anderson conture 2000

8/3/2019 Anderson Conture 2000

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J. FLUENCY DISORD. 25 (2000), 283304

2000 Elsevier Science Inc. All rights reserved. 0094-730X/00/$see front matter

655 Avenue of the Americas, New York, NY 10010 PII S0094-730X(00)00089-9

LANGUAGE ABILITIES OFCHILDREN WHO STUTTER:A PRELIMINARY STUDY

JULIE D. ANDERSON and EDWARD G. CONTUREVanderbilt University, Nashville, Tennessee

The purpose of this study was to examine differences between children who do (CWS) andchildren who do not stutter (CWNS) on standardized tests of receptive/expressive language

and receptive vocabulary. Subjects were 16 boys and 4 girls who stutter (mean age 46.80months) and 16 boys and 4 girls who do not stutter (mean age 47.55 months). Each child

was audio recorded during a loosely structured, 30-minute conversation with an adult. Thisconversational interaction was subsequently assessed to provide information pertinent to thechilds frequency and type of speech disfluency. After completion of the adult-child conver-

sational interaction, each child was administered and responded to standardized tests of syn-tactic, semantic, and phonological abilities and development. Results indicated that the dif-

ference between measures of receptive/expressive language and receptive vocabulary issignificantly greater for CWS than CWNS; however, this difference between receptive/ex-

pressive language and receptive vocabulary scores was not significantly correlated with theoverall stuttering frequency of CWS. Findings were taken to suggest that the semantic de-velopment of CWS may lag behind their syntactic development, a possible imbalance

among components of the speech-language systems of CWS that may contribute to the dif-ficulties they have establishing normal speech fluency. Research supported by an NIH grant(DC00523) to Vanderbilt University. 2000 Elsevier Science Inc.

Key Words: Stuttering; Language; Children

Differences in receptive vocabulary between younger (i.e., preschool-age)

children who do (CWS) and do not stutter (CWNS) have often been reported

(Andrews, Craig, Feyer, Hoddinott, Howie, & Neilson, 1983; Bernstein-Rat-

ner, 1997; Bloodstein, 1995). In specific, young CWS, when compared to

young CWNS, have been found to score lower on the Peabody Picture Vocab-

ulary Test (PPVT) (Dunn & Dunn, 1997), a measure of receptive vocabulary

(Meyers & Freeman, 1985; Murray & Reed, 1977; Ryan, 1992; Westby,

1974). Bloodstein (1995) suggests that this early linguistic disadvantage of

Address correspondence to Julie D. Anderson, M.A., CCC-SLP, Vanderbilt Bill Wilkerson Centerfor Otolaryngology and Communication Sciences and Disorders, Department of Hearing and Speech

Sciences, Vanderbilt University Medical Center, 1114 19th Avenue South, Nashville, Tennessee 37212,

U.S.A. e-mail: [email protected]


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284 J.D. ANDERSON and E.G. CONTURE

young CWS may become less apparent as children advance in age, a sugges-

tion that may account for equivocal findings relative to differences in recep-

tive vocabulary between older CWS and CWNS (Perozzi & Kunze, 1969;Williams, Melrose, & Woods, 1969).

If young CWS do exhibit lower scores on receptive vocabulary measures

relative to their scores on other measures of language (e.g., expressive/recep-

tive language),1 one possible implication is that there is an imbalance among

components or aspects of their language system. This notion is consistent with

Perkins, Kent, & Curlees (1991) model that suggests that when one language

skill is below the level of other language components, the production of lan-

guage is then thrown out of balance as different components arrive at a central

language integrator at different times and thus have a mistimed impact on themotor production of speech (Tetnowski, 1998, p. 242). Perhaps such an im-

balance impacts the ability of CWS to appropriately encode and/or retrieve

lexical items and place them in the appropriate position or slot in the associ-

ated syntactic frame (e.g., noun or verb phrase). If CWS do exhibit subtle,

but consistent quantitative and/or qualitative differences between lexical and

syntactic abilities, these differences may be sufficient enough to disrupt, stall,

or freeze the forward flow of speech production, resulting in repairs/correc-

tions that are overtly manifest as hesitations, repetitions, and prolongations.

In general, studies of lexical characteristics of stuttered events have consis-tently found regularities in terms of the distribution and loci of these events

(see Au-Yeung & Howell, 1998; Bernstein-Ratner, 1997; Bloodstein, 1995).

For example, stuttering tends to be more common on content words for older

children and adults (Brown, 1938a, b; Howell, Au-Yeung, & Sackin, 1999);

conversely, in young children, stuttering is more common on function words

(Bernstein, 1981; Bloodstein & Grossman, 1981; Howell et al., 1999). One

explanation of this latter finding, according to Bernstein-Ratner (1997), may

relate to . . . the overriding effect of syntactic encoding on lexical frequency

in childrens speech (p. 107). One alternative explanation (posed by Howellet al.) is that young children who stutter have difficulties retrieving complex

phonological forms (usually within content words) when the form to be re-

trieved is produced in function word context (e.g., see the dog versus see

dog). Whichever of these accounts best explain the loci of stuttering in young

children, current speculation seems to suggest that various aspects of linguis-

tic formulation (e.g., lexical encoding) may contribute to childhood stuttering.

However, despite increased interest in psycholinguistic attempts to account for

instances of stuttering (e.g., Perkins et al., 1991; Postma & Kolk, 1993; Kolk &

1While there are various ways to assess childhood language with 3- to 5-year olds, using

standardized test instruments, such as the TELD-2, a test of expressive/receptive language, and the

PPVT-III, a test of receptive vocabulary, would appear appropriate to preliminarily assess the issues

under concern.


