INT J LANG COMMUN DISORD, MARCH–APRIL VOL. 50, NO. 2, 151–164

2015,

Research Report Swahili speech development: preliminary normative data from typically developing pre-school children in Tanzania Nazneen Gangji†, Michelle Pascoe† and Mantoa Smouse‡ †Division of Communication Sciences and Disorders, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa ‡School of African Languages and Literatures, University of Cape Town, Cape Town, South Africa

(Received March 2013; accepted May 2014) Abstract Background: Swahili is widely spoken in East Africa, but to date there are no culturally and linguistically appropriate materials available for speech–language therapists working in the region. The challenges are further exacerbated by the limited research available on the typical acquisition of Swahili phonology. Aim: To describe the speech development of 24 typically developing first language Swahili-speaking children between the ages of 3;0 and 5;11 years in Dar es Salaam, Tanzania. Methods & Procedures: A cross-sectional design was used with six groups of four children in 6-month age bands. Single-word speech samples were obtained from each child using a set of culturally appropriate pictures designed to elicit all consonants and vowels of Swahili. Each child’s speech was audio-recorded and phonetically transcribed using International Phonetic Alphabet (IPA) conventions. Children’s speech development is described in terms of (1) phonetic inventory, (2) syllable structure inventory, (3) phonological processes and (4) percentage consonants correct (PCC) and percentage vowels correct (PVC). Results & Outcomes: Results suggest a gradual progression in the acquisition of speech sounds and syllables between the ages of 3;0 and 5;11 years. Vowel acquisition was completed and most of the consonants acquired by age 3;0. Fricatives/z, s, h/ were later acquired at 4 years and /θ /and /r/ were the last acquired consonants at age 5;11. Older children were able to produce speech sounds more accurately and had fewer phonological processes in their speech than younger children. Common phonological processes included lateralization and sound preference substitutions. Conclusions & Implications: The study contributes a preliminary set of normative data on speech development of Swahili-speaking children. Findings are discussed in relation to theories of phonological development, and may be used as a basis for further normative studies with larger numbers of children and ultimately the development of a contextually relevant assessment of the phonology of Swahili-speaking children. Keywords: Swahili, speech, normative data, phonological development, phonetic inventory, Tanzania.

Introduction Swahili is a Bantu language, sub-grouped as one of the Sabaki languages along with Pokomo and Comorian. It is spoken by an estimated 150 million people on the East coast of Africa, who use it either as their first, second or third language (Choge 2009). It is an official language of Tanzania, Kenya and Uganda and serves as a lingua franca for many communities in East Africa. Along with English, Swahili is used as a medium of instruction in schools in Tanzania and Kenya. As in many countries, there is a great diversity of languages and monolingualism is rare. Although it is difficult to describe a typical

pattern of language acquisition, many Tanzanian children will first acquire the language of the family’s ethnic group, with Swahili and English learned thereafter, or they would acquire Swahili first and English thereafter. In this paper we define multilingualism as the case where children are acquiring more than one language, and are able to comprehend and/or produce two or more languages with at least a basic level of functional proficiency, regardless of the age at which the languages were learned (adapted from Grech and McLeod 2012, p. 121, cited in International Expert Panel on Multilingual Children’s Speech 2012).

Address correspondence to: Michelle Pascoe, Division of Communication Sciences and Disorders, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; e-mail: [email protected] International Journal of Language & Communication Disorders C 2014 Royal College of Speech and Language Therapists ISSN 1368-2822 print/ISSN 1460-6984 online  DOI: 10.1111/1460-6984.12118

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Most of the studies on Swahili acquisition have focused on grammar, e.g. Mohamed (2001), Deen (2002) and Choge (2010). A few studies involving adaptation of language assessments for the Swahili population have also been carried out. For instance, Jonasson and Wann (2007) translated the Test for Reception of Grammar, Version 2 (TROG-2) (Bishop 2003) into Swahili and investigated the validity of the assessment in Kenya for children in two age groups (3;11–6;6; 13;9–17;0) in either English or Swahili. The results of their study indicated that TROG-2 was not appropriate for the younger children because of both cultural and linguistic differences. To date there are no published studies focusing on typical Swahili speech development of pre-schoolers, and no assessments are available that have been specifically developed with this population in mind. Where available, speech and language therapists (SLTs) use standardized assessments to analyse children’s phonology, identify children with speech sound disorders, determine intervention goals and monitor intervention progress. Current practices in Tanzania involve the use of assessments developed by clinicians in countries such as the UK or US and translation of these from English to Swahili. These tools, which include the Edinburgh Articulation Test (Anthony et al. 1971) and the Goldman–Fristoe Test of Articulation (Goldman and Fristoe 1986), are not well suited to the local population because they do not take into account the unique aspects of the Swahili language and Tanzanian culture, e.g. the inclusion of pictures unfamiliar to Tanzanian children, and the use of normative data obtained from a different population. These challenges are not unique to the Tanzanian, or even African, context. McLeod et al. (2013) describe these very challenges for SLTs working around the world. A growing acknowledgement of the need to serve multilingual children appropriately in all their languages lead to the development of a Position Paper for SLTs to guide their work with multilingual clients. Swahili phonetics Consonants Mohamed (2001) identified 26 consonants in Swahili and noted that /mb, mv, nd, nz, nj, ŋ/ are also phonemes as they function as single sounds, and when combined with other phonemes form words. Consonant clusters mostly occur in the word initial position, e.g. /sk/ in skati [skirt], although medial clusters are also possible, e.g. /sk/ in askari [soldier]. Swahili does not have consonants in word final position as all words end with vowels. Voiceless plosives may be either aspirated or unaspirated. Voiced plosives are implosive, there are palato-alveolar affricates /ʧ, ɟ/ and velar fricatives. Table 1 details the consonant inventory of Swahili.

