Phonological Development in Dutch-speaking children with Developmental Language Disorder

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Phonological development in Dutch-speaking children

with Developmental Language Disorder

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List of tables and figures

Table 1 Features of segments of Dutch phonological system.

Table 2 Summary of the order of phonological acquisition of Dutch

consonants in syllable-initial and syllable-final position.

Table 3 Phonological simplification processes in Dutch.

Table 4 Occurrence and disappearance of the typical phonological

simplification processes in normally developing Dutch children.

Table 5 Patterns of disappearance of normal phonological simplification

processes.

Table 6 Unusual phonological simplification processes in Dutch.

Table 7 STTP Mean scores of DLD-E and DLD-RE considering word

comprehension, word and sentence comprehension, word production, sentence production and non-verbal intelligence.

Table 8 Examples of calculation procedure for computing the

percentage of acquired consonants.

Table 9 Examples of calculation procedure for computing the

percentage of phonological simplification processes that have been registered.

Table 10 Order of acquisition of contrasts in Dutch in TD children and

children with DLD.

Table 11 Phonological simplification processes in DLD.

Table 12 Maximum occurrence of phonological simplification processes

in TD children.

Table 13 Unusual simplification processes in DLD.

Table 14 Mean number of correct responses in Metaphon Screening Test

for DLD-E and DLD-RE.

Table 15 Order of acquisition of contrasts in Dutch in TD children,

children with DLD-E and children with DLD-RE.

Table 16 Phonological simplification processes in DLD-E and DLD-RE.

Table 17 Unusual phonological simplification processes in DLD-E and

1 DLD-RE.

Table 18 Metaphon Screening Test – words.

Table 19 Metaphon Screening Scoring form for phonological

simplification processes.

Table 20 Features of consonants in Dutch.

Table 21 Overview of phonemes and contrasts in syllable-initial and

syllable-final position in DLD, DLD-E and DLD-RE.

Chart 1 Percentage of consonant acquisition in syllable-initial position

for DLD.

Chart 2 Percentage of consonant acquisition in syllable-final position

for DLD.

Chart 3 Phonological simplification processes in syllable-initial

position for DLD-E.

for DLD-E.

for DLD-RE.

for DLD-E and DLD-E.

for DLD-E.

for DLD-E and DLD-RE.

Chart 9 Phonological simplification processes in DLD.

Chart 10 Phonological simplification processes in DLD-E.

Chart 11 Phonological simplification processes in DLD-RE.

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Chart 13 Unusual phonological simplification processes in DLD.

Chart 14 Unusual phonological simplification processes in DLD-E.

Chart 15 Unusual phonological simplification processes in DLD-RE.

Chart 16 Unusual phonological simplification processes in DLD-E and

DLD-RE.

Chart 17 Total number of correct responses from Metaphon Screening

Test for DLD-E and DLD-RE.

Figure 1 Nonlinear phonological features hierarchy based on Clements

(1985).

Figure 2 Hierarchical representation of Dutch consonant /m/.

Figure 3 Features of consonants.

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1. Introduction

An important process young children undergo in their linguistic development is the development of speech production skills. Children gradually learn how to use phonemes, which are components of words, and often use phonological simplification processes when unable to produce a complex word due to their articulatory limitations. Most typically developing children produce words by the end of their first year. However, there is a group of children who demonstrate difficulties regarding their phonological development.

Those children have a disorder resulting in a different development in their language acquisition with no apparent cause. This language impairment was introduced into the linguistic field by several studies under the name Specific Language Impairment (SLI) (Leonard et al., 1987, Bishop, 1994, Schwartz, 2009). This disorder has different labels in the linguistic and neuropsychological field besides SLI, such as Speech Language and Communication Needs (SLCN) and Developmental Language Disorder (DLD). The latter is currently used by most professionals and will be used in the current study as well. DLD is a neurobiological disorder with a common genetic factor (Stromswold, 1998).

Children diagnosed with DLD demonstrate difficulties with the acquisition of spoken language (Tomblin et al., 1997). The age at which children with DLD start to produce words is approximately two years, which is considered different and delayed compared to their age-matched peers. A number of studies have been carried out to determine the cause of the deficit. Children with DLD appear to have a deficit in several linguistic domains, such as grammar (van der Lely & Christian, 2000), acoustic processing (Rinker et al., 2007) and phonological development (Chiat, 2001), making children with DLD a heterogeneous group. Phonological development in children with DLD is also a broadly studied subject in the linguistic field. Numerous studies have been conducted into phonology in children with DLD, also considering their phonological memory and ability to produce nonsense words (Leonard et al., 1987, Rispens & Parigger 2010) and phonological processing (Loucas et al., 2016).

Several studies have shown that a phonological deficit is one of the main characteristics of DLD (Ramus et al., 2013, Leonard et al., 1987). Studies carried out cross-linguistically (Maillart & Parisse 2006, Beers 1995) also support the above claim. A deficit in phonological development results in poor comprehensibility and not being able to understand a communicative partner, resulting in educational difficulties (Tombil et al., 1997). Despite phonological deficit being a clinical marker for children with DLD, a distinction can be made within the group of children with DLD experiencing phonological problems.

Even though the group of children with DLD is mostly referred to as a heterogeneous group, Leonard (2014) recently divided them in two main groups: children with expressive DLD (DLD-E) and children with receptive and expressive DLD (DLD-RE). The first group, children with DLD-E, refers to children with DLD that have problems with their expressive linguistic skills while language comprehension remains intact. The latter, children with DLD-RE, are children that experience a deficit in the expressive and receptive linguistic skills demonstrating production and comprehension difficulties.

Since the distinction was made between DLD-E and DLD-RE, some studies have examined potential differences between these two groups with regard to linguistic skills. Nickisch and von Kries (2009) carried out a study examining short-term memory constraints regarding the ability to hold a small amount of information in the mind in children with E and DLD-RE compared to TD children. Specifically, they wanted to examine the ability of the children with DLD-E and DLD-RE to process auditory and verbal tasks in their short-term memory.

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Aside from short-term memory abilities, Nickisch and von Kries also conducted tests examining the expressive language abilities of the groups. Surprisingly, the expressive language ability of the participants with DLD-E was no different than that of the participants with DLD-RE. The study did not examine further the phonological development of these two groups, so no conclusions were drawn based on the phonological profiles.

Regardless of the variation in diagnoses and outcomes among children with DLD, a number of studies have shown that children with DLD demonstrate phonological difficulties suggesting the presence of a phonological impairment. These studies imply that phonological impairment is a clinical marker for DLD.