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LANGUAGE ABILITIES OF CHILDREN WHO STUTTER 285

Postma, 1997; Wingate, 1988), there have not been a great deal of empirical in-

vestigations of the lexical abilities of CWS relative to syntactic development

within a psycholinguistic framework. This is rather surprising, given the com-monly reported difference in receptive vocabulary scores between CWS and

CWNS. Although there have been empirical studies of the lexical skills ofadults

who stutter (e.g., Bosshardt, 1993, 1994; Bosshardt, & Fransen, 1996; Prins,

Main, & Wampler, 1997), it is difficult to extrapolate backwards from the skills/

behaviors of adults to those of young children, for as Yairi (1993) suggests, ad-

vanced stuttering is markedly different from the incipient form and because con-

firmed stutterers represent a small minority of people who have ever experienced

the disorder (Andrews & Harris, 1964), continuing attempts to infer its (stutter-

ings) etiology and nature or to prescribe treatment for children who stutter basedon models derived from adult stuttering are indefensible (Conture, 1991; Yairi,

1990) (p. 198).

It would seem, therefore, that further study of the lexical abilities of CWS

might have meaningful implications relative to the circumstances surrounding

childhood stuttering. One reasonable means to begin assessing the lexical abili-

ties of CWS is to compare CWS to CWNS in terms of outcome measures or stan-

dardized scores on tests of receptive/expressive language and similar measures of

receptive vocabulary. While it is recognized that standardized test scores are nei-

ther as dynamic nor as direct a measure of linguistic variables as other, more ex-perimental measures such as speech reaction time, they would appear to be one

logical, first means for discerning whether further empirical study of lexical abil-

ities in relation to syntactic abilities in children who stutter is warranted.

The primary purpose of this preliminary study, therefore, was to determine

whether differences between scores on standardized tests of receptive/expres-

sive language (i.e., TELD-2) and receptive vocabulary (i.e., PPVT-III) were

differentially different between CWS and CWNS. Because it was speculated

that imbalances between lexical and syntactic abilities may contribute to

childhood stuttering, it was predicted that CWS would have a significantlygreater difference between overall measures of language abilities and recep-

tive vocabulary than their peers who do not stutter. If this is the case, then one

might also speculate that these differences would be significantly correlated

with basic measures of stuttering frequency (e.g., total and within-word dis-

fluencies) and most common stuttering disfluency type (e.g., larger differ-

ences associated with greater frequency of stuttering). Therefore, a secondary

purpose of this project was to determine whether there is a significant relation-

ship between the frequency of disfluencies and/or most common disfluency

type and differences in receptive/expressive language and receptive vocabu-lary, as well as in receptive vocabulary and receptive/expressive language

alone. Specifically, the questions were: 1) Do CWS have greater differences

between their receptive/expressive language and receptive vocabulary scores

than do their normally fluent peers? 2) Is there a relationship between differ-


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ences in receptive/expressive language and receptive vocabulary scores and

total frequency of disfluencies for CWS and CWNS? Likewise, is there a rela-

tionship between differences in receptive/expressive language and receptivevocabulary scores and frequency of stuttering for CWS? 3) Do the various de-

pendent measures (e.g., standardized measures of receptive/expressive lan-

guage, receptive vocabulary, and differences between these measures) differ

according to the most common stuttering disfluency type for CWS?

METHOD

Subjects

Subjects were two groups of 20 children (N 40) between the ages of 3;0 and

5;3 (years; months) who do (CWS) (mean age 46.80 month) and do not

stutter (CWNS) stutter (mean age 47.55 months). The CWS were matched

by gender and age ( 3 months) to the CWNS. All subjects were native speak-

ers of American English with no history of neurological, psychological, or in-

tellectual problems per parent report and examiner observation. All subjects

passed a hearing screening test (bilateral pure tone testing at 25 dB SPL from

250 to 4000 Hz and exhibited Type A tympanograms as a result of impedance

audiometry from 800 to 3000 ohms)2

and a general/oral motor functioningscreening test [the Selected Neuromotor Task Battery (SNTB) (Wolk, 1990).]

Children in both the CWS and CWNS groups had no prior treatment for ar-

ticulation, language, or stuttering concerns, and scored at the 20th percentile

or higher on the Goldman Fristoe Test of Articulation (GFTA) (Goldman &

Fristoe, 1986) (Table 1). The average time since parental-reported onset

(TSO) for the CWS was 20.16 months (SD

8.80 months), indicating that

approximately 84% of all CWS had been stuttering for 11 or more months at

the time of testing. All subjects were paid volunteer participants in an ongoing

series of studies concerning the relationship between stuttering and phonology(e.g., Logan & Conture, 1997; Conture, Louko, & Edwards, 1993; Melnick &

Conture, 2000; Yaruss & Conture, 1996).

Criteria for Group Classification

Children who stutter (CWS). A child was assigned to the CWS group

if he/she met the following criteria:

Exhibited three or more within-word disfluencies (WWD) (i.e., sound/syl-

lable repetitions, sound prolongations, broken words) and/or monosyl-

2Four subjects (CWS 3; CWNS 1) who had passedpure tone testing, but had unilateral or

bilateral Type C tympanograms were allowed to participate in the study, because Type C tympanograms

are not typically associated with significant conductive hearing loss.


