Disfluency patterns and phonological skills near stuttering onset

Journal of Communication Disorders 45 (2012) 426–438

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Journal of Communication Disorders

Disfluency patterns and phonological skills near stuttering onset§ Brent Andrew Gregg a,*, Ehud Yairi b a b

University of Central Arkansas, Conway, AR, United States University of Illinois, Urbana-Champaign, IL, United States

A R T I C L E I N F O

A B S T R A C T

Article history: Received 27 October 2011 Received in revised form 31 July 2012 Accepted 10 August 2012 Available online 20 August 2012

There is a substantial amount of literature reporting the incidence of phonological difficulties to be higher for children who stutter when compared to normally fluent children, suggesting a link between stuttering and phonology. In view of this, the purpose of the investigation was to determine whether, among children who stutter, there are relationships between phonological skills and the initial characteristics of stuttering. That is, close to the onset of stuttering, there are differences in specific stuttering patterns between children who exhibit minimal and moderate phonological deviations in terms of frequency of stuttering and length of stuttering events? Twenty-nine preschool children near the onset of stuttering, ranging in age from 29 to 49 months, with a mean of 39.17 months, were divided into two groups based on the level of phonological ability: minimal phonological deviations and moderate phonological deviations. The children’s level of stuttering-like disfluencies was examined. Results revealed no statistically significant differences in the stuttering characteristics of the two groups near onset, calling into the question the nature of the stuttering–phonology link. Learning outcomes: The reader will be able to describe the relation between phonological skills and the initial characteristics of stuttering. More specifically, following the completion of this manuscript, the reader should recognize whether or not, close to the onset of stuttering, there are differences in frequency of stuttering and length of stuttering moments between children who exhibit minimal and moderate phonological deviations. ß 2012 Elsevier Inc. All rights reserved.

Keywords: Stuttering Disfluency Phonological deviations

1. Introduction The notion that stuttering is linked to speech sound production has been around for many years. In one of the early pertinent studies, Johnson and Brown (1935) analyzed more than 300,000 words in the speech of 32 adults who stuttered. Looking at the distribution of stuttering, they found that the most frequently stuttered speech sounds were /z, l, j, t, and g/. Additionally, they reported that not only individual sounds, but also the two main classes of sounds differed in relation to stuttering. Specifically, stuttering occurred significantly more often on consonants than on vowels, a finding Brown confirmed in 1938. Several other early studies also addressed this issue. Hahn (1942) reported that the specific sounds /g, d, th, l, and ch/ were most likely to be stuttered by adults; he also affirmed Brown’s conclusion regarding the consonant/vowel differences in

§ This research was supported by grant number R01-DC00459 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health; Principal Investigator, Ehud Yairi. * Corresponding author at: University of Central Arkansas, Department of Communication Sciences and Disorders, 201 Donaghey Avenue, UCA Box 4985, Conway, AR 72035-0001, United States. Tel.: +1 501 852 2823; fax: +1 501 450 5474. E-mail address: [email protected] (B.A. Gregg).

0021-9924/$ – see front matter ß 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcomdis.2012.08.001

