Consonant production and intelligibility in cri du chat syndrome.

Clinical Linguistics & Phonetics, October 2014; 28(10): 769–784 ß 2014 Informa UK Ltd. ISSN: 0269-9206 print / 1464-5076 online DOI: 10.3109/02699206.2014.904442

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Consonant production and intelligibility in cri du chat syndrome

KRISTIAN E. KRISTOFFERSEN1, NINA GRAM GARMANN2, & HANNE GRAM SIMONSEN1 1

Department of Linguistic and Scandinavian Studies, University of Oslo, Oslo, Norway and Department of Early Childhood Education, Oslo and Akershus University College of Applied Sciences, Oslo, Norway 2

(Received 1 July 2013; revised 10 March 2014; accepted 11 March 2014)

Abstract This article focuses on consonant productions by a group of children with cri du chat syndrome (CdCS) and examines how various aspects of these productions contribute to these children’s overall intelligibility. Eight children and adolescents with CdCS participated in the study, and the following four questions were addressed: (1) What are the characteristic features of the consonant inventories of the subjects in terms of size and types of consonants; (2) how do the subjects render the consonant phonemes of the target language; (3) to what degree do the subjects produce target-like words; and (4) what is the relationship between consonant production and intelligibility? For the majority of our subjects, we found low proportions of correctly produced consonants, small consonant inventories with several recurrent types of deviant consonants, inaccuracy in realization of target phonemes and variable similarity to target words, all of which may contribute to reduced intelligibility.

Keywords: Consonant production, cri du chat syndrome, intelligibility, phonological inventories

Introduction This article investigates the production of consonants in children with cri du chat syndrome (CdCS) acquiring Norwegian. CdCS is a rare genetic disorder with an estimated incidence between 1:20 000 and 1:50 000 births (Niebuhr, 1978; Wu, Niebuhr, Yang, & Hansen, 2005). The syndrome is associated with a partial deletion on the short arm of chromosome 5. The clinical features of CdCS include a high-pitched cry in infancy and childhood (Sohner & Mitchell, 1991; Sparks & Hutchinson, 1980), malocclusion, hyper- and hypotonia and delayed motor development (Carlin & Fraser, 1990), microcephaly (Niebuhr, 1978), mild-to-profound intellectual disability (Cornish, Bramble, Munir, & Pigram, 1999), short attention span, hyperactivity and a stereotypical, aggressive and self-injurious behavior pattern (Collins & Cornish, 2002). Individuals affected with CdCS experience delayed speech and language development; see Kristoffersen (2008a) for a review. According to the literature, many (reports vary from 23 to 50%) do not develop spoken language at all (Baird, Campbell, Ingram, & Gomez, 2001; Carlin & Correspondence: Kristian E. Kristoffersen, Department of Linguistics and Scandinavian Studies, University of Oslo, P.O. Box 1102 Blindern, N-0317 Oslo, Norway. Tel: +4722857634. Fax: +4722857100. E-mail: [email protected]

770 K. E. Kristoffersen et al. Fraser, 1990; Cornish & Pigram, 1996; Wilkins, Brown, & Wolf, 1980). For those who do develop spoken language, however, receptive language skills have been found to be significantly better than expressive language skills (Cornish & Munir, 1998; Cornish, Bramble, et al., 1999; Marignier, Lesca, Marguin, Bussy, Sanlaville, & Portes, 2012).


Phonetic and phonological skills in CdCS Frequent misarticulations and omissions have repeatedly been reported for individuals with CdCS (Cornish, Bramble, et al., 1999; Schlegel, Neu, Carneiro, Reiss, Nolan, & Gardner, 1967; Sparks & Hutchinson, 1980). None of these three studies described the exact nature of these misarticulations explicitly, but in two studies of consonant articulation in a smaller group of Norwegian children with CdCS (Kristoffersen, 2004, 2008b) various substitutions, omissions and cluster reductions were identified. Furthermore, these children had small consonant inventories compared to those of far younger typically developing (TD) children acquiring Norwegian. The inventories also exhibited inter-subject variation both in number and type of consonants. Kristoffersen (2008b) was a longitudinal study of error rates and error patterns in the consonant productions of one Norwegian girl with CdCS. Error rates in single consonants were measured at four observation points (ages 4.6, 5.9, 7.0 and 9.4) in terms of percent consonants correct (PCC-R; Shriberg, 1993; Shriberg, Austin, Lewis, McSweeny, & Wilson, 1997). The PCC-R varied from 22.8% at 4.6 to 69% at 9.4, which is low as compared with both TD children of the same age and children with Specific Language Impairment (SLI) acquiring Swedish, a language closely related to Norwegian (Hansson & Nettelbladt, 2002). Hansson and Nettelbladt reported a PCC of 80.10% for the children with SLI in their group (age range 4.3–5.7 years) and 98.69% for a group of age-matched controls. Note that the age of the participants in this study match the two first observation points in the study of the Norwegian girl with CdCS.

Factors that influence intelligibility Poor intelligibility is a challenge for many children with language disorders. The degree of intelligibility is influenced by a number of factors, including number and types of sound errors, degree of consistency of errors, rate of speech, atypical prosodic features, length and complexity of words and utterances, as well as insufficient vocal intensity, dysphonia, hypernasality and hyponasality (Shipley & McAfee, 2008). Focusing on number and type of speech sound errors and degree of consistency, it is evident that if a child produces words with many different speech sound errors, the result is most often low intelligibility. On the other hand, if errors are consistent, this may improve intelligibility somewhat, since the phonological patterns evident in the child’s word productions are more stable and systematic. This applies to the degree of variation across tokens of the same word type, as well as to the degree of variation across identical phonological contexts in different words. For example, if a child produces eight phonologically different tokens of the same word, he or she may be difficult to understand for communication partners. Conversely, if the extent of variation across these eight tokens is low, intelligibility increases. Furthermore, if the child produces one and the same phoneme in eight different ways in the same phonological context (e.g. between vowels), this may also result in low intelligibility. One way to assess speech skills both in TD children and in children with language disorders is by examining their consonant inventories, often in different word positions (see e.g. Kunnari, 2003; Robb & Bleile, 1994; Stoel-Gammon, 1980). For example, Stoel-Gammon (1980) investigated phonological patterns in the speech of four children with Down syndrome and found that although these children were capable of producing almost all the consonants of the

Consonant production and intelligibility

771

Table 1. Consonant phonemes of Urban East Norwegian (UEN). Word initial (17 phonemes)


Lab P B M F V

Ap

Q

Lam t d n s

Word medial (23 phonemes)

Do k g

Glo

ç j

h

Lab p b m f V

Ap ˜ Q

Lam t d n s l

Do k g ˛ ç j

Word final (21 phonemes) Glo

h

Lab p b m f V

Ap ˜ Q

Lam t d n s l

Do k g ˛

Glo

j

target language, correct productions were often confined to certain positions within the word. Furthermore, even though a particular consonant was attested in the child’s inventory, this consonant was often not used in accordance with the phonotactic rules of the target language.

