UTTERANCE LENGTH AFFECTS ARTICULATION IN CHILDREN WITH
SPEECH SOUND DISORDERS
by
SEAN SNAPP
Submitted in partial fulfillment of the requirements for the degree of
Master of Arts
Department of Psychological Sciences
CASE WESTERN RESERVE UNIVERSITY
May, 2018 1
CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES
We hereby approve the thesis of Sean Snapp
candidate for the degree of Master of Arts*.
Committee Chair Barbara Lewis
Committee Member Lisa A. Freebairn
Committee Member Vera Tobin
Committee Member Jennell Vick
Date of Defense March 30, 2018
*We also certify that written approval has been obtained for any proprietary material contained therein.
2
Table of Contents
Table of Contents 2 List of Tables 3 List of Figures 4 Acknowledgements 5 Abstract 6 Literature Review Introduction 7 Utterance Length in Imitative Speech 8 Utterance Length in Evaluation 9 Utterance Length in Treatment 10 Goals of the Present Study 14 Methods Participants 15 Procedures 16 Results 20 Discussion 25 Appendices Appendix A: Individual Data on Productions of /ð/ by Utterance Length in Morphemes 31 Appendix B: Words in which productions of /ð/ occurred and the accuracy of the /ð/ productions 35 Appendix C: Relationship between MLU and % of productions of /ð/ in error 36 References 37
3
List of Tables
Table 1. Demographic characteristics of study participants 15
Table 2. Results of standardized measures 16
4
List of Figures
Figure 1. Percent productions of /ð/ in error by length of utterance as measured in
morphemes 21
Figure 2. Eleven participants showing greater proportion of errors on 8-morpheme
utterances compared with 3-morpheme utterances 22
Figure 3. Six participants showing greater proportion of errors as utterance length
increases 23
Figure 4. Percent productions of /ð/ in error across utterance positions 24
Figure 5. Percent productions of /ð/ in error across utterance lengths and positions 24
Figure 6. Correlation between percent productions on /ð/ in error and MLU 25
5
Acknowledgements
This research was supported by grant DC00528 from the National Institutes of
Health, National Institute on Deafness and Other Communication Disorders (Barbara A.
Lewis).
6
Utterance Length Affects Articulation in Children with Speech Sound Disorders
Abstract
by
SEAN SNAPP
Objective: The objective of this study was to investigate the effects of utterance length
and utterance position on proportion of errors on voiced-th (/ð/) by preschool-age
children with speech sound disorders (SSD). Method: Productions of /ð/ in spontaneous language samples from 20 children with SSD were categorized as correct or in error.
These productions were pooled to determine patterns of proportions of errors across
utterance lengths and positions. Results: A greater proportion of productions of /ð/ in
error were found in 8-morpheme utterances than in 3-morpheme utterances. A gradual
increase in proportion of errors was observed in productions of /ð/ occurring in utterance-
medial positions. Conclusions: Some support was found for utterance length effects on
articulation and stronger support was found for utterance position effects. Utterance
length and position should receive consideration by SLPs in the assessment and treatment
of preschool children with SSD.
7
Utterance Length Affects Articulation in Children with Speech Sound Disorders
Literature Review
Introduction
Speech sound disorders (SSD) affect 2% to 25% of children ages 5 to 7 years
(Law, Boyle, Harris, Harkness, & Nye, 2000). Children with SSD form a significant portion of pediatric speech-language pathologists’ (SLPs’) caseloads. Data from the
American Speech-Language-Hearing Association’s (ASHA’s) National Outcomes
Measurement System (NOMS) have shown that approximately 75% of pre-K students treated by SLPs received therapy for articulation or intelligibility (Mullen & Schooling,
2010). Diminished intelligibility is the hallmark characteristic of SSD, with perception, production, and mental representation of consonants and vowels, phonotactics, and prosody affected to greater or lesser degree in each child (International Expert Panel on
Multilingual Children’s Speech, 2012).
Among the numerous factors affecting articulation in children with SSD that have been widely accepted in clinical practice, utterance length stands out for its ubiquity as a consideration in assessment and evaluation despite a relatively low level of evidence from research. Investigation of utterance length effects on articulation has been focused on imitative speech, elicitation of samples in evaluation, and target selection in treatment
(Schmauch, Panagos, & Klich, 1978; Panagos, Quine, & Klich, 1979; McLeod,
Rosenthal, & Hayes, 1994; Wolk and Meisler, 1998; Masterson, Bernhardt, and
Hofheinz, 2005; Healy and Madison; 1987; DuBois & Bernthal, 1978; Morrison &
Shriberg, 1992; Klein, 1996). This has left a gap in knowledge of utterance length effects on articulation errors during the spontaneous speech of children with SSD. This is an area 8
worthy of investigation because spontaneous speech will more accurately reflect natural
performance compared with imitative speech and will demonstrate potential issues
related to generalization of treated phonemes.