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relation to the distribution of stuttering. Fairbanks (1937) pursued this line employing different objectives and methodology. Using correlation techniques, he showed that the frequency of stuttering on the different speech sounds (reported by Johnson & Brown, 1935) was positively related to the difficulties of sounds according to developmental data for 2-year old children, as well as with the fundamental pitch of vowels. Stuttering frequency, however, was inversely related to the intensity and duration of sounds and unrelated to sound difficulties for 6-year olds as well as to the frequency of occurrence of sounds. The idea of stuttering–phonology links also was incorporated into the theoretical arena. Fairbanks, in the aforementioned 1937 publication, proposed that the occurrence of stuttering is determined by physiological factors involved in sound production, stating that, ‘‘All of the measures which are related to the variable under investigation appear to be characterized by systematic variations in physiological difficulties, and it is concluded that the latter may be a partial determinant of the spasm distributed over the various sounds’’ (p. 69). Some 60 years later, the covert repair hypothesis (Kolk & Postma, 1997; Postma & Kolk, 1990, 1993), shifted the focus from peripheral to the role of central speech sounds planning and the system’s attempts to correct detected upcoming phonological errors that result in disfluent events. People who stutter have more deficits in their phonetic plans and, therefore, more frequent error corrections resulting in breakdowns of fluent speech. The strongest motivating force for research into these possible links, however, has been the observation of the overlap between the most common period of stuttering onset which is between 18 and 42 months of age (Yairi & Ambrose, 2005), with the period when a child’s development is advancing very rapidly in almost every capacity, including language and phonological skills (Bernstein Ratner, 1997; Yairi, 1983). The associations and co-influences among the developing speech and language domains make it logical to assume that any interference in one aspect could have multiple effects (Watkins & Yairi, 1997). This co-occurrence of developmental processes has given rise to the hypothesis that when difficulties with fluency co-occur with phonological difficulties, the two domains share common etiologies or that the presence of one facilitates the manifestation of the other (Paden, Ambrose, & Yairi, 2002). Hence, unlike the early research cited above (e.g., Hahn, 1942), considerable activity has been devoted during the past few decades to researching a basic proposition of the supposed link: that stuttering does tends to be associated with articulation or phonological delay. This is evident in a body of literature indicating that the percentage of children who stutter and who also exhibit disordered phonology is higher than that among normally fluent children. An early contribution is seen in Schindler (1956) report, showing that 126 school-age children who stuttered not only exhibited more articulation errors than 250 children who did not stutter, but also that the frequency of each type of misarticulation was higher. Three later large studies had a particular strong impact. First, Blood and Seider (1981) surveyed approximately 350 speech-language pathologists who reported 1060 school-aged children who stuttered. Of these, 16% also had articulation disorders. Second, Arndt and Healey (2001) surveyed 241 clinicians who identified 467 children who stutter. Of these, 28% had phonological disorders (14% had only phonological disorders and 14% had both phonological and language disorders). Third, Blood, Ridenour, and Qualls (2003) surveyed 1184 clinicians who identified 2628 children who stuttered. In this group, nearly 34% had concomitant articulation disorders and 13% had concomitant phonological disorders. Other investigators employing smaller samples of varying ages and setting also reported that the percentage of children who stutter simultaneously exhibit disordered phonology was higher than normally fluent children or, in the absence of a control group, considerably higher than expected in the general population of children (Andrews & Harris, 1964; Darley, 1955; Louko, Edwards, & Conture, 1990; Riley & Riley, 1979; St. Louis & Hinzman, 1988; Thompson, 1983; Van Riper, 1992; Williams & Silverman, 1968; Wolk, Edwards, & Conture, 1993; Yaruss, LaSalle, & Conture, 1998). Reviewing the literature, Wolk et al. (1993) concluded that, on average, 30–40% of children who stutter also exhibit disordered articulation or phonology. Nippold (1990, 2001), however, raised valid concerns about the methodology and findings of many of these studies. One of the most compelling questions concerning a possible stuttering–phonology connection is the degree to which the two domains (fluency and phonological skills) are affected. Indeed, research into the stuttering–phonology link also has included investigations into: (a) the correlation between the frequency of disfluencies and the number of phonological errors (Louko et al., 1990; Ryan, 1992, 2001; Yaruss & Conture, 1996); (b) the stuttering behavior of children with normal and disordered phonology (Wolk et al., 1993; Yaruss et al., 1998); (c) the phonological behaviors of children who stutter and normally fluent children (Wolk et al., 1993); (d) phonological complexity/difficulty (e.g., syllable shape and length; location in utterance) and stuttering (Howell & AuYeung, 1995; Throneburg, Yairi, & Paden, 1994); and (e) the relation between the development course of stuttering and phonological skills (Paden & Yairi, 1996; Paden, Yairi, & Ambrose, 1999; Ryan, 2001; Yairi, Ambrose, Paden, & Throneburg, 1996). Among the previous investigations, the Wolk et al. (1993) and Yaruss and Conture (1996) studies are the primary ones that examined the stuttering behavior of children with normal and disordered phonology and the phonological behaviors of children who stutter and normally fluent children. The first team studied 21 boys, ages 4:2 to 5:11, equally divided amongst three groups: (a) stuttering with normal phonology, (b) stuttering with disordered phonology, and (c) normal fluency with disordered phonology. Concomitant phonological disorders were defined as at least two age-inappropriate phonological processes or one or more processes that are not typical of normal development. Their findings indicated that the phonological skills of the stuttering/disordered phonology group and the normally fluent/disordered phonology group were more similar than different as the frequency of occurrence of the phonological processes did not differ significantly. There were no differences on a stuttering severity index between children with disordered phonology and children with normal phonology. Interestingly, though, the children who stuttered and exhibited disordered phonology produced significantly more sound prolongations than the children who stuttered but did not exhibit disordered phonology.

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Yaruss and Conture (1996) included 18 children, ages 3–6, with a history of stuttering of up to three years and a mean of almost two years. One group exhibited stuttering and normal phonological abilities, while a matched control group evidenced stuttering and disordered phonology, using Wolk et al.’s (1993) criteria. No group differences were found in the frequency or duration of disfluencies in conversational speech. Similarly, the correlation between the number of phonological errors and the number of within-word disfluencies was not statistically significant. One weakness of past investigations is that most studied older (school-age) children who had been stuttering for several years, not young children near the onset of stuttering. Consequently, they overlooked basic epidemiological factors regarding the disorder. School-age children represent a small minority, perhaps 20%, of all children who begin stuttering. The other 80% appear to have recovered naturally (e.g., Andrews and Harris, 1964; Mansson, 2000). Furthermore, in addition to some conflicting findings, methodological issues, such as using only boys (Wolk et al., 1993; Yaruss & Conture, 1996), a wide age range from 3 to 6 years and long post-onset intervals of up to 3 years (Yaruss & Conture, 1996), using children of nearly 6 years of age (Wolk et al., 1993), also suggesting long post-onset intervals, or not specifying post onset interval (Ryan, 2001), all give rise to concerns that information reported does not reflect the nature of the two disorders near onset, for it is logical to expect changes in one or both of the domains as the child ages. The length of the stuttering history (post-onset interval) is critical, because both phonological skills and stuttering change as a function of time. As children grow older, their stuttering may increase, decline, or completely remit. Typically, their phonology improves. In short, the co-occurrence of stuttering and phonological disorders has not been sufficiently assessed during the critical period near onset, when a large number of very young children who would soon recover are still available (Ryan, 2001; Yairi, Ambrose, & Niermann, 1993). A delay of even several months would exclude a large percentage of children already recovered from stuttering or who had outgrown early phonological deficiencies. The use of only boys in the Yaruss and Conture (1996) and Wolk et al. (1993) is of concern because the actual male to female ratio near stuttering onset is 2:1 or even smaller (Mansson, 2000), increasing with age to 4:1 or 5:1 (Bloodstein, 1995; Craig, Hancock, Tran, Craig, & Peters, 2002). The increased ratio is at least partially due to a higher recovery rate for females (Bloodstein, 1995; Yairi & Ambrose, 1999a, 1999b). The gender ratio also is a factor in phonological development. At young ages, males are more prone than females to exhibit phonological deficits and their phonological skills progress more slowly as well (Smit & Hand, 1997). Therefore, a sample consisting of all, or unusually high percentage of, boys may incorrectly evidence a higher incidence of phonological difficulties than a sample of a more realistic gender distribution (Yairi, 1999). Thus, one can assume with a high degree of certainty that the investigators who reported data for school-age children or younger children far past stuttering onset, or employed only boys, were in no position to observe and report on the majority of children who exhibit early stuttering. It is likely that past findings reflect, at least partially, a subset of children who were following the path of persistent stuttering, and such samples are more likely to yield higher percentages of children with phonological disorders. The need to consider these factors was demonstrated in a series of publications reporting longitudinal studies concerning the phonological skills of preschool children close to stuttering onset. Paden and Yairi (1996), and Yairi et al. (1996) reported early data indicating that children whose stuttering would persist initially performed more poorly on phonological measures than children who would recover from stuttering. Follow-up studies Paden et al. (1999, 2002) expanded these findings showing that, with time, the children whose stuttering would persist, as a group, gradually had improved to the point that at the two-year follow-up visit, the phonological performance of the two groups was similar. In a previous study, Gregg and Yairi (2007) employed four small groups, each of 7 preschool children, identified soon after stuttering onset. Two groups were comprised based on two pre-selected levels of total number of stuttering-like disfluency (SLD). One group exhibited severe stuttering whereas the second had mild stuttering. The other two groups were formed based two pre-selected levels of phonological skills as determined by test performance. One had mild phonological deviations while the second one had moderate phonological deviations. The objectives were to compare (a) the level of phonological skills of the two groups with different stuttering severity, and (b) the level of stuttering severity in the two groups with different levels of phonological skills. We found that, close to the onset of stuttering, there was little effect of the stuttering severity on phonological skills or of level of phonological skills on the level of stuttering severity. The present study focuses only on children who stuttered selected based on their phonological skills to pursue the next question in this line of inquiry: whether or not there are relationships between phonological skills near the onset of stuttering and several quantifiable characteristics of stuttered speech, that is, specific disfluency types and the length of disfluencies. Hence, only two, but significantly larger, groups based on pre-selected phonological skill were employed. We also revisit the question of whether the level of phonological skills is related to the overall stuttering severity. If there is some validity to the proposed co-occurrence between the two disorders, this line of inquiry may reveal more specific elements that may underlie the relationship, especially because such diverse disfluency types as sound repetitions and sound elongations, involve rather different motor dynamics (e.g., Conture, Brewer, & McCall, 1974). 2. Method 2.1. Participants The 29 participants were selected from a larger pool of children who stuttered who took part in the Stuttering Research Program at the University of Illinois. At the initial visit, they ranged in age from 29 to 49 months, with a mean of 39.17

