How effective is phonology treatment?

Previously I asked whether it made sense to calculate effect sizes for phonology therapy at the within subject level. In other words, from the clinical point of view, do we really want to know whether the child’s rate of change is bigger during treatment than it was when the child was not being treated? Or, do we want to know if the child’s rate of change is bigger than the average amount of change observed among groups of children who get treated? If children who get treated typically change quite a bit and your client is not changing much at all, that might indicate a course correction (and note please, not a treatment rest!). From this perspective, group level effect sizes might be useful so I am providing raw and standardized effect sizes here from three of my past studies with a discussion to follow.

Rvachew, S., & Nowak, M. (2001). The effect of target selection strategy on sound production learning. Journal of Speech, Language, and Hearing Research, 44, 610-623.

The first data set involves 48 four-year-old children who scored at the second percentile, on average, on the GFTA (and 61 percent consonants correct in conversation). They were randomly assigned to receive treatment for relatively early developing stimulable sound targets (ME group, n=24) or late developing unstimulable sound targets (LL group, n=24). Each received treatment for four sounds over 2 six-week blocks, during 12 30 to 40 minute treatment sessions. The treatment approach employed traditional articulation therapy procedures. The children did not receive homework or additional speech and language interventions during this 12 week period. Outcome measures included single word naming probes covering all consonants in 3 word positions and percent consonants correct (PCC) in conversation, with 12 to 14 weeks intervening between the pre- and the post-test assessments. The table below shows two kinds of effect sizes for the ME group and the LL group: the raw effect size (raw ES) with the associated confidence interval (CI) which indicates the mean pre- to post-change in percent consonants corrects on probes and in conversation; next is the standardized mean difference, Cohen’s d(z); finally, I show the number and percentage of children who did not change (0 and negative change scores). These effect sizes are shown for three outcome measures: single word naming probe scores for unstimulable phonemes, probe scores for stimulable phonemes, and percent consonants correct (PCC) obtained from conversations recorded while the child looked at a wordless picture book with the assessor.Effect size blog figure 2.

Some initial conclusions can be drawn from this table. The effect sizes for change in probe scores are all large. However, the group that received treatment for stimulable sounds showed greater improvement for both treated stimulable sounds and untreated unstimulable sounds compared to the group that received treatment for unstimulable sounds. There was almost no change in PCC derived from the conversational samples overall. I can report that 10 children in the ME group and 6 children in the LL group achieved improvements of greater than 5 PCC points, judged to be a “minimally important change”  by Thomas-Stonell et al. (2013). Half the children achieved no change at all however in PCC (conversation).

Rvachew, S., Nowak, M., & Cloutier, G. (2004). Effect of phonemic perception training on the speech production and phonological awareness skills of children with expressive phonological delay. American Journal of Speech-Language Pathology, 13, 250-263.

The second data set involves 34 four-year-old children who scored at the second percentile, on average, on the GFTA (and approximately 60 percent consonants correct in conversation). All of the children received 16 hour-long speech therapy sessions, once-weekly. The treatment that they received was entirely determined by their SLP with regard to target selection and approach to intervention. Ten SLPs provided the interventions, 3 using the Hodson cycles approach, 1 a sensory motor approach and the remainder using a traditional articulation therapy approach. The RCT element of this study is that the children were randomly assigned to an extra treatment procedure that occurred during the final 15 minutes of each session, concealed from their SLP. Children in the control group (n=17) listened to ebooks and answered questions. Children randomly assigned to the PA group (n=17) played a computer game that targeted phonemic perception and phonological awareness covering 8 phonemes in word initial and then word final position. Although the intervention lasted 4 months, the interval between pre-treatment and post-treatment assessments was 6 months long. The table below shows two kinds of effect sizes for the ME group and the LL group: the raw effect size (raw ES) with the associated confidence interval (CI) indicates the mean pre- to post-change in percent consonants correct; next is the standardized mean difference, Cohen’s d(z); finally, I show the number and percentage of children who did not change (0 and negative change scores). These effect sizes are shown for two outcome measures: percent consonants correct (PCC) obtained from conversations recorded while the child looked at a wordless picture book with the assessor; and PCC-difficult, derived from the same conversations but restricted to phonemes that were produced with less than 60% accuracy at intake-in other words, phonemes that were potential treatment targets, specifically /ŋ,k,ɡ,v,ʃ,ʧ,ʤ,θ,ð,s,z,l,ɹ/.

Effect size blog figure 3

The sobering finding here is that the control group effect size for potential treatment targets is the smallest, with half the group making no change and the other half making a small change. The effect size for PCC (all) in the control group is more satisfying in that it is better than the minimally important change (i.e., 8% > 5%); 13 children in this group achieved a change of more than 5 points and only 3 made no change at all. The effect sizes are large in the group that received the Speech Perception/PA intervention in addition to their regular SLP program with good results for PCC (all) and PCC-difficult. This table shows that the SLP’s choice of treatment procedures makes a difference to speech accuracy outcomes.

