2014

http://informahealthcare.com/pdrISSN: 1751-8423 (print), 1751-8431 (electronic)

Dev Neurorehabil, 2014; 17(2): 137–146! 2014 Informa UK Ltd. DOI: 10.3109/17518423.2014.906002

ORIGINAL ARTICLE

Orthographically sensitive treatment for dysprosody in children withChildhood Apraxia of Speech using ReST intervention

Patricia McCabe, Anita G. Macdonald-D’Silva, Lauren J. van Rees, Kirrie J. Ballard, & Joanne Arciuli

Discipline of Speech Pathology, Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia

Abstract

Objective: Impaired prosody is a core diagnostic feature of Childhood Apraxia of Speech (CAS)but there is limited evidence of effective prosodic intervention. This study reports the efficacyof the ReST intervention used in conjunction with bisyllabic pseudo word stimuli containingorthographic cues that are strongly associated with either strong-weak or weak-strong patternsof lexical stress. Methods: Using a single case AB design with one follow-up and replication, fourchildren with CAS received treatment of four one-hour sessions per week for three weeks.Sessions contained 100 randomized trials of pseudo word treatment stimuli. Baseline measureswere taken of treated and untreated behaviors; retention was measured at one day and fourweeks post-treatment. Results: Children’s production of lexical stress improved from pre topost-treatment. Treatment effects and maintenance varied among participants. Conclusions:This study provides support for the treatment of prosodic deficits in CAS.

Keywords

Childhood apraxia of speech, lexical stress,orthography, prosody, dyspraxia,intervention

History

Received 5 January 2014Revised 12 March 2014Accepted 13 March 2014Published online 2 April 2014

Introduction

Dysprosody in Childhood Apraxia of Speech

Atypical prosody is thought to be a key feature of Childhood

Apraxia of Speech (CAS) [1, 2]. The production of lexical

stress, in particular, is an area of weakness in CAS. While

individuals with CAS have been shown to mark stress in

similar ways to younger but typically developing children [3],

they appear to use longer word and segment durations than

their typically developing peers and tend not shorten duration

of vowels in unstressed initial syllables [4]. This paper reports

a study designed to examine use of Rapid Syllable Transition

Training (ReST), in conjunction with orthographically biased

stimuli, to treat disordered prosody in children with CAS.

Prosody is realized acoustically through the manipulation

of vowel duration (ms), vocal intensity (dB), and vocal pitch

(i.e. fundamental frequency or F0 in Hz) [5]. In languages

such as English, stressed syllables carry the longest vowel

duration and higher peak F0 and intensity compared with

other syllables within the word. The dominant lexical stress

pattern for English nouns is strong-weak (SW) where stress is

placed on the first syllable of words and subsequent syllables

are shorter, softer or lower in pitch. English speaking children

who are typically developing show a reliance on this pattern

in their speech when learning other lexical contrasts such as

weak-strong (WS) where the stress is placed on the second

syllable of a word [6–8] and the preceding syllable carries

weaker stress. Thus younger English speaking children having

more success with SW words than WS ones [7, 9].

High levels of variability and inconsistency in the

production of stress are noted in children with CAS when

compared with other children or adults with speech impair-

ments [9–11]. Atypical prosody has been said to differentiate

children with CAS from other children with speech delay or

phonological disorder and higher levels of dysprosody occur

in younger children with CAS than children with other speech

disorders [12]. In their repetition of both SW and WS

nonwords, children with CAS are perceived to match lexical

stress patterns less frequently than phonologically disordered

children, even when no differences are detected on acoustic

measures [13]. Munson and colleagues [14] also noted that

children with CAS mark SW words with pitch and loudness

contrasts and WS words with duration contrasts while other

children do not make this distinction. Excessive, equal or

misplaced stress has also been reported to occur more often in

children with CAS when compared with other pediatric

speech populations and adults with acquired Apraxia of

Speech [13, 15]. These various stress differences between

typically developing children and children with CAS may lead

to the perceived significant difficulties in both understanding

and treating the speech of these children [16].

Prosodic impairments impact significantly on overall

speech intelligibility although relatively few studies consider

prosody when discussing intelligibility. A review of the

literature, looking at the interaction of prosody and speech

intelligibility in disorders of speech such as dysarthria,

emphasized the impact of prosody on overall speech intelli-

gibility [16]. For example, in people with dysarthria,

Correspondence: Dr. Patricia McCabe, Speech Pathology, Faculty ofHealth Sciences, University of Sydney, PO Box 170, Lidcombe, Sydney,NSW 1825, Australia. E-mail: tricia.mccabe@sydney.edu.au

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judgments of both impaired prosody and measures of

articulatory accuracy correlate highly with perceived speech

intelligibility [17]. Thus, prosodic impairment can affect

understanding of speech at similar levels to the loss of

intelligibility caused by the segmental speech impairment.

Additionally, we now know that, in English, both supraseg-

mental and segmental information assist lexical access during

the recognition of spoken words [18–20]. Incorrect placement

of stress has been shown to impede lexical access [21].