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months. The lower age range than that reported in previous investigations was deemed necessary to obtain a sample of children more likely to exhibit phonological problems. To be included, somewhat stricter criteria than those employed in the larger investigation of the Illinois Stuttering Research Program (Yairi & Ambrose, 1999a, 1999b) were imposed: 1. Parental diagnosis: One parent, or both parents when available, regarded the child as exhibiting stuttering. 2. Speech pathologist diagnosis: Two senior investigators and certified speech-language pathologists independently diagnosed the child as exhibiting stuttering. 3. Severity rating (perceptual): The stuttering severity must have been rated at least 3 on an 8-point scale (0 = normal speech; 1 = borderline; 2 = mild; 3–4 = moderate; 7 = very severe stuttering). Ratings were made by the two speechlanguage pathologists and one parent. 4. Number of disfluencies: The child must have produced a minimum of 3 stuttering-like disfluencies (SLD): part-word repetition, single-syllable word repetition, and disrhythmic phonation (sound prolongation and blocks) per 100 syllables produced (based on objective counts). 5. Post-onset interval: The parents must have reported the onset of stuttering to occur no more than 6 months prior to the initial evaluation. 6. Health history: Negative history of neurological involvement. Given that one of our aims was to examine the dynamics of the children’s stuttering, the stuttering severity level was selected to increase the chances that a significant number of disfluencies would be observed during the conversational speech samples. 2.2. Measures and participant selection 2.2.1. Phonology The children’s initial level of phonological ability was evaluated through the Assessment of Phonological Processes-Revised (APP-R) (Hodson, 1986) by eliciting production of 50 single syllable and multisyllable words. It requires children to attempt phonemes in prevocalic and postvocalic positions where they usually occur in American English, focusing on ten basic phonological patterns typically acquired during the age span of the participants and the ones most essential for communication (Paden et al., 2002). All children targeted the same 50 words, and each was required to attempt a phoneme the same number of times (Hodson, 1986). Although the APP-R is based on single-word utterances, Garrett and Moran (1992) compared three phonological measures: phonological deviancy scores (PDS) from the APP-R, percent consonants correct (PCC) from conversational speech, and listener severity ratings for 20 children. Their results indicated that the measures were highly inter-correlated, and the authors concluded that the PCC and PDS are both accurate indicators of severity. Accurate transcription of the children’s word productions at the level required for appropriate scoring was considered essential. In addition to the administrator of the APP-R, who transcribed the children’s responses live, two other team members, including the first author, skilled in phonetic transcription, independently transcribed the children’s responses from audiotape. The three transcriptions for each child were compared and, in instances where they differed, the version upon which two of the three transcribers agreed was used for analysis. Reaching such consensus has been used for many years by a number of investigators (e.g., Compton, 1970; Shriberg, Kwiatkowski, & Hoffman, 1984). Following test instructions, and after transcription of all 50 words, the number of times a targeted pattern was not produced was tallied and divided by the total opportunities for that pattern’s occurrence, yielding a child’s percentage of error on each of the 10 phonological patterns assessed. The mean of all pattern percentages was calculated, resulting in the child’s mean percentage of phonological error score. Because these are error scores, the higher number, the poorer is the phonological performance. Equal scores for groups that are quite different in age, however, do not indicate equal phonological achievement (Hodson, 1986; Paden et al., 1999). Furthermore, as a child grows older, phonological skills should improve and fewer errors be observed. The APP-R specifies that if the child is over 3 years-old, 5 points may be added to the mean percentage of phonological error score for each additional year. These points are intended to weight any deficiency at the ages when most of the phonological abilities are expected. Because phonological development typically is very rapid during the age range of the participants in the current investigation, a more precise age weighting was employed by adding .417 points for each month of a child’s age past (or subtracted if younger than) age 3 years (Paden et al., 1999). This was designated as the child’s Age-Weighted Error Score. According to the APP-R, severity interval categories are derived from the phonological deviancy scores as follows: 0–19% = Mild; 20–39% = Moderate; 40–60% = Severe. For our purposes, a child was regarded as having moderate phonological deviations if he/she received a mean percentage of phonological error score of 39% or more; he/she was regarded as exhibiting minimal phonological deviations if the mean error score was lower than 20%. The differences, between the two phonological classifications sufficiently prevented potential overlap, and clearly separated the groups. 2.2.2. Stuttering In accordance with our criteria, a clinician’s severity rating scale was employed to verify that the participants exhibited above mild stuttering severity; that is, a rating of 3 or higher on the 8-point (0–7) scale described above. The clinician’s