The aim of the present study is to examine phonological development with regard to the acquisition of Dutch consonants in Dutch-speaking children from the ages of three to five years old with DLD. This will be done by demonstrating the phonological profile and specifically the development of speech production and phonological simplification processes in Dutch. Although the phonological development of children with DLD is delayed and can even be characterized as deviant compared to TD children, a longitudinal study is needed to determine whether children with DLD eventually overcome the delay. As the present study does not aim to answer the question of whether the phonological development in children with DLD is either delayed or deviant, the phonological profile of children with DLD will be referred to as different to avoid any confusion concerning that matter. The children participating in this study will also be divided into two groups: children with DLD-E and children with DLD-RE, comparing the phonological profiles and examining the phonological simplification processes the two groups demonstrate.

A theoretical background is given in section two. First, the section provides general information regarding phonology, followed by a section discussing phonological development in typically developing children (hereinafter referred to as TD children). At the end of section two, the phonological development of children with DLD is discussed. Section three contains the research questions the current study addresses, followed by section four, which deals with the method of the experiment. The fifth and sixth sections contain the results and a discussion of the research. Finally, a conclusion is given in section seven.

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2. Phonology and phonological development

2.1 Phonology

First, phonological development in TD children will be discussed in section two, paragraph 2.2, followed by paragraph 2.3, which describes what developmental language disorder is and how children with DLD differ from TD children with regard to their phonological development in Dutch.

2.2 Phonological development in TD developing children 2.2.1 Phonological development

Numerous studies have looked into the acquisition of segment production in TD children and the phonological processes they undergo during this development. The following definition has been given for the term phonological development in children:

- “Phonological development involves the gradual, linguistically determined, expansion of the contrastive system as well as the acquisition of the phonotactic constraints of the target language in connection with the suppression of phonological processes that are used during development in order to relate the target realizations to the system of contrasts a child has available.” – Beers, 1995:13

When children start producing their first words, their realizations are not identical to the adult realization. This is normal considering that a child has not yet acquired all the segments and cannot produce all the individual speech sounds (phonemes) of his/her native language. Until children are able to produce all segments, they tend to undergo a number of phonological processes due to their phonological limitations. This will be discussed further in paragraph 2.2.2.

One of the earliest and most widely known theories of phonological development is Jakobson’s (1941/1968) theory. Jakobson’s goal was to propose a theory that could be applied universally. He investigated the phonological development of contrasts acquired by children across languages. Based on the studied data, Jakobson proposed that the first contrasts a child acquires are universal. The speech sounds that exist in all languages according to Jakobson are /p/, /t/, /m/ and /n/ and are thus first acquired by children everywhere regardless of their native language. This study, however, did not take into consideration something that other studies found, namely that there is variation in the phonological development TD children undergo. Studies that have been carried out for Dutch (Fikkert & Levelt 2006, Beers 1995), found that individual differences do indeed occur among children in the order of acquisition. However, despite individual differences, a pattern emerges picturing the overall phonological development in TD children. The pattern that Beers (1995) and Fikkert and Levelt (2006) demonstrated in their study in Dutch includes the speech sounds Jakobson referred to (see also Table 2). The order of acquisition these two studies demonstrate is supported by the feature hierarchical principles of the Feature Geometry Theory.

The Feature Geometry Theory is a phonological theory proposed, among others, by Clements (1985). According to Clements (1985), each segment has a number of features, and there are three major groups of features: laryngeal features, manner features and place features (see Figure 1).

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Figure 1. Nonlinear phonological feature hierarchy as presumed in the present study based on Clements (1985).

(Beers, 1995:49)

This hierarchical representation shows not only the nature of relations between phonological contrasts that appear in languages, but also the structural complexity of consonants that languages have individually. Each segment has a number of features that are internally organized within the segment. Take for instance the consonant /m/ in Dutch. This consonant in the supralaryngeal node (SL) is characterized as a sonorant (son) and nasal (nas) when referring to the manner (M) of articulation, and a labial (lab) when referring to the place (PL) of articulation (see Figure 2).

Figure 2. Hierarchical representation of Dutch consonant /m/.

(Beers, 1995:50)

Based on The Feature Geometry Theory, Beers carried out research on the phonology of Dutch-speaking children and the phonological simplification processes they demonstrate during their phonological speech production development. Beers took into consideration the segment features, specifically for the consonants having laryngeal, manner and place features (see Figure 3).

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Beers (1995) carried out a study on the phonology of Dutch-speaking children which involved determining the nodes and features of segments for the Dutch language (see Table 1).

Table 1. Features of segments of Dutch phonological system Manner

plosive fricative nasal glide liquid

Voice voiceless voiced voiceless voiced Place labial p b f v m w dental– alveolar t d s z n l r palate – alveolar ʃ j velar k x ŋ x h (Beers, 1995:50)

Using audio fragments, Beers (1995) studied spontaneous language of 45 Dutch-speaking children aged from 1;3 to 4;0 years old. Based on a speech sample consisting of 100 words, Beers studied the segments that appeared in syllable-initial and syllable=final position (example given: boek à /buk/ [buk] = book, papa à pa – pa /papa/ [papa] = father). The children’s word realization was compared to the adult realization to investigate at what age a child was able to produce a segment (example given: adult realization bal à /bal/ [bal] = ball, child realization pa à /pa/ [pa]).

Beers (1995) formulated frequency criteria in order to determine whether consonants are acquired or emerging. First of all, each segment needed to be produced 75% correctly and secondly, at least half of the age-matched children in the group had to have achieved 75% correct realization of that segment. Those two conditions were crucial for Beers in order to describe a segment as having been acquired by that age group.

Her research led Beers (1995) to come up with a model for predicting the order of segment acquisition a Dutch-speaking TD child will undergo during his/her phonological development and specifically his/her speech production development (Table 2).

Table 2. Summary of the order of phonological acquisition of Dutch consonants in syllable-initial and syllable-final position and their contrastive features as determined by the Frequency criterion. Segments for which acquisition could not be determined are also given.

consonants initial C features final C features

Age group A: 1;3 – 1;8 years p t m n j [sonorant] [labial] [coronal] p [labial]

Age group B: 1;9 – 1;11 years k [dorsal] k [dorsal] Age group C: 2;0 – 2;2 years s x h [continuant]1 t

s x

[coronal] [continuant] Age group D: 2;3 – 2;5 years b f ʋ [front]

[round] [voice]

m n [sonorant]

Age group E: 2;6 – 2;8 years l r [lateral] [rhotic] [nasal]

- -

Age group F: 2;9 – 2;11 years d - - - Age group G: 3;0 – 3;2 years- - - - - Acquisition not determined ʃ l n f ŋ

(Beers, 1995:224)

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Gillis and Schaerlaekens (2000) studied the language acquisition of Dutch-speaking children using the order of acquisition model made by Beers (see Table 2). According to Gillis and Schaerlaekens’s (2000) observations using Beers’s (1995) model, children first acquire the labials and coronals (/p/, /t/) in initial position and then the dorsals (/k/). Based on that observation, one could conclude that consonants that are produced at the front of the articulatory area are acquired earlier than consonants that are produced at the back. In the case of the fricatives, however, the /s/, which is dental-alveolar, is acquired first and is then followed by /f/ which is labial and thus produced at the front of the articulatory area, and /x/, which is velar. Taking a closer look at the manner of articulation, it is noticeable that occlusive segments (/p/, /t/, /k/) and nasals (/m/, /n/) are acquired before fricatives (/s/, /x/, /f/). Beers also mentioned in her study that the coronal fricative /s/ would be acquired first, followed by the labial fricative /f/ and lastly the dorsal fricative /x/ (see also Appendix A for all consonant features).

