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Complexity approach for speech sound disorders

Dip your toes into the complexity approach with this research rundown from guest author Dr. Holly Storkel. 

August 4, 2017

Written by Holly Storkel, PhD, of the University of Kansas Word and Sound Learning Lab



“I just read this 2003 article stating… ‘current research has disproved the idea of developmental norms for articulation, and in fact, current best practice involves starting treatment with more difficult sounds.’ But there was no citation… Help!”


– TISLP member Carrie B. 


This article is referencing the complexity approach, which broadly suggests that more complex targets should be prioritized for treatment because that will trigger change in more complex and less complex aspects of speech or language. In complement, the complexity approach argues that teaching less complex aspects of language leads to change in only less complex aspects of language. “Complexity” can be defined in a variety of ways, such as age-of-acquisition, linguistic complexity, person’s knowledge, and many more. A clinical forum in the February 2007 issue of AJSLP describes the approach generally (Thompson, 2007) and then shows its application to phonological disorders in children (Gierut, 2007), naming deficits in aphasia (Kiran, 2007), and  syntactic deficits in aphasia (Thompson & Shapiro, 2007). For phonology, the complexity approach is typically associated with the work of Mary Elbert, Dan Dinnsen, and Judith Gierut (all formerly affiliated with Indiana University). Gierut provides two reviews of the approach summarizing the relevant evidence for a variety of different aspects of phonological complexity (Gierut, 2001, 2007). Baker and McLeod’s review of phonological treatment approaches shows the evidence for a wide variety of phonological treatments (Baker & McLeod, 2011, see Table 5).

Spoiler alert: There are a number of evidence-based phonological treatments, with the complexity approach being one of a number of evidence-based options.

In terms of the complexity approach, Baker & McLeod (2011) identified 16 studies on the complexity approach with most studies using single-subject designs, which are pretty much the norm for phonological treatment research. Interestingly, despite a strong evidence base, a recent survey by Brumbaugh and Smit (2013) suggests that SLPs may not be familiar with or using the complexity approach. Specifically, Brumbaugh and Smit’s survey showed only 8% of SLPs sometimes, often, or always used a complexity approach in treating children with phonological disorders.


If you are interested in implementing the complexity approach, Jennifer Taps Richards runs a great website (SLPath.com) on phonological treatment with many resources related to the complexity approach.

In terms of your more specific question about developmental norms, the treatment efficacy of targeting early versus late acquired sounds was first examined in a pair of single-subject studies (Gierut, Morrisette, Hughes, & Rowland, 1996). In one study, early sounds were defined as those that were acquired one year before the child’s current chronological age, based on the norms of Smit and colleagues (Smit, Hand, Freilinger, Bernthal, & Bird, 1990). In contrast, late acquired sounds were sounds that were typically acquired one year or more beyond the child’s chronological age based on the Smit norms. Based on this definition, three children were taught early acquired sounds (i.e., k, g, f) and three were taught late acquired sounds (i.e., r, θ, s). Both groups learned the treated sound and generalized the treated sound to untreated words. Likewise, both groups improved production of sounds that shared manner with the treated sound. The main outcome that differentiated the groups is that children taught early acquired sounds made minimal change in untreated sounds that were unrelated to the treated sound, whereas children taught late-acquired sounds learned sounds that were unrelated to the treated sound. Thus, treatment of later acquired sounds seemed to trigger greater system-wide change than treatment of early acquired sounds.
A follow-up randomized controlled group design by Rvachew and Nowak (2001) seemed to contradict this finding. Specifically, 48 children received 12 weeks of phonological treatment on four early or four late acquired sounds (i.e., two treated sounds per six-week treatment block). However, age-of-acquisition was coupled with the child’s knowledge of the sounds in selecting treatment targets. Thus, children were taught either more knowledge (e.g., some production accuracy) early acquired sounds or least knowledge (e.g., no production accuracy) late acquired sounds. This contrasts with the prior study by Gierut and colleagues (1996) where children were always taught a least knowledge sound: specifically, least knowledge early acquired versus least knowledge late acquired. Rvachew and Nowak showed that children taught least knowledge late acquired sounds completed fewer steps in treatment than children taught more knowledge early acquired sounds. In particular, the highest treatment step achieved, on average, by children taught least knowledge late acquired sounds was 2.83 (step 2 = imitated words, step 3 = spontaneous words). In contrast, the highest treatment step achieved, on average, by children taught more knowledge early acquired sounds was 4.7 (step 4 = imitated patterned sentences, step 5 = spontaneous patterned sentences). This also contrasts with the prior study by Gierut where treatment continued until children met an accuracy criterion for spontaneous production of treated words (i.e., everyone completed the same treatment steps). In terms of change in accuracy of the treated sounds, children taught least knowledge late acquired sounds through the word level showed lower accuracy in producing the treated sound in untreated words than children taught more knowledge early acquired sounds through the sentence level. However, there were no significant differences between the groups in overall accuracy of sound production.