Vowels All Swahili words contain vowels that may occur initially and medially, and always occur finally (Choge 2010). Swahili is generally noted to have five vowels: /a, ε, i, ‫כ‬, u/ (Kihore et al. 2008), however Mohamed (2001) identified nine vowels (five cardinal vowels and four secondary vowels: /ɪ, ε, u, ‫כ‬/) and Choge (2009) reported 12 vowels (five cardinal vowels, five long vowels /i:, ε:, a:, u:, ‫כ‬:/ and two diphthongs /au, ‫כ‬a/). These differences may be due to dialectal and idiolectal variations. Syllable structure Swahili has single vowel syllables where each vowel is counted as a syllable, e.g. ua [flower] (Mohamed 2001). Preconsonantal nasals /m/ and /n/ function as syllabic peaks in Swahili words, e.g. mtu [person]. A cluster of two or three consonants with a vowel can also form a syllable, e.g. mwezi [month] and ngwena [crocodile] (Mohamed 2001). Swahili has few monosyllables and usually they are not stressed. Some of the longest words in the language are loan words from other languages, such as English and Arabic. Speech assessment Independent analysis Independent analysis explores and identifies consonants and vowels, syllable-word shapes, and syllable-stress patterns that a child can produce regardless of accuracy and relationship to the adult target. A large number of studies have focused on the acquisition of consonants in English (e.g. Bernhardt and Stemberger 1998, Dodd et al. 2003, Smit et al. 1990) as well as many other languages (see McLeod 2007 for a comprehensive description of studies). Consonant acquisition varies across languages, e.g. the fricative /s/ is acquired at 2;6 years in Putonghua (Hua and Dodd 2000), 4;6 years in Cantonese (So and Dodd 1995) and after 6 years in Korean (Kim and Pae 2005). This variation indicates the importance of establishing norms for specific languages, also emphasized by McLeod et al. (2013). Further, the important influence of methodological choices should be noted: variation exists between the criteria used to consider a sound acquired, sample size, age range of the participants and elicitation methods. A total of 75% in two or three word positions is the criteria that has been most frequently used in normative studies of English speaking children. In terms of phonological processes, Roberts et al. (1990) considered only one occurrence of a simplification pattern as evidence that a pattern was used by the 145 children in their study. In contrast, Dodd et al. (2003) used a minimum of five occurrences of a phonological process in each child’s large representative speech sample

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Table 1. Consonant Inventory of Swahili Classes according to mode of articulation Place of articulation Bilabial Labiodental Dental Alveolar Palato-alveolar Palatal Velar Glottal

Plosives

Affricates

Fricatives

ʧɟ

fv θð sz ʃ

pb td

Nasals

Lateral

m

kG

xɣ h

n ɲ ŋ

Semi-vowels w

1r j

(based on Mohammed, 2001)

for establishing norms. Some studies have used conversational speech, often focusing on only a small number of children over an extended period of time. For example, Ayyad and Bernhardt (2009) investigated the phonological acquisition and syllable structure development in three young children acquiring Kuwaiti Arabic. In cross-sectional studies, a number of children are selected from different age groups. The speech produced by the children in different age categories is analysed at a point in time with the assumption that if a sufficient number of participants is sampled, typical developmental will be established with minimized individual differences in rate and patterns of development (Hua 2006). Although there are cross-sectional studies that have included large numbers of participants (e.g. Dodd et al. 2003, n = 684), many exploratory studies into less researched languages have included smaller sample sizes, e.g. Naidoo et al. (2005) investigated 18 children acquiring isiZulu. Vowel acquisition has also been investigated in a range of languages although it is not always included in normative studies perhaps due to an assumption that vowel acquisition occurs early and with fewer difficulties than that of consonants. In English children master vowels in stressed syllables by 3 years (Bankson and Bernthal 1998) and in unstressed syllables refinement may continue until 5 years (James 2001). There are no published studies that detail the development of the Swahili inventory, although there are studies that focus on development of other indigenous African languages such as isiXhosa (Mowrer and Burger 1991, Pascoe and Smouse 2012), Sesotho (Demuth 2007) and Zulu (Naidoo et al. 2005). There is less research focusing on development of syllable structures. There is a tendency for simple syllables to occur more often in a language than complex syllables, and these are mastered earlier. Naidoo et al. (2005) reported that isiZulu syllable structure develops primarily before 3 years. Grech (2006) found that Maltesespeaking children mastered complex syllable structures and multisyllabic words by 3;6 years. Phonological

saliency is a syllable based concept and accounts for each syllable in a word (Hua and Dodd 2000). Children tend to acquire components with higher saliency than components with lower phonological saliency. This concept is supported by findings of some studies (Mowrer and Burger 1991, So and Dodd 1995). Establishing a child’s phonetic inventory is essential as it can be used as a baseline to determine the developmental appropriateness of a child’s speech production. Speech sounds or syllables noted in a child’s inventory may be used by the child, but not correctly used within the language. Therefore phonetic inventory analysis needs to be supplemented with other assessments of a relational nature. Relational analysis Relational analysis compares a child’s productions with the adult target and aims to determine the pattern of errors relative to the target. Phonological process analysis and quantitative metrices are two examples of relational analyses. There are many studies that describe the phonological processes used by typically developing English-speaking children (Dodd et al. 2003, StoelGammon and Dunn 1985, Cohen and Anderson 2011). Studies of phonological processes used by children acquiring languages other than English are more limited, although these have been undertaken in, for example, German (Fox and Dodd 1999) and Maltese (Grech 2006) and indicate that some of the processes are common across languages whilst others are markedly different. Percentage consonants correct (PCC) and percentage vowels correct (PVC) (Shriberg et al. 1997) are metrices widely used to assess children’s phonological performance, quantify the degree of difficulty experienced and evaluate progress over time. PCC is scored based on the number of consonants correctly realized against the total number of consonants in the sample. It is reported in several studies of phonological development

