The DSM-IV implicitly assumes that development is uniform across ability domains, which implies that relationships between ability measures do not differ across development. We assessed whether correlations between measures of nine ability constructs differed across samples of children aged 3 - 5 (n = 117), 6 - 8 (n = 116), 9 - 11 (n = 124) and 12 - 14 years (n = 92). LISREL analyses show that correlations in each age group differ from those of each other age group. Parallel analyses indicate that the latent structure of ability differs across age groups. We conclude that shared maturational processes, including changes in the connectivity of neural systems, are responsible for decreasingly and increasingly strong relationships between some ability measures.