Taken together, the findings from Rvachew and Nowak and those from Gierut are complementary, rather than contradictory. Rvachew and Nowak show that treatment of more knowledge early acquired sounds results in quicker progress through therapy steps than treatment of least knowledge late acquired sounds and that this may lead to better learning of the treated sound but this does not translate into differences in broad system-wide generalization. Gierut and colleagues showed that treatment of least knowledge early acquired sounds and least knowledge late acquired sounds does produce differential sound learning when the end of treatment is based on performance criteria (i.e., same treatment steps completed).

Take-home message: If rapid completion of treatment steps in a set number of sessions and/or learning of the treated sound primarily is the goal of treatment, then treatment of more knowledge early acquired sounds may be optimal. On the other hand, if global change in phonology is the goal of treatment, then treatment of least knowledge late acquired sounds to a performance criterion may be optimal.


Baker, E., & McLeod, S. (2011). Evidence-based practice for children with speech sound disorders: Part 1 narrative review. Language, Speech, and Hearing Services in Schools. https://doi.org/10.1044/0161-1461(2010/09-0075)  [available to ASHA members]


Brumbaugh, K. M., & Smit, A. B. (2013). Treating children ages 3-6 who have speech sound disorder: A survey. Language, Speech, and Hearing Services in Schools. https://doi.org/10.1044/0161-1461(2013/12-0029)  [available to ASHA members]


Gierut, J. A. (2001). Complexity in phonological treatment: Clinical factors. Language, Speech, and Hearing Services in Schools. https://doi.org/10.1044/0161-1461(2001/021)  [available to ASHA members]


Gierut, J. A. (2007). Phonological complexity and language learnability. American Journal of Speech-Language Pathology.

https://doi.org/10.1044/1058-0360(2007/003)  [available to ASHA members]


Gierut, J. A., Morrisette, M. L., Hughes, M. T., & Rowland, S. (1996). Phonological treatment efficacy and developmental norms. Language, Speech, and Hearing Services in Schools. https://doi.org/10.1044/0161-1461.2703.215  [available to ASHA members]


Kiran, S. (2007). Complexity in the treatment of naming deficits. American Journal of Speech-Language Pathology.

https://doi.org/10.1044/1058-0360(2007/004)  [available to ASHA members]


Rvachew, S., & Nowak, M. (2001). The effect of target-selection strategy on phonological learning. Journal of Speech, Language, and Hearing Research. https://doi.org/10.1044/1092-4388(2001/050)  [available to ASHA members]


Smit, A. B., Hand, L., Freilinger, J. J., Bernthal, J. E., & Bird, A. (1990). The Iowa Articulation Norms Project and its Nebraska replication. Journal of Speech and Hearing Disorders. https://doi.org/10.1044/jshd.5504.779  [available to ASHA members]


Thompson, C. K. (2007). Complexity in language learning and treatment. American Journal of Speech-Language Pathology. https://doi.org/10.1044/1058-0360(2007/002)  [available to ASHA members]


Thompson, C. K., & Shapiro, L. P. (2007). Complexity in treatment of syntactic deficits. American Journal of Speech-Language Pathology. https://doi.org/10.1044/1058-0360(2007/005)  [available to ASHA members]

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