Utterance Length in Imitative Speech
In imitative speech, increased articulation errors, especially on late-developing
sounds, have been found in a sentence context compared to a noun phrase context in both
children with comorbid speech and language disorders and children with SSD only
(Schmauch, Panagos, & Klich, 1978; Panagos, Quine, & Klich, 1979). These findings,
which support the commonly held notion that increased utterance length is related to an
increased rate of errors of articulation, should be interpreted cautiously. The use of
imitation to elicit all productions of short and long phrases may have influenced
participants’ speech and therefore may not have reflected their performance in
spontaneous speech. The use of imitation to elicit responses introduces aspects of
memory that were not controlled for and may have confounded the results. Shorter
utterances may have been easier to store in short-term memory and repeat with greater
precision than longer utterances. In addition, these studies investigated productions of 14-
20 early- to late-developing phonemes with limited productions of each. In their analysis of the results, differences in the production of different phonemes was not considered.
This makes it difficult to draw conclusions about the effect of utterance length on any one phoneme, as it is not known whether utterance length had differential effects based on phoneme. Variables such as manner, place, and order of acquisition could have confounded the results. Coarticulation effects, including the influence of phonological
processes, were also not considered. 9
Utterance Length in Evaluation
In order to rule out the presence of SSD, or alternatively, to determine the type
and severity of a child’s disorder, SLPs complete a comprehensive evaluation that
typically includes pre-screening, interviewing parents, assessing stimulability and
intelligibility, and elicitation of single words (typically through standardized testing measures) and connected speech, including conversational speech (McLeod & Baker,
2014). One purpose of the speech sample is to determine the developmental appropriateness child’s phonetic inventory and to select target speech sounds for therapy.
In a national survey of assessment practices for children with SSD that included 312
ASHA-affiliated SLPs across the United States, 74.1% of respondents reported always using single-word tests to determine percentile rank and score (17.8% reported sometimes using single-word tests); only 36.2% of respondents reported always using a connected speech sample (43.7% reported sometimes using a connected speech sample)
(Skahan, Watson, & Lof, 2007). Given the important role that choosing a representative speech sample has in maintaining the integrity of an assessment of articulation and phonology, it is imperative that SLPs be able to justify the use of one type of speech sample over the other with evidence from research.
Research investigating the relative accuracy of single-word sampling and
conversational speech sampling in the assessment of children with SSD has produced
mixed results. Many studies have found single-word tasks and conversational speech sampling to produce comparable results (e.g., McLeod, Hand, Rosenthal, & Hayes, 1994;
Wolk and Meisler, 1998; Masterson, Bernhardt, and Hofheinz, 2005). Other studies have found significant differences in the interpretations of data collected single-word and 10 conversational speech samples. For example, Healy and Madison (1987) found a significantly greater proportion of errors were produced in connected speech samples by children with SSD than in single word utterances. Similarly, DuBois & Bernthal (1978) found that children with SSD produced significantly more errors in a continuous speech task than in a modeled continuous speech task or a spontaneous picture-naming task.
Morrison & Shriberg (1992) found that productions of established sounds of children with SSD were more accurate in conversational speech and emerging sounds were more accurate in single-word sampling.
The differing conclusions of these studies suggest the presence of confounding variables affecting accuracy of speech sound production and presence of phonological processes that have yet to be considered. Coarticulation effects, for instance, were not considered. In single-word testing, these effects word be within words only, but in connected speech there would also be effects between words. Another area that has consistently not been adequately controlled is the influence of syntax at either the phrase level or the word level. At the phrase level, factors such as clausal density and number of grammatical morphemes in a phrase may influence the production of certain speech sounds. At the word level, word class may similarly have an effect.
Utterance Length in Treatment
Within current practice in the United States, treatment of SSD in children includes a wide range of approaches. A national survey of 489 SLPs who provided treatment to children with SSD between the ages of 3 and 6, investigated use of 18 interventions and found an eclectic mix of approaches, including motor-based, phonological, and linguistic
(Brumbaugh and Smit, 2013). Traditional articulation therapy was found to be the most 11
frequently used approach, with 49% of participants reporting using it often or always and
33% of participants reporting using it sometimes. Among SLPs who used traditional articulation therapy in their clinical practice, phonetic placement was the most commonly used elicitation technique, with 70% of participants reporting using it often or always.
These figures demonstrate the ubiquity of this approach within a crowded field of interventions and high degree of uniformity with regard to elicitation of target sounds.
The traditional approach to articulation therapy was laid out by Charles Van Riper
in his seminal textbook Speech Correction: Principles and Methods (1939), with few
modifications in subsequent editions (Van Riper & Emerick, 1996). It was developed as
an alternative to the most widely used articulation therapy approaches of the time, which
heavily emphasized modeling, auditory bombardment, and whole-word drilling with little
regard to accuracy of productions. Van Riper and Emerick proposed that in order to
correct articulation errors that had become entrenched in clients’ speech through incorrect
practice and an inability to recognize incorrect productions, a systemized approach that
targeted one or two target sounds in a series of operational levels would lead to the best
outcomes. In traditional articulation therapy, target sounds are addressed first at the
isolated sound level, then the syllable level, then the word level, and finally at the
sentence level. Each level is further broken down into sensory/perceptual training and producing, stabilizing, and transferring stages. According to Van Riper and Emerick, the purpose of this process was to renew the process of self-monitoring of individual speech sounds that characterized early speech sound acquisition for client and ultimately return to the automaticity of proprioceptive controls via a series of supported contexts that matched the client’s current abilities and led progressively to conversational speech. 12
Despite the ubiquity of traditional articulation therapy in current clinical practice,
its effectiveness has been brought into question by researchers who note the low level of
evidence to support it. In their review of service delivery for children with SSD, McLeod
& Baker (2014) noted that despite the fact that there is minimal evidence to support
traditional articulation therapy and that the research that exists is of variable quality, it is
used with greater frequency by SLPs than newer forms of treatment with higher levels of
evidence, such as cycles (Hodson & Paden, 1983), minimal pairs (Weiner, 1981), or multiple oppositions approaches (Williams, 2000). These newer forms have moved away from the traditional therapy methods and goals. In traditional therapy, sounds in error are
treated individually, with emphasis on creating motor patterns with correct placement of
articulators and correct productions. Newer phonological approaches have addressed
phonological rules, with the focus on overall intelligibility and positive reinforcement
given following productions that demonstrate the correction of a rule rather than
following correct productions of the target phoneme (e.g., Klein, 1996).