Rvachew, S., & Brosseau-Lapré, F. (2015). A randomized trial of twelve week interventions for the treatment of developmental phonological disorder in francophone children. American Journal of Speech-Language Pathology, 24, 637-658. doi:10.1044/2015_AJSLP-14-0056

The third data set involves data from 64 French-speaking four-year-olds who were randomly assigned to receive either an output oriented intervention (n = 30) or an input-oriented intervention (n = 34) for remediation of their speech sound disorder. Another 10 children who were not treated also provide effect size data here. The children obtained PCC scores of approximately 70% on the Test Francophone de Phonologie, indicating severe speech sound disorder (consonant accuracy is typically higher in French-speaking children, compared to English). The children received other interventions as well as described in the research report (home programs and group phonological awareness therapy) with the complete treatment program lasting 12 weeks. The table below shows two kinds of effect sizes for the ME group and the LL group: the raw effect size (raw ES) with the associated confidence interval (CI) indicates the mean pre- to post-change in percent consonants correct; next is the standardized mean difference, Cohen’s d(z); finally, I show the number and percentage of children who did not change (0 and negative change scores). These effect sizes are shown for two outcome measures: percent consonants correct with glides excluded (PCC), obtained from the Test Francophone de Phonologie, a single word naming test; PCC-difficult, derived from the same test but restricted to phonemes that were produced with less than 60% accuracy at intake-specifically /ʃ,ʒ,l,ʁ/. An outcome measure restricted to phonemes that were absent from the inventory at intake is not possible for this group because French-speaking children with speech sound disorders have good phonetic repertoires for the most part as their speech errors tend to involve syllable structure (see Brosseau-Lapré and Rvachew, 2014).

Effectsize blog figure 4

There are two satisfying findings here: first, when we do not treat children with a speech sound disorder, they do not change, and when we do treat them, they do! Second, when children receive an appropriate suite of treatment elements, large changes in PCC can be observed even over an observation interval as short as 12 weeks.

Overall Conclusions

  1. In the introductory blog to this series, I pointed out that Thomas-Stonell and her colleagues had identified a PCC change of 5 points as a “minimally important change”. The data presented here suggests that this goal can be met for most children over a 3 to 6 months period when children are receiving an appropriate intervention. The only case where this minimum standard was not met on average was in Rvachew & Nowak (2001), a study in which a strictly traditional articulation therapy approach was implemented at low intensity with no homework component.
  2. The measure that we are calling PCC-difficult might be more sensitive and more ecologically valid for 3 and 6 month intervals. This is percent consonants correct, restricted to potential treatment targets, so those consonants that are produced with less than 60% accuracy at intake. These turn out to be mid- to late-developing frequently misarticulated phonemes, therefore /ŋ,k,ɡ,v,ʃ,ʧ,ʤ,θ,ð,s,z,l,ɹ/ in English and /ʃ,ʒ,l,ʁ/ in French for these samples of 4-year-old children with severe and moderate-to-severe primary speech sound disorders. My impression is that when providing an appropriate intervention an SLP should expect at least a 10% change in these phonemes whether assessed with a broad based single word naming probe or in conversation-in fact a 15% change is closer to the average. This does not mean that you should treat the most difficult sounds first! Look carefully at the effect size data from Rvachew and Nowak (2001): when we treated stimulable phonemes we observed a 15% improvement in difficult unstimulable sounds. You can always treat a variety of phonemes from different levels of the phonological hierarchy as described in a previous blog.
  3. Approximately 10% of 4-year-old children with severe and moderate-to-severe primary speech sound disorders do not improve at all over a 3 to 6 month period, given adequate speech therapy. If a child is not improving, the SLP and the parent should be aware that this is a rare event that requires special attention.
  4. In a previous blog I cited some research evidence for the conclusion that patients treated as part of research trials achieve better outcomes than patients treated in a usual care situation. There is some evidence for that in these data. The group in Rvachew, Nowak and Cloutier that received usual care obtained a lower effect size (d=0.45) in comparison to the group that received an extra experimental intervention (d=1.31). In practical terms this difference meant that the group that received the experimental intervention made four times more improvement in the production of difficult sounds than the control group that received usual care.
  5. The variation in effect sizes that is shown in these data indicate that SLP decisions about treatment procedures and service delivery options have implications for success in therapy. What are the characteristics of the interventions that led to relatively large changes in PCC or relatively large standardized effect sizes? (i) Comprehensiveness, that is the inclusion of intervention procedures that target more than one level of representation, e.g., procedures to improve articulation accuracy and speech perception skills and/or phonological awareness; and (ii) parent involvement, specifically the inclusion of a well-structured and supported home program.

If you see other messages in these data, or have observations from your own practice or research, please write to me in the comments.

 

 

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How to choose phonology goals?

