Developmental studies examining relations between word reading (WR) and decoding in typical and dyslexic populations routinely cut the reading distribution to form distinct groups. However, dichotomizing continuous variables to study development is problematic for multiple reasons. Instead, we modeled and visualized the parallel growth of WR and nonword reading (NWR) factor scores longitudinally in a Grade 1-4 developmental sample (N = 588). The results indicate that while WR and NWR growth factors are highly related (r = 0.71), the relation between WR and NWR trajectories change as a function of initial WR. Results are interpreted within computational models of dyslexia in which children with dyslexia overfit orthography [right arrow] phonology relations at the level of the word, limiting the development of sublexical representations needed to read nonwords.