time - physiology, Longitudinal Studies, Language Tests, Language, Humans, Fixation, Ocular - physiology, Female, Eye Movements - physiology, Child, Preschool, Child, Time Factors