Treatment for CAS

Most existing interventions for CAS focus primarily on

articulatory parameters and little consideration has been given

to treatment of prosodic impairments and particularly to

measurement of resultant improved prosody in this disorder.

With the exception of the team led by Strand [22–24] who

described Dynamic Temporal and Tactile Cueing (DTTC)

intervention and the ReST intervention [25], no studies report

treatment for prosody specifically.

DTTC intervention includes instruction for varying pros-

ody within treatment trials while focusing on the articulatory

accuracy of target words. In DTTC, children imitate words or

phrases with varied intonation patterns following a model

provided by the clinician. This variation in prosody is not

variation in lexical stress but rather variation in sentence

stress. To date DTTC studies have not reported measurement

of prosody to document changes to prosodic accuracy as a

direct result of this approach.

By contrast, the ReST treatment specifically targets the

ability to control relative durations in the production of SW

and WS pseudo words while simultaneously producing

accurate speech segments at an age appropriate speech rate.

Thus, ReST involves targeting production of lexical stress.

Ballard and colleagues [25] reported that treatment stimuli

consisting of cloze sentences with target three syllable pseudo

words as the final word in the sentence were modeled by the

clinician in the pre-practice phase where the children imitated

the clinician. The stimuli were then read by the children

without a model in the practice phase [25]. All three

participants in that multiple baseline design study improved

prosodic control including duration, loudness, and/or pitch

contrasts for both SW and WS stress patterns and generaliza-

tion was noted to untreated but similar stimuli.

A separate body of work by Arciuli and colleagues has

demonstrated that there are orthographic markers for lexical

stress present in the spelling patterns of English words [8, 26–

28]. Analyses of both child and adult corpora have revealed

that the beginnings and endings of bisyllabic words are

indicators of stress position. Most recently, Arciuli et al. [8]

examined a database of almost 20 000 disyllabic words from

children’s reading materials in an effort to identify probabil-

istic orthographic cues to lexical stress. To illustrate the kinds

of findings they reported, the analyses revealed that most

bisyllabic words beginning with ‘‘be’’ and most bisyllabic

words ending with ‘‘oon’’ have WS stress. In behavioural

testing of 186 typically developing children aged 5–12 years

using carefully constructed pseudo words that contained these

probabilistic cues, Arciuli and colleagues demonstrated that

children are sensitive to these cues. That is, when presented

with an orthographically biased pseudo word such as

‘‘bedoon’’ the children tended to assign a WS pattern

during reading aloud. Older children were found to be more

sensitive to these cues than younger children and this

developmental trajectory was further explored using compu-

tational modeling. It was concluded that sensitivity to these

probabilistic orthographic cues is most likely the result of

implicit learning that grows over time with increasing

exposure to a broader range of written materials.

Van Rees and colleagues recently drew on Arciuli’s work

in their use of orthographic stimuli containing probabilistic

cues to lexical stress in a study examining explicit training of

stress assignment in typically developing children [29]. Using

the approach outlined by Ballard et al., Van Rees et al.

reported using explicit instruction to attend to the relative

length of each syllable as a part of the training and reported

perceptual judgment of stress production as the primary

outcome measure. Typically developing children were ran-

domly allocated to either learn the stimuli (the experimental

group) or be in a control group. Children in the experimental

group learnt to say the pseudo word stimuli in minimum time

while children in the control group did not. Van Rees et al.

concluded that this approach could be applied in future

studies, in an attempt to remediate dysprosody.

Indeed, no previous prosodic intervention for CAS has

been taken into account the biases toward different lexical

stress patterns that may arise with various orthographic

stimuli. It seems possible that the use of orthographic stimuli

may either enhance or hinder the treatment depending on

whether the stimuli contain spelling patterns that are in line

with the stress patterns that the child is being asked to

produce. This applies to studies using either real words or

pseudo words. However, pseudo words are especially

appropriate for use in treatment because they are not

influenced by previously learned motor plans, or differences

in frequency or familiarity across participants [30]. To

illustrate the role of orthographic bias, if a child was being

presented with a written pseudo word such as ‘‘bedoon’’ and

was being asked to produce SW stress, that child could,

potentially, struggle to overcome a preference for assigning

WS stress. Presentation of the written pseudo word

‘‘bedoon’’ in conjunction with instruction on the production

of a WS pattern might be likely to facilitate success in stress

production.

Here, we extend the ReST intervention for CAS [25] by

using Van Rees et al.’s [29] pseudo word stimuli. This is the

first prosody intervention study to use such treatment stimuli.

Hypotheses for this study were:

(1) Children with CAS will show significant improvement in

the ability to contrast SW and WS lexical stress patterns

in both treated and similar untreated exemplars of biased

two-syllable pseudo words.

(2) The effects of treatment will be retained up to four weeks

post-treatment and will generalize to similar untrained

stimuli.

(3) Treatment effects will generalise to connected speech as

a measure of ecological validity.

(4) Treatment effects will not generalize to improved recep-

tive vocabulary skills, demonstrating experimental

control.

138 P. McCabe et al. Dev Neurorehabil, 2014; 17(2): 137–146

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Method

Participants

This research was approved by The University of Sydney

Human Research Ethics Committee (number 11317).