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Table 1. Subject Characteristics

ID Sex Age TELD PPVT GFTA MLU TD WWD SSI

Children Who StutterS1 M 36 98 88 50 99 31.00 29.00 26S2 M 37 97 34 30 88 19.50 15.87 20S3 M 37 99 92 37 99 36.00 33.00 25S4 M 37 99 70 44 51 11.78 8.75 14S5 F 38 99 21 99 99 16.44 16.44 18S6 M 39 88 19 95 99 24.00 22.00 24S7 M 40 92 42 28 82 17.00 13.00 23S8 F 40 79 86 88 90 15.30 9.30 16S9 F 42 99 87 99 99 10.30 10.30 24

S10 M 44 99 66 43 99 20.00 16.70 34S11 M 45 66 53 48 37 16.70 12.00 23S12 M 48 99 99 99 98 12.30 9.30 22S13 M 49 99 81 59 94 15.00 18.00 18S14 M 50 81 7 23 75 14.00 5.00 16S15 F 51 95 23 57 93 14.47 13.46 21S16 M 52 89 68 43 24 15.20 6.50 20S17 M 59 73 77 42 36 11.30 9.00 14S18 M 59 98 81 34 55 15.00 14.00 25S19 M 63 99 94 70 N/A 23.30 13.30 25S20 M 70 42 25 57 N/A 12.30 6.70 22

Children Who Do Not StutterNS1 M 37 99 68 74 99 1.67 0.42 0NS2 M 38 98 93 81 97 1.68 1.01 6NS3 M 40 97 66 95 87 7.00 2.00 8NS4 M 37 99 73 31 99 1.84 1.17 2NS5 F 41 99 98 94 49 1.33 1.00 6NS6 M 42 85 96 37 99 5.00 1.33 8NS7 M 39 99 63 90 99 2.02 1.01 2NS8 F 42 99 70 84 81 4.00 0.60 8NS9 F 42 96 68 84 99 3.69 2.00 0

NS10 M 44 98 96 80 68 2.30 1.00 6NS11 M 46 99 73 88 97 1.34 0.30 6NS12 M 51 99 99 43 81 4.00 0.70 8NS13 M 46 99 98 63 98 0.70 0.00 0NS14 M 49 99 79 62 99 1.33 0.00 8NS15 F 50 98 79 68 11 1.30 0.67 6NS16 M 54 99 99 85 98 0.67 0.67 6NS17 M 59 98 99 90 62 1.30 0.70 8NS18 M 60 99 91 77 97 5.00 1.00 8NS19 M 63 98 75 99 N/A 5.38 0.67 2

NS20 M 71 68 77 99 N/A 2.67 0.00 0

Note. TELDTest of Early Language Development-2(percentile rank); PPVTPeabody Picture Vocabu-lary Test-III

(percentile rank); GFTA

Goldman-Fristoe Test of Articulation

(percentile rank); MLU

meanlength of utterance (percentile rank); TD

mean frequency of total speech disfluencies (percent); WWD

mean frequency of within-word disfluencies (percent); SSI

Stuttering Severity Instrument-3

.


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labic whole-word repetitions per 100 words of conversational speech3

(Bloodstein, 1995; Conture, 1990) (no child in the CWS group scored lower

than 5% WWD), Received a total overall score of 11 or above (i.e., a severity equivalent

of at least mild) on the Stuttering Severity Instrument-3 (SSI-3)4 (Ri-

ley, 1994) (no child in the CWS group scored below 14 on the SSI; four

were classified as mild, 15 moderate, and one severe), and

Had people in his/her environment who were concerned about his/her

speech fluency and/or believed that he/she was a child that stuttered or at

a very high risk for becoming one.

Children who do not stutter (CWNS). A child was assigned to the CWNSgroup if he/she met the following criteria:

Exhibited two or fewer within-word and/or monosyllabic whole-word

repetitions per 100 words of conversational speech5 (Conture & Kelly,

1991; Zebrowski, 1987) (no child in the CWNS group scored above 2%

WWD),

Received a total overall score of 10 or below (i.e., a severity equivalent

of less than mild) on the SSI-3 (no child in the CWNS group scored

above 8 on the SSI), and

Had no people in his/her environment who were concerned about his/her

speech fluency and/or believed that he/she was a child that stuttered or at

a very high risk for becoming one.

PROCEDURES

Speaking/Testing Conditions

Subjects were tested in their homes6 as part of a screening procedure for a se-

ries of studies assessing the speech and language development of children

who stutter (e.g., Logan & Conture, 1997; Melnick & Conture, 2000; Yaruss

& Conture, 1996). All subjects participated in an informal clinician-child con-

versational interaction to permit the perceptual analysis of speech disfluencies

and analysis of syntactic/morphological development [e.g., mean length of ut-

3For the 20 CWS, mean number of WWD 13.72 (range 5.0033.00).4Data for the computation of the SSI-3 (mean stuttering frequency, mean duration of three longest

stuttering events, and physical concomitants) was obtained from a videotaped session of a 300-word

parent-child interaction in the clinic.5For the 20 CWNS, mean number of WWD 0.81 (range 0.002.00).6One CWS subject was assessed during a stuttering diagnostic evaluation at the Syracuse University

Gebbie Speech-Language-Hearing Clinic.


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terance (MLU) (Brown, 1973)], and all were administered and appropriately

responded to standardized tests of speech and language.

Clinician-child interaction. In the childs home, with the mother and/orfather present, but not participating, a 300-word conversational speech sample

was elicited during a loosely structured clinician-child interaction, lasting ap-

proximately 1530 minutes. The clinician and child were seated next to each

other on the floor or at a small table with the childs favorite toys situated di-

rectly in front of him/her. The clinician and child interacted verbally with each

other while playing with the toys.

