andrea macleod

NOVA Comprehensive Perspectives on Child Speech Development and Disorders

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Chapter 6 The Trajectory Towards Mastery of the

Phonological System: From Toddlers to School-Aged Children

Andrea MacLeod


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Introduction• To identify a speech sound delay or disorder in a given individual, speech-

language pathologists need to understand the developmental trajectory • This chapter reviewed 31 studies selected by the following criteria:

– Age range: 2 to 13 years– Typical development– Monolingual English– Publication in scientific journals, written in English

• Studies were based on data from children in Australia, Canada, New Zealand, and the United States of America

• Criteria of interest– Accuracy– Inventory– Error patterns


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Toolkit for Measuring Accuracy• You start with a conversational sample (recommended size: at least

25 utterances but 100 is better), transcribe it, and calculate the following:– Percent Consonants Correct (PCC): the number of correctly produced

consonants, divided by all consonants produced, multiplied by 100 (errors must be substitutions or omissions)

– Percent Vowels Correct (PVC): the number of correctly produced vowels, divided by all vowels produced, multiplied by 100

– Percent Phonemes Correct (PPC): the number of correctly produced phonemes, divided by all phonemes produced, multiplied by 100

– Articulation Competency Index (ACI): the number of correctly produced consonants, divided by all consonants produced, multiplied by 100 (errors can be distortions, e.g., [l] or [d] that is fronted. Similar to PCC but errors can include distortions -> useful for assessing older children and adults


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• Intelligibility Index: Percent of words judged to be intelligible by a trained transcriber• Phonological Mean Length of Utterance (PMLU): a measure of the number of

phonemes in the produced word plus the number of accurately produced consonants– Example: [næna]/banana: 4 + 2 = 6– The score from all the words in the sample are then averaged– A child who mostly produces short words accurately will have a similar PMLU as a child who

attempts longer words but omits sounds• Whole Word Proximity (WWP): a measure of the child’s PMLU as a proportion of the

target PMLU– Example: [wi]/week: PMLU child 2 + 1 = 3;PMLU target [wik]: 3 + 2 = 5– WWP 3/5 = .6– A child who mostly produces short words accurately will have a higher WWP compared to a

child who attempts longer words but truncates them. Therefore, the child’s and the target PMLU should be considered separately as well as a ratio.

• Proportion Whole-Words Correct (PWC): a measure of how many words in a sample were completely correct


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Sound Inventory for One Child• Start with a conversational speech sample or single-word productions from an

articulation test and transcribe what the child said• Independent analysis results in a phonetic inventory (other terms: segmental

inventory, absolute inventory)– Simply make a list of all the phonemes you heard – can group them by place, manner,

voicing• Relational analysis results in a phonemic inventory (other term: relational

inventory)– Compare the the child’s productions to the adult form and count only those sounds as

correct that are correct relative to the adult form• Example:

– [θʌn]/sun– [fʌm]/thumb– [fud]/food

• Independent analysis: / d, θ, f, m, n, ʌ, u/ (just the sounds you heard)• Relational analysis: / d, f, m, n, ʌ, u/ but /s, θ/ are missing. Why???


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Sound Inventory for a Group of Children

• At what age do children typically acquire a certain sound or sound class?

• Another way of asking: What proportion of same-age children should produce the sound or sound class correctly for it to be considered “acquired”? Studies vary:– 75% of the children– 90% of the children


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Phonotactic Inventories

• May include all words in the sample or only those whose syllable and word shapes match the adult target

• Word shapes: “Me want cookie”:– X (monosyllabic word), Xx (disyllabic word, strong

+ weak syllable)• Syllable shapes: “Me want cookie”– CV, CVCC, CVCV


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Error Patterns (Phonological Processes)

• Assimilation processes: sound changes that achieve greater similarity to neighboring sounds

• Can occur by anticipation (right to left) or perseveration (left to right)– Place:

• Labial [bɔb]/ball• Velar [kek]/take• Alveolar [tet]/take• Nasal [mun]/moose

– Voicing• Prevocalic voicing [baɪ]/pie• Postvocalic devoicing [pɪk]/pig• Prevocalic devoicing [pʊk]/book• Postvocalic voicing [bʊg]/book


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• Word or syllable structure processes– Weak syllable deletion [nænǝ]/banana– Cluster reduction [kul]/school– Final consonant deletion [bʊ]/book– Initial consonant deletion [ʊk]/book– Coalescence [tet]/skate– Epenthesis [bəlu]/blue– Doubling [dɔdɔ]/dog– Reduplication [wawa]/water (this is also considered an assimilation

process, syllable harmony)– Glottal replacement [ʔʊʔi]/cookie– Metathesis [æmɪnəl]/animal– Migration [pæsgɛdi]/spaghetti


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• Substitution processes, e.g.,– Gliding [wɪŋ]/ring, [jaɪt]/light– Stopping [tʌn]/sun– Fronting [ti]/key (velar), [si]/she (palatal)– Backing [gɔg]/dog (note: this could also be assimilation!)– Depalatization [si]/she] (same as palatal fronting)– Palatization [ʃʌn]/sun– Affrication [tsʌn]/sun– Deaffrication [ʃiz]/cheeze, [tiz]/cheese (some consider the second case as

stopping) – Vowelization (also called vocalization) [bado]bottle– Denasalization [bud]/moon– Neutralization (replacing multiple consonants with the same sound, often [d]

or [h]


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Notes About the Meta-Analysis Reported in Chapter 6

• 31 studies from English-language journals• Studies are numbered in Table 6.1 and cited

with superscripts• Errors are listed if they occurred in – Over 5% of opportunities across the data

collections– Over 5% of the children in the samples


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2-Year-OldsFocus Questions1. How is accuracy

different for vowels and consonants?

