Taxometric analyses of specific language impairment in 3- and 4-year-old children.

Specific language impairment (SLI), like many diagnostic labels for complex behavioral conditions, is often assumed to define a category of children who differ not only in degree but also in kind from children developing language normally. Although this assumption has important implications for theoretical models and clinical approaches, its validity has not been tested. In this study, distributions of language scores from children at ages 3 (N = 620) and 4 (N = 623) years were analyzed using a taxometric procedure known as "mean above minus below a cut" (MAMBAC; P. E. Meehl and L. J. Yonce, 1994). Language scores were distributed dimensionally at both ages, failing to support the hypothesis of a qualitatively distinct group corresponding to children with SLI.