Standardized speech-language tests and hearing screening. After

completion of the clinician-child interaction and while still in the home, sub-

jects were administered three standardized speech-language tests: the PeabodyPicture Vocabulary Test-III (PPVT-III) (Dunn & Dunn, 1997),7 a measure of

receptive vocabulary; the Test of Early Language Development-2 (TELD-2)

(Hresko, Reid, & Hamill, 1991),8 a measure of expressive/receptive language

ability; and the Sounds in Words subtest of the Goldman-Fristoe Test of Ar-

ticulation (Goldman & Fristoe, 1986), a measure of speech sound develop-

ment. On a subsequent day, under clinical conditions, where ambient noise

could be minimized, each childs hearing was screened using pure-tone and

impedance audiometry.

Data Collection/Instrumentation

A certified speech-language pathologist and/or a graduate clinician trained in

the assessment of stuttering administered all formal/informal tests and partici-

pated in the clinician-child interaction. All data collection sessions began with

the clinician-child interaction, followed by the administration of aforemen-

tioned standardized tests (PPVT-III, TELD-2, GFTA), and the experimenter-

developed SNTB (Wolk, 1990). All subjects were audiotaped with a Bell &

Howell Model 3191A audio tape recorder during data collection sessions last-

ing approximately 1 to 1 1/2 hours. A pressure-zone microphone was placedwithin 61 cm of each subjects mouth to obtain the child and examiners

acoustic voice signal.

Analysis of Speaking Condition

Stuttering. After obtaining a 300-word conversational speech sample, the

investigator made the following speech disfluency measures for all subjects:

7Eleven subjects had been tested using the Peabody Picture Vocabulary Test-R (PPVT-R) (Dunn &Dunn, 1981) during the early part of the study, as the PPVT-III was not yet available. To achievecomparability of findings, all PPVT-R scores were converted to PPVT-III scores using published

conversion guidelines described in Dunn & Dunn (1997).8The Test of Early Language Development-2 (TELD-2) (Hresko, Reid, & Hamill, 1991) was

selected to measure the expressive/receptive language abilities of CWS and CWNS, because it is one of

the only norm-based tests to examine children below the age of 5 years.


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Mean frequency of all speech disfluencies (within- and between-word

disfluencies) per 100 words, based on the 300-word speech sample.

Mean frequency of within-word disfluencies (sound/syllable repetitions,sound prolongations, broken words) and monosyllabic whole-word repe-

titions per 100 words, based on the 300-word speech sample.

Most common disfluency type (within-word or between-word disfluen-

cies) throughout the 300-word speech sample.

Mean length of utterance (MLU). To provide some independent assess-

ment of the validity of the TELD-2 to assess language skills in young chil-

dren, each childs MLU was measured. MLUs for all subjects were based on

the first 30 or more intelligible utterances obtained during the clinician-childinteraction and calculated in accordance with the morpheme selection rules

described by Brown (1973). MLUs were later converted to percentile ranks

using a z-score formula in attempts to compare MLU more directly to other

standardized scores like the TELD-2 [i.e., z score

(childs observed

MLUpredicted mean MLU for childs chronological age)/predicted MLU

standard deviation]. Predicted means and standard deviations for MLU were

obtained from Miller & Chapman (1979), as cited in Miller (1981).

Analysis of Testing Condition

Age-based percentile ranks were obtained for the PPVT-III and TELD-2, and

age/gender percentile ranks were obtained for the Sounds-in-Words sub-

test of the GFTA using the standard scoring methods described for each test.

Data Analyses

Within- and between-group comparisons. Central tendency (i.e., mean)and dispersion (i.e., standard deviation) of speech disfluency measures (total

and within-word speech disfluencies), standardized speech-language tests

(PPVT-III and TELD-2), and MLU percentile ranks were assessed using a 2

2 mixed analysis of variance (ANOVA), and follow-up t

-tests, where appro-

priate. In specific, the ANOVA was used to make between-group comparisons

and to determine whether there was a statistically significant interaction be-

tween the standardized speech-language tests and subject group (e.g., CWS,

CWNS). Pearsons product moment correlation coefficients were used to de-

termine if a relationship exists between the PPVT-III/TELD-2 differences andspeech disfluency measures for CWS.

Interjudge and intrajudge measurement reliability.

Intrajudge (author)

and interjudge (author versus an independent judge) reliability measures were

obtained for two speech disfluency measuresthe mean frequency of all


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speech disfluencies (within- and between-word disfluencies) and the mean

frequency of within-word disfluencies. Ten subjects from both talker groups

were selected at random. Four utterances per subject, drawn from conversa-

tional speech samples in the childs home,9 consisting of about 38 words per

utterance, were selected randomly. This resulted in 10% of the total data (4 ut-

terances 20 subjects 80 utterances) being used for intrajudge and inter-

judge measurement reliability. Intrajudge reliability was assessed by having

the first author judge each utterance for the mean frequency of total and

within-word speech disfluencies on two separate occasions, separated by a pe-

riod of one-month. Interjudge reliability was assessed by having a doctoral

candidate trained in the assessment of stuttering judge each utterance for the

two speech disfluency measures. Intrajudge and interjudge reliability scores

for total and stuttered speech disfluency measures were assessed across sub-

jects using Sanders (1961) Agreement Index (AI) [AI

Agreements/(Agree-

ments

Disagreements)]. Intrajudge reliability for the mean frequency of to-

tal and stuttered speech disfluencies was .97 and .94, respectively, and

interjudge reliability for the overall mean frequency of total and stuttered

speech disfluencies was .93 and .96, respectively.