The acquisition model demonstrating the order of phonological acquisition of consonants in Dutch (see Table 2) generated by Beers (1995) is used as a guideline when examining the phonological development of a Dutch-speaking child. The order of acquisition model by Beers (1995) helps one examine the phonological profile of a child and determine whether it is different compared to the phonological development in TD Dutch-speaking children. Beers (1995) was not the only one to be influenced by the Feature Geometry Theory in studying phonological development in Dutch-speaking children.

Fikkert & Levelt (2006) studied five Dutch-speaking children for one year in order to detect a developmental pattern considering the Place of Articulation structures (hereinafter referred to as PoA) despite possible individual differences. In phonology and specifically phonetics, PoA refers to the place where the articulation of a phoneme occurs. This can be anywhere from the area of the lips to the back of the throat. A phoneme, for example, that is articulated in the upper lip area as the PoA is called a labial (see Figure 3). A developmental pattern was indeed found, considering the PoA structure based on the children’s productions divided into five stages. The first stage is when Dutch-speaking children first produce either coronal, labial or dorsal consonants (see Figure 3) to produce a word, for example, /mi/ or /mim/ when referring to huis “house”. Stage two is where consonants remain the same as in stage one but the vowel is now differentiated from the one used in stage one (for example, mam). In the third stage, children start to produce consonants in different places of articulation although the pattern they use is still restricted to labial and coronal (for example pot) followed by the fourth stage, where dorsal consonants make their appearance in a child’s speech sample (for example, pok). The fifth and final stage is when children produce different combinations of consonants in syllable-final and syllable-initial position with regard to the PoA. According to Fikkert & Levelt (2006), the PoA developmental stages and the lexical representations a child has go hand in hand. The more words a child possesses in his/her mental lexicon, the more phonemes he/she is able to produce.

2.2.2 Phonological simplification processes

One of the theories of how infants proceed with their phonological development is the “Natural Phonology theory”, introduced by Stampe (1969). Stampe proposed in his theory that children undergo processes that are innate, the so-called ‘natural processes’, until they finally

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succeed in producing an adult realization of words. The definition of a phonological process according to Stampe (1979) is:

-“A phonological process is a mental operation that applies in speech to substitute, for a class of sounds or sound sequences presenting a common difficulty to the speech capacity of the individual, an alternative class identical but lacking in the difficult property” - Stampe, 1979 (to be found in Beers, 1995:35).

During their phonological development, children undergo a number of phonological processes until they acquire all the segments in their native language. These processes are known as phonological simplification processes. Phonological simplification processes are necessarily formed and are part of phonological development. These phonological processes are a result of the structural and contrastive restrictions children have at the time due to their phonological system, which is still developing. While the phonological system develops, these processes gradually vanish from the child’s speech.

Beers (1995) included in her study an investigation of phonological simplification processes TD Dutch-speaking children undergo in their phonological development, taking into consideration individual variation. Beers’s (1995) prediction of the phonological simplification processes Dutch-speaking children undergo was influenced by the view of Stampe, who proposed that phonological simplification processes have universal and natural origins across languages.

Beers predicted that Dutch-speaking children might use the same processes as children across languages use, with some influence expected from the native language the child learns, in her case, Dutch. Beers found the following processes that reflect the phonological simplification of the structures children demonstrate compared to the adult word realization:

Table 3. Phonological simplification processes in Dutch Simplification process Explanation Example Syllable structure processes

Cluster reduction Consonant clusters that consist of two or more consonants are reduced to one or two.

klaar ‘ready’ /kla:r/ à [ka:] paard ‘horse’ /part/ à [pat] Final consonant

deletion

The final consonant of a word is not realized. dak ‘roof’ /d^k/ à [d^]

Reduplication A target form consisting of two syllables with different syllable structure is realized as two syllables with the same syllable structure.

bal ‘ball’ /b^l/ à [b^-b^]

Weak syllable

deletion

One or more syllables of a polysyllabic word are deleted. kado ‘present’ /ka-do:/ à /do:/

gekocht ‘bought’ /xəә- kɔxt/ à [kɔxt] Assimilatory processes Regressive consonant assimilation

The feature make-up of one or more consonants is influenced, completely or partially, by a following consonant.

geven ‘to give’ /xe-fəә/ à [fe-fəә] doek ‘cloth’ /duk/ à [guk] Other

assimilations

Included are contiguous and non-contiguous assimilations, such as CV-assimilation, voice CV-assimilation, nasal-assimilation and rounding harmony.

boom ‘tree’ /bom/ à [mom] (nasal-assimilation)

Substitution processes

Fronting Dorsal segments are realized as coronals or labials, which are made in

the front part of the mouth.

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Gliding of liquids The liquids /l/ and /r/ are replaced by /ʋ/ or /j/. rood ‘red’ /rot/ à [jot], [ʋot]

Stopping of

fricatives

Fricatives are replaced by their non-continuant counterparts. zei ‘said’ /sɛi/ à [dɛi]

Devoicing Voiced consonants are realized as voiceless or as an intermediate lax form.

brug ‘bridge’ /brʏx/ à /[pʏx]

Voicing Voiceless consonants are replaced with their voiced counterparts.

/p/ à /b/ /t/ à /d/

poes ‘cat’ /pus/ à [bus]

(Beers 1995:89)

Beers (1995) created the following developmental matrix (Table 4) demonstrating the phonological simplification processes TD Dutch-speaking children undergo during their phonological development. The developmental matrix is based on the spontaneous language analysis per age group of 20 Dutch-speaking children from the age of 1.3 to 3.6 years and 10 Dutch-speaking children from the age of 3.6 to 4 years participated in Beers’s study (1995). By studying 100 realizations per child retrieved from the spontaneous speech throughout audio fragments, Beers (1995) could determine the number of phonological simplification processes. Beers (1995) counted the demonstration of phonological processes that occurred per word, taking into consideration that multiple phonological simplification processes could appear in one word. If a child, for example, says soe [su] instead of snoep ‘candy’, two phonological simplification processes are being demonstrated: cluster reduction (sn à s) and final consonant deletion (p à x). Based on the studied data, Beers (1995) was able to demonstrate the patterns of disappearance of the phonological simplification processes during a child’s phonological development (see Table 4). Aside from the patterns of disappearance, the frequency with which a phonological simplification process appears in the spontaneous speech of a TD Dutch-speaking child was also demonstrated based on Beers’s (1995) studied data (see Table 5).