Consonants in Norwegian The consonant and vowel inventories of Urban East Norwegian (UEN), the regional variety of Norwegian spoken in and around Oslo, the capital of Norway, are displayed in Table 1. Among a total of 23 consonants, there are two distinct sets of coronal consonants, one laminal (/t d n s l/) and one apical (/ ˜ /). There are only voiceless fricatives. Moreover, UEN has an apical r-sound (an apical tap), and an apico-postalveolar flap //. The distribution of UEN consonants are restricted in several ways. First, the apical plosives /, ˜/, the apical nasal /˛/, the flap // and the dorsal nasal /˛/ cannot occur in word initial position. Second, the fricatives /h/ and /ç/ cannot occur in word final position. Third, the voiceless plosives have two allophones, an aspirated one, which occurs at the beginning of a stressed syllable and word-initially, and an unaspirated one, which occurs in all other positions. While the phonotactic characteristics described for UEN also hold for other Norwegian dialects, there are some differences as to particular speech sounds. We will comment on two of these. First, two different rhotic sounds exist in Norwegian dialects. Most dialects, including UEN, have an apical r. The remaining dialects, mainly along the southern and western coast (extending to a varying degree into the interior), have a uvular r. Second, the dialects with an apical r also have a class of what is commonly termed retroflex consonants, i.e. the apical consonants of Table 1. Generally speaking, the dialects with a uvular r lack these consonants. Most of the participants in this study have an eastern variety of Norwegian as their target language.1 The exceptions are participant C (see Table 3 below), who lives in Sweden with a UEN-speaking mother, and participant A, who is Southern Norwegian, which includes the uvular r, as her target language. The phonemes that are marked in bold are common to all Norwegian dialects represented in this study.

Previous research on phonetic and phonological skills in Norwegian children Simonsen (1990) studied three Norwegian-speaking TD children (Tomas, Vera and Nora) in the age range two to four years and found that the children mastered most of the phones in the target 1 When we describe these children’s target dialect as an eastern variant of Norwegian, we are referring to a larger geographical region within Norway than that covered by the UEN variety. However, for the purposes of this study, this difference is of little significance.

772 K. E. Kristoffersen et al. Table 2. Size of consonant inventories in children acquiring Norwegian (Simonsen, 1990)a.

Tomas (2.0) Vera (2.2) Nora (2.3) Mean size


a

Word initial

Word medial

Word final

15 18 16 16.3

15 13 16 14.7

8 6 6 6.7

Only consonants that occur three times or more in the data are included in the counts.

Table 3. Participants’ gender, age, utterance length, utterance type, and intelligibility. Rated by the first author.

Participant

Age

Gender

Number of utterances produced in the taska

Utterance type (in conversation)

Intelligibility

A B C D E F G H

6.4 6.9 5.4 12.3 10.8 10.0 9.2 4.6

F F F F F M M F

90 110 146 36 134 96 60 116

Multi-word Multi-word Multi-word One-word Multi-word One-word One-word One-word

High Medium Medium Low Low Low Low Low

a

Given the nature of the task, most of these utterances consisted of one word. However, since a few also consisted of more than one word, the column head refers to utterances, not words.

language, with some clear exceptions related both to word position and phone type. Concerning the latter, fricatives and the rhotic were acquired late. Second, labials were acquired late in final position. Third, VOT was a challenge (more so in word initial than in word medial and word final position) throughout the period investigated. Finally, across the three children, Simonsen observed more variability in initial than in medial and final position. Simonsen (1990) provided information on the size of consonant inventories in her subjects. Table 2 lists number of consonants in word initial, word medial and word final position for all the three children, in addition to the mean values.

Research questions Against this background, the following four questions will be addressed in this article:2 (1) What are the characteristic features of the consonant inventories of the subjects in terms of size and types of consonants; (2) how do the subjects render the consonant phonemes of the target language; and (3) to what degree do the subjects produce target-like words? Our answers to these three questions will provide three different perspectives on question (4): What is the relationship between consonant production and intelligibility?

2 In the introductory discussion, we have pointed to variability as a factor contributing to lack of intelligibility. One of the reviewers has commented that our data does not allow for much examination of variability. We agree and have therefore not included a separate question on variability.