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severity ratings were derived from overall impressions of the child’s speech throughout the assessment. The scale (see Yairi & Ambrose, 1999a) is based on other published scales (Darley & Spriesterbach, 1978; Riley, 1981) and is composed of four components: number of SLD, duration or length of disfluency, tension, and accessory characteristics. The first three are rated from 0 to 6, and their mean is then calculated. On this scale, 0 is described as normally fluent speech, 1 as ‘‘borderline,’’ and 6 as ‘‘severe stuttering.’’ Accessory characteristics are rated from 0 to 1, and this number was added to the mean of the first three items. Thus, a maximum score of 7 (‘‘very severe’’ stuttering) could be obtained if frequency, duration, and tension were rated as 6 and accessory characteristics as 1. As mentioned, severity was judged by two speech-language clinicians independently. Ratings that differ by up to half a point were set at the higher of the two estimates. In rare cases where greater differences occurred, the videotaped sample was reviewed to obtain a mutually agreed-upon rating. 3. Participant groups The 29 children were divided into two groups, one of 15 and one of 14 children. An attempt was made to have the children age- and gender-matched, maintaining a gender ratio representative of the population under investigation. Hence, a maleto-female ratio close to 2:1 was established. Each group was defined according to the level of the children’s phonological ability. Scores on the Assessment of Phonological Processes-Revised (APP-R) (Hodson, 1986), the age-weighted mean percentage of phonological error scores, were used to assign children to the groups. Additionally, as indicated above, every child must have been rated at least a 3 or higher on the stuttering severity rating scale, indicating above mild severity. 3.1. Group I: stuttering and moderate phonological deviations The group was composed of 14 children, 10 boys and 4 girls, ranging in age from 29 to 49 months (M = 39.2) at the initial visit. They exhibited moderate phonological deviations, each having achieved a mean percentage of error on the APP-R of 39% or greater. Table 1 features individual information for the children in this group. 3.2. Group II: stuttering and minimal phonological deviations The group consisted of 15 children, 10 boys and 5 girls, ranging in age from 31 to 48 months (M = 39.1) at the initial visit. They exhibited minimal phonological deviations, each having achieved a mean percentage of phonological error on the APPR of lower than 20%. Table 2 features individual information for the children in this group. 4. Procedures 4.1. Speech samples A conversational speech of approximately 1000 words was obtained from each child at the initial visit. The conversations between the child and one parent took place in a sound-treated room and were simultaneously audio- and video-recorded. Each child’s utterances were listened to and orthographically transcribed and screened for disfluencies. Unintelligible utterances were deleted. The five staff members of the project also identified and classified disfluencies and counted the number of syllables in the speech sample. All listeners have had extensive experience with the task. The speech sample Table 1 Individual data, means, and standard deviations for the stuttering and moderate phonological deviations group, including age, gender, severity rating, and initial APP-R score. Subject

Age (months)

Gender

APP-R

Severity rating

P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14

49 48 38 33 47 37 48 29 35 47 36 36 30 36

M F M F M F M F M M M M M M

39.02 39.49 40.04 40.18 43.27 43.61 43.67 43.89 44.75 44.86 45.25 45.29 49.11 61.47

4.50 3.83 3.17 4.92 6.06 5.16 6.25 4.37 3.16 3.00 3.42 3.67 3.00 3.50

Mean SD

39.2 7.09

44.56 5.59

4.14 1.09

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Table 2 Individual data, means, and standard deviations for the stuttering and minimal phonological deviations group, including age, gender, severity rating, and initial APP-R score. Subject

Age (months)

Gender

APP-R

Severity rating

G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15

38 45 48 32 36 42 42 31 39 48 41 41 31 34 39

M M F M M M M F M F M M F F M

4.77 5.38 7.55 7.70 8.06 9.43 11.43 12.82 12.92 13.43 14.11 14.79 17.78 18.99 19.39