Table 4. Occurrence and disappearance of normal phonological simplification processes in normally developing Dutch children. Processes in bold face are regularly used in that period; normal type face indicates infrequent use of a process; a dash (-) indicates that a process is no longer in use.

Age group A + B 1;3 – 1;11 Age group C + D 2;0 – 2;5 Age group E + F 2;6 – 2;11 Age group G + H 3;0 – 3;6 Age group I 3;6 – 4;0

Vocalization Vocalization Vocalization Vocalization Vocalization Reduplication Reduplication Reduplication - -

Voicing Voicing Voicing - -

Assimilation Assimilation Assimilation - -

Weak Syllable Deletion Weak Syllable Deletion Weak Syllable Deletion Weak Syllable Deletion - Final Consonant Deletion Final Consonant Deletion Final Consonant Deletion Final Consonant Deletion Final Consonant Deletion

Stopping Stopping Stopping Stopping -

Fronting Fronting Fronting Fronting -

CC Reduction CC Reduction CC Reduction CC Reduction CC Reduction Devoicing Devoicing Devoicing Devoicing Devoicing

Gliding Gliding Gliding Gliding Gliding

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Table 5. Patterns of disappearance of typical phonological simplification processes. Mean, maximum and minimum occurrence of normal simplification processes in normally developing children in five age groups with a time interval of six months.

age period 1;3 – 1;11 (N = 20) 2;0 – 2;5 (N = 20) 2;6 – 2;11 (N = 20) 3;0 – 3;5 (N = 20) 3;6 – 4;0 (N = 10)

processes mean – max – min mean – max – min mean – max – min mean – max – min mean – max – min

CC Reduction 14 24 3 14,4 30 5 8,1 17 2 7,1 14 2 5,5 7 2 Final C Deletion 14,5 32 6 11,3 20 5 11,5 20 5 9,4 16 5 9,5 12 6 Weak Syll. Del. 7,4 19 2 7,9 56 1 3,6 7 1 2,3 7 1 1,6 2 1

Reduplication 4,2 9 1 2 3 1 2 4 1 1,5 2 1 0 0 0 Assimilation 4 13 1 2,1 6 0 2 5 1 0,7 2 0 0,6 2 1 Fronting 1,9 4 1 2,1 8 1 3,1 8 1 1,3 2 1 2 4 1 Gliding 3,1 7 1 3,7 8 1 4 7 1 4,3 11 1 4,2 12 1 Stopping 3,4 7 1 2,2 5 1 3,6 7 1 2,9 8 1 1,7 3 1 Devoicing 8,8 21 1 7,2 18 2 6,4 17 1 3,7 9 1 1,6 2 1 Voicing 2,9 6 1 2,3 8 1 2,4 4 1 1,7 3 1 1,2 2 1 Vocalization 1,6 4 1 1,6 5 1 1,7 3 1 1,6 3 1 1.8 5 1 (Beers, 1995:285)

Beers’s (1995) prediction of phonological simplification processes considered Dutch-speaking children, but according to Stampe, phonological simplification processes have universal and natural origins across languages. Different studies that have been carried out cross-linguistically have shown that phonological simplification processes occur in the early stages of language acquisition in, for example, Mexican-Spanish (Macken, 1978), English (Ingram, 1989) and Korean (Kim & Stoel-Gammon, 2009), and may sometimes even be the same.

One of the phonological simplification processes, for example, that appears early on in a child’s phonological development in Korean, Dutch, English and Mexican-Spanish is fronting. When a child is not yet able to produce the segments that are produced at the body of the tongue (dorsal sounds, like /k/), these will be substituted with a sound produced at the front of the tongue (coronal sounds, like /t/). The phonological simplification process where a dorsal sound is substituted with a coronal sound is called fronting. Fronting is one of the numerous phonological simplification processes that a TD child demonstrates at the beginning of his/her phonological development (see Table 2).

Apart from TD children, Beers (1995) also studied children with DLD, who at that time were characterized as language-impaired, to see whether their phonological development coincided with that of the TD children. Interestingly, children with DLD demonstrate a phonological development different from the one that TD children demonstrate. The phonological development of children with DLD is discussed further in section 2.3 below.

2.3 Phonological development in children with DLD 2.3.1 Phonological development

Several studies carried out in different languages such as French (Maillart, 2006), Spanish-Catalan (Aguilar-Mediavilla et al., 2002), English (Bortolini & Leonard, 2000), Italian (Bortolini & Leonard, 2000) and Dutch (Beers, 1995), have provided evidence that children with DLD demonstrate phonological production problems compared to TD children.

Maillart (2006) investigated the spontaneous speech of 16 French-speaking children with DLD and 16 age-matched TD French-speaking children. One of the tasks in that experiment measured the percentage of phonemes that were produced correctly by the participants (PCC); while the other tasks focused on the mean length of utterances (MLU), the number of syllables and the quality of syllable production, etc. The outcome of this study suggested that overall the

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French-speaking children with DLD had phonological difficulties compared to the age-matched TD French-speaking children.

Aguilar-Mediavilla et al. (2002) analysed the phonology of five Spanish Catalan-speaking children with DLD, five with a language delay and five TD children, respectively. The children were examined, including for PCC performance, at segmental level. The scores recorded for the children with DLD were different compared to both LD and TD children, indicating that phonology in children with DLD is different compared to the other two groups.

Bortolini and Leonard (2000) examined Italian-speaking and English-speaking children, both groups with DLD, investigating the phonological characteristics those children had compared to younger TD children. The 18 English-speaking children with DLD were between the ages of 3.7 and 5.9 years and participated in tasks such as sentence completion, word production, etc. One of the tasks the children with DLD were given was to produce the same word several times. The 24 Italian-speaking children with DLD had the same tasks the English-speaking children underwent. In one of the tasks, the children with DLD were not consistent in their word pronunciation, showing a difference in use of consonant segments compared to the younger TD children. The overall conclusions drawn by that study suggest that both Italian and English-speaking children with DLD had phonological limitations.