773

Methods


Subjects The eight subjects – two boys and six girls – were recruited through the Cri du chat family support group in Norway. In our analyzes, we have taken into consideration that their target dialects varied along a few parameters, most notably the rhotic sound (apical vs. uvular) and presence vs. absence of apical sounds (see the outline of Norwegian above and Table 7 below). Table 3 lists age and gender of each of the subjects, as well as characteristics of their language and intelligibility. The intelligibility ratings were made by the first author on the basis of the children’s utterances during the experiment, and in this study, we were interested in finding out to what extent these ratings corresponded to other more formal measures that might be related to intelligibility (see below). Since data were collected by a naming task based on pictures and objects, the rater knew what the children were likely to say. To check to what extent the first author’s ratings were reliable, the recordings were also rated by five other persons, all with experience in rating and analysing disordered language production.3 For four of the eight children (A, F, G and H; see Table 3 below), all raters agreed. For two of the remaining four (C and D) agreement with the first author was 80%, whereas for the two last children (B and E), agreement with the first author’s rating was surprisingly low, 20%. For both these children, the raters provided all three values (high, medium and low intelligibility). It is important to note that the first author based his ratings on the children’s productions in the test sessions, whereas the other five raters based their ratings on recordings, which necessarily contain much less information. We therefore chose to base our comparisons in what follows on the ratings of the first author. At the same time, it would be interesting to look more into those children where the agreement was lowest, i.e. B and E, to find out what may have caused this lack of agreement. Since B was judged with medium intelligibility by the first author, the variation between low, medium and high by the other raters is not so surprising. However, it is more surprising that E, who was judged as having low intelligibility by the first author, got both medium and even high intelligibility scores by the other raters. In Table 3, the subjects are ranked from A to H based on intelligibility; within the same intelligibility rating, the children are ranked from the oldest to the youngest. One of the subjects – A – is different from the others, in the sense that she does not show any signs of the motor problems associated with the syndrome, and has only minor problems with language as compared to the other seven subjects. A few descriptions of this atypical phenotype exist in the literature, where language skills are reported to be relatively good. A most probably belongs in this group (Cornish, Cross, Green, Willatt, & Bradshaw, 1999). One possible objection against a sample like the present one is that it is very heterogeneous, both with respect to the participants’ age and their ability to communicate with spoken language. However, since CdCS is an extremely rare condition and the possibility of recruiting a more homogenous group therefore is almost non-existent, the only viable alternative is to study single or several individual cases. We think that for purposes of treatment, this heterogeneity might also be useful, since speech therapists will meet the same heterogeneity in their work, to the extent that they actually meet more than one person with this syndrome during their career.

3 One of CLP’s reviewers expresses a reservation about the validity of measuring intelligibility on the basis of a single word task (and for which the rater knew the targets). We agree to some extent with this. However, given the limitations on these children’s language, this type of test is perhaps the only possible way to collect speech data from children with CdCS, and we have therefore chosen to include these measures.

774 K. E. Kristoffersen et al. Task


All subjects were given a noun elicitation task, developed by the first author for a previous case study (Kristoffersen, 2008b). Seven of the subjects were given the same task, where a number of photos, drawings and objects were used. Ideally, all of the children should have been given the same task, but with one on them (G), we had to make certain individual adaptations based on information obtained from the parents prior to the elicitation session. In his case, we used a photo album with pictures of family members and caretakers. In the task variant given to the majority of the subjects, the items were chosen so that the target words offered an opportunity to produce all consonant phonemes in initial, medial and final position in the target language. In the stimuli given to G, this was not possible.

Recording procedure In order to elicit the test items, the subjects were shown photos, drawings and objects representing the items and then asked ‘‘What is this?’’ Sometimes, it was necessary to provide them with additional information to elicit the items. At the same time, care was taken to avoid using the target words immediately before showing them the pictures and objects included in the test material. Words that were direct imitations of what the experimenter said were omitted from the data set. The recording equipment used was a MiniDisc recorder and an electret condenser microphone (E, F, G and H), an external sound card connected to a computer and an electret condenser microphone (A, C and D). B was recorded with a HD recorder with a built-in microphone. The subject and the experimenter were seated side by side at a table upon which the test materials and the microphone/HD recorder were placed (no more than 40 cm from the subject).

Transcription The elicited utterances were narrowly transcribed in extIPA for disordered speech (Ball & Mu¨ller, 2005) by a first transcriber. Twenty percent of the utterances were then independently transcribed by a second transcriber. The transcriptions of the utterances were compared pairwise as to similarity of consonants. Differences in voicing were counted as disagreement. Transcription agreement was calculated by dividing the number of agreed consonants by the total number of consonants in the original transcription. Agreement between the two transcriptions was 71%. This figure is comparable to the one Simonsen (1990) got for TD 2–4 year olds (76%, recalculated in Hansen, 2011). It is low, however, compared to 90% agreement in Robb & Bleile (1994) for typical children and 93.6% in Hansson & Nettelbladt (2002) for atypical children. One reason for the low figures here and in Simonsen (1990) may be that differences in voicing are considered as transcription disagreements. Furthermore, the agreement scoring was made on the basis of detailed phonetic transcriptions, not on phonemic transcriptions. A third factor that may have contributed to the low agreement rate is that many of the utterances in these data sets were extremely difficult to transcribe for several reasons. Of the most important among these was the fact that our subjects’ utterances deviated from their targets not only in terms of their containing different segments but also in terms of factors like voice quality, nasality, timing of phonetic features and addition of features that were not present in the target words. For example, as we shall see below, several of the subjects produced a type of sound sequence, which can be analyzed in one of three ways; as a voiceless plosive with lateral release ([kl]; often with an additional element of affrication); as a consonant cluster with a plosive as its first element and


775


a lateral approximant as its second ([kl]); or as an affricate with a lateral fricative as its second element ([k¸]). It turned out to be a particularly difficult task to draw a principled line between these three types, based on perceptual judgment alone. To determine in which of the three categories the sequence belonged, we used, in part, phonetic and, in part, phonological criteria to maximize the target likeness of the transcription. To be specific, if the sequence corresponded to a target consonant cluster with a lateral as second element in the target word, it was classified as a consonant cluster. If, on the other hand, the sequence corresponded to a single segment in the target, it was analyzed as a plosive with a lateral release if no element of friction was involved. If an element of friction was involved, it was analyzed as an affricate. Data analysis All measurements were based on the first transcriber’s transcriptions. All identifiable consonant phones in these utterances were classified according to manner and place of articulation, nasal vs. oral, voiced vs. voiceless and lateral vs. central, yielding inventories of consonant phones for each of the eight participants. The individual consonants in the subjects’ utterances were scored according to the measure PCC, based on the PCC-R of Shriberg et al. (1997). PCC-R is intended for use with children with disordered speech and measures average accuracy of the different consonant tokens. According to this procedure, accuracy is measured broadly for place and manner, but voicing is disregarded. For example, plosives with the correct place of articulation but wrong Voice Onset Time will be scored as correct. Furthermore, a target fricative /s/ can be pronounced in a number of ways; as long as the manner of articulation is coronal fricative, it will be scored as correct. In this study, PCC-R was calculated independently by the first and second authors for two of the children, F and G. Inter-rater agreement was 95%. Next, the degree of similarity to target words was measured by a procedure described by Ingram (2002) – Proportion of Whole word Proximity (PWP). PWP is based on the construct Phonological Mean Length of Utterance (PMLU). Child PMLU is calculated by adding the number of consonants and vowels in the child’s word to the number of correct consonants in the same word. For example, the child form [ba] for ball has one consonant [b] and one vowel [a] as well as one correct consonant [b]. The child PMLU for [ba] is accordingly 1 + 1 + 1 ¼ 3. The PWP for the word is then calculated by dividing the child PMLU by the target PMLU, which is based on two consonants, one vowel and two correct consonants (2 + 1 + 2 ¼ 5). That is, PWP for the child word [ba] is 3/5 ¼ 0.6. In other words, in terms of PWP [ba] is 60% similar to the target word ball. Finally, the utterances were examined to see how the subjects rendered the various phonemes of the target language. For every target phoneme, the child’s productions were sorted into word initial, word medial and word final consonants, where sounds occurring only once or twice in the data were classified as marginal (cf. Grunwell, 1985, p. 31). Results In what follows, we present our findings for the size and contents of consonant inventories, the PCC-R values, the PWP values and the renderings of the target phonemes for all eight subjects. In Table 4, we display the number of consonants produced by the eight subjects word initial, word medial and word final position, with mean and range for all three positions. In addition, we present the overall size of the inventories. Table 4 shows that there is considerable variation in number of consonants in all three word positions, with the range in word initial and word medial position being quite similar. In word final position, there are fewer consonants than in the two other positions. For all eight