2. How is the phoneme inventory different for early and late 2-y-olds?

3. What classes of consonants are in the inventory at age 2;11? Missing or mostly missing from the inventory?

Table 6.2 Summary of phonological development from 2;0 to 2;11 years of age


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Focus Questions1. Which types of phonological processes are seen most frequently in the overall productions of 2-

year-old children (column 3)?2. Which types of phonological processes are seen in the greatest proportion of children (column 4)?3. What could explain the difference between the high percentages of children who show certain

errors and the overall low incidence of the errors across the samples?

Table 6.4 Error patterns observed for children aged 2;0-2;11, reported by percentage frequency of occurrence across the group, and percent of children producing the pattern (n/a notes unavailable data)


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3-Year-OldsFocus Questions1. How has the

consonant inventory changed from age 2 in terms of sound classes?

2. What are some troublesome sounds that 75% but not 90% of 3-year-olds can produce?

3. What is the predominant word shape?



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Focus Questions1. Which types of phonological processes are seen most frequently in the

overall productions of 3-year-old children (column 3)?2. Which types of phonological processes are seen in the greatest proportion

of children (column 4)?3. How are these findings different from children age 2 years?

Table 6.7 Error patterns observed for children aged 3;0-3;11 reported by frequency of occurrence and percent of children producing the pattern (n/a notes unavailable data)


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4-Year-OldsFocus Questions1. How have PCC and PVC

changed from age 3 years?

2. How has the consonant inventory changed since age 3 years in terms of sound classes?

3. Which are the most troublesome sounds at age 4 years (those that 75% of the children can produce but not 90% of them?)



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Focus Questions1. Which types of phonological processes are seen most frequently in the

overall productions of 34-year-old children (column 3)?2. Which types of phonological processes are seen in the greatest proportion

of children (column 4)?3. How are these findings different from children age 3 years?



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Ages 5 to 9 Years

Focus Questions1. What are the last

phonemes to be acquired between age 5 and 9 years?

2. What are the last few phonological processes observed in children in this age range?



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Focus Questions1. What trends are evident across ages 5 to 7 years?2. If a 7-year-old child still says [gwin]/green, how unusual is that?



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From a Synchronic to a Diachronic Perspective

• Synchronic: investigating many characteristics of a sample at one point in time

• Diachronic: investigating one characteristic across time


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Accuracy

Figure 6.1 Measures of accuracy (PCC, PVC and PPC) across the targeted age range: means are represented by the points, and error bars represent +/- 1 standard deviation averaged across studies


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Inventory

Table 6.14 Phonetic and phonemic inventory for children across the targeted age range; blank cells denote accuracy below 75%; n/a notes unavailable data


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Error Patterns

Figure 6.2. Percent Frequency of Occurrence of the three categories of error patterns across the targeted age range: (a) Assimilation Patterns; (2) Substitution Patterns; and (3) Syllable Structure Patterns.


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Connections• Chapter 1 reviews the history of child phonology and describes different

theoretical approaches to studying typical speech development• Chapter 2 provides a an overview of measures to describe and measure

child speech development• Chapters 4 and 5 describe pre-speech and speech development in

infants and young toddlers• In Chapter 9 on crosslinguistic trends, developmental trends for sound

inventories by sound classes and trends for error patterns are mentioned.

• In the chapters on speech sound acquisition in languages other than English, language-specific patterns of acquisition are described

• Chapter 20 on diagnostic guidelines shows how to use normative data to determine the presence and nature of a speech delay or disorder


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Concluding Remarks

• By age 4 years, children have a large phoneme inventory and are able to use it with increasing accuracy

• Speech development does not occur in isolation; it goes hand in hand with other areas of development, for instance lexical and syntactic growth

• The milestones of typical development provide guidance when assessing a child for the presence of a speech delay or disorder


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Sidebar 6.1 Feature ProductionInstead of looking at inventories, some researchers have reported on the development of feature contrasts. Children are thought to build their phonological system by establishing feature contrasts (Jakobson, 1968), thus the goal is to identify the features that children are contrasting and the order in which the feature contrasts are acquired. Stokes and colleagues14 have reported on the percent of two-year-old children that contrast different features. They found that 100% of children produced the consonantal, sonorant, coronal and voicing contrasts, that 75-95% of children produced the anterior, continuant and nasal contrasts, and that less than 50% of children produced a delayed release (i.e., affricates), lateral or strident contrasts. Based on their research, Prather et a.l 12 proposed the following order of feature acquisition (from earliest to latest): continuant, strident, diffuse, voice, nasal, grave.


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Sidebar 6.2 ProsodyBeyond segmental accuracy, it is important to consider stress, intonation, and rate. As is noted in Chapter 7, few studies have described the prosody of preschool aged children, despite the important role it can play in word accuracy. Rate has been studied among three-year-old children from New Zealand and the United States of America28. This studied showed that children from New Zealand speak a little faster than their American peers with a rate of syllables per minute of 208 versus 182, respectively. Regarding the length of utterances, the mean number of syllables per utterance was 4.7 for New Zealand and 4.5 for American children. Intonation has been studied among 5-year-old children29. Children were found to use the basic functions of intonation, including chunking, affect, and focus. Children, however, have been found to have difficulty incorporating two words to correctly mark the stress of a compound word. For example, children have difficulty shifting the stress placement from the noun in “a black bird”, to the first syllable in “a blackbird”. Children at this age also have difficulty placing the phrase-level accent in non-final position for indicating a change in focus (“The CAT jumped on the hat”). These abilities continue to improve through to the age of 13 years.

andrea macleod

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