Beers (1995) studied 15 Dutch-speaking children with DLD between the ages of 4 and 6 years by examining their spontaneous speech recordings. By examining their phonological development and comparing it to that of the 45 TD children in her study, Beers observed a developmental order with regard to the acquisition of segments that was rather unlikely to appear in the development of a TD child. One of the children with DLD, for example, acquired coronal and dorsal contrasts while the labial had not yet been acquired, which has not been found in TD phonological development. Beers showed in her study that phonological development in Dutch-speaking children with DLD is different compared to age-matched TD children.

A different study, carried out by Rescorla and Ratner (1996), examined phonological development in children with DLD, and specifically DLD-E, comparing this with phonological development in age-matched TD children. The outcome of this study suggested that the phonological development of children with DLD-E is different compared to TD age-matched children. The consonants repertoire of the children with DLD-E that participated in Rescorla’s and Ratner’s study was restricted, resulting in poor communication and word production limited to consonant-vowel syllable shapes (for example, for words such as me à CV).

Phonological development in children with DLD is often characterized as delayed and in some cases even deviant. The phonological profile of a child that is characterized as delayed matches the contrastive system and segment acquisition of younger normally developing children and will improve over time. This is a typical case of a late talker, whose phonological development will eventually match that of the age-matched peers (Williams & Elbert, 2003). Williams and Elbert (2003) carried out a study examining longitudinal data of five late talkers between the ages of 22 to 42 months old and their phonological development. Their goal was to determine whether the phonological development could be characterized as delayed or deviant. The late talkers produced fewer words, the percentage of correct consonants (PCC) was lower and even the mean length of their utterances (MLU) was lower compared to their age-matched TD peers. Three of the five children eventually caught up and resolved their phonological delay to match the phonological development of their age-matched TD peers and were characterized as late talkers with a delay in their phonological development.

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Two of the five late talkers still demonstrated a delayed/deviant phonological system. It has been stated that a child that outgrows his/her delay by the age of 30 months will eventually catch up with his/her age-matched TD peers regarding his/her phonological development. The two children who appeared to still demonstrate difficulties regarding their phonological system were identified as late talkers by the age of 30 months.

This, however, has not been studied for children with DLD whose phonological development has been characterized as delayed by some studies. A longitudinal study of children with DLD needs to be carried out in order to examine whether their phonological development is delayed and will eventually catch up with that of their age-matched peers. In the current study, neither the term deviant nor the term delayed will be used when referring to the phonological development of children with DLD.

Children with DLD have an impairment that is persistent and they have a phonological profile that is different from the one we see in TD children. Children with DLD often have a limited number of contrasts available and thus fail to produce words correctly and distinguish between them, resulting in communication problems. A Dutch-speaking child with DLD, for example, that has acquired the contrastive segments plosive/fricative and labial/coronal /p/, /t/, /s/ but is missing the coronal fricative /f/ will probably replace /f/ with the coronal /t/. So the word foto “photo” will become toto, leading to communication problems, since the word toto can suggest a different meaning. Another thing that differentiates children with DLD from TD children in their phonological development is the way they acquire, or rather fail to acquire, contrasts in their native language. A TD child, for example, when trying to acquire the contrast between fricatives and plosives or plosives and nasals in let’s say syllable-initial position, produces variant forms that gradually change into the adult realization (for example, toep [tup] à soep [sup] “soup”). In contrast, a child with DLD does not demonstrate the same method in order to acquire contrastive segments, showing a lot of variation or no variation at all in the patterns he/she uses. A child with DLD, for example, who tries to acquire the contrast between plosive and nasal in word-initial position will produce a lot of variation considering the consonant (for example toep [tup] à boep [bup] à foep [fup]) and will still fail to acquire the contrast.

Furthermore, studies have also demonstrated that the development of phonological simplification processes in children with DLD does not match the behaviour TD children show. Despite the majority of phonological simplification processes children with DLD demonstrate being common, there are anomalies in their demonstration. The use and persistence of these processes tends to be more frequent and insistent compared to TD children, making this process different than the one TD children undergo.

Apart from differences concerning the segmental accuracy in production in children with DLD, Aguilar-Mediavilla et al., (2002) also found differences in the demonstration of phonological simplification processes. Even though no differences were found regarding the syllabic simplification processes between Spanish-Catalan children with DLD, LD and TD children, the children with DLD did more often demonstrate cluster reduction (for example, tren “train” à ten), and consonant deletion in syllable-initial, syllable-medial and syllable- final position (for example, casa “house” à caa).

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Bortolini and Leonard (2000) observed in their study that the English-speaking and Italian-speaking children with DLD were different regarding the phonological simplification processes they demonstrated compared to younger TD children. In the case of the English-speaking children with DLD, they demonstrated, among other phonological simplification processes, a high percentage of cluster reduction in syllable-final position. In the case of the Italian-speaking children with DLD, a similar outcome was found, since these children also demonstrated a high percentage of cluster reduction in syllable non-final position.

While the majority of phonological simplification processes are common, a number of processes can be characterized as ‘unique’ (Ingram, 1976). The ‘unique’ or rather different processes are phonological simplification processes that either have not been demonstrated by TD children, or appear very rarely in their speech. Beers (1995) investigated phonological development in Dutch-speaking children with DLD as mentioned above, comparing their phonological development to TD children.

During her research, Beers (1995) encountered a number of phonological simplification processes while examining spontaneous speech recordings of the 15 Dutch-speaking children with DLD. The phonological simplification processes were categorized in three types: syllable structure processes, substitution processes and assimilatory processes (see Table 6). Based on the appearance of the phonological simplification processes in the typical development, the processes that were infrequent or did not emerge at all in the phonological development in Dutch-speaking children were characterized as ‘unusual’.

Table 6. Unusual phonological simplification processes in Dutch

Simplification process Explanation Example

Unusual Syllable Structure Processes

Cluster deletion A cluster consisting of two or three

consonants is not realized as a whole. This process occurs in all positions.

kant ‘side’ [k^nt] à [ka:]

Cluster creation A single consonant in the target form is

realized as a cluster.

banaan ‘banana’ [ba- ‘nan] à [‘bra-nəә]

Syllable creation An extra syllable is created before or

after the already existing syllable(s).

witte ‘white’ [‘ʋI=t-əә] à [təә-‘lIt- əә]

Schwa insertion A schwa, /əә/, is inserted between the

members of a consonant cluster. This commonly occurs in initial position in clusters of the [obst][son]-type.

kletsnat ‘soaking wet’ [‘klεts-n^t] à [kəәlεts-n^t]

Syllable conflation Syllables are deleted only partially, i.e.

one of the segments, either C or V, remains.

ophangen ‘to hang’ [‘ɔp-h^=ŋ-əә] à [əә-‘h^ ŋ]

Initial consonant deletion The first consonant of the syllable is

not realized.

wielen ‘wheels’ [‘ʋi-ləә] à [‘əәy-ləә]

Initial consonant addition A consonant is added in initial position

to a word which has no onset in adult pronunciation.

alleen ‘alone’ [^-‘len] à [kəә-‘len]

Metathesis The order of segments in syllable

structure is reversed. Reversal of segments may occur at many different levels of prosodic structure.

water ‘water’ [‘ʋa-təәr] à [‘ra-təә]

Unusual Assimilatory Processes

Progressive consonant assimilation A consonant influences the feature

make-up of one or more of the subsequent consonants. Assimilation may be complete or partial. In the case

gelukkig ‘happy’ [xəә-‘lY=kIx] à

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of complete assimilation, the

subsequent consonant(s) is/are

replaced by the preceding, triggering consonant. Partial assimilation takes place when one or more of the features of the triggering consonant have spread.