Participants were recruited through electronic advertisements,

the university clinic and community speech language path-

ologists. Four children met the inclusion criteria: history and

current diagnosis of CAS; normal receptive language skills

(Clinical Evaluation of Language Fundamentals, 4th edition,

Australian Standardization CELF-4 [31]); Peabody Picture

Vocabulary Test, PPVT [32]; normal hearing acuity [33]; no

known other developmental or genetic diagnosis; and English

as their first language and at least one parent with English as

their first language. Oral motor examination [34] revealed no

abnormalities in orofacial structure, muscle strength, muscle

tone, or reflexes for any participant. Connected speech

samples were collected for each child, following McLeod’s

procedures [35], with at least 50 utterances collected for each

child, transcribed phonemically and entered into the

Computerized Profiling program to calculate speech accuracy

measures [36]. The ASHA core CAS features [37] were used

by two independent and experienced speech pathologists to

confirm CAS diagnosis from the single word, inconsistency

and connected speech samples reported in Table I. These

features included inconsistent sound errors on repetitions of

syllables or words (as scored on the DEAP inconsistency

subtest [38]); the presence of poor control of coarticulatory

transitions between sounds and syllables; and inappropriate

prosody, particularly of lexical or phrasal stress. Table I

contains a summary of test results for both eligibility and

description of participants.

Reading ability

As the treatment centered on visually presented stimuli,

reading ability was assessed using the Neale Analysis of

Reading Ability, 3rd edition (NARA-3) [39] and the Word

Table I. Pre-treatment assessment battery results for P1, P2, P3, and P4.

P1(male, 8 y; 6 m)

P2(male, 6 y; 7 m)

P3(male, 6 y;6 m)

P4(male, 5 y; 5 m)

Test (used for) Std CI Std CI Std CI Std CI

Peabody Picture Vocabulary Test – 4th edition Form A(receptive vocabulary)

90 83–97 90 83–97 91 84–98 117 109–124

Clinical Evaluation of Language Fundamentals – 4th edition (receptive & expressive language ability)Core Language Score 57* 49–55 81 74–88 76 69–83 89 84–94Receptive Language Index 103 93–113 96 87–105 103 94–112 105 97–103Expressive Language Index 53* 44–62 76* 68–84 74* 66–82 80* 74–86

Test of Auditory Processing – 3rd editionWord Discrimination(auditory discrimination of real words)

5* 3.7–6.3 8 6.4–9.6 8 6.4–9.6 9 7.3–11.6

Word Memory (verbal memory) 6* 4.6–7.4 10 8.6–11.4 6* 4.6–7.4 12 10.7–13.3

Woodcock Reading Mastery Test – RevisedBasic skills cluster 88 86–89 127 126–129 94 88–100 104 101–107

Word identification (reading level) 90 88–91 129 127–130 98 90–102 104 99–108Word attack (nonword reading) 89 87–91 121 119–122 81* 28–103 105 94–110

Lower Case Letters checklist percent(letter name knowledge)

89 – 94 – 48 – 59 –

Comprehensive Test of Phonological Processing Std ±SEM Std ±SEM Std ±SEM Std ±SEM

Phonological Awareness Composite score 64* 59–69 106 103–109 85 82–88 85 82–88Phonological Memory Composite score 70* 64–76 91 84–98 88 81–95 88 82–94

Memory For Digits (verbal memory) 6* 4–8 10 9–11 7 6–8 8 7–9Non-word Repetition (nonword repetition) 4* 3–5 7 6–8 9 8–10 8 7–9

Rapid Naming Composite score 91 86–96 94 89–99 118 113–123 136 131–141

Neale Analysis of Reading Ability – 3rd edition(reading level)

Readingage ±SEM

Readingage ±SEM

Accuracy 6.2 – 56.0–6.8 – 7.0 – 6.5–7.7 –Comprehension 6.11 – 6.3–7.3 – 6.9 – 6.3–7.5 –Rate 7.4 – 6.8–8.0 – 12.9 – 11.7–413 –

Connected speech % % % %

Percent Vowels Correct (PVC) 74 – 77 – 90 – 85 –Percent Consonants Correct (PCC) 81 – 95 – 70 – 60 –Stress pattern match percent (core CAS feature) 46 – 53 – 79 – 63 –Inconsistency percent (Dodd, 2002) (core CAS feature) 20 24 36 40

Standardized tests scores (Std) and 95% confidence intervals (CI) or Standard Errors of Measurement (SEM) are reported as appropriate forassessments.

– Refers to assessments and/or subtests not administered due to age/ability or where range scores not available.* Indicates a score 1 or more standard deviations below the mean.% indicates a percentage score.

DOI: 10.3109/17518423.2014.906002 Prosodic treatment of CAS 139

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Identification subtest of the Woodcock Reading Mastery Test-

Revised (WRMT-R) [40]. These were used to determine each

participant’s reading level. Nonword reading was assessed

using the WRMT-R Word Attack subtest. Nonword speech

repetition was assessed using the Comprehensive Test of

Phonological Processing (CTOPP) [41]. Participants P1 and

P2 were able to read passages from the NARA-3, identify

words in the Word Identification subtest, and decode

nonwords in the Word Attack subtest of the WRMT-R and

so judged capable of independently reading the stimuli

presented in treatment. Participants P3 and P4 were unable

to identify words or decode nonwords and so were not

administered the NARA-3 and were supported in treatment

with clinician spoken modeling of stimuli for direct imitation.