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covering a range of languages, e.g. English (Dodd et al. 2003), Jordanian Arabic (Amayreh and Dyson 1998) and German (Fox and Dodd 1999). Limited information about the typical speech development of Swahili-speaking preschool children and the lack of Swahili speech assessments suggest an urgent need for research in this area. Information about the typical development of speech in children who are acquiring Swahili is particularly important in the East African context, but given globalization and increasing mobility of populations, it is important for SLTs around the world to have access to normative data about a range of different languages which they may encounter wherever they work (McLeod et al. 2013). The purpose of this study was: (1) to contribute to the body of knowledge regarding multilingual children’s phonological development by examining evidence from the East African language of Swahili; and (2) to provide information about the typical development of phonology in this language in order to support SLTs working with multilingual children in the region. This study aimed to describe the Swahili speech development in typically developing multilingual (Swahili, English plus other language/s) children aged 3;0 to 5;11 years. The study objectives were to detail (1) phonetic inventory, (2) syllable structure inventory, (3) phonological processes, and (4) PCC and PVC, for the Swahili speech of children in each of the age groups. Methods Research design A descriptive, cross-sectional design was used to identify trends relating to speech development. The crosssectional design allows one to gain a picture of the speech of children at different ages at one point in time. Participants The sample consisted of 24 first language Swahilispeaking children between the ages of 3;0 and 5;11 years. Participants were selected from a pre-school in Dar es salaam, Tanzania, where Swahili was the medium of instruction. All participants were multilingual with Swahili as their main language, and English and other additional languages specific to their ethnic group, also spoken. The teachers at the school, first language Swahili speakers themselves, helped identified children who met the criteria of having Swahili as a main language. The participants were grouped into six categories, with four children in each age group (two girls, two boys), i.e. Group 1: 3;0–3;5 years, Group 2: 3;6–3;11 years, Group 3: 4;0–4;5 years, Group 4: 4;6–4;11 years, Group 5: 5;0–5;5 years, and Group 6: 5;6–5;11 years. Partic-

ipants who were available and willing to participate were selected according to the following criteria: (1) first language Swahili speakers aged 3;0 to 5;11 years, (2) attending pre-school, (3) following typical speech and language development as judged by the teacher and parents/guardians, (4) no sensory, motor or cognitive difficulties, and (5) who had never attended or been referred for speech and language therapy services. The information was obtained from teachers as well as parents or guardians via a biographical data sheet (see appendix A). Children who did not meet the selection criteria were excluded from the study. Ethical considerations Approval was obtained from the Human Research Ethics Committee of the University of Cape Town, Faculty of Health Sciences and the Ethics Committee at Temeke Municipal Council, Dar es Salaam, Tanzania. Informed consent was obtained from the principal, teachers and parents/guardians of the child participants. In addition, the children gave their assent to participate in the study. Materials Wordlist In order to develop a linguistically and culturally appropriate assessment tool for the purposes of this study, we followed guidelines from Hua (2006). A list of approximately 150 words was generated with the help of a Swahili first language-speaking linguist. The wordlist provided opportunities for all phonemes of the language to be produced in word initial and medial positions, a range of word shapes that included words of two to four syllables and words that were culturally appropriate, likely to be in a preschool child’s vocabulary and able to be represented by a picture. A discussion panel was organized with two Swahili first language-speaking pre-school teachers in order to validate the wordlist. They were asked to consider each word in terms of its frequency, appropriacy for young children, general cultural appropriacy and phonetic structure (Hua 2006). When words did not meet one (or more) of these criteria they were discarded and alternatives suggested. The list was reduced to 48 words which contained words that met all the criteria (see appendix B). Some of these words included loan words from English which was unavoidable given that much of Swahili is comprised of loan words. Picture booklet A picture booklet was created using black and white line drawings from the Early Language Training

Swahili speech development of pre-school children in Tanzania Manual (Karanth et al. 2010) or similar drawings that were commissioned from an illustrator. The booklet depicted all the words in the wordlist and was designed to elicit naming responses from each child. Field testing was undertaken where the speech assessment was administered to a total of twenty two children from the same population as the study participants. The purpose of this pilot study was to ensure that the pictures were linguistically and culturally appropriate for the children. Some difficulties were noted with the pictures used, e.g. for the picture of a doctor most children produced ‘father’. Changes had to be made in preliminary versions of the assessment based upon these responses, and some minor amendments to illustrations were made. Apparatus A SONY audio recorder TCM-150 was used to record the responses of each child during the session. This permitted repeated listening, more accurate transcription, intra-rater and inter-rater reliability checking and qualitative analysis of the data. Procedures Data collection The assessment was administered to individual children in a quiet classroom. An oral peripheral evaluation took place to rule out any structural or functional abnormalities. The picture booklet devised for response elicitation purposes was presented to the child. If the item was given the appropriate semantic label, the child’s production of that label (whether accurate or inaccurate) was transcribed and the next picture produced. In cases where a child did not know the name of a picture, imitation was used to elicit word productions, and this was noted in the recording sheet. In such cases, children were given three attempts to produce the target word correctly and the most accurate production was used for further analysis. Repetitions were also recorded in the recording sheet. If a child was unable to imitate the word correctly, the researcher attempted to elicit the target sound in isolation. On site transcription was done using the International Phonetic Alphabet (IPA) transcription convention. The participants’ responses were audio recorded for cross checking and reliability purposes. Data analysis The researcher re-transcribed the speech samples to ensure consistency and reliability. The intra-rater reliability for consonants and vowels was 96.5% and 98%