A number of studies have compared the relative effectiveness of traditional
articulation therapy and phonological approaches. In their randomized controlled trial
investigating the effects of traditional and phonological interventions on the treatment
time required to treat compensatory articulation disorder (CAD) in children between 3
and 7 with cleft palate, Pamplona, Ysunza, & Espinosa (1999) found that the mean time
required to normalize the speech of participants receiving the articulatory intervention
was significantly greater than that of participants receiving the phonological treatment.
Bias toward the phonological intervention may have complicated the findings, however.
In treatment, the goal of therapy for participants receiving traditional therapy was correct 13 production of speech sounds; for participants receiving the phonological intervention, the goal was to increase overall intelligibility without regard for correct production of individual speech sounds. The use of increased intelligibility as the criterion for discontinuation of treatment introduced bias toward the phonological approach, as increased intelligibility was not the goal for participants receiving traditional articulation therapy.
In other studies that have compared traditional and phonological approaches, utterance length may have affected treatment length and outcomes. As defined by Van
Riper & Emerick (1996), traditional therapy is based on a gradual progression from isolated phoneme to word to sentence in targeting sounds in error. Strictly speaking, this has not been considered a feature of the phonological approach, although it has been part of phonological therapy as defined in studies by Hesketh, Nightingale, & Hall (2000) and
Klein (1996). In their comparison of traditional and phonological approaches for children ages 3;6 to 5;0 with developmental phonological disorders (PD), Hesketh, Adams,
Nightingale, & Hall (2000) found no significant differences in the improvement of metaphonological abilities or percent consonants correct (PCC) after 10 weekly sessions.
Children receiving phonological therapy worked first on phonological awareness, including rhyming, syllable clapping, alliteration, blending and segmenting games.
Production was addressed in the last two weeks of therapy, with contrasting sounds and minimally paired words. Although these targets are phonologically based, they show the progression from sound to word that matches the target sequence in traditional therapy. In a retrospective group comparison that investigated the relative effectiveness of a traditional approach to articulation therapy for children with SSD ages 3 to 6 years to a 14
phonological approach, Klein (1996) found that children receiving phonologically based
therapy had a greater reduction in the severity of their disorder, with treatment lasting
fewer sessions and fewer months. Although these results appear to show the phonological
approach to be more effective, the authors note that phonological approaches included in the study included treatment of phonological rules in contexts that progressed from the nonsense syllable level to higher levels once the client’s accuracy had reached 100%.
Taken together, these studies suggest that utterance length may play a role in therapy for correcting speech sounds, with progressively shorter contexts facilitating correct production of individual speech sounds or suppression of phonological processes.
Goals of the Present Study
The first question investigated in the present study is as follows: are longer utterances, measured by number of morphemes, associated with a greater proportion of incorrect productions of voiced-th (/ð/) in the spontaneous speech of children with SSD?
The phoneme /ð/ was chosen for investigation it is a late-developing sound, established by Shriberg (1993) as being among the final group of 8 sounds to emerge in children’s speech. Because it is a late-developing sound, it is less likely to be produced correctly with consistency by young children, particularly those with SSD. It was hypothesized that a greater proportion of incorrect productions of /ð/ would be associated with longer utterances, as measured by number of morphemes.
The second goal of the study was to examine the effect of utterance position on articulatory accuracy and investigate its interaction with utterance length. It has been well-established that word position (i.e., initial, medial, final position of a sound within a single word) has a great influence on articulation (Templin, 1957; Rvachew & Andrews, 15
2002; Flipsen & Ogiela, 2015)., but utterance position (i.e., initial, medial, final position
of a sound within an utterance) has not received the same level of consideration in
clinical practice, despite some evidence of potential effects. A study on omission of
singular –s in the spontaneous speech of children ages 2;9 to 3;2 found a greater
proportion of omissions in five-word utterances compared to three-word utterances but
only in the utterance-medial position (Mealings & Demuth, 2014). To investigate the role
of utterance position on articulation, the following second question of the present study
was posed: is advanced utterance position associated with a greater proportion of errors
on /ð/ in the spontaneous speech of children with SSD, and is a greater proportion of
errors on /ð/ associated with longer utterances within each utterance position? In this
study, initial utterance position was defined as the first word in an utterance, final utterance position was defined as the last word in an utterance, and medial utterance position was defined as any word that was not first or last in an utterance. It was
hypothesized that the relationship between increased rate of errors on /ð/ and utterance
length would be strongest in the medial utterance position.