Experimental design

A single case AB design with one follow-up with replication

was employed to test treatment-related changes from pre- to

post-treatment in the four children. All participants completed

three baseline sessions, followed by 12 one-hour treatment

sessions over three weeks. Experimental probes were admin-

istered after every fourth session, on a separate day to

treatment, and a single probe was completed at four weeks

post-treatment. No feedback on production accuracy was

provided during these probes, which tested for acquisition and

retention of treated behaviors and generalization of treatment

effects to untrained stimuli. In addition, a connected speech

sample was collected at each testing point to evaluate

generalization of treatment effects in a more ecologically

valid context. Receptive vocabulary skills were tested pre-

and post-treatment as a measure of experimental control as

this treatment that uses pseudo words was not expected to

accelerate the development of receptive vocabulary.

Stimulus materials and equipment

Baseline/experimental probe and treatment stimuli consisted

of the same 30 bisyllabic pseudo words used in van Rees’ study

[29] which were orthographically biased to either a strong-

weak (SW; e.g., mandan) or a weak-strong (WS; e.g., bedoon)

stress pattern, based on the work of Arciuli and colleagues

[8,26] (Appendix). Pseudo words were used as these cannot be

influenced by learned motor or linguistic plans, which may be

related to frequency of use or familiarity, that are present when

using real words [25,30]. Speech interventions using pseudo

words have been shown to stimulate generalization of

treatment effects to real words [42].

Nineteen treatment pseudo words were selected randomly

from the list of 30 with the remaining 11 serving as probes to

assess acquisition of skills to untreated related stimuli. All

pseudo words were displayed orthographically on flash cards

in 72 point Times New Roman font on 13.2� 4.7 cm index

cards with a different picture of an alien accompanying each

word [43]. Pictures were provided for each pseudo word to

make them visually more interesting thereby enhancing the

distinctiveness of each of the pseudo words.

All baselines and experimental probes were digitally

recorded in a sound-treated booth using a Layla 24/96

Multitrack Recording System with C420III – PP Micro-Mic II

head-mounted microphone (AKG Acoustics) and Adobe

Audition 1.0 [44] with a sampling rate of 44 100 Hz [45].

A 5 cm microphone-to-mouth distance was used.

Treatment procedures

Following Ballard et al. [25] and van Rees et al. [29],

treatment sessions were of 60 min duration, four days per

week for three weeks (total 12 sessions per participant).

Participants and their parents were instructed to undertake no

additional practice of treatment targets outside of these

sessions. Neither children nor their parents were advised of

the hypotheses; however, it was not possible to blind

clinicians to the research hypotheses. Clinicians received a

treatment manual and explicit instruction, training, and

demonstration of treatment procedures prior to commencing

sessions [46]. All sessions were video-recorded for later

scoring of reliability on dependent measures. Consistent with

a PML approach [47], sessions consisted of a pre-practice

component (10–20 min) and a practice component (40–

50 min), as follows.

Pre-practice

During pre-practice, clinicians first presented a randomly

selected stimulus item and asked the child to identify whether

it had a SW (long-short) or a WS (short-long) pattern. If

necessary, the clinician corrected the response. Next, the

clinician modeled the pseudo word for imitation and provided

100% knowledge of performance (KP) feedback on stress

pattern (e.g., ‘‘Try to make the first part even shorter’’) to

shape further attempts. All models were presented with

sentence intonation pattern. Other cues were offered as

appropriate such as hand tapping to cue rhythm and target

length of syllables. This feedback and shaping cues allowed

participants to experience successful production. Although

knowledge of results (KR) feedback (i.e., indicating only the

correctness of a response) was given on segmental errors, no

specific articulatory or phonetic placement instructions were

provided. Participants were moved to the practice phase when

they had produced five consecutive correct trials, including

both SW and WS tokens.

Practice

The 19 orthographic treatment stimuli were presented in

random order with at least 100 trials per session, for a minimum

target of 1200 trials per child. Participants were instructed

either to read the word aloud or to repeat the word after the

clinician dependent on the presentation method assigned from

pretesting. KR feedback was given (i.e. ‘‘good’’/"not good’’)

for combined prosodic and segmental accuracy on 50% of all

trials, fading from high to low frequency across the session,

with a delay between response and provision of feedback of

3–5 s. No KP feedback was provided. Mastery was set at 80%

correct over three consecutive sessions. It should be noted that

typically developing children achieve this mastery on an

average within 3–4 sessions [29].

Variation to practice procedure

Across sessions one to five, it was noted that all participants

had consistent idiosyncratic, incorrect productions for some

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pseudo words. For example, P1 produced ‘‘mandan’’ as

/m"nd|d/ (a real word) instead of /mænd|n/ (a pseudo word).