155 respectively. In order to establish inter-rater reliability, the entire data set was independently transcribed by an experienced linguist and first language speaker of Swahili. A further 10% of the speech samples was transcribed by an experienced SLT. The inter-rater reliability for consonants and vowels with the linguist was 93% and 97% respectively. Similarly, the inter-rater reliability with the SLT was 97% for consonants and 100% for vowels. Where differences were noted, discussion took place in order to resolve the differences and reach a consensus. The analysis involved description and tabulations of the data according to the age groups of the participants in order to profile phonological development in terms of phonetic inventory, syllable structure inventory, phonological processes and PCC/PVC.

r Phonetic inventory. The criteria used to include a phoneme in the inventory were as follows: (1) Phonemes that were produced correctly by at least three out of the four participants within each group were included in the inventory regardless of the response being spontaneous or imitated; and (2) where there was a difference in scores across word positions they were averaged, i.e. word initial (WI) score for /s/ = 100% (4/4 children correct) and word medial (WM) score for /s/ = 50% (2/4 children correct); average of WI and WM = 75% and therefore considered as acquired. r Syllable structure inventory. A syllable structure was considered to be present in the inventory of the age group when three out of four (75%) participants produced the syllable structure at least once in their sample. r Phonological processes. A phonological process was attributed to an age group if two participants out of the four were found to exhibit the same simplification process on at least one word. r PCC and PVC. All consonants and vowels were considered when calculating PCC and PVC. The two quantitative measures were calculated using the following formulae (from Shriberg et al. 1997): Percentage consonants correct (PCC): # C s correct × 100 # C s targeted Percentage vowels correct (PVC): # V s correct × 100 # V s targeted

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Nazneen Gangji et al. Results Phonetic inventory across age categories

Tables 2 and 3 summarize the phonetic inventory and the performance of each age group in word initial and medial position respectively. All the six groups were able to produce all the vowels and the following consonants: plosives /p, b, t, d, k, G/, nasals /m, n, ɲ, ŋ/, approximants /w, j/, affricates /ʧ, ɟ/, lateral /l/ and fricatives /v, f, ð, ʃ / in both word initial and medial positions. Fricatives /z, s, h/ are present in the inventory of older groups (Groups 3–6) suggesting children tend to produce these sounds accurately when slightly older. The sounds /θ / and /r/ were most challenging for the children to produce and only children of the oldest group were able to produce these sounds correctly. Syllable structure inventory across age categories The syllable structure analysis was done irrespective of whether the target word or sound was produced correctly at a segmental level. The results of the syllable structure analysis are shown in Table 4, which displays the presence or absence of the structures across the six groups. All six groups were able to produce up to four syllable words. Groups 1 and 2 were able to produce various CV combinations comprising of one-, two- and threesyllable words except for the following: CCVCCVCV (e.g. mwamvuli [umbrella]) whereas Groups 3–6 were able to produce this combination with less difficulty. The words with four syllables of CVCVCVCV combination (e.g. themanini [eighty]) were not difficult for the participants to produce and most of the children including those in Group 1 were able to produce them. The following complex combination with four syllables: CVCCVCVCV (e.g. hospitali [hospital]) was not present in the inventory of any of the six groups. Overall, the results of syllable structure analysis suggested that shorter and simple syllable structures are acquired earlier than the longer and complex syllables with clusters. Phonological processes across age categories Table 5 displays the phonological processes exhibited by the Swahili-speaking children. The participants used processes that are commonly used in other languages such as weak syllable deletion and cluster reduction. They also used the following patterns: initial consonant deletion, metathesis and lateralization. There was considerable variability in the use of the phonological processes across groups (e.g. Group 1 used seven phonological processes, and Group 6 used only two phonological processes). Some participants also

used processes (e.g. stopping and affrication), which did not meet the criteria for inclusion in the group data trend in table 5. These processes were considered as isolated or idiosyncratic processes in the sample. The most widespread process that occurred across all the age groups was lateralization. In all age groups, the majority of the participants substituted /r/ with /l/ e.g. /lεdi‫כ‬/ for redio [radio]. Given that /r/ was shown to be one of the most challenging consonants to be acquired and was not included in the inventory of children from Groups 1–5, it was not surprising that some form of substitution, predominantly of /l/, took place. Weak syllable deletion was mostly observed in words with three or more syllables. The participants did not face difficulty when producing a disyllabic word. Groups 1–5 exhibited weak syllable deletion, e.g. /nini/ themanini [eighty]. The children in Group 6 were able to produce longer words with complex syllable structure. Similarly, Groups 1–5 exhibited sound preference substitution, whereby a phoneme is replaced by another phoneme from the same category. Some of the most common substitutions observed were replacing /θ / with /s/ in both word initial and word medial position, (e.g. /sεlasini/ thelathini [thirty]), and replacing /z/ or /ð/ with /ʒ/. The participants exhibited initial consonant deletion in words which were of three or four syllables. Cluster reduction was present in Groups 1 and 2. Metathesis and palatalization were present only in the data of Group 1. Overall, the use of phonological processes was seen to decrease with age which fits with the picture of increasing inventories described in the phonetic inventory section.

PCC and PVC across age categories PCC and PVC were calculated for each group. The mean percentages and standard deviations for PCC and PVC for each age group are shown in Table 6.

Percentage consonants correct (PCC) PCC was calculated for each child and considered for each age group. The findings indicated a gradual progression from Group 1 to Group 6. The median PCC ranged from 93.75% (Group 1) to 96.54% (Group 6). The data for Group 4 did not fit with the developmental trend: the median PCC for Group 4 was 89.47%, which was lower than all other groups including children in the youngest group. Two of the children from Group 4 showed some inconsistencies which resulted in a lower mean PCC score compared to the other groups. The interquartile range for the PCC scores of Groups 1 and 2 is relatively high, highlighting the individual variation within the groups.