Progressive vowel assimilation One or more vowels are changed,

completely or partially, under the influence of a subsequent vowel.

auto ‘car’ [‘^u-to] à [‘əәy-təәy]

Regressive vowel assimilation One or more vowels are changed,

completely or partially, under the influence of a subsequent vowel.

pinda ‘peanut’ [‘pIn-da] à [‘pan-a]

Unusual Substitution Processes

Backing A segment is replaced by a segment

whose place of articulation is further back in the oral cavity. Backing is scored in cases where labials and coronals are realized as dorsals.

opnemen ‘to record’ [ɔp-ne-məә] à [ɔk-ne-məә]

Gliding Segments, other than liquids or labials,

are replaced by /w/ or /j/.

kijk ‘look’ [kεik] à [ʋεi]

schapen ‘sheep’ [‘sxa-pəә] à [‘sʋa- pəә]

Stopping Segments other than fricatives, viz.

liquids, nasals and glides, are replaced by non-fricatives: /p/, /t/, /k/, /b/ or /d/

weet ‘know’ [ʋet] à [pet]

Nasalization A segment is replaced by a homorganic

nasal segment, or a segment is prenasalized, that is a homorganic nasal segment is realized directly prior to the target segment.

bij ‘with’ [bεi] à [məә]

Lateralization A consonant is replaced by a lateral /l/

or realized with lateral release.

watten ‘wadding’ [‘ʋ^=t-əә] à [‘l^=t-əә]

Fricativization Stops are realized as affricatives, i.e. a

stop followed by a fricative which corresponds to the place of articulation. Fricativization is also scored in the case of sonorants realized as fricatives, but not in the case of stops being replaced by fricatives (see Frication).

brood ‘bread’ [brot] à [pfot]

Frication Stops are replaced by fricatives papa ‘dad’ [‘p^=p-a] à [‘p^=f-a]

Depalatalization Palatal consonants are replaced by

coronals. In Preisser, Hodson and Paden (1988), this process was found in more than two-thirds of the normally developing, English-learning children investigated. In Beers’s (1995) study, they expected that process to be

infrequently used in normal

development since palatals are not as frequent in Dutch as in English. Depalatalization is therefore treated as an ‘unusual’ process.

doosje ‘box’+ (diminutive) [‘do-ʃəә] à [‘do-səә]

Palatalization Coronals are realized as palatals.

Mostly, this process is applied in the case of /s/. In Preisser, Hodson and Paden (1988), it was noted that this process occurred infrequently in normal development.

zwart ‘black’ [sʋ^rt] à [ʃʋ^t]

Dentalization Labials are replaced with coronals. klimmen ‘to climb’ [‘klI=m-əә] à

[‘kε=n-əә]

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(Beers, 1995:126-130)

Taking into consideration the phonological simplification processes Beers (1995) found in the speech recordings of 15 Dutch-speaking children with DLD (see Table 6) and the phonological simplification processes in the 45 TD children (see Table 3), one can see that there are differences between the two groups. Aside from phonological simplification processes that the children with DLD demonstrate which are similar to those of the TD children, there are some unusual phonological simplification processes that the TD children do not demonstrate in their development. This implies that the overall phonological development in children with DLD differs from that of TD children with regard to the demonstration of phonological simplification processes.

To my knowledge, no in-depth study has been carried out examining phonological development in children with DLD with regard to phonological production and phonological simplification processes for the Dutch language. Also, the differences between the phonological development of speaking children with DLD-E compared to that of Dutch-speaking children with DLD-RE have not been studied either.

The aim of the current study is therefore to examine phonological development in Dutch-speaking children with DLD from the age of 3 to 5 with regard to their phonological production and simplification processes. Also, a closer look will be taken at the differences in phonological development of those children who are diagnosed with DLD-E or DLD-RE. In the following section (section three), the research questions of the current study are presented, followed by section four, which deals with the method of the experiment.

the reverse pattern of Dentalization.

Labial lenition Labial consonants are realized as /ʋ/. paard ‘horse’ [part] à [ʋat]

h-ization Consonants are replaced with /h/. In

most cases, this process applies to /r/-sounds.

moeten ‘have to’ [‘mu-tœ] à [‘hu-təә]

Glottalization Consonants are realized as a glottal

stop.

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3. Current study

As discussed above, the phonological development of Dutch-speaking children with DLD differs from the phonological development of Dutch-speaking TD children. However, the question of what the profile of Dutch-speaking children with DLD looks like based on the order of acquisition model for Dutch (see Table 2) made by Beers (1995) has not yet been answered.

Additionally, in the study carried out by Leonard (2014), it has been shown that the heterogeneous group of children with DLD can be differentiated into two groups: children with expressive DLD (DLD-E) and children with receptive-expressive DLD (DLD-RE).

This raises the question of whether phonological development differs between the two groups, more specifically, whether the phonological development in Dutch-speaking children with expressive DLD is less severe or different than in Dutch-speaking children with receptive-expressive DLD.

Aside from segment acquisition, children undergo a number of phonological simplification processes during their phonological development. By examining the phonological simplification processes separately, one could find evidence that children with DLD demonstrate processes that can be characterized as unusual. An unusual phonological simplification process is a process that does not emerge in the phonological development of TD children. Children with DLD also tend to use phonological simplification processes more frequently than TD children do. With that in mind, the current study examines the phonological simplification processes demonstrated by the participants. Apart from examining the simplification processes this group demonstrates as a whole, the current study also examines the simplification processes demonstrated by the two groups (DLD-E and DLD-RE) separately.

The current study therefore investigates how phonological development in Dutch-speaking children with DLD compares to that of TD children with regard to phonological production, focussing on consonant acquisition and simplification processes, and examining whether a difference can be seen between the DLD-E and DLD-RE groups with regard to their phonological development.