I find out via Twitter (don’t you love twitter!) that “teach complex sounds first” is making the rounds again (still!) and I am prompted to respond. Besides the fact that I have disproven the theoretical underpinnings of this idea, it bothers me that so many of the assumptions wrapped up in the assertion are unhelpful to a successful intervention. Specifically, we should not be treating “sounds”, there is no agreed upon and universal ordering of targets from simple to complex, and there is no reason to teach the potential targets one at a time in some particular order anyway. So what should we do? I will describe a useful procedure here with an example.

There is this curious rumour that I promote a “traditional developmental” approach to target selection that I must lay to rest. In fact, I have made it clear that I promote a dynamic systems approach. An important concept is the notion of nonlinearity: if you induce gradual linear changes in several potential targets at once, a complex interaction will result causing a nonlinear change across the system known as a phase shift. How do you choose the targets to work on at once? Francoise and I show how to use a “quick multilinear analysis” to identify potential targets  at all levels of the phonological hierarchy, in other words phrases, trochaic or iambic feet, syllables, onsets, rimes or codas, clusters, features or individual phonemes. Many case studies and demonstrations are laid out in our book that will shortly appear in a beautiful second edition. Then we show how to select three targets for simultaneous treatment using Grunwell’s scheme designed to facilitate progressive change in the child’s phonological system. I will demonstrate both parts of this process here, using a very brief sample from a case study that is described in our book. The child’s speech is delayed for her age of two years which can be established by comparing the word shape and phonetic repertoire to expectations established by Carol Stoel-Gammon.

case-study-6-3-sample-for-blog

Potential treatment targets can be identified by considering strengths and weaknesses at the prosodic and segmental tiers of the phonological hierarchy (full instructions for this quick multilinear analysis are contained in our book). The table below describes units that are present and absent. Note that since her language system is early developing, her phonology is probably word-based rather than phoneme based; therefore ‘distinction’ refers to the presence of a phonetic distinction rather than a phonemic contrast.

case-study-6-3-quick-multilinear-analysis

Now that we have a sense of potential targets from across the whole system, how do we select targets using Grunwell’s scheme? We want to ensure that we address word shape and segmental goals. We also want to choose one goal to stabilize a variable structure in the system, another to extend something that is established to a new context, and a third to expand the system to including something new. Here are my choices (others are possible):

case-study-6-3-grunwell-goals

There is a good chance that fricatives and codas will emerge spontaneously with this plan because we will have laid down the foundation for these structures. If they don’t it should not be hard to achieve them during the next therapy block. The idea that you can only induce large change in the system by teaching the most complex targets first is clearly not true as I have explained previously – in fact, complex sounds emerge more easily when the foundation is in place. Furthermore, Schwartz and Leonard (1982) also recommended in their study on selection effects in early phonological development that it was best to teach IN words to children with small vocabulary sizes – in other words expand the vocabulary size gradually by using word shapes and phonemes that are in the inventory, but combined in new ways.

It would be possible to use the stabilize-extend-expand scheme and choose different, more complex goals. For example, we could consider the nonreduplicated CVCV structure (cubby, bunny, bootie) to be the stabilize goal. Then we could introduce word final labial stops as the extend goal, generalizing these phones from the onset where they are well established to a new word position (up, tub, nap). Finally, we could introduce a word initial fricative as the expand goal (see, sock, soup). This plan with more complex targets might work but you are risking slower progress, given the empirical findings reported in Rvachew & Nowak (2001) and in Schwartz & Leonard (1982). Furthermore, you would be failing to recognize a major constraint on the structure of her syllables (the limitation to only 2 segments, VV or CV with CVV and CVC currently proscribed). If you focus only on introducing “complex sounds” without attending to this major issue at the prosodic levels of her phonological system, you will be in for a rough ride.

I attach here another example, this one a demonstration from the second edition of our book, chapter-8-demonstration-8-2, to appear in December 2016. Francoise and I have taken a great effort to show students how to implement an evidence based approach to therapy. I invite readers to take a peak!

Reading List

Rvachew, S., & Brosseau-Lapré, F. (2018). Developmental Phonological Disorders: Foundations of Clinical Practice (Second Edition). San Diego, CA: Plural Publishing. (Ready for order in December 2016)

Grunwell, P. (1992). Processes of phonological change in developmental speech disorders. Clinical Linguistics & Phonetics, 6, 101-122.

Stoel-Gammon, C. (1987). Phonological skills of 2-year-olds. Language, Speech & Hearing Services in Schools, 18, 323-329.

Rvachew, S., & Bernhardt, B. (2010). Clinical implications of the dynamic systems approach to phonological development. American Journal of Speech-Language Pathology, 19, 34-50.

Rvachew, S. & Nowak, M. (2001). The effect of target selection strategy on sound production learning. Journal of Speech, Language, and Hearing Research, 44, 610-623.

Schwartz, R., & Leonard, L. (1982). Do children pick and choose? An examination of selection and avoidance in early lexical acquisition. Journal of Child Language, 9, 319-336.