Methods
Participants
Twenty children with moderate SSD were selected for analysis from an ongoing
longitudinal family study of speech and language disorders (Lewis et al., 2011).
Participants were referred to the ongoing study by speech-language pathologists at
community speech and hearing centers or in private practice in the greater Cleveland
area. All participants had received a diagnosis of SSD and met the following criteria:
hearing within normal limits, normal peripheral speech mechanism, absence of a history 16 of neurological disorders or developmental disorders other than speech and language, and nonverbal intelligence within normal limits. Participants in this study were within the normal range for language ability. None of the participants had a diagnosis of childhood apraxia of speech.
Eleven of the participants were male, and nine of the participants were female.
Two of the participants were sisters. Participants ranged in age from 3.5 to 5.83. Nineteen of the participants were Caucasian and one participant was African American/Pacific
Islander. The Hollingshead Four Factor Index of Social Class (Hollingshead, 1975) was used to determine the socioeconomic status of the participants’ families. Demographic characteristics of participants in the present study are summarized in Table 1.
Table 1. Demographic characteristics of study participants
Variables n % Sex Male 11 55 Female 9 45 Age (M = 4.45, SD = 0.6) 3.5-3.99 5 20 4.0-4.49 6 30 4.5-4.99 7 35 5.0-5.49 1 5 5.5-5.99 1 5 Race Caucasian 19 95 African American/Pacific Islander 1 5 Family’s Holingshead SES (M = 4.42, SD = 0.84) 0 0 1 (lowest) 1 5 2 1 5 3 6 30 4 11 55 5 (highest) 1 5 Unreported
17
All participants of the present study met the following additional criteria:
participated in the ongoing longitudinal study; fell within the ages of 3;6 and 5;11 at the
time of first participation; were diagnosed with SSD with no comorbid diagnosis of
specific language disorder, autism or childhood apraxia of speech; and participated in
language sampling from which at least 50 utterances could be used to determine mean length of utterance (MLU). All participants had received a diagnosis of SSD as defined by scoring in the 1 – 48 percentile range on the Goldman-Fristoe Test of Articulation
(GFTA; Goldman & Fristoe, 1986) Sounds-in-Words subtest and on the Khan-Lewis
Phonological Analysis (KLPA; Khan & Lewis, 1986). Mean Length of Utterance (MLU)
of 3.3 or greater based on the first 50 utterances of their conversation sample was the
criterion used to determine normal language abilities. Percent Consonants Correct (PCC)
was calculated for each participant based on the first 50 utterances of their conversation
sample to determine severity, with a resulting range of 75.54 – 94.16% (Shriberg &
Kwiatkowski, 1982). Out of the 20 participants, 13 participants received PCC scores in
the mild-moderate range (75.54-85.15%) and 7 participants received scores in the mild
range (86.5-94.16%) Results of standardized measures of speech and language are
summarized in Table 2.
Table 2. Results of standardized measures
Measures Range M SD GFTA (%tile) 1 – 48 17.37 12.14 KLPA (%tile) 1 – 48 19.63 15.59 First 50 utterances of language sample MLU 3.35 – 5.83 4.56 0.7 PCC 75.54 – 83.23 5.56 94.16
18
Procedures
Participants were tested individually either in their homes or at a community
speech and hearing clinic in Cleveland, Ohio. Testing was performed by two trained,
licensed speech-language pathologists. Recordings of measures of speech production
were created using a Sony Professional Walkman (model WM-D6C) with an Audio
Technica omnidirectional microphone (model AT804). These recordings were used to
create phonetic transcriptions. The University Hospitals of Cleveland Institutional
Review Board provided approval. Informed consent from participants’ parents and assent
from participants was obtained before the beginning of testing. Recordings were played
through the internal speakers on a Dell Inspirion 13-7378 laptop in order to complete
transcriptions.
Speech and Language Measures. The GFTA Sounds in Words subtest was administered in order to assess individual speech sounds of participants as well as level of severity of SSD. The Khan-Lewis Phonological Analysis (KLPA; Khan & Lewis, 1986)
was completed to identify phonological processes.
Language sampling was completed through conversation and play between the
participant and administering speech-language pathologist. The first 50 utterances from
each participant’s sample was transcribed literally and phonetically in order to calculate
mean length of utterance (MLU) and percent consonants correct (PCC). Utterances were
segmented into communication units (C-units), each consisting of an independent clause
and any associated modifiers, with one-word utterances, unintelligible utterances, and
elliptical responses excluded from analysis. 19
All productions of one-syllable function words with /ð/ in word-initial position from each language sample were transcribed phonetically. A full list of words meeting these criteria is presented in Appendix B. Each production was marked as either correct or in error by a graduate student in speech-language pathology. Correct productions were defined as those in which a clear linguodental sound was apparent in the initial consonant as measured by perceptual analysis. Incorrect productions of /ð/ were defined as those in which there was a substitution for /ð/, a distortion of /ð/ (i.e., a clear linguodental sound was not apparent), or an omission of /ð/, as measured by perceptual analysis. Productions of the pronoun them as the object in the utterance in which the first phoneme was omitted were not included in analysis in order to accommodate for regional dialect. All productions of one-syllable function words with voiceless-th in consonant-initial position were marked as being in utterance-initial position if they were the first word in the utterance, utterance-final position if they were the last word in the utterance, and utterance-medial position if they were neither the first nor last word in the utterance.