4.29 4.83 5.50 5.79 3.75 5.08 4.50 5.58 3.00 6.16 3.58 5.50 4.83 4.50 4.33

Mean SD

39.1 5.57

11.90 4.70

4.75 0.88

recordings were played and replayed multiple times until the listener was satisfied that each instance of disfluency had been correctly identified and classified in the appropriate category. The Systematic Analysis of Language Transcripts (SALT; Miller & Chapman, 1996) program was used for transcript and disfluency entry. 4.2. Disfluency analysis All perceived stuttering-like disfluencies (SLD) were marked on the transcripts with corresponding symbols, including instances when more than one disfluency occurred in the same syllable (e.g., repetition followed by prolongation). The speech samples were analyzed using a system of six disfluency categories (Yairi & Ambrose, 1992) as follows: (a) part-word repetition; (b) single-syllable word repetition; (c) disrhythmic phonation (blocks and sound prolongation); (d) multisyllabic word or phrase repetition; (e) interjection; (f) revision/incomplete phrase. Of these, only the first three categories are considered SLD and were used in this investigation. The numbers of each the three types of SLD and the total number of SLD and repetition units (defined below) in the entire sample then were counted for each subject using the SALT (Miller & Chapman, 1996) program. Because of the differences in speech sample length, these numbers were converted to reflect the frequency of disfluencies per 100 syllables. A syllablebased metric was used because it more accurately reflects the quantity of speech affected by disfluency (Yairi, 1997). Furthermore, it should be noted that frequency per 100 syllables is not the same as percent of syllables disfluent because there can be more than one disfluency per syllable. 4.2.1. Repetition units Previous investigations have shown that reliable measures of the number of repeated units per repetition event can be made from tape-recorded speech sample (Ambrose & Yairi, 1995; Johnson, 1959; Yairi & Lewis, 1984; Zebrowski, 1991). Following Johnson (1959) and Yairi and Lewis (1984), a repetition unit (RU) was defined as an extra production of a segment. An example of one unit would be ‘‘b-but’’ or ‘‘and-and’’, etc. An example of two units would be ‘‘b-b-but’’ or ‘‘and-and-and’’, etc. For each child in the two groups, the mean number of RU for every instance of single-syllable and part-word repetition was calculated. Each transcript was used to calculate the mean number of repetition units, or extra iterations, for all instances of part-word and monosyllabic word repetition. 5. Reliability Reliability estimates for disfluency data were derived by dividing the number of agreements for type and location of SLD by the number of agreements plus disagreements (Sander, 1961). The formula for this estimate is as follows: Total agreements Total agreements þ disagreements Point-by-point reliability values above .80 are considered good, whereas reliability of .90 is considered high (Cordes & Ingham, 1994). Interjudge reliability for the disfluency identification was calculated between the first author and another very experienced listener (N. Ambrose) who made the final judgment of disfluency in previous published studies (e.g., Yairi & Ambrose, 1999a), using speech samples of the same children. In those studies, reliability estimates yielded an interjudge

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agreement coefficient of .86 for SLD. In the present study, to verify accuracy of previous reports concerning identification and classification of stuttering, and to provide additional precision, the investigator re-listened and re-checked the original SLD markings for 40% of the speech samples used in the study. The comparisons yielded an average of .87 point-by-point interjudge agreement coefficient. With regard to interjudge reliability for repetition units, comparisons produced an average .88 point-by-point agreement.

6. Results 6.1. Stuttering severity Visual inspection of Tables 1 and 2 reveals no apparent relationship between individual members’ phonological scores and their rated severity of stuttering. A Pearson correlation between the two scores was calculated. Results revealed no statistically significant correlations: minimal phonological deviations/stuttering, r = .094 (p = .739); moderate phonological deviations/stuttering, r = .279 (p = .335). 6.2. Stuttering frequency near onset Individual and group means for each of the three SLD types and for the total SLD are presented for each of the two phonology-based groups. Data for the moderate phonological deviation group are shown in Table 3. The total SLD per 100 syllables revealed considerable individual variability ranging from 4.04 to 24.47. Visual inspection, however, reveals no apparent relationship between individual phonological abilities and the total SLD scores. Indeed, a Pearson analysis revealed no statistically significant correlation between the two sets of data (r = .146; p = .604). For part-word repetitions, a range from 1.38 to 9.55 was exhibited. Single-syllable word repetitions ranged from 0.54 to 10.70, and disrhythmic phonations from 0.09 to 7.67. It should be noted that 8 children exhibited moderate to severe stuttering; that is, more than 10 SLD per 100 syllables. The remaining children had either mild (below 5) or mild-tomoderate (6–8) SLD levels. Data for the minimal phonological deviations are presented in Table 4. Here too the total SLD per 100 syllables revealed considerable variability, ranging from 4.79 to 26.83. The span of 22.04 points from the lowest to the highest total SLD is only 1.61 points larger than that of the moderate deviations group. Here too, visual inspection reveals no apparent relationship between individual phonological abilities and the total SLD scores. A Pearson correlation between the two sets of scores was calculated, and no statistically significant correlation was found (r = .276; p = .339). The individual instances of part-word repetitions, however, revealed a span of 16.3 points, almost twice as large as that of the moderate deviations group. The difference between the highest and lowest counts for single-syllable word repetitions and disrhythmic phonations produced ranges of 8.18 and 5.58, respectively, both somewhat smaller than that of the moderate deviations group. Again, it should be noted that eight children in the minimal phonological deviations group exhibited moderate to severe stuttering. The remaining children in this group exhibited mild-to-moderate levels of SLD, mainly between 7 and 8 per 100 syllables. Overall, perhaps the most important observation in Tables 3 and 4 is that there were eight children in each phonologybased group who exhibited moderate to severe stuttering. Also note that, of the eight in each group, five were males and

Table 3 Individual data, means, and standard deviations at initial visit for the moderate phonological deviations group for age, gender, total stuttering-like disfluencies (SLD), part-word repetitions (PW), single-syllable word repetitions (SSW), and disrhythmic phonations (DP) per 100 syllables. Subject

Age (months)