776 K. E. Kristoffersen et al. Table 4. Size of consonant inventories in the eight children with CdC, ranked according to overall inventory size. Intelligibility

Word initial

Medium High Low Medium Low Low Low Low

15 15 17 12 9 9 8 3


B (6;9) A (6;4) E (10;8) C (5;4) G (9;2) D (12;3) H (4;6) F (10;0) Mean Range UEN phonemes

11 3–17 17

Word medial 18 17 17 13 9 8 7 3 11.5 3–18 23

Word final

Overall size

14 10 15 6 2 5 4 0 7 0–15 21

20 19 18 13 13 11 10 3 13.375 3–20

Table 5. Consonant inventoriesa. Subject

Intelligibility

Labial

Coronal

Dorsal

Glottal

A B

High Medium Medium Low Low Low Low Low

t, d, n, s, l, (¸) t, t…, (t}), y, (D), (˜), d, n, (hn) s, s9, (), (z), l, (l 8), (¸), Q t, t ¸, d, (d ¸), n, s, l, ¸, () t, d, n, s, l, (¸) t, t…, d, (d…), (), n, s, y, l, Q

k, c, g, (˛), C, j, R, g, g8 , k, k…, (kn), (fi), ˛, j k, k ¸, g (k), g, (C), (˛), (j) k, k…, c…, (g), (fi), j (˛) k, ˛k, g, ˛g, ˛, ç (k), c, (cj), fi, j

h h, (?)

C D E F G H

p, b, m, f, V, v p, b, (b8), m, (m 8), f, V p, b, m, (f), (V) p, b, m, f p, b, (mp), m, f, V p, (b), (w) m b, p, m p, m, (mp), (V)

d, nd, n n, (l), (l 8)

? h ?, h ? h

a

The phonetic symbols in parentheses represent marginal phones, i.e. sounds, which occur only once or twice in the data (cf. Grunwell, 1985, p. 31).

subjects, the number of consonants in word final position is lower than in the two other word positions. We turn now to the contents of the consonant inventories. Table 5 presents for each of the eight subjects, all consonants produced in word initial, word medial and word final position for four places of articulation, labial, coronal, dorsal and glottal. In the inventories in Table 5, no reference is made to the target system. The first thing to note about Table 5 is that labial stops are present in all children. This is also the consonant type that is among the earliest to be acquired in TD children (see e.g. Simonsen, 1990). Second, we note that rhotic sounds and sibilants are infrequent. These sound types are acquired late in TD children learning Norwegian, too. Third, we note that each of the children appear to have their own individual range of sounds in each place of articulation. In Tables 4 and 5, we see that the number of consonants is highest in the children with intelligibility ratings high/ medium, except for E, who is rated as having low intelligibility, but who has more consonants than C, who is rated as having medium intelligibility. Furthermore, we see from Table 5 that there is extensive variation both within subjects and across subjects. For example, only some of the children produced coronal fricatives and not all of them had coronal plosives. Furthermore, only two of the subjects (B and E) had a coronal rhotic (note that A and C did not have this sound in their target dialects, cf. Table 8 below). Furthermore, all of the subjects had one or more consonants that deviated from the target language consonants (for an overview of these, see Table 8 below). These consonants largely fell into three groups.


777


Table 6. PCC-R. Participant

Age

Intelligibility

PCC-R (%)

A B E C D G H F

6.4 6.9 10.8 5.4 12.3 9.2 4.6 10.0

High Medium Low Medium Low Low Low Low

93 83 72 52 49 35 23 2

Table 7. Degree of similarity to target words measured in terms of PWP. Participant

Age

Intelligibility

PWP (%)

A B E D C G H F

6.4 6.9 10.8 12.3 5.4 9.2 4.6 10.0

High Medium Low Low Medium Low Low Low

93 89 74 74 66 47 45 38

The first of these was prenasalized consonants, for example, the first consonant in the form [˛gO~kO~] for [sku:] ‘‘shoe’’, by G. Prenasalized consonants were also found in the inventories of E and H. The second type of deviant consonant was stops with a lateral release, for example, the final segment in [f@lacl] for [flag] ‘‘flag’’, by E. This type was also present in the inventories of B and C. The third and last type of deviant consonant was a lateral fricative, for example, the second member of the word initial cluster in [k¸ol] for [skol] ‘‘saucer’’, by C. Four of the eight subjects (A, B, C, and D) had examples of this type in their inventories, although only marginally in A, B and D. We note, then, that some children have more than one deviant consonant type: B and C have both lateral fricatives and stops with lateral release, and E has both prenasalized consonants and stops with lateral release. While deviant lateralization is found in children ranked for high, medium and low intelligibility, prenasalization is only found in children with low intelligibility. Next, in Table 6, we show the PCC-R for each of the children, who are ranked according to their PCC-R values. As we can see, there is much inter-subject variation, ranging from F, who had 2% correct consonants, to A, who had 93% correct consonants. The mean PCC-R for all eight children is 51.1%, and we found a moderate correlation (r ¼ 0.71) between the impressionistic intelligibility ratings and the PCC-R values. Note that participant E has a higher percentage of correct consonants than C, even though E is judged by the first author to have a lower intelligibility than C. In Table 7, we present our findings concerning the extent to which the subjects produce targetlike words, measured in terms of Ingram’s (2002) PWP. The children are ranked according to their PWP values. As could be expected from the other measures, there is extensive variation also in the degree of similarity to target words, but as was the case with the PCC-R values, there was a moderate positive correlation (r ¼ 0.72) between the intelligibility ratings and the PWP values. At the lower