RESULTS

Descriptive Information

Figure 1 depicts group means for the CWS and CWNS talker groups on the

three standardized tests (i.e., PPVT-III, TELD-2, and GFTA) and two speech

Figure 1. Mean standardized test, speech disfluency measures, and MLUs for chil-

dren who do (CWS) and do not stutter (CWNS).

9Utterances for two subjects (8 utterances total) were drawn from the audio portion of a videotaped

session of a 300-word parent-child interaction in the clinic, due to technical difficulties with the at-home

recorded audiotapes.


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disfluency measures (total and within-word speech disfluencies). As would be

expected, CWS exhibited significantly greater mean total [t(38) 9.66,p

0.01], as well as within-word [t(38)

8.01, p

0.01] speech disfluenciesthan did CWNS. While Pearsons product-moment correlation coefficients in-

dicated no significant correlation between mean TELD-2 and MLU percentile

ranks for CWNS (r0.120, p .636), modest significant correlations

were present for CWS (r 0.567, p .014) and for both the CWS and

CWNS combined (r 0.387, p .020). The non-significant correlation be-

tween mean TELD-2 and MLU percentile ranks for CWNS may relate to the

fact that, when compared to CWS, CWNS were 50% less variable in their

TELD-2 scores (SD 14.91 and 7.34 for CWS and CWNS, respectively).

It will be recalled that children with clinically significant speech sound ar-ticulation problems were excluded from this study [i.e., children scoring at or

below the 19th percentile on the GFTA (approximately 1.0 standard deviation

or more below the mean), a norm-referenced test of speech sound articula-

tion]. Despite the fact that all subjects, in both talker groups, scored at or

above the 20th percentile on the GFTA, CWNS scored (M 76.20; SD

20.00) significantly higher [t(38) 2.610,p 0.05] than the CWS (M

57.25; SD 25.59). Most importantly, however, for the purposes of this

study, there were no significant correlations between the GFTA and the

studys main dependent measures (i.e., PPVT-III, TELD-2, and mean TELD-2/PPVT-III difference) for CWS, CWNS, and both CWS and CWNS com-

bined (r-values ranged from 0.234 to 0.209). Thus, even though there were

differences in the GFTA between the two talker groups, there was no signifi-

cant relationship between this measure of speech sound articulation and the

dependent measures.

Below are presented inferential statistical analysis of group trends, how-

ever, before doing so, some brief description of individual performance seems

appropriate. Overall, 75% of the 40 children (20 CWS and 20 CWNS) exhib-

ited higher TELD-2 than PPVT-III scores, with more CWS (N 17) thanCWNS (N 13) exhibiting this tendency. Interestingly, more CWNS (N 6)

than CWS (N 1) exhibited equal or comparable (i.e., 3 percentage points)

TELD-2 and PPVT-III scores, with about the same number in each group

(CWNS 1 and CWS 2) exhibiting opposite scoresthat is, PPVT-III

greater than TELD-2 scores. In essence, while the following statistical analy-

sis reports clear group differences in terms of central tendency, this study, like

the study of many other aspects of stuttering (e.g., adaptation, Bloodstein,

1995, p. 328), reports central tendencies that do not always reflect individual

differences, an issue we will return to in Discussion.Research Question 1. Do CWS have greater differences between their

receptive/expressive language and receptive vocabulary scores than do their

normally fluent peers?

Figure 2 shows the mean percentile rank by subject group (e.g., CWS,


11/22


CWNS) for the two standardized speech-language tests (PPVT-III, TELD-2).

A 2 2 mixed analysis of variance (ANOVA) was used to determine whether

a significant group x standardized speech-language test interaction existed.

The ANOVA revealed a significant between-groups effect for subject group,

F (1, 38) 10.18, MSE 415.87, p .01, as well as a significant group x

standardized speech-language test interaction, F (1, 38) 4.76, MSE

255.58,p .05. In other words, when compared to CWNS, CWS scored sig-

nificantly lower on both standardized speech-language tests; however, the dif-ference between PPVT-III and TELD-2 test scores was significantly larger for

CWS than CWNS, findings consistent with the data portrayed in Figure 1.

Research Question 2. Is there a relationship between differences in re-

ceptive/expressive language and receptive vocabulary scores and total fre-

quency of disfluencies for CWS and CWNS? Likewise, is there a relationship

between differences in receptive/expressive language and receptive vocabu-

lary scores and frequency of stuttering for CWS?

A series of Pearsons product-moment correlation coefficients indicated no

significant correlation between the mean TELD-2/PPVT-III difference andfrequency oftotal speech disfluencies for CWS and CWNS (r 0.277,p

0.083) and the mean TELD-2/PPVT-III difference and frequency ofstuttered

disfluencies for CWS (r 0.033,p .891). In other words, differences in re-

ceptive/expressive language and receptive vocabulary scores were indepen-

dent of measures of speech disfluency (i.e., the frequency of total and stut-

tered disfluencies). However, power analyses for these correlational tests

revealed power levels of .40 and .05, respectively ( .05, two-tailed), sug-

gesting that the chance of obtaining a significant correlation was very low,

presumably due to the relatively small sample size.Research Question 3. Do the various dependent measures (e.g., stan-

dardized measures of receptive/expressive language, receptive vocabulary,

and differences between these measures) differ according to the most common

stuttering disfluency type for CWS?