Gender

Total SLD

PW

SSW

DP

P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14

49 38 33 47 37 48 29 35 47 36 36 30 36 48

M M F M F M F M M M M M M F

6.90 8.61 20.23 12.60 12.89 24.47 14.30 11.19 4.21 12.08 10.34 4.65 6.85 4.04

2.99 5.22 9.18 8.60 6.15 9.55 3.22 7.77 2.70 5.15 5.45 2.57 1.39 1.38

3.36 3.30 3.83 3.90 4.37 7.25 10.70 2.96 0.54 6.69 1.50 1.33 1.39 1.28

0.54 0.09 7.22 0.10 2.37 7.67 0.39 0.46 0.97 0.16 3.38 0.75 4.07 1.38

Mean SD

39.2 7.09

10.95 5.95

5.09 2.83

3.74 2.82

2.11 2.57

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Table 4 Individual data, means, and standard deviations at initial visit for the minimal phonological deviations group for age, gender, total stuttering-like disfluencies (SLD), part-word repetitions (PW), single-syllable word repetitions (SSW), and disrhythmic phonations (DP) per 100 syllables. Subject

Age (months)

Gender

Total SLD

PW

SSW

DP

G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15

38 45 48 32 36 42 42 31 39 48 41 41 31 34 39

M M F M M M M F M F M M F F M

12.22 12.27 20.22 26.83 7.78 14.97 9.03 12.90 8.00 9.72 8.06 9.66 22.91 4.79 10.59

7.43 8.15 5.31 17.40 1.10 12.18 2.49 5.19 4.04 1.71 4.03 4.05 13.24 2.68 7.73

4.11 2.39 9.23 5.96 6.62 3.66 4.88 2.68 3.89 4.86 3.19 3.55 4.68 1.05 2.48

0.68 1.73 5.68 3.46 0.00 0.13 1.66 5.03 0.07 3.15 0.84 2.06 4.99 1.05 0.38

Mean SD

39.1 5.57

12.66 6.17

6.44 4.67

4.21 1.99

2.06 1.94

Table 5 Range, group means, and standard deviations at the initial visit for age, total SLD, PW, SSW, and DP per 100 syllables. Moderate phonological deviations group

Age (mos). Total SLD PW SSW DP

Minimal phonological deviations group

Range

Mean

SD

Range

Mean

SD

29–49 4.04–24.47 1.38–9.55 0.54–10.70 0.09–7.67

39.2 10.95 5.09 3.74 2.11

7.09 5.94 2.83 2.82 2.57

31–48 4.79–26.83 1.10–17.40 1.05–9.23 0.00–5.68

39.1 12.66 6.44 4.21 2.06

5.57 6.16 4.67 1.99 1.94

three were female. Aside from the commonality in number and gender, there was no other apparent influence of gender or age involved, as the individual ages were quite varied within each of the sub-groups. 6.3. Stuttering frequency near onset: group data Table 5 presents descriptive statistics of the group means and standard deviations of both groups for each of the measures. As can be seen, the two groups present very similar sets of data. If at all, the minimal phonological deviations group exhibited a higher mean total SLD, reflecting primarily the difference in part-word repetitions. 6.4. Length of the stuttering events Individual subject and group means for RU for both groups are presented in Table 6. The 14 children in the moderate deviations group exhibited a range of 1.21–2.81 with a mean of 1.54 (SD = 0.46). For the 15 children in the minimal phonological deviations group, the RU ranged from 1.14 to 2.33, slightly smaller than that of the moderate phonological deviations group, with an almost identical mean of 1.58 (SD = 0.29). Overall, the two sets of data for disfluency length are quite similar. In fact, the two means are close to the 1.54 reported by Ambrose and Yairi (1999) for larger groups of children who stutter. 7. Statistical analysis To compare the two groups on the various measures, a multivariate analysis of variance was employed to determine if differences were statistically significant. Table 7 contains the results of the MANOVA. No statistically significant differences at the .05 level of confidence existed between the moderate and minimal phonological deviations groups in the frequency of the various types of disfluencies identified in the children’s speech samples, as well as in the number of repetition units. Because analysis of each of the components of total SLD revealed no significant differences, it can be inferred that no significant differences exist between total SLD for either phonology-based group.

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Table 6 Individual data for repetition units at the initial visit for the moderate and minimal phonological deviations groups. Moderate deviations

Minimal deviations

Subject

RU

Subject

RU

P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14

1.23 1.29 2.05 1.60 1.70 2.81 1.96 1.34 1.21 1.41 1.30 1.22 1.23 1.21

G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15

1.53 1.81 1.48 2.33 1.33 1.40 1.40 1.62 1.36 1.84 1.41 1.53 1.96 1.14 1.53

Group mean SD

1.54 0.46

Group mean SD

1.58 0.29

Table 7 Summary of multivariate analyses of variance for the frequency of stuttering-like disfluencies and repetition units at the initial visit. Test

df

Multivariate analysis of variance Part-word repetition Single-syllable word repetition Disrhythmic phonation Repetition units

4, 1, 1, 1, 1,

24 27 27 27 27

F

p

.273 .874 .274 .004 .078

.892 .358 .605 .953 .782

8. Discussion As our review of the literature has shown, a number of past investigations into the co-occurrence of stuttering and disordered phonology have supported some links between the two. Other reviews (Nippold, 2001, 2002), however, have questioned that link. It also was pointed out that recent research has hinted that such relations might differ between subgroups of young children who eventually exhibit natural recovery from, and those who eventually would persist in, stuttering, with the latter initially showing poorer phonology that improves with the passage of time. Despite the fair amount of research done to date, little has focused on children near the critical time of stuttering onset in order to better understand the nature of the said relations. The limited research that did focus on young children who stutter has provided contradictory results, with one team (Wolk et al., 1993) reporting significantly more sound prolongations in children with disordered phonology, while the other (Yaruss & Conture, 1996) reported no significant differences between the groups on any disfluency measures. Another point of concern is that these studies have overlooked essential epidemiological factors, including natural recovery, gender distribution, and time from stuttering onset. Improving on past methodologies, the present investigation employed children: (a) within 6 months of stuttering onset, (b) within a narrow age-range, (c) who composed a more appropriate gender distribution for the age under study, and also employed (d) carefully defined groups represented by at least a moderate level of stuttering severity and disparate levels of phonological ability. Thus, although the groups are of modest size, they composed very rare epidemiologically defined samples, bringing the issue at question into a unique focus. 8.1. Comparisons of disfluency characteristics One main finding is the lack of statistically significant differences between group means for the total number of SLD events in the speech of children with minimal and moderate phonological deviations. This finding agrees with the Yaruss and Conture (1996) study but not with the results of Wolk et al. (1993) study. Furthermore, considerable similarities, as well as unexpected differences, are seen across the two groups. First, more than half of the participants in each had 10 or more SLDs per 100 syllables, a level considered moderate to severe stuttering on several scales (e.g., Darley & Spriesterbach, 1978; Van Riper, 1971), and was also so indicated by comparisons of frequency counts and severity ratings (Ambrose & Yairi, 1999). In fact, on one hand, the minimal phonological deviations group exhibited a higher (though not statistically significant) mean total SLD than the