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Table 2. Phonetic inventory of each of the six groups, with reference to manner of articulation Inventorya Group

Age group

Vowels

1 2 3 4 5 6

3;0-3;5 3;6-3;11 4;0-4;5 4;6-4;11 5;0-5;5 5;6-5;11

a, ε, i, ‫כ‬, u a, ε, i, ‫כ‬, u a, ε, i, ‫כ‬, u a, ε, i, ‫כ‬, u a, ε, i, ‫כ‬, u a, ε, i, ‫כ‬, u

Plosives

Nasals

Affricates

Lateral

Approximants

b, p, t, d, k, ɡ b, p, t, d, k, ɡ b, p, t, d, k, ɡ b, p, t, d, k, ɡ b, p, t, d, k, ɡ b, p, t, d, k, ɡ

m, n, ɲ, ŋ m, n, ɲ, ŋ m, n, ɲ, ŋ m, n, ɲ, ŋ m, n, ɲ, ŋ m, n, ɲ, ŋ

ʧ, ɟ ʧ, ɟ ʧ, ɟ ʧ, ɟ ʧ, ɟ ʧ, ɟ

l l l l l l

w, j w, j w, j w, j w, j w, j

Fricatives f, v, ð, ʃ, f, v, ð, ʃ, z, f, v, ð, ʃ, z, s, h, f, v, ð, ʃ, z, s, h, f, v, ð, ʃ, z, s, h, f, v, s, ð, ʃ, z, s, h, θ

Trill

r

Note: a Criteria for inclusion: Phonemes that were produced correctly by at least three out of the four participants within each group were included in the inventory regardless of the response being spontaneous or imitated.

Percentage vowels correct (PVC) The results indicated scores approaching ceiling for all age groups with median PVC of 96.8% (Group 1) to 98.7% (Group 6). In English, PVC scores are typically higher than PCC (Velleman 2009). Most of the children have higher PVC than PCC across age categories, although 3 children had slightly lower PVC than PCC scores. Discussion A gradual developmental progression was outlined based on the data obtained from the children in each of the groups of increasing age. Despite the fact that many studies which document children’s speech development in a range of languages agree on the developmental progression, there is disparity in terms of the exact nature and time frame of phoneme and syllable acquisition across languages. All the children in this sample consistently used all the vowels and the following consonants: plosives /p, b, t, d, k, G /, nasals /m, n, ɲ, ŋ/, approximants /w, j/, affricates /ʧ, ɟ/, lateral /l/ and fricatives /v, f, ð, ʃ/ in both word positions that were investigated. The results showed that the 3-year-olds had already acquired a complete vowel inventory and much of the consonantal inventory of their language. Similar findings are reported for other Bantu languages such as isiXhosa (Mowrer and Burger 1991), Sesotho (Demuth 2007) and isiZulu (Naidoo et al. 2005) where children acquire most of the phonemes by 2;6–3;0 years. Swahili is classed in the Bantu language group along with isiXhosa, isiZulu and Sesotho. Although the languages are linked by common origin, they represent different subgroups of the large Bantu category. In terms of consonants, fricatives were found to be challenging for the children to produce and differences were noted between the six age groups. The fricatives that were noted to be difficult for the younger children to produce include /z, s, h, θ /. /θ / was found to be the most difficult fricative to produce and only the oldest group could produce the sound accurately. Similarly, the

trill /r/ was found to be difficult to produce by many of the children. According to Bleile (2009), the phonemes /θ / and /r/ are amongst eight sounds ‘the late eight’ that English-speaking children acquire relatively late. A total of 75% of English-speaking children acquire /θ / and /r/ by 6;0 years of age (Dodd et al. 2003, Smit et al. 1990). The results of this study also show that Swahilispeaking children acquired them relatively late, but by the age of 6;0 years. Looking cross-linguistically similar findings have been reported. In Ayyad and Bernhardt’s (2009) study of Kuwaiti Arabic, they found that coronal fricatives and /r/ are some of the last acquired phonemes. Donohue et al. (1983) reported that in Welsh /θ / and /r/ are the latest acquired consonants. The age of acquisition for some phonemes reported in this study varies from the data reported for other languages. For example, the affricate /ʧ/ is reported to be acquired in the range of 5;0 to 7;0 years in English (Bleile 2009, Smit et al. 1990) and by 3;6 years in Maltese (Grech 2006), but was found to be acquired by Swahilispeaking children in this sample at 3;0 years of age. Results suggest that children acquiring Swahili master simple syllable structure by 3;0 years but their syllable structure inventory is incomplete and development of complex and multisyllabic words continues after 5;11 years. All six groups were able to produce simple syllable structures consisting of two to four syllables, and showed a gradual progression in the development of syllable structures with age. According to Bernhardt and Stemberger (1998), simple syllable structures occur frequently in a language and are mastered earlier than complex structures. The children of Group 1 (3;0–3;5) and Group 2 (3;6–3;11) were able to produce various CV combinations of three syllable words except for the following combination CCVCCVCV as in the target word mwamvuli [umbrella] which contains two consonant clusters. The older children of Groups 3–6 were able to produce mwamvuli correctly and the syllable structure was included in their inventory. The children in Groups 5 and 6 were found to produce longer and complex structures and made few syllable simplification errors compared to the younger groups. Naidoo et al. (2005)

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Nazneen Gangji et al. Table 3. Performance of each group in word initial and word medial position

Notes: WI, word initial position; WM, word medial position.

reported that isiZulu syllable structure develops primarily before 3 years, and that shorter syllable structures develop earlier than longer syllable structures. Despite the fact that isiZulu belongs to a different group of Bantu

languages, the findings of the syllable structure inventory from that study are similar to this study. The four syllable word hospitali [hospital] was not documented in any of the six groups: like many words in Swahili, this

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Table 4. Summary of the syllable structures produced by Swahili speaking children Age Group No. of Syllables