Figure 2. Mean percentile rank by subject group (CWS, CWNS) for the standardizedspeech-language tests (PPVT-III, TELD-2).


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Figures 3 and 4 show, respectively, the mean TELD-2/PPVT-III difference

and the mean PPVT-III and TELD-2 percentile ranks for the most common

stuttering disfluency types (e.g., sound-syllable repetitions (SSR), whole-

word repetitions (WWR), and sound prolongations (SP)) produced by CWS.For the CWS, one-way ANOVAs were used to determine if significant differ-

ences exist between the most common stuttering disfluency types. The ANO-

VAs revealed non-significant differences between the most common stutter-

ing disfluency types for the mean TELD-2/PPVT-III difference, the mean

TELD-2 percentile rank, and the mean PPVT-III percentile rank. However,

Figure 4. Mean PPVT-III and TELD-2 percentile ranks by most common stutteringdisfluency type for CWS.

Figure 3. Mean TELD-2/PPVT-III difference by most common stuttering disfluencytype for CWS.


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findings for the mean PPVT-III percentile rank suggested that there may be

somewhat of a difference [F (2, 16) 2.77, MSE 782.41,p .09].

DISCUSSION

The purpose of the present study was to examine the hypothesis that CWS ex-

hibit a greater difference between overall measures of language abilities and

receptive vocabulary than CWNS, and that this difference will be correlated

with speech disfluency measures (i.e., larger differences associated with

greater frequency of stuttering). This speculation was supported by the finding

that CWS, when compared to CWNS, had a quantifiable greater difference be-tween measures of receptive/expressive language and receptive vocabulary.

This was taken to suggest that there may be an imbalance among components

or aspects of the speech-language systems of CWS, a difference that might be

sufficient enough to temporarily disrupt ongoing speech-language production,

resulting in disruptions in the forward flow of speech-language production

(e.g., stuttering). However, results did not support the related speculation that

this difference would be significantly correlated with the total frequency of

disfluencies for CWS and CWNS, as well as to CWSs stuttering frequency

and most common type of stuttering (e.g., sound-syllable repetitions, whole-word repetitions, and sound prolongations).

While there was no significant difference between the most common stut-

tering disfluency types and the various dependent measures for CWS, visual

inspection of Figures 3 and 4 suggests a tendency for children who exhibit

whole-word repetitions as their most common disfluency type to also exhibit

larger TELD-2/PPVT-III differences and lower PPVT-III percentile ranks.

Conversely, those for whom sound-syllable repetitions were their most com-

mon disfluency type exhibited smaller TELD-2/PPVT-III differences and

higher PPVT-III percentile ranks. It seems reasonable to suggest that the rela-tively small sample size and large variability in speech disfluencies within the

group of CWS may have appreciably reduced chances for finding significant

results. However, a counter argument to this caveat is the fact that Meyers &

Freeman (1985) found a significant negative correlation between the Peabody

Picture Vocabulary Test-R (PPVT-R) (Dunn & Dunn, 1981) and frequency of

total speech disfluencies (r0.42,p .05) with only 24 subjects.

Theoretical Implications

In recent years, there has been increasing speculation that instances of stutter-

ing may be a by-product of disruptions in syntactic, lexical, and/or phonologi-

cal processing skills (Au-Yeung & Howell, 1998; Bernstein-Ratner, 1997;


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Howell, Au-Yeung, & Sackin, 2000; Kolk & Postma, 1997; Wijnen & Boers,

1994). Findings from this study suggest that the lexical abilities of CWS as a

group may be less well developed than their syntactic/morphologic abilities.Perhaps, as suggested by Bernstein-Ratner (1997), young children begin to

experience disruptions in their speech fluency when their vocabularies and

grammatical systems undergo periods of rapid acquisition. In specific, Bern-

stein-Ratner speculates that the coexistence of rapid lexical growth with the

emergence of inflectional morphology and phrase structure expansion may

trigger problems in efficient retrieval of lemmas and their mapping onto lex-

emes (p. 114). She goes on to suggest that if young CWS have difficulty ac-

quiring the properties of the lemma (i.e., syntactic word; see Levelt, Roelofs,

& Meyer, 1999) needed to construct a syntactic plan, then they should exhibita difference between the size of their lexicons and the use of early morpholog-

ical markers or mature syntax, a speculation that seems supported by the ma-

jor finding of this study.

As previously suggested, one interpretation of these findings is that CWS

may exhibit an imbalance between lexical and syntactic/morphologic compo-

nents of their language system. Any such differences may be sufficient, at

least theoretically, to disrupt, stall, or freeze the forward flow of speech pro-

duction, or as some have suggested, resulting in repairs/corrections that are

overtly manifest as hesitations, repetitions, and prolongations. According tothis latter view, repairs/corrections would be seen as responses to errors in lin-

guistic planning (e.g., see Levelt, 1989, pp. 458499). At this point, however,

it is quite unclear whether stuttering relates to errors in linguistic planning

or problems with access or retrieval of linguistic elements (e.g., word

forms) or some complex combination of the two.

Given the possibility, based on current findings, that CWS exhibit an im-

balance between semantic and morphosyntactic abilities, one could posit at

least one processing difficulty leading to speech disfluencies: the syntactic

word (lemma) not being available at the appropriate point in time relative tomorphosyntactic construction. This difficulty, of course, could relate to a fun-

damental inability to select, in a timely manner, the desired syntactic word

from among all available, competing or similar words. Of course, CWNS may

also experience, on occasion, such processing difficulties. However, because

most CWNS, when compared to CWS, probably have a greater degree of

equilibrium or balance among components of their speech-language pro-

duction system, they may be able to better compensate for transient interfac-

ing difficulties between semantic and morphosyntactic encoding.