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group with moderate deviations, and it had only one child who exhibited mild stuttering. The remaining members demonstrated at least a moderate or higher level of stuttering severity (in terms of SLD), eight of them tended toward a high level. On the other hand, the child with the lowest SLD count in the entire study was a member of the moderate deviations group. What is interesting is the fact that a substantial number of children in each group exhibited moderate to severe stuttering. It means that whereas a child who exhibits moderate phonological deviations may indeed exhibit more severe stuttering, having good phonological skills does not necessarily reduce the risk for that child to exhibit severe stuttering. Second, the breakdown of the total SLD into its three components (part-word repetitions, single-syllable word repetitions, and disrhythmic phonations) reflects similar patterns of no significant, or appreciable, differences between the groups on any of the three. This is especially interesting in view of the very different motor/physiological dynamics of repetitions and sound prolongations. Furthermore, a summary glance at the individual data for the specific types of SLD shows that whereas there were three children in the minimal deviations group who exhibited part-word repetition counts of 10 or more per 100 syllables, not a single child in the moderate deviations group demonstrated part-word repetitions that reached the level of 10. Also, the minimal deviations group included five children with disrhythmic phonation counts of 3 or more, compared to four children in the moderate deviations group. Third, in the measure of the length of the disfluencies (repetition units), a similar trend was observed, with no apparent significant group differences. Overall then, if a relationship existed between stuttering and disordered phonology at the very early stage of stuttering, common sense would dictate one to expect more frequent and longer (more severe) stuttering to be associated with poorer phonology. This was not the case in the present investigation. The unsystematic trends seen in group and individual data for total SLD, specific disfluency types, and the length of disfluency, would seem to lead to a conclusion that a stuttering–phonology connection (if it exists) is not related to the level of phonological skill in a direct, parallel fashion. In other words, it is not related to phonological disorders. Moreover, the present findings show that the lack of a clear relation is evident at the very early stages of stuttering because the level of the phonological skills has no apparent impact on the measures of stuttering employed. Although the proposed link has been examined in a variety of ways, looking at the disparate conditions of minimal and moderate phonological deviations, where strongest mutual influences should logically be expected, did not provide a promising lead. The main point here is that an obvious candidate parameter for supporting a stuttering-disordered phonology link in the early stages of stuttering was not evident in the present results. That such a link is not a one-on-one relation also could be inferred from the basic pattern of past findings showing only 30 percent of children who stutter exhibiting some degree of phonological problems, if this figure is indeed valid. The fact that the majority of children who stutter do not show apparent links to phonological skills has not been adequately addressed, if at all. Though past research has reported that the phonology of children who persist in stuttering initially progress more slowly than that of children who recover, implicating a possible influence of stuttering on phonological development, our findings indicate that there is no apparent influence of the level of phonological ability on the characteristics of stuttering at the very early stages of the stuttering disorder. Interpretations of these data indicating no link between disordered phonology and stuttering, however, should not be confused with implications of no apparent link between phonology and stuttering. As mentioned earlier, given the amount of research examining the underlying phonological processes and stuttering (e.g., Anderson, Wagovich, & Hall, 2006; Byrd, Conture, & Ohde, 2007; Hakim & Bernstein Ratner, 2004; Weber-Fox, Spruill, Spencer, & Smith, 2008), it is possible that additional research will uncover factors unrelated to the severity of stuttering or phonological skills that might underlie the proposition of the stuttering–phonology link. 8.2. Further considerations of the stuttering–phonology links So far, the main support for a link between stuttering and phonology has been reports of their high rate of co-occurrence in school age children. Previous investigations into various possible elements of this co-occurrence (e.g., phonological characteristics, stuttering characteristics, and severity) have yielded little or no positive evidence. Inasmuch as the mere association (the co-occurrence), reported mostly in studies of school-age children, is taken as the main evidence for a link, the link can be questioned although not dismissed. A decade ago, a review of the relevant literature by Nippold (2002) concluded that, collectively, the literature does not support the argument that stuttering and phonological disorders interact in young children. According to her, none of these studies were able to show that stuttering severity differed in children with phonological disorders compared to those with normal phonological development, and none were able to show that phonological behavior differed in children who stuttered compared to those who were normally fluent. The present investigation addressed many of Nippold’s methodological concerns but, still, no differences were found. Nevertheless, the proposed stuttering–phonology link is not a closed issue. We keep in mind findings of some differences in phonological skills in early childhood between children who eventually persisted in, and those who recovered from, stuttering (Yairi et al., 1996; Paden et al., 1999, 2002). Thus, there is room for exploring additional longitudinal information from the participants in the current investigation. Additionally, when one examines the findings of previous studies describing severity of phonological disorders related to persistence in stuttering (Paden & Yairi, 1996), it would seem logical to discuss the possibility that the stuttering–phonology link may emerge stronger in children further from onset, that is, the minority that persists might be more prone to also have weaker phonological skills. In this respect, recall Morley’s (1957) study, conducted in England, in which 37 CWS were seen three times at about 2-year intervals. Only at the oldest age (6;6)