Syllables

Examples

English translation

1 2

CCCV CVV CVCV CCVCV CVCCV CVCVV CVVCV CCVCVV CVCVCV CCVCCVCV CVCVCVCV CVCCVCVCV

mbwa yai paka ndizi tembo fagio viatu mshumaa samaki mwamvuli themanini hospitali

dog egg cat banana elephant broom shoes candle fish umbrella eighty hospital

3

4

1

2

3

4

5

6

3;0-3;5 + + + + + + + + + − + −

3;6-3;11 + + + + + + + + + − + −

4;0-4;5 + + + + + + + + + + + −

4;6-4;11 + + + + + + + + + + + −

5;0-5;5 + + + + + + + + + + + −

5;6-5;11 + + + + + + + + + + + −

Note: · Plus (+):Syllable structure present · Minus (−):Syllable structure absent · Abbreviations: C= Consonant, V= Vowel

is a loan word. It contains a consonant cluster which is relatively uncommon in Swahili. The word was selected in our attempt to include a wide range of different word shapes. A wide range of phonological patterns were noted in the speech productions of Swahili-speaking children between the ages of 3;0 and 5;11 years. The use of phonological processes reduced gradually across age groups both in terms of frequency and range of processes used. Some phonological processes that are often described for other languages such as English (Dodd et al. 2003, Stoel-Gammon and Dunn 1985), German (Fox and Dodd 1999), Cantonese (So and Dodd 1995), and Putonghua (Hua and Dodd 2000) are similar to those found in this study e.g. cluster reduction and weak syllable deletion. The other developmental processes used by the Swahili-speaking children include: lateralization, sound preference substitution, initial consonant deletion and metathesis. The most widespread phonological process that was used across age groups was lateralization: the majority of the participants substituted /r/ with /l/, e.g. /lεdi‫כ‬/ for redio [radio]. Given that /r/ was found to be one of the most challenging sounds to produce and was acquired last, it was not unexpected that some form of substitution took place. Weak syllable deletion was the second most frequent process used by the Swahili-speaking children: children in Groups 1–5 exhibited weak syllable deletion in words with three or four syllables (e.g. /nini/ themanini [eighty]). Weak syllable deletion is a common process reported in a range of languages such as English (Stoel-Gammon and Dunn 1985), Maltese (Grech 2006), Cantonese (So and Dodd 1995) and German (Fox and Dodd 1999). Another frequently used phonological process was sound preference substitution,

mostly replacing /θ / with /s/. Given that the fricative /θ / is one of the last acquired consonants in Swahili and was not present in the inventory of Groups 1– 5, it was not surprising that the children substituted the sound with another fricative. In English, the substitution of /θ / with /s/ is common. There were instances where /z/ or /ð/ was substituted by /ʒ/. /ʒ/ is not part of the Swahili phonetic inventory, and yet five of the children produced the sound across several age groups. This may be due to the fact that English was their second language. In Tanzania (and indeed much of Africa) multilingualism is the norm. The children in this study reflected that norm and are typical in terms of language acquisition in this context. McLeod et al. (2013) emphasize that multilingual speech acquisition is different to monolingual acquisition, and this example may illustrate the influence of another language, English, shared by the children. An alternative explanation may be that the production of /ʒ/ in this instance illustrates a backing process, which may be a typical developmental process in Swahili. More data would be needed to determine which of these explanations is more appropriate. Cluster reduction was exhibited by children in Groups 1 and 2. In English, cluster reduction and weak syllable deletion do not typically persist after 4 years of age (Cohen and Anderson 2011, Dodd et al. 2003). Although weak syllable deletion was found to be used by children aged between 3;0 and 5;6 years, the results of cluster reduction for Swahili-speaking children are consistent with the English pattern. Besides English, cluster reduction is a common process in German (Fox and Dodd 1999) and Maltese (Grech 2006). In the present study, cluster reduction was mainly noted in the words mwamvuli [umbrella] and hospitali [hospital]. Clusters

160

Nazneen Gangji et al. Table 5. Summary of phonological processes exhibited by Swahili speaking children Phonological

Examples

Age Groups

Processes Lateralisation

/ledio/ redio [radio]

Sound

/ðawadi/ zawadi [gift]

1

2

3

4

5

6

3;0-3;5

3;6-3;11

4;0-4;5

4;6-4;11

5;0-5;5

5;6-5;11

preference substitution Weak

/nini/ themanini [eighty]

syllable deletion Initial consonant /anasi/ nanasi deletion

[pineapple]

Cluster

/mavuli/ mwamvuli

reduction

[umbrella]

Palatalisation

/ȉamaki/ samaki [fish]

Metathesis

/roli/ lori [lorry]

Note: The solid bar corresponding to each phonological process indicates the presence of the pattern in an age group as determined by the occurrence of the process in at least 50% of the participants (n = 2) per category.

are not common in Swahili, which may mean that SLTs working in that language do not need to accord this process much emphasis, but conversely many children may struggle to produce consonant clusters because of their low frequency in the language. If children are also acquiring English, a language in which there are many clusters, they may have ample opportunities to produce them. Adult speakers of Swahili produce words such as hospitali with no difficulty. Pollock (2002), looking at a much larger total sample of 162 children aged between 1;6 and 6;10, reported that English-speaking children between 3;0 and 3;5 years produced consonants with 92% accuracy and children aged 5;5–5;11 produced consonants with 96% accuracy. Pollock and Berni (2003) reported that Englishspeaking children between 3;0 and 3;11 produced vowels with 97% accuracy and children aged 4;0–6;11 years produced vowels with more than 98% accuracy. While the PCC and PVC findings of these studies are broadly

comparable, these studies and our own should be compared with caution. Pollock’s work was undertaken with a larger sample of children and both single word and connected speech data was used to obtain the indices. In our study, the PCC score of children in Groups 1 and 6 were 93.75% and 96.54% respectively. PVC results ranged from a mean of 96.8% for Group 1 to over 98% for Groups 2–6. In English, PVC scores are typically higher than PCC (Velleman 2009) as vowels are acquired earlier than consonants. Most of the children had higher PVC than PCC across age categories, although three children were found to have lower PVC than PCC. Since no previous research has been carried out with regards to PCC and PVC in Swahili, it is difficult to draw conclusions about whether a lower PVC than PCC score is atypical or not, although in all cases the differences between the scores was small. The findings of this study suggest that vowel development is complete before 3 years in Swahili.