Analysis. To determine if a greater number of incorrect productions of /ð/ was associated with longer utterances, as measured by number of morphemes, the Cochran-
Armitage trend test was used. This test is a linear trend statistic for testing independence of variables in l x 2 tables with one ordinal variable and one variable with two levels. In this study, the ordinal variable was the utterance length in morphemes and the variable with two levels was the accuracy of the /ð/ production (correct or in error). The variable l represented utterance length in morphemes. Analysis included utterances that were 3 to 8 morphemes in length because of low levels of data for longer and shorter utterances. In addition, the Cochran-Armitage trend test was completed to compare proportions of 20
correct to incorrect productions of /ð/ in 3-morpheme utterances and 8-morpheme utterances.
To determine if incorrect productions of /ð/ were more likely to appear in initial, medial, or final positions, a chi-square test of independence was completed. The
Cochran-Armitage trend test was completed to determine the effect of utterance length on accuracy of utterance-medial /ð/ productions. The effect of utterance length on accuracy of utterance-initial and final /ð/ productions was not examined because of low levels of
data.
Three exploratory measures were also completed. First, chi-square test for independence was done to determine if there was a relationship between the word in which a production of /ð/ occurred and the accuracy of the /ð/ production. Secondly, a
Pearson correlation coefficient was calculated to determine the relationship between
MLU and percent of /ð/ productions in error.
Results
Data showed an increase in proportion of errors on /ð/ as utterance length
increased. Individual data is summarized in Appendix A. Analysis of two separate
comparisons was completed. The first comparison was of error rates on /ð/ in utterances
that were 3, 4, 5, 6, 7, and 8 morphemes long. A greater rate of errors on /ð/ as utterance
length increased from 3 to 8 morphemes was found. This comparison was summarized in
(Figure 1). Comparisons of the error rates on /ð/ in utterances that were 3, 4, 5, 6, 7, and 8
morphemes long using the Cochran-Armitage trend test showed that it did not reach
statistical significance, χ2 (5, N = 6) = 3.39, p < .05.
21
Figure 1. Percent productions of /ð/ in error by length of utterance as measured in morphemes
100 90 80 Error 70 60 50 40 30 20 10
Percent Productions in in Productions Percent 0 3 4 5 6 7 8 Length of Utterance in Morphemes
The second comparison was of error rates on /ð/ in 3-morpheme utterances and 8-
morpheme utterances. Analysis of the difference in error rates using the Cochran-
Armitage trend test showed the higher rate of errors in 8-morphemes compared to the rate
of errors in 3-morpheme utterances did reach statistical significance, χ2 (1, N = 2) = 6.77,
p < .05.
Individual differences in error rate of /ð/ over increased utterance length were
noted. Of 19 participants whose language samples included 3- and 8-morpheme
utterances with /ð/, 11 participants had a greater of productions of /ð/ in error to correct
productions on 8-morpheme utterances compared to 3-morpheme utterances (Figure 2).
Of these 11 participants, 5 participants showed a strong trend of increasing errors on /ð/
as utterance length increased from 3 to 8 morphemes (Figure 3). For the other 6
participants, the proportion of productions of /ð/ in error to correct productions was
relatively stable as utterance length increased. Two participants showed no difference in
proportion of /ð/ productions in error to correct productions in 3-morpheme utterances
and 8-morpheme utterances (one 0% of productions of /ð/ in error in both utterance 22 lengths and one with 100% of productions of /ð/ in error in both utterance length). Four participants showed a higher proportion of /ð/ productions in error to correct productions in 3-morpheme utterances compared to 8-morpheme utterances. Of these four participants, the proportion of productions of /ð/ in error to correct productions was relatively stable as utterance length increased.
Figure 2. Eleven participants showing greater proportion of errors on 8-morpheme utterances compared with 3-morpheme utterances
100% 90% 80% Error 70% 60% 50% 40% 30% Percent Productions in in Productions Percent 20% 10% 0% 3 8 Length of Utterance in Morphemes
23
Figure 3. Six participants showing greater proportion of errors as utterance length increases
100% 90% 80% Error
in 70% 60%
of /ð/ of /ð/ 50% 40% 30% 20% 10%
Percent Productions Productions Percent 0% 3 4 5 6 7 8
Length of Utterance in Morphemes
Support was found for the hypothesis that proportion of errors in productions of
/ð/ increased with advanced utterance position (Figure 4). Analysis of the difference in
proportion of errors on /ð/ productions in utterance-initial, utterance-medial, and
utterance-final using the chi-square test of independence showed that it did reach
statistical significance, χ2 (2, N = 3) = 55.88, p < .01. Support was also found for the
hypothesis that utterance length affected proportion of errors in productions of utterance- medial productions of /ð/ (Figure 5). Analysis of this relationship using the chi-square
test of independence showed that it did reach statistical significance, χ2 (5, N = 6) =
18.96, p < .01. Although data were too few to complete statistical analyses of the effects of utterance length on the proportion of errors in productions of utterance-medial productions of /ð/, it appeared that utterance length did not affect articulatory accuracy.
