Phonologic Error Distributions in the Iowa-Nebraska Articulation Norms Project

The errors on consonant singletons made by children in the Iowa-Nebraska Articulation Norms Project (Smit, Hand, Freilinger, Bernthal, & Bird, 1990) were tabulated by age range and frequency. The prominent error types can usually be described as phonological processes, but there are other common errors as well, especially distortions of liquids and fricatives. Moreover, some of the relevant phonological processes appear to be restricted in the range of consonants or word-positions to which they apply. A metric based on frequency of use is proposed for determining that an error type is or is not atypical. Changes in frequency of error types over the age range are examined to determine if certain atypical error types are likely to be developmental, that is, likely to self-correct as the child matures. Finally, the clinical applications of these data for evaluation and intervention are explored.