Swahili speech development of pre-school children in Tanzania

161

Table 6. Summary of PCC and PVC across age categories PCC

PVC

Group

Age Group (years)

Median

IQRa

Median

IQRa

Participants

PCC

PVC

1

3;0 – 3;5

93.75

9.35

96.8

1.9

2

3;6 – 3;11

93.1

7.10

98.1

0.65

3

4;0 – 4;5

94.35

3.75

98.7

0.59

4

4;6 – 4;11

89.47

3.34

98.7

0.95

5

5;0 – 5;5

96.26

4.35

98.1

0.95

6

5;6 – 5;11

96.54

2.25

98.7

1.2

1A 1B 1C 1D 2A 2B 2C 2D 3A 3B 3C 3D 4A 4B 4C 4D 5A 5B 5C 5D 6A 6B 6C 6D

92.5 97.5 95 81.3 96.8 93.1 82.6 93.1 96.8 90.6 93.7 95 94.4 90.06 88.89 88.89 94.4 99.37 94.4 98.13 96.2 96.2 96.89 100

97.4 95.5 98.1 96.2 98.1 98.1 97.4 98.7 98.7 99.3 98.7 98.1 98.7 98.1 98.7 100 98.1 98.1 98.1 100 98.1 98.1 99.3 99.3

Note: a IQR: Interquartile range

The general order of Swahili consonant acquisition was found to be plosives, nasals, lateral, approximants and affricates followed by fricatives and trills. The youngest children were able to produce all the vowels, plosives, nasals, lateral, approximants, affricates and the fricatives /f, v, ð, ʃ/ suggesting that most of the sounds develop before or by 3 years of age in Swahili. The affricates /ʧ, ɟ/ were acquired before all the fricatives in Swahili. In languages such as English (Bleile 2009) and isiXhosa (Pascoe and Smouse 2012) affricates are reported to be acquired late. While isiXhosa phonology contains 11 affricates, Swahili has only two (Mohamed 2001) and they occur frequently in the Swahili vocabulary. This may be the possible reason Swahili-speaking children acquire affricates earlier. Further, the phonemes /s/ and /v/ which are part of the phonemic inventories of Swahili, English and Maltese appear to be acquired earlier in Swahili than in the other languages. It is evident that the findings of this study are broadly similar to those reported in other languages in terms of acquisition of vowels, acquisition of some consonants such as /p, n, m/ and phonological process such as weak syllable deletion and cluster deletion. At the same time there are several unique differences such as early acquisition of affricates, age of acquisition of sounds such as /s/ and /v/ and the frequent use of phonological processes such as lateralization.

Clinical implications The normative data arising from this study may be a useful starting point in assisting SLTs in their assessment and management of Swahili-speaking children with speech difficulties. For example, based on the preliminary normative data from this study, a 3-year-old child acquiring Swahili as a first language might be expected to be able to produce all vowels, and many of the consonants, excluding /z, s, h, θ , r/. Phonological processes such as lateralization may also be noted. The findings emphasize the importance of establishing norms for Swahili since SLTs use norms in their practice to assess children with speech difficulties and make clinical decisions. While the sample size used in this study was small, it starts to detail phonological features used by Swahili-speaking children at each age and this preliminary data could be used by SLTs in the assessment and management of Swahili-speaking children with some caution, until more generalizable data becomes available. Given that the participants of the study were multilingual Swahili-speaking children, the findings should be applied with caution to children who speak different combinations of languages. All of the children in this study shared English as an additional language and the possible influence of English phonology on Swahili speech was noted in some instances. However, detailed

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language profiles were not described for each participant (e.g. full range of languages and dialects the child is exposed to; age and sequence in which the language exposure occurred). Given each child’s unique profile of multilingualism and acknowledged cross-linguistic influences, norms from a given population of children must be applied with care. De Lamo White and Jin (2011) detail procedures and approaches for assessing speech and language of multilingual children. These authors conclude that a socio-cultural approach may be the most effective for assessing such children. A socio-cultural approach, may include the use of normreferenced measures, but pays explicit consideration to the child’s language and cultural background so that comparison with normative data takes place with explicit and detailed consideration of these factors. There are many different dialects of Swahili and this would also need to be taken into account in future studies. James (2009) carried out work on ‘long words’ and found ten words which are ‘clinically useful’ in assessing speech production difficulties of English-speaking children. Words of three or more syllables have been suggested to be diagnostic in discriminating between typically developing children and those with speech difficulties, and they are more likely to reveal differences in the speech production abilities of younger and older children. In the present study words such as thelathini [eighty], mwamvuli [umbrella] and hospitali were used as examples of long words. They yielded information not only with regards to syllable structure inventory but also phoneme acquisition, phonological processes and PCC/PVC. They may be examples of clinically useful words that could be used to tap into the speech abilities of older children. For example, one of the oldest children in the study experienced few difficulties, but produced /h‫כ‬pistali/ for hospitali [hospital]. This is similar to the types of errors made with multisyllabic words by typically developing children in English for the word ‘hospital’ (James 2009) and should not be a cause for concern. However, it is interesting in that it shows the child’s speech system under strain, and a clinical useful assessment should contain a range of items from easy to more challenging. Future studies There is a need for further studies investigating the acquisition of speech in East Africa. This exploratory study used a very small number of children with only four children per 6-month age band. We focused on the children’s acquisition of one language—Swahili—in a multilingual context. Having a larger sample size would allow for greater generalization to the population, and, for example, help to determine whether the processes described as ‘idiosyncratic’ in this study are in fact unusual or are