Individual differences were not examined because of low levels of data for each
individual participant. 24
Figure 4. Percent productions of /ð/ in error across utterance positions 100% 90% 80% Error 70% in 60%
of /ð/ of /ð/ 50% 40% 30% 20% 10% 0%
Percent Productions Productions Percent Initial Medial Final Utterance Position
Figure 5. Percent productions of /ð/ in error across utterance lengths and positions 100% 90%
Error 80% in 70% 60% of /ð/ of /ð/ 50% 40% 30% 20% 10% 0% Percent Productions Productions Percent 3 4 5 6 7 8
Length of Utterance in Morphemes Initial Medial Final
The first exploratory measure, a chi-square test for independence was done to
determine if there was a relationship between the word in which a production of /ð/
occurred and the accuracy of the /ð/ production, found that there was a significant
relationship, χ2 (15, N = 16) = 95.3, p < .01. These results are summarized in Appendix
B. The second exploratory measure, a Pearson correlation coefficient to determine the relationship between MLU and percent of /ð/ productions in error, found a moderate negative correlation, r (18, N = 20) = -0.62, p < .01. These results are summarized in 25
Figure 6 and Appendix C. This showed that as MLU increased, the percent of /ð/ productions in error decreased.
Figure 6. Correlation between percent productions on /ð/ in error and MLU Mean Length of Utterance and % Voiced-th Productions in Error 100 90 80 Error
in 70
/ð/ 60 50 40 30 20 10
Percent Productions on Productions Percent 0 3 3.5 4 4.5 5 5.5 6 Mean Length of Utterance
Discussion
The results of this study demonstrated some support for a positive association between the proportion of incorrect productions of /ð/ and utterance length, as measured by number of morphemes, in the spontaneous speech of children with SSD. In general, participants were more likely to produce /ð/ in error in utterances that were 8 morphemes long compared to utterances that were 3 morphemes long. For some participants, there was a gradual increase in errors as utterance length increased. These findings are consistent with previous research that found an increase in errors of articulation in sentence-length utterances produced in imitation compared with noun phrase-length utterances produced in imitation (Schmauch, Panagos, & Klich, 1978; Panagos, Quine, &
Klich, 1979). These results suggest that there is a greater burden on motor planning as 26
utterance length increases. The increased articulatory complexity of a longer utterance
may magnify coarticulation effects, as demands on processing and memory also increase.
Utterance position appeared to have a much stronger association with articulatory accuracy than utterance length. Participants were much more likely to produce /ð/ correctly when it occurred in the first word of an utterance and much more likely to produce /ð/ in error when it occurred in the last word of an utterance. In utterance-medial productions of /ð/, where the overall proportion of errors was close to the overall proportion of errors in all utterance positions, increased utterance length was associated with an increase proportion of productions of /ð/ in error. The isolation of utterance length effects within the utterance-medial position is consistent with the research of
Mealings & Demuth (2014), where increased rates of omission of third person –s were found only in the utterance-medial position. Mealings and Demuth speculated that lower planning demands toward the end of the sentence might explain the medial position effects found in their study. This explanation is inconsistent with the findings of the present study, which included a greater proportion of errors with advanced utterance position. Instead, the results of the present study suggest greater planning demands on the end of an utterance, which may have been great enough to nullify effects of utterance length. It may be that utterance-initial productions of /ð/ benefitted from low planning demands to such a degree they also nullified the effects of utterance length. Percentage of utterance-medial productions of /ð/ in error was close to percentage of overall productions of /ð/, so utterance-medial productions may have been more vulnerable to utterance length effects than utterance-initial or utterance-final productions. 27
There are some limitations that should be considered when interpreting the
findings of this study. It has been established that boys are more likely than girls to have
a SSD (Shriberg, Tomblin, & McSweeny, 1998), but in this study, boys and girls were
represented nearly equally. In the statistical analysis of /ð/ productions, productions from
all participants were pooled together, resulting in a sample in which some participants
were over- or under-represented at different utterance lengths. This may have resulted in
patterns of errors that were representative of certain participants more than others. The strong relationship between individual participants’ MLU and their proportion of errors on /ð/ further suggests that larger patterns of errors demonstrated by pooling all participant data may not represent individual differences based on MLU.
The scope of this study was deliberately limited to a single phoneme, /ð/.
Although this approach led to a clearer understanding of utterance length and position effects on that single phoneme than if a group of phonemes were considered together, the results of this study may not be generalizable to other phonemes. It may be speculated that similar effects could occur with other late-8 sounds, but further investigation is required before any conclusions may be drawn about other sounds. By focusing solely on a single phoneme, /ð/, effects of coarticuluation and phonological processes may have been overlooked. Other errors in words and utterances included in analysis may have influenced productions of /ð/.
It appeared that the specific word in which productions of /ð/ appeared to play an
important role in whether or not /ð/ was produced correctly or in error. This was
demonstrated despite the fact that all target words were monosyllabic function words in
which /ð/ occurred in initial position. Of productions of /ð/ in the words that’ll and these, 28
0% were in error. Of productions of /ð/ in the words their and than 75% and 100% were in error, respectively. The presence of a bound grammatical morpheme appeared to have an effect. Of the 5 words with the lowest proportion of errors on /ð/, 4 words had bound morphemes (that’ll, they’ll, they’re, there’s). Only one word with a bound morpheme
(that’s) had a relatively high proportion of errors on /ð/ (58%). This may be because the negative correlation between MLU and percent of productions of /ð/ in error. It is likely that participants who used the words that’ll, they’ll, they’re, and there’s had higher
MLUs, as use of these morphemes emerges later. Since these participants had a lower overall proportion of errors on /ð/, it would follow that their productions of /ð/ in the words that’ll, they’ll, they’re, and there’s would be more likely to be correct.