Although the lexical stress pattern was correct, we decided to

eliminate these idiosyncratic productions with short blocks of

trials. This short-block procedure was triggered when the

error occurred on a trial that had, a priori, been randomly

selected to receive KR feedback. That is, a participant was

given KR feedback on prosodic and segmental accuracy on

the first attempt at the stimulus item; that is, if the production

was correct the child received KR feedback and was presented

with the next trial, but if the idiosyncratic production occurred

s/he received modified KR feedback (e.g. ‘‘good pattern,

wrong sounds’’) and was prompted to try again. Up to three

extra attempts were allowed with KR feedback on each

attempt. The block trials were interwoven with, but in

addition to, the 100 trials per session.

Dependent measures

Productions of pseudo word stimuli during baselines and

experimental probes and during treatment sessions were

judged perceptually as correct or incorrect based on the three

measures – (1) stress pattern correct; (2) all segments correct;

and (3) simultaneously correct stress and segments; the latter

having been shown in studies by Ballard et al. [25] and

McCabe et al. [48] to be harder than either separately. For

stress pattern, a response was judged as correct if the vowel in

the strong syllable was perceived as a full vowel (i.e. not

reduced) and the vowel in the weak syllable was perceived as

a schwa. For segmental accuracy, responses were further

subcategorized as percent vowels correct (PVC) and percent

consonants correct (PCC) as calculated in the PROPH module

of Computerized Profiling [36].

Connected speech samples were collected at each probe

session to examine for generalisation of treatment effects to a

functional speaking task. A minimum of 50 utterances were

phonemically transcribed and entered into Computerized

Profiling [36].

Data analysis

Perceptual treated and untreated probe item data were

graphed for visual analysis and treatment effects analyzed

using percent nonoverlapping data (PND). Scruggs and

Mastropieri [49] (p. 224) suggested that a value of over

70% datapoints nonoverlapping across baseline and treatment

phases of the study for treated or untreated stimuli suggests

a clear treatment or generalization effect, respectively, while

scores between 50 and 70 have questionable effect and scores

under 50 should be interpreted as no demonstration of treat-

ment effect. Sub-analysis of SW and WS accuracy is reported

as raw scores for each participant.

Reliability

Inter- and intra-rater reliability on dependent measures was

calculated for 20% of trials for each treatment session for all

participants; that is, inter-rater agreement on judgment of

response accuracy during treatment and intra- and inter- rater

agreement on phonemic transcription of responses. As per

Ballard et al. [25] and Van Rees et al. [29], to be recorded as

an accurate production, the pseudo word had to be correct for

both stress and segments. Intra-rater agreement on phonemic

transcription ranged from 95 to 97% across participants, and

inter-rater agreement from 83 to 90%.

Reliability of perceptual intra-rater and inter-rater agree-

ment was also calculated on a random 14% of baseline and

experimental probe data for each participant. The intra-rater

agreement was 93% and the inter-rater agreement was 88%.

Reliability of treatment provision (fidelity) was calculated

on compliance with the protocol during the practice phase.

A random block of 20 stimulus–response pairs was examined

for each session and scored for treatment fidelity. Trials were

considered to have fidelity if all components were correct

including: (1) correct presentation of stimulus, including

correct phonemic and prosodic spoken model for P3 and P4;

(2) provision of delayed feedback; (3) provision of KR

feedback only; and finally (4) provision of feedback only on

the pre-randomized items. Fidelity was as follows P1 mean

78% SD 13; P2 mean 76% SD 15, P3 mean 83% SD 16, and

p4 mean 70% SD 17. For the whole group, fidelity was

therefore mean 75% SD 16. Most lapses in fidelity were due

to errors in delaying feedback (both substantially shorter and

longer delays than the desired 3 s) and occurred more

frequently in earlier sessions than in later ones.

Results

Performance on treated pseudo words during practice

During treatment sessions, all participants demonstrated

improved prosodic and segmental accuracy of SW and WS

bisyllabic pseudo words, although none reached the mastery

criterion of 80% correct over three consecutive sessions

(Supplementary figures). P1 initially demonstrated both

prosodic and segmental accuracy below 10% correct and

steadily improved to 66% on both measures in the final

session. P2 initially had prosodic accuracy below 30% and

segmental accuracy below 10%; with prosodic accuracy

reaching 82% correct in the final session and segmental

accuracy fluctuating between 39 and 59% over the final three

sessions. Initially, the P3’s prosodic accuracy was 15% and

the segmental accuracy was about 50%. Both measures

improved over time, reaching a peak of 75% in the second last

session. P4 initially demonstrated prosodic accuracy around

30% and segmental accuracy around 50%. Prosodic accuracy

increased to an average of 58% in the final three sessions and

segmental accuracy increased to an average of 79%.

Treatment, retention, and generalization effects

As this was a within-subject experimental design study,

results are interpreted for each participant individually.

Figure 1 shows the perceptual measures of treated and

untreated probe items for each participant and Online

Supplementary Figures 2–5 show the analysis of SW and

WS items for each participant.

