Date of Award

January 2014

Document Type


Degree Name

Master of Science (MS)


Communication Sciences & Disorders

First Advisor

Alycia Cummings


The purpose of the current study was to evaluate the role of word lexicality between Tier Two vocabulary (T2) words and nonwords (NWs) in effecting phonological change in children's sound systems. Often children with functional speech sound disorders (SSD) make slow progress in the treatment of their SSD due to their prior experiences with the words used in treatment. One way to avoid possible biases associated with life experience and semantics (Leonard, Newhoff, & Mesalam, 1980) in the treatment of SSD is to use NWs (e.g. Bryan & Howard, 1992; Gierut & Morrisette, 1998; Gierut, Morrisette, & Champion, 1999; Storkel, 2004). NWs have been shown to cause change in the children with SSD because they are low frequency and have not been improperly produced repeatedly by the child prior to treatment. Gierut and Morrisette (2010) suggested that treatment of a sound in NWs leads to levels of articulation proficiency that are equal to if not better than those of production accuracy levels achieved in treatment with real words. Thus, NWs serve a critical role in causing system wide change in children with SSD. The fact that NWs can cause system wide change due to the elimination of previous life experiences suggests that T2 words might also be promising treatment targets. Specifically, T2 words can eliminate participant familiarity and frequency since they are by definition, acquired later in development. Yet, T2 words appear frequently a wide variety of texts, and in oral and written language of mature language users. The biggest advantages of using T2 words over NWs is that they have lexical value and promote early academic success. While T2 words are good for vocabulary instruction,

they might also be useful for SSD treatment. Young children interpret T2 words as novel words due to their low frequency. Moreover, T2 words are better treatment targets than NWs due to their lexicality, in that they are meaningful and children will have opportunities to hear and use them in and outside of the therapy setting.

The current study recruited four 3- to 6-year-old children with functional speech sound disorders (SSD). Treatment was provided two times weekly in 1-hour sessions, for a total of 10 sessions. The participants were randomly assigned to two treatment groups: NWs and T2 words. The participants in both treatment groups received the same amount of exposure to the targeted treatment words through the presented story. The children in the T2 treatment group were provided with a brief definition through an incidental learning approach in addition to the exposure of each targeted word. The two word types differ in terms of their lexicality, in that the T2 words were real, meaningful words while NWs do not have any meaning in the ambient English language.

The first aim of the study was to examine phonological change in the participants in both treatment groups. The low frequency of NWs has been proven to be efficacious in the treatment of SSD because the words have not been repeatedly produced and used incorrectly by the children. Since T2 words and NWs are both low frequency, they were predicted to make similar changes to a child's sound system. T2 words showed greater changes on some aspects of the children's sound system but not all. The second aim of the study was to examine vocabulary expansion through incidental learning. Positive changes did occur in the T2 word treatment group in terms of vocabulary expansion, while the NW group participants did not add any of the treatment words to their repertoires. T2 vocabulary words appeared to promote later academic achievement and the evidence of T2 vocabulary expansion in the T2 treatment group adds to the efficacy of using T2 words in the treatment of SSD. Children with SSD often have lower expressive language scores and unintelligible communication, which can have a negative impact on their lexical development (Camarata, 1996; Smith & Camarata, 1999), putting them at risk for early academic failure. This study illustrates the efficacy of using T2 vocabulary in speech treatment.