Word learning, and in particular, productive word learning is associated with three important processes in the phonological domain: first, the child must encode the acoustic-phonetic form of the word in the language input; second the child must transform this representation into a lexical representation, generally considered to take on a more abstract phonological form; finally the child must retrieve the representation to reproduce it. The first process is reliant on speech processing abilities that have been shown to be impaired in many children with speech, language and reading deficits, as shown by for example by Ben Munson and colleages (@benjyraymunson) and Nina Kraus and colleages. Phonological encoding is enhanced by access to repeated high-quality but variable inputs as shown by Richtmeier et al for normally developing children and by Rice et al for children with SLI. The majority of children with SSD have difficulties with encoding: we have a paper in press with the American Journal of Speech-Language Pathology showing that speech accuracy in these children can be improved with an approach that focuses largely on the provision of intense high quality input – I will have more to say on this subject when it (finally) emerges in print.
The second process, forming a phonological representation and storing it in the lexicon, involves articulatory recoding which can be a serious problem for children with severe SSD, accounting for deficits in speech accuracy (especially in association with inconsistency), nonword repetition, word learning, productive vocabulary, word finding, rapid automatic naming, and other phonological processing skills. These children are often diagnosed with motor planning disorders but I have pointed out previously that the problem is actually at the level of phonological planning. I have further pointed out the very close relationship between speech planning and memory. Children who are having difficulty with phonological planning may not show the same benefit from a therapy approach that is focused on the provision of high quality inputs. Therefore a new paper on the use of orthographic inputs to teach new words caught my eye. Ricketts et al taught children with SLI and ASD as well as younger and age-matched children with typical language to label nonsense objects with new names, using a computer program. For some words, the children were exposed only to the object–auditory word pairing; for others they saw the object, heard the word and saw a printed version (orthographic representation) as well. All children found it easier to learn the new words when they were exposed to the orthographic representation along with the auditory word.
This study reminded me of the research we are doing with children who are referred to our clinic with an apraxia diagnosis due to inconsistent speech errors. So far, 40% of those children have difficulty with phonological planning rather than motor planning as revealed by the syllable repetition test, as I have explained in a previous blog. We have been using a single subject randomization design to compare the relative efficacy of two treatment approaches with these children. The Phonological Memory & Planning (PMP) intervention pairs the phonemes in the target words with visual referents that include letters as shown here. Imitative models are avoided and the child is encouraged to create their own phonological plan and produce the word using the visual symbols when necessary. An alternative treatment, the Auditory-Motor Integration (AMI) Treatment is quite different with a heavy emphasis on prior auditory stimulation and self-judgments of the match between auditory inputs and outputs. A third condition is a usual care CONtrol condition focusing on high intensity practice. In all cases we teach nonsense words paired with real objects, with the words structured to target the children’s phonological needs in the segmental and prosodic domains.
The results are assessed by applying a resampling test to probe scores and then combining p-values across the children. These are the statistical results (F and t tests by resampling test) for the Same Day Probe Scores, with p-values combined across the 5 children who have proven to have phonological planning problems in concert with a severe inconsistent speech disorder:
The results in the third column show that all of the children obtained a significant treatment effect. The findings in the remaining columns pertain to planned comparisons with positive t values being in the expected direction. The combined p values indicate that all treatments are significantly different from each other and inspection of the mean scores across children show that the pattern of results is PMP > CON > AMI. The result is made more interesting by the fact that the pattern of results is the exact opposite for children with a motor planning disorder. Tanya Matthews and I will compare these two subgroups with data and video during our presentation at ASHA 2016 in Denver this coming fall.
Session Number: 1429
Session Title: Differential Diagnosis of Severe Phonological Disorder & Childhood Apraxia of Speech
Day: Friday, November 13, 2015
Time: 1:00 PM – 3:00 PM
Session Format: Seminar 2-hours
For now, the take away message is that learning new words involves (at least) three important processes: encoding the sound of the new word, memory processes for storing and retrieving the phonological representation and motor planning processes for planning and programming articulatory movements prior to production of the new word. There are published studies showing that intervention procedures targeting each of these processes help children with speech, language and reading difficulties. Increasing frequency of high quality input improves quality of the acoustic-phonetic representation. Pairing phonological segments with visual symbols helps with storage and retrieval of the phonological representation. High intensity speech practice with appropriate stimulation and feedback improves motor planning and motor programming. The trick is to figure out which children require which procedures at which time.