Participant 1

PND across three probes and retention on treated items was

75 and on untreated items was 25. With regard to SW and WS

stimuli, P1 improved from 0% accuracy to 50% correct for

DOI: 10.3109/17518423.2014.906002 Prosodic treatment of CAS 141

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prosody on SW pseudo words but only 10% combined

accuracy immediately post-treatment (i.e. the third and final

probe during the treatment phase), with stable retention

four weeks post-treatment. WS pseudo words were at

0% accuracy during baseline and, while prosodic and

segmental accuracy each improved to 15–20% post-treatment,

combined accuracy remained at 0%. Interestingly, this

participant reached 60% combined accuracy, with 90%

prosodic accuracy at retention, despite receiving no interven-

tion during this four-week period.

Participant 2

PND across three probes and retention on treated items was

100 and on untreated items was 25. With regard to SW and

WS items, P2 improved from 0 to 10% accuracy on prosody

and combined accuracy for SW pseudo words in baseline to

between 35 and 50% correct at post-treatment. There was

some loss of skills at retention, but performance remained

above baseline levels on treated items. WS pseudo words

showed clear improvement from 0 to 5% accuracy on all three

perceptual measures in baseline to 40–45% accuracy at post-

treatment. Again, performance deteriorated during the reten-

tion phase but remained above baseline levels.

Participant 3

PND across treatment and retention on treated items was 75

and on untreated items was 75. Regarding SW versus WS

stimuli, P3 showed improvement on SW pseudo words during

treatment primarily for segmental and combined accuracy

(from �12% to �50%), with gains remaining stable in

retention. Prosodic accuracy was reasonably stable around

60–67% in baseline and treatment phases but increased to

88% at retention, despite receiving no intervention during this

four-week period. WS pseudo words showed a trend to

declining accuracy during baseline but ended above baseline

levels at post-treatment with 55–60% correct prosody and

segments, respectively, and 40% combined accuracy. Prosody

continued to improve during retention, to 68%, but segmental

and combined accuracy deteriorated to baseline levels.

Participant 4

PND across three within treatment probes and retention on

treated items was 100 and on untreated items was 0.

Regarding SW and WS stimuli, data from baseline 1 were

unavailable due to failure of recording equipment. Over time,

P4 improved on all three perceptual measures for SW pseudo

words, but accuracy appeared to improve in baseline and

continue on a similar slope through treatment and retention

phases, not supporting a specific intervention effect. For WS

pseudo words, prosodic accuracy was high in baseline

(�70%) then dropped during treatment to stabilize around

54% at post-treatment and retention. Segmental and combined

accuracy showed no evidence of a treatment effect, fluctuat-

ing between 5 and 35% correct over the three phases.

0%10%20%30%40%50%60%70%80%90%

100%

P1: Percent perceptual accuracy

P1 Treated P1 Untreated

PND Treated 75%Untreated 25%

0%10%20%30%40%50%60%70%80%90%

100%

P2: Percent perceptual accuracy

P2 Treated P2 Untreated

PND Treated 100%Untreated 25%

0%10%20%30%40%50%60%70%80%90%

100%

P3: Percent perceptual accuracy

P3 Treated P3 Untreated

PND Treated 75%Untreated 75%

00.10.20.30.40.50.60.70.80.9

1

P4: Percent perceptual accuracy

P4 Treated P4 Untreated

PND Treated 100%Untreated 0%

Figure 1. Overall perceptual performance for each participant on treated and untreated probe items across three periods (baseline, in treatment probes,4 week follow up). Percent is number of probe items child was perceived to have both correct prosody and articulation as a percent of number of trialsrespectively on treated and untreated items. PND – Percent non overlapping data.

142 P. McCabe et al. Dev Neurorehabil, 2014; 17(2): 137–146

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Generalization to connected speech

Changes in PVC, PCC and stress pattern matches obtained

from connected speech samples at pre-treatment (baseline 3),

post-treatment (1 day immediate post) and retention (4 weeks

post) probe time points are presented in Table II. All

participants increased in their ability to produce correct

stress patterns during connected speech from pre-treatment to

the retention probe. P1, P2, and P3 increased in stress matches

by 19–23 percentage points from pre-treatment to retention,

while P3 increased by 6 percentage points.

Segmental accuracy increased in connected speech for

some participants. Small positive changes in PVC over time

were noted for P1, P2, and P4, with these participants

showing increasing PVC values over time by 6–10 percentage

points. For PCC, P1 and P2 showed deterioration in accuracy

from pre-treatment to retention (27 and 7 points, respect-

ively). P3 and P4 showed small increases in PCC of 4 and 6

percentage points, respectively.

Experimental control

Results of post-treatment language assessment are reported in

Table III. While small improvements were noted for receptive

vocabulary scores on the PPVT [32], these were within the

95% confidence interval of the mean suggesting no systematic

change related to the treatment, as expected.

Discussion

This study evaluated a treatment protocol targeting improved

prosody and segmental accuracy in children with CAS.