778 K. E. Kristoffersen et al. end, F and H had 38% and 45% PWP, respectively. At the other end, we find A and B with very high scores, 93% and 89%, respectively. Participants E and D, who are judged by the first author as having a low intelligibility, have a higher PWP than C who is judged as having a medium intelligibility. Finally, we turn to the question of how the various consonant phonemes of the target language were articulated by the eight subjects. Table 8 displays the realizations of target phonemes in word initial, word medial and word final position for each subject. Again, we observe extensive variation across and within subjects. A, for example, rendered most target phonemes accurately, with a few exceptions. The most notable of these was that she occasionally rendered medial /p/ and /t/ with a voiced variant, that initial /s/ was sometimes missing (this happened when /s/ was the first member of a word initial consonant cluster), and also some other irregularities related to her attempts at target consonant clusters. At the other extreme, we have F, who in most cases omitted target consonants, or produced a glottal consonant instead. This subject had very few oral consonants at all, and his words were mostly composed of vowels and glottal consonants. If we look in more detail at the different consonant types, we see, first, that labial plosives /p, b/ are rendered relatively accurately in word initial position, and less so in word medial and word final position. There are also more accurate realizations across subjects with the voiceless than with the voiced labial plosive. Furthermore, the coronal plosives /d, t/ are realized relatively accurately, but at this place of articulation, the voiced consonant is rendered more accurately than the voiceless across subjects. Furthermore, the labial and coronal nasals /m, n/ look on the whole well rendered across positions and subjects. With the dorsal plosives /k, g/, on the other hand, there is much variation, and thus less accuracy in realization of the target, in all word positions and also for most subjects. The same is the case with the dorsal nasal /˛/, the fricatives /f, s, ç, h/, the approximants /V, , j/ and the rhotics /Q, /. There is much variation and inaccuracy across place of articulation, across word position and across subjects. In Table 9, we present average number of alternative renditions for different phonemes across children for each of the three word positions. In other words, final consonants are less variably produced than medial ones, which are in turn less variable than initial ones.

Discussion The main objective of this study was to examine quantitative and qualitative aspects of consonants produced by eight children with CdCS in terms of four measures, size and content of consonant inventories, PCC-R, whole word similarity to target words and realization of target consonant phonemes, comparing these measures to impressionistic intelligibility ratings. We found that PCC-R varied considerably from 2% to 93%, i.e. from almost none to almost all consonants correct. Furthermore, the children’s consonant inventories varied extensively, in both size and content. Furthermore, there were several types of deviant consonants in these inventories – prenasalized stops, stops with a lateral release and a lateral fricative, none of which are part of the target consonant inventory. In her study of the phonology of three toddlers acquiring Norwegian, Simonsen (1990) found that when these children were between 2.0 and 2.3, consonant inventories ranged between 15 and 18 in word initial position, between 13 and 16 in word medial position and between 6 and 8 in word final position (cf. Table 2 above). Comparing these ranges to the ones found for the CdCS children who participated in this study, we see more extensive variation in the latter group, and also a lower average number of consonants in word initial and word medial position, but not


779

Table 8. Realization of consonant phonemes of the target language.


A p– –p– –p b– –b– –b –– – –˜– –˜ t– –t– –t d– –d– –d k– –k– –k g– –g– –g m– –m– –m –– – n– –n– –n –˛– –˛ f– –f– –f – –– – s– –s– –s ç– –ç– h– –h– V– –V– –V – –– – j– –j–

