The purpose of the Iowa Articulation Norms Project and its Nebraska replication was to provide normative information about speech sound acquisition in these two states. An assessment instrument consisting of photographs and a checklist form for narrow phonetic transcription was administered by school-based speech-language pathologists to stratified samples of children in the age range 3-9 years. The resulting data were not influenced by the demographic variables of population density (rural/urban), SES (based on parental education), or state of residence (Iowa/Nebraska); however, sex of the child exerted a significant influence in some of the preschool age groups. The criteria used to determine acceptability of a production appeared to influence outcomes for some speech sounds. Acquisition curves were plotted for individual phoneme targets or groups of targets. These curves were used to develop recommended ages of acquisition for the tested speech sounds, with recommendations based generally on a 90% level of acquisition. Special considerations were required for the phonemes /ng s z/.

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.

SLPs reported that they provided children ages 3-6 who had SSD with 30 or 60 min of treatment time weekly, regardless of group or individual setting. More SLPs indicated that they used traditional intervention than other types of intervention. However, many SLPs also reported using aspects of phonological interventions and providing phonological awareness training. Fewer SLPs indicated that they used nonspeech oral motor exercises than in a previous survey ( Lof & Watson, 2008). Recently graduated SLPs were no more familiar with recent advances in phonological intervention than were their more experienced colleagues. Discussion This study confirms previous findings ( Mullen & Schooling, 2010) about the amount of service provided to children ages 3-6 who have SSD. Issues related to the use of traditional and phonological intervention with children who have phonological disorder are discussed, along with concerns related to evidence-based practice and research needs.

Table 1 published in a recent article (LSHSS/July 1986) contained a number of errors. The author has submitted a corrected version of this table (see below).

Speech sound disorders appear to be an overt manifestation of a complex interaction among variables influencing literacy skills, including nonlanguage cognition, vocabulary, letter knowledge, and phonological awareness. These interrelationships hold across the range of speech sound production skill, as children with superior speech sound production skill experience superior literacy outcomes.