Coarticulation effects within words with word-position /ð/ did not appear to have an effect. Final consonant sound did not appear correlated with a greater proportion of errors on /ð/. Coarticulation effects with other words in the utterance may have had an effect, as well as syntactic and semantic context.
It is recommended that in future studies, greater validity of results may be achieved reliability procedures. Greater intra-rater reliability can be achieved through a single rater listening to samples at multiple time points before establishing correct versus incorrect ratings of /ð/ productions. Inter-rater reliability can be achieved through multiple raters listening to a portion of the samples and reaching consensus on correct versus incorrect ratings of /ð/ productions.
The results of this study may be informative for clinicians who see children with
SSD in their clinical practice. When assessing a child’s articulation in spontaneous speech, inconsistent productions of a certain sound may be attributable to utterance 29
length, especially if the utterance is very long or very short. It may also be attributable to
the sound’s position within the utterance, with incorrect productions more likely to occur
in the final word of the utterance. This will be important to consider in single-word testing and connected speech sampling for assessment of articulation. In single-word testing, there may be a lower proportion of errors on target sounds because of utterance length and position effects. In connected speech sampling, productions may be inconsistent, depending on the length of the utterance in which the target sound appears and its position within the utterance.
When creating stimuli for treatment, placing the target sound at the beginning of the utterance may increase the likelihood of a correct production. Placing the target sound at the end of the utterance may increase its level of difficulty for the child, so clinicians may want to do so only when the child has achieved some mastery of the target sound.
The limited effects of utterance length on articulation suggest that traditional articulation therapy, in which utterance length is the primary variable manipulated as treatment progresses, may be inadequate for the treatment of certain sounds. Phonological approaches, in which utterance length is but one variable to be manipulated among many, may be more effective.
The goals of this study were to investigate the effects of utterance length and position on proportion of errors on /ð/. Results demonstrated limited effects of utterance length and relatively strong effect of utterance position, with some caveats. The findings of this study most strongly recommend further investigation into the effects of utterance position on other sounds. Use of language samples in which specific sounds and words are elicited in controlled contexts can more effectively reduce the effects of confounding 30 variables like co-articulation effects within and between words, syntactic and semantic context, and presence or absence of grammatical morphemes in the target words. Further research in this area of articulation would aid clinicians in assessing inconsistent sound errors during spontaneous speech. It would help in increasing efficiency of assessment and therapy by informing the creation of stimuli for assessment and therapy that allow for a gradual, methodical increase in difficulty of articulation.
31
Appendix A
Individual Data on Productions of /ð/ by Utterance Length in Morphemes
Participant Number of Number of Total % of Correct Productions in Number of Productions in Productions Error Productions Error Participant 1 3 morphemes 1 1 2 50 4 morphemes 0 2 2 100 5 morphemes 2 2 4 50 6 morphemes 1 3 4 75 7 morphemes 6 2 8 25 8 morphemes 1 2 3 66.67 Total 11 12 23 52.17 Participant 2 3 morphemes 3 0 3 0 4 morphemes 5 0 5 0 5 morphemes 4 1 5 20 6 morphemes 7 1 8 12.5 7 morphemes 6 1 7 14.29 8 morphemes 3 1 4 25 Total 28 4 32 12.5 Participant 3 3 morphemes 3 4 9 55.56 4 morphemes 4 1 6 83.33 5 morphemes 5 3 8 62.5 6 morphemes 6 1 9 88.89 7 morphemes 7 1 3 66.67 8 morphemes 0 0 0 0 Total 10 25 35 71.43 Participant 4 3 morphemes 0 1 1 100 4 morphemes 3 8 11 72.73 5 morphemes 2 5 7 71.43 6 morphemes 4 9 13 69.23 7 morphemes 2 5 7 71.43 8 morphemes 0 2 2 100 Total 11 30 41 73.17 Participant 5 3 morphemes 2 1 3 33.33 4 morphemes 9 1 10 10 5 morphemes 4 1 5 20 6 morphemes 6 3 9 33.33 7 morphemes 6 2 8 25 8 morphemes 9 2 11 18.18 32