B

C

D

E

F

G

H

m p p p p ?, h, Ø b, p p, Ø p p, d, l p p, b Ø, h, ? p p, Ø p ID ID p Ø ID Ø, m b, p b b, d p Ø, ?, p p, mb, d p, Ø, mp, h p, ? ID ID b b ID b, p, mp, m b8 ID f b Ø ID ID ID t ID ID ID ID ID t Ø ID ID ID Ø ˜ ID ID ID ID ID ID ID ID ID ID ID ID ID t t, t}, y t, Ø, p, t ¸ t t, t… ?, Ø, h ID h, c, fi, p, c”, Ø t, d, s, k t, Ø t, Ø, d, p, t ¸ t, d, b, Ø t…, t, d, Ø ?, Ø d, k, ˛g, Ø Ø, c, V t t t, Ø Ø t Ø ID ID n d d t, Ø d d, t Ø, b d, d Ø d d, Ø t, k ¸, Ø t d ?, Ø ID p ID ID ID ID d Ø ID ID k k k, t, k ¸, d t t…, k…, c…, k ?, h, w, ˛, Ø ˛, ˛g Ø, k, p ˛ k, c k, g, k…, kn,t…, s, Ø k ¸, k, Ø, g k, t, d, Ø t…, t, k…, cl, k, Ø Ø, ?, h g, g, ˛ Ø, k k, c, Ø k, t Ø t, Ø c…, k Ø ID Ø ˛ g g, k, k…, d g, d, k ¸, t Ø t…, c… ?, Ø, h, p g c, Ø, h ID g, Ø k ¸, t ¸ ID c…, d… Ø ID ID g g, g8, d, t… Ø g c…, g Ø ID j, Ø m m, m 8 m, Ø, p, b m, b m ?, p, Ø, h m m, p m m, n, ˛ m, Ø, b m, n, p m, n, d Ø, h, ? m, Ø m, Ø ID m ID ID m, n Ø Ø m n, ? ID ID ID Ø ID ID n ID ID ID Ø ID ID n n, l n, m, l, k ¸ n, d n ˛, h, Ø n, ˛g n, Ø n, Ø n, l n, Ø, l, d ID n, Ø ?, Ø n n, Ø, m n n, h8n, Ø Ø, n ID n Ø Ø, ç n, m, fi, Ø ˛ fi, ˛ n ˛ fi, n h, Ø n, ˛k fi, Ø ˛ ˛ Ø ID ID ID ID Ø f f, p m, V f f, h ?, Ø ID Ø, p f f, p Ø ID Ø, f ?, Ø ID p, m, c ID ID f ID f ID ID ID ç s, , z d, Ø m s ?, Ø ID Ø ID s ID ID y ID ID ID ID s , Ø ID ID Ø ID ID s, Ø, ¸ s, s9, y, z, Ø Ø, k ¸, s, t, b Ø, s, d Ø, s, y, tl ?, Ø, p, h Ø Ø, c, h, p s, Ø, t s, y s, Ø, n, m s, ¸, Ø Ø, y, s Ø, ? Ø Ø s s, y s, Ø s, ç s, y Ø ID Ø ç s, d ¸ ID s, y Ø ID ID ID ID ID ID ID ID ID ID h h n, d, Ø, k ¸, t, b ? h ?, h, Ø ID h ID ID Ø ID ID ID ID ID V V d, Ø ID V ? ID h, m, Ø V, v, f, g V, Ø l, d, Ø ID V, Ø, n, l ?, Ø ID Ø ID V Ø ID V Ø ç ID l l l, n, d, b, Ø d l ?, Ø Ø, ? Ø, m l l, Ø, 8l l, Ø, ¸ Ø, l l, n, Ø, j, t ?, Ø ID Ø, l, 8l l l, ¸, Ø l, Ø, ¸ l, Ø l, Ø Ø ID Ø j j Ø, t, k ¸, n j j, l ?, h, Ø ID Ø, m j j, Ø l ID j, Ø Ø ID Ø, l

p p, b ID b ID ID

(continued )

780 K. E. Kristoffersen et al. Table 8. Continued


–j Q– –Q– –Q –– –

A

B

C

D

E

F

G

H

j

ID Q, j, D Q, j, l, Ø, D, , y j, Ø, l, n, y

ID

ID ID l, Ø l, Ø

j l l, m, Ø, Q, l, Q, Ø

ID ?, Ø ?, Ø Ø

ID ID ID Ø

ID Ø Ø Ø

ID R, R,

Ø, k ¸, d Ø, l, k ¸ l, Ø, n

Grey shading indicates that the phoneme does not exist in the subject’s target dialect. ID = insufficient data.

Table 9. Average number of alternative phoneme realizations across children. Initial position Medial position Final position

1.89 1.59 0.85

in word final position (see Table 4 above). At the same time, there is a clear similarity between the two groups in that the inventories in word initial and word medial position are larger than the one in word final position. Furthermore, rhotics and fricatives represent articulatory challenges for both groups, but again there is more variation among the CdCS children (see Table 8). There are no studies applying the measure PCC(-R) to Norwegian children with typical language development. However, as noted above, Hansson and Nettelbladt (2002) reported in their study of Swedish SLI children and TD age-matched controls PCC values of 80.1% for the SLI children and 98.69% for the TD controls. In this study, only two of the participants reached the PCC level of the Swedish SLI children, A with 93% and B with 83%. One subject had 72%, whereas the remaining subjects in our study had PCC-R values ranging from 2% to 52%. As was pointed out in the introduction, extent of intelligibility is influenced by a number of factors, including the number of sound errors. And with only half or less of their consonants correct, the result is bound to be reduced intelligibility. But intelligibility is also related to the types of sound errors. If we focus on the contents of the consonant inventories of the children who participated in this study, the deviant consonants that were identified in several of the subjects must also be considered a potential source of reduced intelligibility. Previous research on language skills in CdCS referred to misarticulations, and a few studies also noted a few concrete misarticulations (Cornish, Bramble, et al., 1999; Schlegel et al., 1967; Sparks & Hutchinson, 1980). The findings from our study provide a more complete picture in identifying particular consonant types that pose a challenge for these children. Furthermore, it is possible to link the existence of these deviant sound types to the fine motor problems associated with the syndrome. Kristoffersen (2008b) did this for the subject of his case study, and his conclusions are strengthened by this study. Both prenasalized stops and stops with lateral release might be linked to reduce fine motor skills, in particular those involving the soft palate and the sides of the tongue. The presence of a lateral fricative where the target language lacks such a consonant might likewise be seen as an indication of reduced motor control, with a wider gap between the articulators than the closest counterpart in the target system, the lateral. Another aspect related to the contents of the consonant inventories is that even though several of the target consonants could be identified, these sounds were not always used in all the positions