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4. Method

4.1 Participants

A total of 41 Dutch-speaking children with DLD with a mean age of 3.5 years participated in the current study. The children had been admitted to the Royal Dutch Kentalis language institution for children with Developmental Language Disorder in the Netherlands. The participants were administered the Schlichting Test for Language Production in Dutch (STTP,

Schlichting & Spelberg 2010) in order to measure their expressive language skills, and the Schlichting Test for Language Comprehension in Dutch (STTB, Schlichting & Spelberg 2010)

and Peabody Picture Vocabulary Test-III-NL in Dutch (PPVT, Dunn et al., 2005) in order to measure their receptive language skills. All the children were examined with the Dutch version of the standardized psychological test SON-R (Snijders-Oomen 1989).

In order to assign a child to either the DLD-E or the DLD-RE group, the child underwent STTP, STTB and PPVT tests measuring the expressive and receptive language abilities. Specifically, the receptive abilities were measured by testing the semantic development with regard to passive lexicon (WBQ) by administering the PPVT, and the comprehension of words and sentences with regard to the grammatical development (TBQ) by administering the STTB. The expressive abilities were measured by testing word production (WQ) and sentence production (ZQ) by administering the STTP. The child would be diagnosed with DLD-E if he/she performed more than 1.5 SD below the mean on the STTP in either WQ or ZQ. The child would be diagnosed with DLD-RE if he/she performed more than 1.5 SD below the mean on the STTB or PPVT in either TBQ or WBQ, respectively. The first group includes 15 children with DLD-E and the second group includes 26 children with DLD-RE.

Table 7. STTP mean scores of DLD-E and DLD-RE regarding word comprehension, word and sentence comprehension, word production, sentence production and non-verbal intelligence.

Group Mean WBQ (Word comprehension) Receptive

Mean TBQ (Word and sentence comprehension) Receptive Mean WQ (word production) Expressive ZQ (Sentence production) Expressive Non verbal IQ Expressive 94 91 83 81 108 Receptive/Expressive 84 71 69 75 89

4.2 Materials and procedure

The Metaphon Screening Test task from the Metaphon Box (Dean et al. 2002) was used to register information on the consonants and phonological simplification processes the participants demonstrate. This task contains 42 Dutch words, specifically nouns, consisting of one to two syllables. Each word is easy to visualize and predictable. A couple of examples are sleutel “key” and huis “house” (see also Appendix A). Even though the Metaphon Screening Test also examined the production of clusters, the current study focuses only on studying the consonants in syllable-initial and syllable-final position.

The child was shown a picture representing a word that he/she had to produce. Some words were provoked by using three-dimensional objects, for example, bal “ball”, sok “sock” etc. For each word, the examiner would ask the question: “What is this..?” or “What is the child doing..?” in order to provoke a response from the child. The answers were recorded the moment the child produced them. The words a child said with the marked segments correctly produced, regardless of the rest of the segments, was scored as a correct response. If a child,

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for example, said haas instead of huis “house”, it would be scored correctly since the phonemes that are being tested are /h/ and /s/, which are produced correctly. Each child participating in the current study produced all 42 words. At the end, a percentage of correctly produced consonants was computed. The correctly produced words will from now on be referred to as correct responses.

Apart from correctly produced consonants, the Metaphon Screening also counts the number of simplification processes a child demonstrates when pronouncing the 42 words. The percentage of each simplification process that was demonstrated in total was computed. The total number of processes a child produced was also computed for each child separately (see Appendix B). Since no control group was used in the current study, the norm scores of Beers’s (1995) study will be used for TD Dutch-speaking children (see Table 2 and Table 5) in order to draw conclusions about the phonological development of Dutch-speaking children with DLD.

4.3 Analysis

The data of the Metaphon Screening Test were analysed in two different ways. The first thing that needed to be done was to demonstrate the phonological profile of the 41 Dutch-speaking children with DLD. In order to do that, the table made by Beers (1995) demonstrating the order of acquisition of contrasts in Dutchneeded to be filled in based on the acquired consonants in syllable-initial and syllable-final position (see Table 2). Each segment appeared twice in syllable-initial and twice in syllable-final position. Following the frequency criteria established by Beers (1995), in order for a segment to be characterized as acquired, the percentage of correct consonant production must be at least 75. Only then can a consonant be characterized as acquired. In computing the percentage at which a consonant was correctly produced, each consonant appeared with two percentages, since it appeared twice in the list of 42 words. If the consonants were produced correctly for 75 per cent or higher in both cases, then the segment was characterized as acquired. However, if a consonant was produced between 50 – 75 per cent correctly, the consonant was characterized as emerging (see Appendix B). Whenever a numerical value of a division contained a half (see Table 8), it was rounded down by a half. Any consonant that scored lower than 50 per cent was considered as not acquired and not emerging.

Table 8. Examples of calculation procedure for computing the percentages of acquired consonants

Consonant Percentage Acquired or Emerging

d_ = 34 out of 41 children produced this consonant in the word deur “door” correctly

d_ = 31 out of 41 children produced this consonant in the word duim “thumb” correctly (34 + 31) / 2 = 32.5 32 / 41 = 78% Acquired _l = 20 out of 41 children produced this consonant in the word bal “ball” correctly _l = 25 out of 41 children produced this consonant in the word geel “yellow” correctly

(20+25) / 2 = 27.5 27/41 = 53%

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Further, the simplification processes these children demonstrated were counted and differentiated into two categories: phonological simplification processes and unusual phonological simplification processes. All the phonological simplification processes were counted based on the Metaphon Screening scoring form (see Appendix A). To calculate the percentage of the simplification processes all 41 children demonstrate, each simplification process had to be examined individually. The reason for this was that each simplification process had a different group of words that the Metaphon Screening used in order to detect the simplification process (see Table 8).

Table 9. Examples of calculation procedure for computing the percentage of phonological simplification processes that have been recorded.

Simplification process Number of words Percentage

h-ization This process can appear in the 14 words

a child produces during the Metaphon Screening Test.

Each child produces 14 words where h-ization can be demonstrated. The group that participated consists of 41 children. The maximum number of times this process can appear is 14 * 41 = 574.

In our group of 41 children, this process appeared 86 times. The percentage that this simplification process was demonstrated by this group is thus

86/574 = 15%.

Fronting initial This process can appear in the4 words a

child produces during the Metaphon Screening Test.

Each child produces 4 words where fronting in syllable-initial position can be demonstrated. The group that participated consists of 41 children. The maximum number of times this process can appear is

4 * 41 = 164.

In our group of 41 children, this process appeared 47 times.

The percentage that this

simplification process was

demonstrated by this group is thus 47/164 = 28%.