Specifically, we examined the use of ReST intervention using

bisyllabic pseudo word stimuli orthographically biased for

particular lexical stress patterns. We hypothesized that (1)

children would improve in their ability to produce lexical

stress in novel two-syllable pseudo words; (2) treatment

effects would be retained up to four weeks post-treatment;

(3) treatment effects would generalise to connected speech;

and (4) experimental control would be demonstrated. The

hypotheses were supported, however, the magnitude of the

treatment effect, retention, and generalization varied across

participants. Based on perceptual judgments of prosodic,

segmental and combined accuracies (the ability to produce

both correct stress pattern and correct phonemes), all children

improved in their ability to produce both lexical stress

contrasts and segmental accuracy from the initial to final

treatment sessions in treated words, thus a treatment effect

occurred. Participants also produced noticeable differences

between SW and WS stimuli at more than one time point as

was expected with the focus of treatment being the vowel

length produced in the weak syllable with criterion set at

production of the schwa vowel.

Both children who read the stimuli (P1 and P2) improved

their production of treated words and the effects of treatment

generalized to untrained probe items and to connected speech.

Thus, reading orthographically biased stimuli may be a

functional approach to treatment of CAS and it may be that

imitation of a clinician model, which is common practice in

speech intervention, is not required by older children with

CAS. This finding may help ameliorate a number of the

problems reported by parents to be associated with regular

home practice including finding time for daily practice [50]

and knowing that they are providing an accurate model for their

child [51]. It should be noted, however, that reading ability and

difficulties decoding pseudo words may influence both stress

assignment and segmental accuracy of spoken stimuli. While it

is difficult to control for this effect during treatment (i.e.,

determining if errors are the result of misreading and/or

misarticulation), it needs to be considered when determining if

children are going to be asked directly to read treatment

stimuli. Gillon and colleagues have shown that children with

CAS may experience delays in reading ability [52,53] and,

therefore, clinicians should cautiously consider written-only

orthographically biased stimulus. This applies not only to

prosodic interventions but also to treatments targeting other

characteristics of CAS such as segmental errors.

Where written stimuli are used, particular attention should

be paid to the nature of these stimuli as it seems possible that

certain stimuli may enhance or hinder the treatment depend-

ing on whether the stimuli contain spelling patterns that are in

line with the stress patterns that the child is being asked to

produce. This applies to studies using either real words or

pseudo words. The combination of this study and that of Van

Rees et al. [29] suggests that the use of appropriately selected

written stimuli which are orthographically biased can enhance

production accuracy for children with CAS and those with

typical speech development.

Participants also made changes in segmental accuracy both

in therapy and in the generalization measure of connected

speech. This occurred even though only simple Knowledge

of Results [47] feedback on correct/incorrect production

was provided on segmental accuracy. That is, participants

were only told that sounds were correct or incorrect in the

pre-practice phase and not in the practice phase and no direct

teaching on sound accuracy was provided at any stage. This

finding echoes work with adults with acquired apraxia of

speech where both Mauszycki and Wambaugh [54] and

Table II. Percent vowels correct (PVC), percent consonants correct(PCC), and percent stress pattern matches (stress %) during connectedspeech at pre-treatment (Pre), post-treatment (Post) and retention (Ret)for each participant..

P1 P2 P3 P4

Pre Post Ret Pre Post Ret Pre Post Ret Pre Post Ret

PVC 74 81 80 78 87 87 90 88 92 85 84 91PCC 81 80 54 95 95 88 70 86 74 60 70 66Stress % 46 43 70 53 81 76 79 77 85 64 68 83

Table III. Post-treatment assessment results for P1, P2, P3, and P4.

P1 P2 P3 P4

Test Std CI Std CI Std CI Std CI

Peabody PictureVocabularyTest – 4th editionForm B

84 78–91 96 89–103 90 83–97 119 111–125

Standardized tests scores (Std) and 95% confidence intervals (CI) arereported, % indicates a percentage score.

DOI: 10.3109/17518423.2014.906002 Prosodic treatment of CAS 143

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Brendel and Zeigler [55] reported training rate or rhythm

alone also improved segmental accuracy.

All participants had difficulty synchronously producing

both correct stress patterns and correct segments. These

difficulties are reflected in the perceptual judgments of both

treatment and probe data where most participants had poor

performance on simultaneous production of the correct stress

pattern whilst maintaining segmental accuracy. This inability

to combine performance across speech elements may be

hypothesized as causally linked to an increased load on the

overall speech system. For example, P3 maintained only

prosodic accuracy after treatment and P4 was able to achieve

accurate prosody alone on most occasions with segmental

accuracy apparently sacrificed to achieve prosodic accuracy

[56]. Stress pattern matches during connected speech

increased while PCC values decreased for P1 and P2 also

suggesting a sacrifice of segmental accuracy to achieve

prosodic accuracy. Such a trade-off between development of

lexical stress and segmental accuracy is seen in the develop-

ment of polysyllabic words in typically developing children

with prosodic and/or segmental accuracy sacrificed at differ-

ent stages of development until an adult like production is

realized [57]. Therefore, participants in this study may be

following a normal developmental pattern in the development

of lexical stress with positive changes to stress production

triggered as a result of treatment [6].