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did she report a larger proportion of the group with articulation disorders than in a control group of 113 normally fluent children. Similarly, findings we cited earlier of American studies reporting 30% or so of CWS who exhibited concurrent phonological deficiencies (e.g., Blood et al., 2003) pertained to older, school age pupils. Although this figure is very high, one has to remember that this group constitutes a very small minority, only 20% or fewer, of the original population of children who stutter. Those are the children who exhibit more robust stuttering disorders and, therefore, unlike the other 80% of the children who recover naturally, they persist in stuttering in spite early intervention many of them had received as reported by the school speech clinicians and by Yairi and Ambrose (1999a, 1999b). Both statistical (Ambrose, Cox, & Yairi, 1997) and biological (Suresh et al., 2006) genetic studies have reported indications of genetic differences between persistent and recovered children. Thus, survey findings that higher percentages of school age children who stutter exhibit phonological disorders than nonstuttering peers may indeed reflect the children’s more involved and complicated stuttering disorder, influenced by additional genetic factors. Yairi and Seery (2011, p. 302) suggested that this is an important reason for difficulties encountered in therapy with school age children who stutter. Returning to Nippold questioning the 20–30% stuttering/phonological incidence in school-age children, she has continued to support her argument with some data indicating that only 71% of clinicians prescribe therapy for stuttering only cases as compared with 94% for cases exhibiting stuttering and at least one additional disorder (Nippold, 2004). She stated that ‘‘The results provide reason to question the widespread belief that children who stutter have a high rate of concomitant disorders, especially when it is based on caseload surveys’’. (p. 145). This is a rather gross overstatement. Accepting that nearly 1/4 of clinicians’ caseload is biased, as seen in the discrepancy between her two figures (71% and 94%), and going even further, reducing the 20–30% by half, the remaining a 10–15% incidence is still way above the normal incidence of phonological disorders. Currently, we witness a growing literature dedicated to examining the stuttering–phonology link, with studies giving specific attention to evidence of atypical phonological characteristics reported in children who stutter. For example, Anderson et al. (2006) investigated the nonword repetition abilities of preschool-aged children who stutter. They reported that the children who stutter produced significantly fewer correct two- and three-syllable nonword repetitions and made significantly more phoneme errors on three-syllable nonwords relative to normally fluent children. A study by Byrd et al. (2007) found preschool-aged children who stutter to be delayed in making the developmental shift in phonological encoding from holistic to incremental processing (relative to speech reaction times), which, the authors suggested, may contribute to difficulties in establishing fluent speech. 9. Caveats and future research Future studies should include more rigorous methods than those employed in many past investigations, such as direct testing of children’s speech (as opposed to parent or teacher report of phonological deficiencies or based on clinicians’ caseloads that could be biased), and also should set clear and acceptable criteria for phonological disorders. In terms of phonological ability, one of the criteria for subject selection in the present study was the child’s mean percentage of phonological error obtained from the APP-R. Unlike the stuttering measure employed, the phonological ability was determined based on productions of single words. Hence, using more comprehensive measures to elicit the production of sounds in a variety of phonetic contexts, both at the isolated word level and in spontaneous conversational speech, should be considered. Studies also could compare incidence of phonological disorders in children who stutter against acceptable norm. With school age children, the gender ratio must be carefully considered because at this age range a large majority, 75% or more, of children who stutter are boys (boys are more prone to phonological disorders than girls), a factor not controlled in past studies (Yairi, 1999). A very important avenue for future research could be to examine longitudinally both stuttering and phonological skills as they develop during over time in children who exhibit different levels of phonological skills. More specifically, if phonological skills remain stable or improve, are there corresponding changes in stuttering? Furthermore, what is the relation between the initial level of phonological ability and stuttering in children who would eventually persist in, and those who would eventually recover from, stuttering? Appendix A. Continuing education questions 1. Of all the speech-language problems that co-occur with stuttering, which of the following are the most commonly cited? a. Voice disorders b. Phonological disorders c. Expressive language deficits d. Receptive language deficits 2. Improving on the methodology of past studies investigating the link between stuttering and phonology, the present investigation employed which of the following: a. carefully defined groups represented by at least a moderate level of stuttering severity and extreme levels of phonological ability b. children within 6 months of stuttering onset c. children within a narrow age-range and a more appropriate gender distribution d. all of the above

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3. With regard to the relationship between individual phonological abilities and the total SLD scores of the participants, a Pearson analysis revealed which of the following? a. A negative correlation b. A positive correlation c. No correlation d. A perfect correlation 4. Regarding the stuttering characteristics of the phonology-based groups, which of the following statements best summarizes the findings of the investigation: a. Statistically significant differences in the stuttering characteristics of children with minimal and moderate phonological deviations near onset, with the minimal deviations group exhibiting more part-word repetitions. b. Statistically significant differences in the stuttering characteristics of children with minimal and moderate phonological deviations near onset, with the moderate deviations group exhibiting more single-syllable word repetitions and disrhythmic phonations. c. Statistically significant differences in the stuttering characteristics of children with minimal and moderate phonological deviations near onset, with the moderate deviations group producing more ‘‘other (non-SLD) disfluencies.’’ d. No statistically significant differences in the stuttering characteristics of children with minimal and moderate phonological deviations near onset. 5. Regarding the length of the stuttering moments of the phonology-based groups, which of the following statements best summarizes the findings of the investigation: a. Statistically significant differences in the length of the stuttering moments, with the minimal deviations group exhibiting more repetition units. b. Statistically significant differences in the length of the stuttering moments, with the moderate deviations group exhibiting more repetition units. c. No statistically significant differences in the length of stuttering moments between the two groups. d. Repetition units were not analyzed in the present investigation.

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