Conversely, it could be argued that the current observation of imbalancebetween semantic and morphosyntactic abilities has little to do with stuttering,

rather instances of stuttering may result from a slowness in retrieval of com-

plex phonological forms (usually within content words) in function word con-

texts (e.g., Howell, Au-Yeung, & Sackin, 1999). While the latter hypothesis is


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plausible and appears to have some preliminary empirical support, it is diffi-

cult to understand how slowness in retrieval of complex phonological forms

could account for the present finding that CWS scored lower than CWNS on anon-speaking task that merely required the child to point to a picture! What-

ever the case, it is presently unknown, of course, whether stuttering results

from difficulties with the interface of semantic and morphosyntactic encod-

ing, slowness in retrieval of complex phonological forms, or other processing

disturbances. What is known, however, is that more and more researchers,

such as ourselves, Howell and his colleagues, Bernstein-Ratner, and others are

beginning to increasingly speculate that stuttering relates to linguistic pro-

cesses above the level of motor execution, a shift in the zeitgeist from exclu-

sive considerations of stuttering as a motor disturbance to one involving, atleast in part, linguistic processes.

At first glance, the present findings seem inconsistent with those of Wat-

kins, Yairi, & Ambrose (1999), who found that children with persistent and

recovered stuttering have average to above-average expressive language

skills. However, present findings are actually consistent with Watkins et al. in

that we found CWS and their age-, sex-matched CWNS did not significantly

differ in terms of their overall expressive and receptive language skills [in

fact, many CWS scored in the 90th percentile on the norm-based test of ex-

pressive and receptive language we employed (TELD-2)]. The two studies dodiffer, however, methodologically, in that the present study employed a norm-

referenced test of receptive vocabulary, whereas Watkins et al. did not report

doing so. Furthermore, we found that CWS, on average, scored in the average

percentile range (M 60.65; SD 29.83) on a norm-based test of receptive

vocabulary. So, our study, like Watkins et al., did not find that CWS exhibit

lower language scores than CWNS. What we did find, however, that Wat-

kins et al. apparently did not study or report, is that CWS, when compared to

CWNS, exhibit a significantly greater imbalance between receptive vocabu-

lary and expressive/receptive language, an imbalance in ability and/or devel-opment that one might speculate contributes to stuttering. Interestingly, such

imbalances have also been studied with developmentally language-disordered

children, particularly those with frequent speech disfluencies (Hall, 1996;

Hall, Yamashita, & Aram, 1993), with the findings being opposite to ours: ex-

pressive and receptive vocabulary abilities being higher than morphosyntactic

abilities! Obviously, therefore, the nature of the imbalance may not be as im-

portant as the merepresence of an imbalance. Of course, this, like all studies,

must await replication with more and different subjects, as well as different

norm-based instruments.In essence, findings from this study are taken to suggest that young CWS

are somewhat delayed in storing lexical items, a delay that may make it diffi-

cult to quickly and correctly place such items in a syntactic frame. Further-

more, for those CWS who most markedly display these concerns (assuming


16/22


no other linguistic or motor difficulties), the resulting disruptions in fluency

appear to consist primarily of whole-word repetitions.

Other Considerations

Differences in receptive vocabulary between older and younger CWS.

To these writers knowledge, the receptive vocabulary abilities of older ( 8

years) CWS have been examined in only two published studies, with mixed re-

sults. Perozzi and Kunze (1969) found no significant difference between second

and third grade (M 8.5 years) CWS and CWNS (N 40) on the Van Alstyne

Picture Vocabulary Test(VAPVT) (Van Alstyne, 1960). Mean raw scores ob-

tained by the CWS and CWNS on the VAPVT were 56.4 and 55.0, respectively.Conversely, Williams, Melrose, and Woods (1969) examined the receptive vocab-

ulary skills of 100 CWS and 300 CWNS, all sixth graders, using the Vocabulary

subtest of the Iowa Tests of Basic Skills (Lindquist & Hieronymus, 1964), and

found that the CWS performed significantly below the CWNS on this subtest.

In light of these equivocal findings, and in contrast to the present findings, it

seems possible that differences in receptive vocabulary between CWS and CWNS

may become less apparent as children advance in age. At least two possibilities

could account for this developmental change. The first possibility is that dif-

ferences in receptive vocabulary development for CWS, as a group, whencompared to their CWNS peers, are not discernibly related to continuedor

persistentstuttering. In this case, children who recover from stuttering may be

the only CWS who exhibit delayed receptive vocabulary development, with these

delays becoming less apparent along with their stutterings as they grow older.

In other words, only children who recover from stuttering exhibit delays/depres-

sion in receptive vocabulary abilities, while those children who persist never

or minimally exhibit such concerns. Thus, difficulties with semantic storage,

retrieval, and/or encoding are not a major concern for those CWS who persist.

A second possibility is that for many CWS, delays/difficulties in vocabulary/semantic abilities are related to stuttering. However, with maturity and/or edu-

cation, their receptive vocabulary abilities develop to a level similar to that of

their non-stuttering peers. This developmental catch-up in receptive vocab-

ulary is, however, not sufficient for some CWS, particularly those who persist.