781

they are used in the target language (for concrete examples, see Table 8 above). This is also a factor that contributes to reduced intelligibility. Furthermore, this feature is found both in the speech of far younger TD children and in children with Down syndrome (Stoel-Gammon, 1980). Directly related to this issue are also our findings answering research question 2, concerning how the subjects rendered the target phonemes. In the introduction, we reasoned that if the errors produced by a child with disordered language are consistent, this might improve intelligibility somewhat, since the phonological patterns evident in the child’s word productions would then be more stable and systematic and thus lead to more predictable interpretations of the child’s utterances. For several of the children in our study, the extensive variation in the realization of target phonemes might be responsible for the opposite outcome – that it is almost impossible to decode the words attempted because there is little systematicity in the mapping between target phoneme and the child’s realization. This issue cannot be addressed properly without further research, though. The findings relating to the third question, concerning the extent of similarity between the words the children produced and the corresponding target words as measured by the PWP, have a bearing on the issue of intelligibility. As Ingram (2002, p. 730) points out, the PWP measure ‘‘has the potential to be a relatively quick way to reach an indicator of a child’s intelligibility’’. In his analysis of data from a three-year-old child with a phonological impairment, he found the PWP to be 0.33. In comparison, the PWP values resulting from his analyzes of data from a group of children with typical development aged 0.11 to 1.10 were all above 0.50, with a mean of 0.64. Turning to the subjects of our study, it is interesting to see that only three of the children had PWP values below 0.50. Thus, if this measure is taken to be a ‘‘quick way to reach an indicator of a child’s intelligibility’’, it appears to rate the intelligibility of these children higher than the other measures in this study. However, since a substantial part of this measure relates to the number of segments produced by the child relative to the number of segments in the target word, a child with very deviant sound productions still gets a high PWP if the number of segments is correct.4 Finally, we turn to the fourth research question and look into the intelligibility rating in more detail. Recall that all eight subjects were rated impressionistically with respect to intelligibility by the first author, cf. Table 3 above. It is interesting to see to what extent these ratings correspond to the two measures PCC-R and PWP. Clearly, there is no perfect match here, but we reported a moderate positive correlation in both cases (r ¼ 0.71 between intelligibility ratings and PCC-R and r ¼ 0.72 between intelligibility ratings and PWP). Focusing on individual participants, we note that A got a ‘‘high’’ in the impressionistic rating, and she also had high PCC-R (93%) and PWP (93%) scores. Similarly F, with a ‘‘low’’ in the impressionistic rating, had the lowest PCC-R in the group (2%) and also the lowest PWP (38%). However, E also received a ‘‘low’’ impressionistic rating, but her PCC-R and PWP values were relatively high, 72% and 74% respectively. Furthermore, these values are higher than those of C (PCC-R ¼ 52% and PWP ¼ 66%), who had medium intelligibility according to the impressionistic rating. In this study, it is interesting to note that four of the five raters who rated intelligibility on the basis of the recordings of the test session disagreed with the first author’s ratings (low); three of them rated E’s speech as highly intelligible and one rated it as medium intelligible. Several factors might contribute to this situation. One would be that the first author’s ratings are not reliable, and that the PCC-R and PWP measures are more trustworthy measures. However, it is also possible that the types of errors that E produces contribute to the overall intelligibility. For example, we found that E was the only child having both prenasalization and lateral release of 4 We have not investigated the effect of deviant vowel productions on intelligibility. However, Kristoffersen (2005) examined vowel productions of three children with CdCS and found that they were both variable and to a little extent similar to target vowels.


782 K. E. Kristoffersen et al. stops in her production. This combination may have been perceived as more or less deviant by the raters. Since both PCC-R and PWP are quantitative measures, they will not provide information about error type. Furthermore, since the subjects’ utterances deviated from their targets not only in terms of different segments but also in terms of factors like voice quality, nasality, timing of phonetic features and addition of features that were not present in the target words, it comes as no surprise that consonant accuracy measures will never entirely capture intelligibility. Therefore, it is also important to provide qualitative analyzes of the consonant productions, for example, in terms of contents of consonant inventories and renderings of target phonemes, as we have done in this article. Furthermore, it will be necessary to take into account linguistic and extra-linguistic contextual factors to obtain a more complete picture of what contributes to intelligibility or lack thereof.

Conclusion In this study, we have seen that children with CdCS to a varying degree have problems with producing the consonants of the target language. For the majority of our subjects, we found low PCC-R values, small consonant inventories with several recurrent types of deviant consonants (relative to the target language), inaccuracy in the realization of target phonemes and variable similarity to target words, all of which may contribute to reduced intelligibility. At the same time, the measures applied in this study clearly miss important aspects of the speech production of these children. For example, two of the participants, A and B, have about the same PWP score, i.e. their word productions are comparable in terms of similarity to the targets. But their language skills are very different: A speaks fluently in multi-word sentences, whereas B speaks in two and three word utterances and with markedly deviant prosodic features, which are not present in the speech of A. To cover the whole picture, analyzes and measures like those applied in this study must be supplemented with instruments assessing prosody, and of course also skills in other areas, like morphology, lexicon and syntax. Furthermore, as we have noted above, due to limitations of our method, we have not been able to examine variability across tokens of the same word produced by the same participant. Thus, future research should also include measures of variability. Finally, we still have little knowledge about the factors underlying the problems identified in this study. We may speculate, as we indeed have done, that some of the problems identified have their basis in reduced fine motor skills. But to our knowledge so far, no study has addressed this issue. Thus, research is still needed to resolve questions related to the underlying factors causing the speech problems associated with CdCS.

Acknowledgements We would like to thank the children who participated in this study and their parents. We also thank our five colleagues who provided intelligibility ratings for the speech of the eight children. Also thanks to Marilyn Vihman, Marianne Lind and Inger Moen for generous and critical comments, from whom the paper has improved in many respects. The two CLP reviewers also gave us a number of useful comments and suggestions. This research has been presented at the following conferences: Preconference workshop on phonological acquisition at the 13th Meeting of the International Clinical Linguistics and Phonetics Association, 2010, and the 2nd Nordic Conference in Clinical Linguistics, 2011. We are grateful to the audiences at these conferences for their valuable feedback.


783

Declaration of interest The authors report no conflicts of interest.