While the above analyses consider all 41 participants with DLD, to answer the research question regarding differences between speaking children with DLD-E and Dutch-speaking children with DLD-RE, a selection of data was made. The data of all 41 participants with DLD were divided in two groups: children with DLD-E and children with DLD-RE. The children with DLD-E were 15 in total and there were 26 children with DLD-RE. In order to have two symmetrical groups consisting of 15 children each, the first 15 children with DLD-RE were chosen from the total number of 26 children. With these two symmetrical groups, calculations were made for the percentage of consonant acquisition and the percentage of simplification processes demonstrated for each group separately.

The analysis of consonant acquisition and the number of phonological simplification processes demonstrated by the two groups were made and calculated in the same way as in the case of the 41 participants. The only adjustment made in the case of the children with DLD-E and with DLD-RE was that the calculation was made based on the data of the 15 participants per group.

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To answer the question of whether a significant difference can be found between the DLD-E and DLD-RE groups with regard to the number of correct responses in the Metaphon Screening Test, a linear model with one binary factor was used. The results of the linear model with one binary factor revealed whether there is a significant difference between the DLD-E and DLD-RE groups regarding the number of correct responses given in the Metaphon Screening Test. Aside from the linear model, a Pearson correlation coefficient was computed to examine whether there is a correlation between the number of correct responses and the number of phonological simplification processes demonstrated by the DLD-E and DLD-RE groups. Also, a Pearson correlation coefficient was computed to examine the correlation between the expressive and receptive language skills and the number of correct responses in DLD-E and DLD-RE. The results of the data analysis are discussed further in section five below.

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5. Results

5.1 Segment acquisition: DLD

By administering the Metaphon Screening Test, it was possible to examine the consonants that are acquired by or emerging in the children with DLD participating in the current study. Based on the 42 words produced by each child individually, and afterwards examining the consonants in the DLD group, the order of acquisition of contrasts in Dutch (Table 2) as shown by Beers (1995) was filled in including the data analysis that was made for the DLD group (see Table 10). The table demonstrating the order of acquisition in Dutch contrasts for both TD children and children with DLD (see Table 10) provides an overall picture of the phonological profile of all 41 Dutch-speaking children with DLD with a mean age of 3.5 years that participated in the current study (see also Appendix B for a detailed view on acquired and emerging consonants in children with DLD). A consonant is characterized as acquired when it appears at least 75 per cent correctly in the speech sample in at least two observations. When a consonant appears between 50 to 75 per cent, it is characterized as emerging. Any consonant that scored lower than 50 per cent was considered as not acquired and not emerging. Consonants that were emerging may not be taken into consideration when calculating the phonological age, according to Beers (1995).

Table 10. Order of acquisition of contrasts in Dutch in TD children and children with DLD.

As can be seen above (Table 10), the profile of the children with DLD shows that the acquired consonants in syllable-initial position are /p/, /t/, /m/, /n/, /b/, /h/, and /d/. The contrasts that these children acquired based on the acquired consonants are labial and sonorant. As the coronal contrast has not yet been acquired, the phonological development of the current participants is in the phonological age range of younger than 1.3 years.

Considering the consonants in syllable-final position, the consonants /p/, /t/, /k/, /s/, and /m/ are acquired. The contrasts labial, dorsal, coronal and fricative are also acquired. The phonological age for the syllable-final position is in the range of 2. to 2.2 years.

Consonants initial C n = 45 (Beers, 1995) features final C features consonants initial C DLD (mean age 3;5) n = 41 features DLD final C DLD features DLD Age group A: 1;3 – 1;8 years p t m n j [sonorant] [labial] [coronal] p [labial] p t m n [labial] [sonorant] p [labial] Age group B: 1;9 – 1;11 years

k [dorsal] k [dorsal] k [dorsal]

Age group C: 2;0 – 2;2 years s x h [continuant] t s x [coronal] [continuant] h t s [coronal] [continuant] Age group D: 2;3 – 2;5 years b f ʋ [front] [round] [voice] m n [sonorant] b m Age group E: 2;6 – 2;8 years l r [lateral] [rhotic] [nasal] - - Age group F: 2;9 – 2;11 years d - - - d - Age group G: 3;0 – 3;2 years- - - - - - Acquisition not determined ʃ l n f ŋ

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5.2 Phonological simplification processes: DLD

The phonological simplification processes demonstrated during the Metaphon Screening Test are divided into two categories: the phonological simplification processes that occur in typical phonological development (see Table 11), and the unusual phonological simplification processes that occur in an impaired phonological development, which will be further discussed in paragraph 5.2.2.

First, the maximum number of demonstrations per phonological simplification process that could be registered in the Metaphon Scoring form based on 41 participants was calculated. Then, the actual number of demonstrations per phonological simplification process was filled in based on 41 Dutch-speaking children with DLD (see Table 11). In order to compare the number of demonstrations with the maximal number of demonstrations in TD children, the occurrence of phonological simplification processes table by Beers (1995) will be used based on the data of 20 TD Dutch-speaking children (see Table 12). See also Appendix B for the percentage of phonological simplification processes that occurred in the speech sample of the DLD.

Table 11. Phonological simplification processes in DLD

Max. number of demonstrations Metaphon Scoring (N=41) Number of demonstrations in Metaphon Screening DLD (N=41) Processes Fronting Initial 164 47 Fronting Final 246 64 Stopping Initial 164 36 Stopping Final 246 20 Gliding Initial 164 35 Gliding Final 164 36 Devoicing 164 14 Consonant deletion Final 451 47 Cluster reduction Initial 451 313 Cluster reduction Final 320 166

Table 12. Maximum occurrence of phonological simplification processes in the typically developing children in five age groups with a time interval of six months based on Beers’s (1995) study.

age period 1;3 – 1;11 (N = 20) 2;0 – 2;5 (N = 20) 2;6 – 2;11 (N = 20) 3;0 – 3;5 (N = 20) 3;6 – 4;0 (N = 10) processes mean – max –

min mean – max – min mean – max – min mean – max – min mean – max – min CC Reduction 14 24 3 14,4 30 5 8,1 17 2 7,1 14 2 5,5 7 2 Final C Deletion 14,5 32 6 11,3 20 5 11,5 20 5 9,4 16 5 9,5 12 6 Fronting 1,9 4 1 2,1 8 1 3,1 8 1 1,3 2 1 2 4 1 Gliding 3,1 7 1 3,7 8 1 4 7 1 4,3 11 1 4,2 12 1 Stopping 3,4 7 1 2,2 5 1 3,6 7 1 2,9 8 1 1,7 3 1 Devoicing 8,8 21 1 7,2 18 2 6,4 17 1 3,7 9 1 1,6 2 1

Phonological Development in Dutch-speaking children with Developmental Language Disorder