Total 36 10 46 Participant 6 3 morphemes 0 2 2 100 4 morphemes 2 3 5 60 5 morphemes 1 7 8 87.5 6 morphemes 1 3 4 75 7 morphemes 0 1 1 100 8 morphemes 0 3 3 100 Total 4 19 23 82.61 Participant 7 3 morphemes 1 7 8 87.5 4 morphemes 1 6 7 85.71 5 morphemes 2 7 9 77.78 6 morphemes 3 2 5 40 7 morphemes 1 7 8 87.5 8 morphemes 2 6 8 75 Total 10 35 45 77.78 Participant 8 3 morphemes 1 3 4 75 4 morphemes 1 4 5 80 5 morphemes 2 2 4 50 6 morphemes 2 3 5 60 7 morphemes 0 3 3 100 8 morphemes 0 1 1 100 Total 6 16 22 72.73 Participant 9 3 morphemes 6 1 7 14.29 4 morphemes 3 3 6 50 5 morphemes 6 3 9 33.33 6 morphemes 9 4 13 30.77 7 morphemes 8 4 12 33.33 8 morphemes 1 0 1 0 Total 33 15 48 31.25 Participant 10 3 morphemes 2 0 2 0 4 morphemes 5 1 6 16.67 5 morphemes 10 3 13 23.08 6 morphemes 2 2 4 50 7 morphemes 5 1 6 16.67 8 morphemes 2 2 4 50 Total 26 9 35 25.71 Participant 11 3 morphemes 2 5 7 71.43 4 morphemes 6 7 13 53.85 5 morphemes 2 2 4 50 6 morphemes 5 7 12 58.33 33
7 morphemes 2 6 8 75 8 morphemes 3 5 8 62.5 Total 20 32 52 61.54 Participant 12 3 morphemes 0 2 2 100 4 morphemes 3 4 7 57.14 5 morphemes 5 1 6 16.67 6 morphemes 3 1 4 25 7 morphemes 1 4 5 80 8 morphemes 6 2 8 25 Total 18 14 32 43.75 Participant 13 3 morphemes 0 0 0 0 4 morphemes 0 2 2 100 5 morphemes 0 0 0 0 6 morphemes 1 2 3 66.67 7 morphemes 1 2 3 66.67 8 morphemes 1 1 2 50 Total 3 7 10 70 Participant 14 3 morphemes 4 2 6 33.33 4 morphemes 3 1 4 25 5 morphemes 2 5 7 71.43 6 morphemes 2 2 4 50 7 morphemes 3 2 5 40 8 morphemes 0 10 10 100 Total 14 22 36 61.11 Participant 15 3 morphemes 2 0 2 0 4 morphemes 9 0 9 0 5 morphemes 2 3 5 60 6 morphemes 5 4 9 44.44 7 morphemes 1 4 5 80 8 morphemes 5 2 7 28.57 Total 24 13 37 35.14 Participant 16 3 morphemes 4 1 5 20 4 morphemes 3 5 8 62.5 5 morphemes 1 1 2 50 6 morphemes 3 6 9 66.67 7 morphemes 3 2 5 40 8 morphemes 1 1 2 50 Total 15 16 31 51.61 Participant 17 3 morphemes 9 1 10 10 4 morphemes 8 8 50 50 34
5 morphemes 15 18 54.55 54.55 6 morphemes 10 12 54.55 54.55 7 morphemes 6 12 66.67 66.67 8 morphemes 6 8 57.14 57.14 Total 54 59 52.21 52.21 Participant 18 3 morphemes 1 3 4 75 4 morphemes 2 0 2 0 5 morphemes 0 3 3 100 6 morphemes 1 2 3 66.67 7 morphemes 1 3 4 75 8 morphemes 0 0 0 0 Total 5 11 16 68.75 Participant 19 3 morphemes 2 0 2 0 4 morphemes 5 3 8 37.5 5 morphemes 4 6 10 60 6 morphemes 1 2 3 66.67 7 morphemes 5 10 15 66.67 8 morphemes 5 11 16 68.75 Total 22 32 54 59.26 Participant 20 3 morphemes 5 4 9 44.44 4 morphemes 8 12 20 60 5 morphemes 13 8 21 38.1 6 morphemes 14 10 24 41.67 7 morphemes 8 8 16 40 8 morphemes 3 6 9 66.67 Total 51 48 99 48.48
35
Appendix B
Words in which productions of /ð/ occurred and the accuracy of the /ð/ productions
Participant Number of Number of Total % of Productions Correct Productions Number of in Error Productions in Error Productions That’ll 1 0 1 0 They’ll 1 0 1 0 They’re 15 4 19 21.05 Those 13 4 17 23.53 There’s 9 4 13 30.77 They 34 20 54 37.04 Them 20 12 32 37.5 Then 22 21 43 48.84 The 118 114 232 49.14 There 20 21 41 51.12 That 45 54 99 54.54 That’s 14 20 34 58.82 This 74 111 185 60 These 14 26 40 65 Their 1 3 4 75 Than 0 3 3 100
36
Appendix C
Relationship between MLU and % of productions of /ð/ in error
Number of Number of % of Correct Productions Total Productions Participant MLU Productions in Error Productions in Error Participant 1 4.91 11 12 23 52.17 Participant 2 5.38 28 4 32 12.50 Participant 3 4 12 26 35 74.29 Participant 4 5.2 11 30 41 73.17 Participant 5 5.5 36 10 46 21.74 Participant 6 4.42 4 19 23 82.61 Participant 7 3.67 10 35 45 77.78 Participant 8 4.33 6 16 22 72.73 Participant 9 5.42 33 15 48 31.25 Participant 10 4.83 26 9 35 25.71 Participant 11 4.92 20 32 52 61.54 Participant 12 4.91 18 14 32 43.75 Participant 13 3.35 3 7 10 70.00 Participant 14 3.83 14 22 36 61.11 Participant 15 5.83 24 13 37 35.14 Participant 16 3.91 15 16 31 51.61 Participant 17 3.75 54 59 113 52.21 Participant 18 4.5 5 11 16 68.75 Participant 19 4.58 22 32 54 59.26 Participant 20 4.08 51 48 99 48.48
37
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