References Baird, S. M., Campbell, D., Ingram, R., & Gomez, C. (2001). Young children with cri-du-chat: Genetic, developmental, and behavioral profiles. Infant-Toddler Intervention, 11, 1–14. Ball, M. J., & Mu¨ller, N. (2005). Phonetics for communication disorders. Mahwah, NJ: Lawrence Erlbaum Associates. Carlin, M. E., & Fraser, W. I. (1990). The improved prognosis in Cri-du-chat (5p-) syndrome. Key issues in mental retardation research. London: Routledge. Collins, M. S. R., & Cornish, K. (2002). A survey of the prevalence of sterotypy, self-injury and aggression in children and young adults with Cri du Chat syndrome. Journal of Intellectual Disability Research, 46, 133–140. Cornish, K., Bramble, D., Munir, F., & Pigram, J. (1999). Cognitive functioning in children with typical cri du chat (5p-) syndrome. Developmental Medicine and Child Neurology, 41, 263–266. Cornish, K., Cross, G., Green, A., Willatt, L., & Bradshaw, J. (1999). A neuropsychological-genetic profile of atypical cri du chat syndrome: Implications for prognosis. Journal of Medical Genetics, 36, 567. Cornish, K., & Munir, F. (1998). Receptive and expressive language skills in children with cri-du-chat syndrome. Journal of Communication Disorders, 31, 73–81. Cornish, K., & Pigram, J. (1996). Developmental and behavioural characteristics of cri du chat syndrome. Archives of Disease in Childhood, 75, 448–450. Grunwell, P. (1985). PACS. Phonological assessment of child speech. San Diego: College Hill Press. Hansen, P. (2011). Atypisk konsonantproduksjon hos et norsk barn (MA thesis). University of Oslo, Oslo. Retrieved March 28, 2014, from http://urn.nb.no/URN:NBN:no-30288. Hansson, K., & Nettelbladt, U. (2002). Assessment of specific language impairment in Swedish. Logopedics Phoniatrics Vocology, 27, 146–154. Ingram, D. (2002). The measurement of whole-word production. Journal of Child Language, 29, 713–733. Kristoffersen, K. E. (2004). Consonant productions in three children with cri du chat syndrome. In B. E. Murdoch, J. Goozee, B.-M. Wehlan, & K. Docking (Eds.), Proceedings of the 26th International Association of Logopaedics and Phoniatrics 2004. Brisbane: IALP. Kristoffersen, K. E. (2005). Vowel productions in the speech of three children with cri du chat syndrome. Journal of Multilingual Communication Disorders, 3, s128–135. ISSN 1476-9670. Kristoffersen, K. E. (2008a). Speech and language development in cri du chat syndrome: A critical review. Clinical Linguistics & Phonetics, 22, 443–457. Kristoffersen, K. E. (2008b). Consonants in Cri du chat syndrome: A case study. Journal of Communication Disorders, 41, 179–202. Kunnari, S. (2003). Consonant inventories: A longitudinal study of Finnish-speaking children. Journal of Multilingual Communication Disorders, 1, 124–131. Marignier, S., Lesca, G., Marguin, J., Bussy, G., Sanlaville, D., & Portes, V. (2012). Childhood apraxia of speech without intellectual deficit in a patient with cri du chat syndrome. European Journal of Medical Genetics, 55, 433–436. Niebuhr, E. (1978). The cri du chat syndrome. Human Genetics, 44, 227–275. Robb, M. P., & Bleile, K. M. (1994). Consonant inventories of young children from 8 to 25 months. Clinical Linguistics & Phonetics, 8, 295–320. Schlegel, R., Neu, R., Carneiro, L., Reiss, J., Nolan, T., & Gardner, L. (1967). Cri-du-chat syndrome in a 10 year old girl with deletion of the short arms of chromosome number 5. Observations on dermatoglyphics, maxillo-mandibular measurements and sound spectrograms. Helvetica Paediatrica Acta, 22, 2–12. Shipley, K. G., & McAfee, J. G. (2008). Assessment in speech-language pathology: A resource manual. Clifton Park: Cengage Learning. Shriberg, L. D. (1993). Four new speech and prosody-voice measures for genetics research and other studies in developmental phonological disorders. Journal of Speech and Hearing Research, 36, 105–140. Shriberg, L. D., Austin, D., Lewis, B. A., McSweeny, J. L., & Wilson, D. L. (1997). The percentage of consonants correct (PCC) metric: Extensions and reliability data. Journal of Speech, Language and Hearing Research, 40, 708–722. Simonsen, H. G. (1990). Barns fonologi: system og variasjon hos tre norske og et samoisk barn (Doctoral dissertation). University of Oslo, Oslo. Sohner, L., & Mitchell, P. (1991). Phonatory and phonetic characteristics of prelinguistic vocal development in cri du chat syndrome. Journal of Communication Disorders, 24, 13–20. Sparks, S., & Hutchinson, B. (1980). Cri du chat: Report of a case. Journal of Communication Disorders, 13, 9–13.

784 K. E. Kristoffersen et al.


Stoel-Gammon, C. (1980). Phonological analysis of four Down’s syndrome children. Applied Psycholinguistics, 1, 31–48. Wilkins, L. E., Brown, J. A., & Wolf, B. (1980). Psychomotor development in 65 home-reared children with cri-du-chat syndrome. The Journal of Pediatrics, 97, 401–405. Wu, Q., Niebuhr, E., Yang, H., & Hansen, L. (2005). Determination of the ‘critical region’ for cat-like cry of Cri-du-chat syndrome and analysis of candidate genes by quantitative PCR. European Journal of Human Genetics, 13, 475–485.

Dermatoglyphics in Cri du Chat syndrome.

Peters anomaly in cri-du-chat syndrome.

Cri-du-chat syndrome: dental considerations and report of case.

When Cri du chat syndrome meets Edwards syndrome.

Orofacial manifestations in the Cri du Chat syndrome (5p-).

The Cri du Chat syndrome: epidemiology, cytogenetics, and clinical features.

Anesthetic experience of a patient with cri du chat syndrome.

Neoplasia in Cri du Chat Syndrome from Italian and German Databases.

Cri du chat syndrome and primary ciliary dyskinesia: a common genetic cause on chromosome 5p.

Phonatory and phonetic characteristics of prelinguistic vocal development in cri du chat syndrome.

A clue in the diagnosis of Cri-du-chat syndrome: Pontine hypoplasia.

Cri-Du-Chat Syndrome: Clinical Profile and Chromosomal Microarray Analysis in Six Patients.

Cri du chat syndrome due to meiotic recombination in a pericentric inversion 5 carrier.

Anesthesia in Cri du Chat syndrome: Information on 51 Italian patients.

Parental origin of chromosome 5 deletions in the cri-du-chat syndrome.

L’année du Chat.

Partial translocation of NOR and its activity in a balanced carrier and in her cri-du-chat fetus.

or possible chromosome 5p chromothripsis.

Familiarization Effects on Consonant Intelligibility in Dysarthric Speech.

Consonant production in children receiving a multichannel cochlear implant.

Analysis of stop consonant production errors in developmentally dysphasic children.

Intraoral air pressure as a feedback cue in consonant production.

Aided cortical response, speech intelligibility, consonant perception and functional performance of young children using conventional amplification or nonlinear frequency compression.

Stabilizing the production of nonnative consonant clusters with acoustic variability.