Generalization

Generalization to non-treated pseudo word items mirrored the

results for treatment stimuli in all participants; however, the

changes were less pronounced. Generalization to connected

speech was also observed with change over time in measures

of stress pattern match and PVC. Prior to treatment all

children had prosodic impairments in connected speech in the

moderate to severe range. Although connected PCC measures

were mostly mild to moderate prior to treatment, in combin-

ation with poor prosody, this resulted in a high level of

perceived unintelligibility. The connected speech generaliza-

tion reported here is a highly desired outcome, as an increase

in matching prosodic patterns will lead to increased speech

intelligibility [58]. Additionally, generalization to connected

speech suggests that the use of orthographically biased pseudo

word stimuli may promote learning during treatment and

promote generalization to more complex untreated but

desirable behaviors. This suggestion requires further investi-

gation but such generalization from pseudo words has been

reported for other speech disorders in children [42].

Limitations

The design of the current study limits the generalization of

these results but provides preliminary evidence of treatment

efficacy. When combined with the extant Ballard et al. [26]

and Van Rees et al. [30] studies, the findings reported here

suggest that ReST intervention is a promising treatment

worthy of further investigation.

A number of additional constraints on the generalizability

of the research exist. Each child was treated by a different

clinician and so there may have been a confound of treating

clinician. However, participant–clinician pairs were randomly

assigned and all clinicians were required to demonstrate

treatment fidelity and so delivered the protocol as intended.

A ceiling effect was observed for P4 with the bisyllabic

stimuli in isolation being insufficiently challenging. Future

studies should manage this effect through the provision of

more complex orthographically biased stimuli and the use of

such stimuli in cloze sentences as per Ballard et al.’s

approach [25].

These four single cases provide evidence that a treatment

effect can be obtained using the current protocol. Additional

research is needed to further test this treatment approach in

a larger group of children with CAS using both imitation

and spontaneous reading of the stimuli and to assess the

effects of orthographically biased treatment stimuli in a range

of prosodic disorders. Further development of the protocol

and validation with a wider range of children with CAS is also

required before we can be assured of the efficacy of this

promising intervention.

Conclusions

Prosodic impairments can be treated in children with CAS

using ReST intervention in conjunction with orthographically

biased stimuli. The use of stimuli orthographically biased to

particular lexical stress patterns resulted in positive treatment

outcomes for all children with maintenance and generalization

of treatment skills.

Acknowledgements

Thanks to Tal Schwarzmann, Katrina Wu, Henna Chaudhry,

and Nicole Willcox for assistance with data collection and the

four children and their families.

Declaration of interest

The authors are not aware of any conflicts of interest

associated with this paper. The authors are solely responsible

for the content and writing of this paper. Parts of this study

were presented at the 2010 Conference on Motor Speech in

Savannah, GA, USA, and the 2010 Speech Pathology

Australia National Conference in Melbourne, VIC, Australia.

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Appendix

Table A1. Treatment and non-treatment stimuli set with treatment words in bold (based on Arciuli et al. [1] and used inVan Rees et al. [2]).

SW orthographyPhonemic transcription and

production used for imitation WSPhonemic transcription and

production used for imitation

coddol /kodFl/ adibe /Fdib/combol /kombFl/ adoon /Fdun/condan /kondFn/ amade /FmeId/condey /kondF/ apoon /Fpun/copet /kopFt/ bemade /bFmeId/covan /kovFn/ bemiss /bFmIs/mandan /mændFn/ bepade /bFpeId/mapet /mæpFt/ beribe /bFraIb/mappol /mæpFl/ bevade /bFveId/maran /mæ7Fn/ abade /FbeId/combet /kombFt/ amiss /FmIs/conol /konFl/ bedibe /bFdaIb/mambey /mæmbF/ bediss /bFdIs/mandol /mændFl bedoon /bFdun/manet /mænFt/ bemoon /bFmun/

References[1] Arciuli J, Monaghan P, Seva N. Learning to assign lexical stress during reading aloud: Corpus, behavioral, and

computational investigations. Journal of Memory and Language 2010;63(2):180-196.[2] van Rees LJ, Ballard KJ, McCabe P, Macdonald-D’Silva AG, Arciuli J. Training production of lexical stress in

typically developing children with orthographically biased stimuli and principles of motor learning. American Journalof Speech-Language Pathology 2012:1058-0360_2012_11-0008.

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Figure 2. P1s performance across the baseline and experimental probes. The panel shows percent correct for production of stress, segments, and

both combined, as perceptually judged, for treated strong-weak (SW) nonwords (A) and treated weak-strong (WS) nonwords (B).

A B

Figure 3. P2s performance across the baseline and experimental probes. The panel shows percent correct for production of stress, segments, and

both combined, as perceptually judged, for treated strong-weak (SW) nonwords (A) and treated weak-strong (WS) nonwords (B).

Figure 4. P3s performance across the baseline and experimental probes. The panel shows percent correct for production of stress, segments, and

both combined, as perceptually judged, for treated strong-weak (SW) nonwords (A) and treated weak-strong (WS) nonwords (B).

A B

Figure 5. P4s performance across the baseline and experimental probes. The top panel shows percent correct for production of stress, segments,

and both combined, as perceptually judged, for treated strong-weak (SW) nonwords (A) and treated weak-strong (WS) nonwords (B).

A B