widely used in typical development. A wider age range (e.g. 2;0–8;0 years) could be used to document phonological development, and map the emergence of the more challenging words such as mwamvuli and hospitali. Individual factors should also be considered in future research in more detail, e.g. socio economic status, gender, and monolingual versus multilingual acquisition. The children who participated in this study were multilingual speakers of Swahili, yet only their Swahili was investigated. A shortcoming of the study is that we did not document the complete language profiles of the multilingual children, beyond the fact they are first language Swahili speakers and second language English speakers. Future studies should include assessment of their other languages in order to yield a more holistic picture of phonological development (McLeod et al. 2013) and allow for more in depth discussion of crosslinguistic influences. The wordlist used in this study was specifically created for the purposes of the project since there was no Swahili speech assessment available. The wordlist and picture booklet were designed to be culturally and linguistically appropriate, allow for the production of all Swahili speech sounds in different word positions, as well as being able to be visually represented and appropriate for pre-school children. A small independent expert panel was asked to review and comment on the tool. Despite these measures, the tool obtains limited data about speech sounds in particular contexts. Having a larger set of stimuli would allow for some of the preliminary hypotheses detailed here to be further explored, e.g. would lateralization occur more widely if more words were included that offer the opportunity to use that process? Much of the evidence for lateralization comes from the production of /lεdi‫כ‬/ for redio [radio]. If more words containing /r/ in initial or medial position had been used, there would be more evidence to confirm or refute this argument. The length of a wordlist needs to be balanced so that it is not so long as to be impractical to administer to young children, but contains items that yield sufficient information to inform clinical decision-making. Studies need to be carried out on PCC and PVC on a larger sample using connected speech to yield more information since this study analysed single word productions of the children. There is some controversy regarding the exact number and nature of vowels in Swahili (Choge 2009, Mohamed 2001) and future studies might include a larger range of vowels in the assessment. Conclusion Language specific norms are critical for assessing children with speech difficulties and making clinical decisions. It is important for SLTs to know when phonemes

Swahili speech development of pre-school children in Tanzania and syllables are acquired in a particular language in order to judge whether a child’s speech is typical or not. This study was motivated by the Position Paper drafted by the International Expert Panel on Multilingual Children’s Speech and described by McLeod et al. (2013). It aims to contribute to knowledge of the Swahili language by describing the phonetic inventory, syllable structure inventory, phonological processes and PCC/PVC in a small sample of typically developing Swahili-speaking children aged between 3;0 and 5;11 years. The findings indicated that all vowels and most of the consonants in Swahili are acquired by 3 years of age. The phonemes /θ / and /r/ were found to be among the last sounds acquired by the children only by 5;11 years. Simple syllable structures were found to be acquired earlier than the complex syllables. Complex and longer syllable structure appeared to be common among older children and mastered at 5;11. A gradual decrease in the use of phonological processes with age indicated that older children tend to produce speech sounds more accurately and use fewer simplification patterns in their speech. The findings presented here highlight the need for establishing assessments in Swahili considering the variation existing in speech acquisition across languages. A larger cross-sectional study containing more stimuli would yield more information on speech development of Swahili-speaking children and ultimately lead to development of norm-referenced standardized assessments for children acquiring Swahili, however it would be important to investigate the other languages of the multilingual participants since the speech development of multilingual children should not be viewed as the same as acquisition in monolingual children. Acknowledgements Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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Appendix A: Biographical information sheet Name of the child: . . . . . . . . . . . . . . . . . . . . . . . . Date of birth: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Age: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mother tongue: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other languages spoken: . . . . . . . . . . . . . . . . . . .. At what age did you child start? · Sitting . . . . . . . . . . . . . . . . . . . . . . · Standing . . . . . . . . . . . . . . . . . . . . . . · Walking . . . . . . . . . . . . . . . . . . . . . . · First words . . . . . . . . . . . . . . . . . . . . . . Please circle the appropriate response

(1) Does your child have any vision problems? YES/NO (2) Does your child have any hearing problems? YES/NO (3) Does your child speak age adequately as compared to the children of his age? YES/NO (4) Has your child visited an ENT for any problem? YES/NO If yes please specify ... ... ... ... ... ... ... ... ... ... ... ... ... .... (5) Does our child have any relevant medical / cognitive/ physical and /or health problems? YES/NO If yes please specify ... ... ... ... ... ... ... ... ... ... ... ... ... .... (6) Has your child attended or been referred to speech therapy services? YES/NO If yes please specify ... ... ... ... ... ... ... ... ... ... ... ... ... .... Thank you for filling the questions. Please note all the information will be treated in a strictly confidential manner. Appendix B Table B1. Swahili Wordlist Swahili word English translation Swahili word English translation paka bata tembo dirisha kitabu gari chupa shati samaki zawadi fagio viatu meza nanasi nyumba ngombe lori redio watu yai jikoni themanini dhahabu hospitali sketi

cat duck elephant window book car bottle shirt fish gift broom shoes table pineapple house cow lorry radio people egg kitchen eighty gold hospital skirt

mdudu macho kisu ndizi kofia mwamvuli mshumaa miwani panya mlango gilasi gari mbwa mayai kijiko thelathini fedha sahani funguo simba kabati lala kiti moto

insect eyes knife banana cap umbrella candle Spectacles mouse door glass car dog eggs spoon thirty money plate Key lion cupboard sleep chair fire

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Swahili speech development: preliminary normative data from typically developing pre-school children in Tanzania.

Swahili is widely spoken in East Africa, but to date there are no culturally and linguistically appropriate materials available for speech-language th...
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