For these CWS, learned reactions, possibly exacerbated by temperamental char-

acteristics (e.g., persistent, strong reactions to differences, mistakes, and changes),

maintain their hesitant, repetitive, and prolonged speech productions. Whatever

the possibility, future research may want to consider in greater detail the influ-

ence of chronological age on the relationship between speech, language, andrelated abilities and speech (dis)fluency in CWS.

Possible relationship of expressive vocabulary to the speech fluency of

CWS. It is also interesting to consider the extent to which delays and/or dif-

ficulties in expressive vocabulary abilities may relate to the speech fluency of


17/22


CWS. One normed-based measure of expressive vocabulary in young children

below the age of 5 years is the Expressive Vocabulary Test (EVT) (Williams,

1997). Williams (1997) states that the EVT and PPVT-III are similar in thatthey both measure vocabulary knowledge, but they differ in that the EVT also

measures word retrieval, since the examinee must not only know a word, but

also retrieve it from memory. This interpretation is supported, according to

Williams (1997), by the fact that there is a high correlation between the EVT

and PPVT-III (Forms A and B) (rvalues ranged from .62 to .82,p .05 for

children aged 2;6 to 6;0), suggesting that . . . both tests are measuring vocab-

ulary knowledge, and that EVT is also measuring something uniqueword

retrieval (p. 70). Thus, while still an empirical question, one would expect,

given the close correlation of the PPVT-III and EVT, that similar findings tothose of the present study would result if the EVT was substituted for the

PPVT-III.

Caveats

One should, however, be cautious when interpreting the present findings. This

is due to the fact that 1) the sample size was relatively small, 2) the linguistic

abilities of CWS/CWNS were indirectly measured via standardized testscores, rather than directly by experimental measures (e.g., reaction time), 3)

the standardized language tests may overlap somewhat in measurement, and

4) these group findings may not account for individual and/or subgroup

trends. First, a relatively small sample size and large variability in speech dis-

fluencies within the CWS talker group limited statistical power, which likely

influenced the inferential statistical analyses of the data. However, the seem-

ingly adequate representativeness of the subjects, care with which subjects

were excluded/included, etc. would seem to lend these findings, although pre-

liminary, a reasonable degree of credence. Second, the use of outcome mea-sures (i.e., standardized test scores) to assess the lexical and syntactic abilities

of CWS is clearly not as straightforward a measure of linguistic processing as

a more dynamic measure like the time taken to access words or speech reac-

tion time. Third, it is nearly impossible to administer (in)formal tests of recep-

tive/expressive language and receptive vocabulary where there is not some de-

gree of correlation. This is certainly true for this study, where a moderate,

significant correlation was found between the TELD-2 and PPVT-III (r

0.379,p .02). However, despite this relationship, differences between these

tests were found between the two talker groups, suggesting that at the veryleast, the two talker groups are responding differently to these two measures

of speech and language behavior. In other words, if results on these two tests

were always correlated, one would not expect to find significant differences

between these tests for the two talker groups.


18/22


Fourth, informal assessment of the data indicate that some CWS in this

study actually exhibited smaller TELD-2/PPVT-III differences than their gen-

der-, age-matched peers who do not stutter, suggesting that there may be asubgroup of CWS who exhibit disparities in semantic and syntactic/morpho-

logic abilities. However, the non-homogenous nature of individuals who stut-

ter, although long recognized, has not dissuaded researchers from making

generalized comments about the nature of stuttering. For example, the adapta-

tion effect, since it first appeared in the stuttering literature 60 years ago (e.g.,

Johnson & Knott, 1937), has been commonly viewed as a phenomena associ-

ated with stuttering, even though individuals who stutter . . . differ widely in

the extent to which they adapt; many do not appear to show any adaptation at

all, and some may show increased stuttering with repeated readings (Blood-stein, 1995, p. 328). In essence, while findings in this study suggest that the

linguistic abilities of CWS, as a group, differ from a group of their normally-

fluent peers, the notion of a subgroup of CWS exhibiting disparities in their

lexical and syntactic/morphologic abilities may warrant consideration in fu-

ture investigations.

Conclusion

In summary, based on standardized, norm-referenced tests, a disparity appearsto exist between the lexical and syntactic abilities of young CWS, when com-

pared to their gender-, age-matched peers. It is tempting to speculate that such

a disparity may contribute to the frequent hesitations, prolongations, or repeti-

tions that characterize the speech disfluencies (e.g., stuttering) of CWS. If this

is true, and CWS do exhibit subtle imbalances among components of their

language systems, such an imbalance may be sufficient enough to disrupt or

freeze the forward flow of speech production, resulting in repairs/correc-

tions that are overtly manifest as hesitations, repetitions, and prolongations.

Indeed, our preliminary results suggest that future studies of the lexical andsyntactic abilities of young CWS using experimental measures are warranted.

In specific, it would seem most productive to employ processing measures

(e.g., reaction time) to more directly determine whether disparities or imbal-

ances exist between lexical and syntactic abilities. Hopefully, results of this

study will motivate continued research into the lexical and syntactic process-

ing skills of CWS, since this appears to be a most promising line of investiga-

tion, and one that may eventually lead to improved clinical assessment and

treatment strategies for young CWS.

This research was supported in part by an NIH grant (DC00523) to VanderbiltUniversity. The authors would like to thank Drs. Robert T. Wertz and WandaG. Webb for their thoughtful and insightful reviews of earlier versions of this


19/22


paper. The authors would also like to thank Dr. Daniel Ashmead for his adviceregarding statistical procedures and Mark Pellowski for his help with inter-judge measurement reliability. The authors are also grateful to the parents andchildren who participated in this study.

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