David Ingram
1, Lynn Williams
2, Nancy J. Scherer
3[email protected], [email protected], [email protected]
1Arizona State University, 2East Tennessee State University,
3Arizona State University
Abstract. An articulatory disorder is one that is solely articulatory, that is, the child can’t produce the sound or sounds in question, e.g., lisping. A child with a phonological disorder also has an articulation problem, but the articulation is influenced by the acquisition of phonological representations. One way this may be seen involves a substitution shift, i.e. using a sound as a substitution but not as a correct consonant. An example would be a child producing /ʃ/ as [s], e.g.,
‘shoe’ [su], but producing /s/ as [t], e.g., ‘Sue’ [tu]. Another way is when a child shows an interaction between consonant correctness and word complexity. For example, a child can produce a sound correctly in simple words, but has lower rates of correctness in more complex words, e.g., an /s/ in “Sue” versus an /s/ in “surprise”. Substitution shifts and effects of word complexity are common in typical phonological acquisition. They are also found in a subtype of children with speech sound disorders, those who are primarily having a phonological delay. They are less common with other children who have speech sound disorders, who can be considered to be having a phonological disorder. The patterns of the latter group of children are not comparable to those of younger, typically developing children. These children are more apt to be unable to produce certain sounds regardless of word complexity. At the same time, they show patterns in their speech production that provide evidence that they are attempting to form and use phonological representations. That is, they do not solely have an articulation disorder. This article proposes that children with speech sound disorders fall along a spectrum, with articulation at one end and phonology at the other, e.g., lisp > disorder > delay. We demonstrate this with the case study of a child CS, and with a group study of children with cleft lip/palate. CS could not produce any fricatives other than /f/, nor affricates, and liquids. The substitution patterns were /s/ and /ʃ/
[θ], /tʃ/ [t] or [θ], /z/ [ð], /dʒ/ [d] or [ð], /θ/ [f], /v/, /r/ /l/ [w]. His errors show articulatory difficulties, yet he also used a substitution shift with [θ]. The second example is a study of 20 children with cleft lip/palate. The children showed a range of atypical phonological patterns triggered by the articulatory difficulty resulting from the repaired clefts. These had the look of children with phonological disorders. Samples taken later showed marked improvement, a shift from looking disordered to looking delayed. These cases suggest that assessment needs to identify the articulatory and phonological influences on a child’s speech, and recognize that they fall along a spectrum from one to the other.
Keywords: articulation, phonology, speech disorders, markedness
Articulation versus phonology
It is the case that categorical perception, at least metaphorically, is a part of a number of areas of language acquisition. One such case is in the discussion of children’s speech sound disorders (SSD).
SSD are commonly discussed as being either articulatory or phonological in nature. This is also reflected in book titles on the topic over several years, e.g., Phonological Disability in Children (Ingram, 1976), Articulation Disorders (Sommers, 1983), Normal and Disordered Phonology in Children (Stoel Gammon & Dunn, 1983), etc. Very recently, the term SSD has been coined to reflect a neutral position as to which is being discussed as in Children’s Speech Sound Disorders (Bowen, 2015).
At one end, there is some consensus that certain SSD are articulatory in nature. Some possible candidates for this account are problems with tongue thrusting referred as lisping, [r] problems, and possibly cleft lip/palate. These cases (at least the two first) involve a distorted phoneme, not the merger of one phoneme with another. Another example from children with clefts are backed
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compensatory substitutions. Both phonemic merger and phonological contrast are at the heart of the claims of a phonological influence on early speech. One of the earlier and most well-known proposals for the influence of phonology on speech development is that of Roman Jakobson in his seminal work Child Language, Aphasia, and Phonological Universals (Jakobson, 1941/1968). At the heart of Jakobson’s view is the notion of maximal contrast. Suppose (contrary to Jakobson) that ease of articulation was the reason that children acquire consonants in the order that they do. One would anticipate that the earliest consonants would be unaspirated [p] and [t], then [k]. Jakobson, however, emphasized that such an account only works when surface productions are taken into consideration.
Patterns of substitution, however, show the influence of phonology that underlies the child’s productions. Early in his book, Jakobson discusses a Russian child who showed the patterns in (1).
(1) Maximal Contrast /g//t/: /t/ pronounced as [t]; /k/ pronounced as [t]; /g/ pronounced as [k]
In this example, the child does not produce a [k] for /k/, but does so for /g/. To say that the child could not articulate a [k] would be incorrect. He could, but only when it functioned to capture a maximal phonological difference within the stops, between /g/ and /t/.
These two simple cases are relatively clear and lead to a conclusion that children with speech sound disorders are articulatory if they show problems like lisping, and are phonological if they show patterns as in (1). Further, children can additionally distinguished by those who are typically developing, and those who are having a phonological delay. The latter group would be children showing instances of maximal contrast like Jakobson’s Russian case, but who are older and thus slower developing. More in depth analyses show that the distinction is not always as easy to separate as suggested above. This was known even before Jakobson’s work. A little cited study by Margaret Nice entitled “A child who would not talk” (Nice, 1925) demonstrated this. Nice studied the speech and language development of four of her children over several years. In this article, she contrasted the speech development of her fourth child with the other three. This child was a slow language learner, with a vocabulary of just around 50 words at age 3. Further, she demonstrated a very restricted inventory of speech sounds, suggestive of an articulation disorder. At the same time, she showed usage of reduplication, a phonological pattern that enabled her to expand her limited vocabulary despite her speech limitations. She showed both articulatory problems plus phonological development. She was delayed, but also could be claimed to be disordered. Without any speech intervention, however, she showed tremendous gains in both speech and language after 3,0 and caught up with her sisters by age four.
What we would like to suggest is that the distinction between articulatory and phonological development should not be treated categorically. We suggest alternatively that the two should be seen as end points on a ‘spectrum’. A child whose speech is entirely explainable by articulation would be at one end, while other children showing both articulatory and phonological influences would fall along the spectrum toward a stronger influence of phonological factors. This will be done by demonstrating instances where a child’s speech development shows a mix of both articulatory and phonological patterns.
There are two topics in particular that we will discuss. One is an examination of the spectrum proposal with a focus on ‘whole word complexity’. It will be shown that some, but not all children show a correlation between consonant correctness and whole word complexity. That is, rates of consonant correctness are higher in simpler words than in more complex words. The second focus will be on the distinction between phonological delay and phonological disorder. We will demonstrate that this distinction can be made when children’s whole word complexity is analyzed. Children who show a correlation between whole word and consonant correctness fall on the phonological end of the spectrum, while children who do not, fall towards the articulation side.
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Whole word complexity
Recent work by the first author has examined whole word complexity in children by measuring consonant correctness in relation of word complexity (WC). WC is a relative term, with many possible levels. The initial research has focused on two aspects that influence word complexity, these being the occurrence of consonant clusters, and the occurrence of multiple syllables. This two dimensions lead to the four categories listed in (2).
(2) a. monosyllabic words with just single consonants (mono single) b. monosyllabic words with consonant clusters (mono cluster) c. multisyllabic words with just single consonants (multi single) d. multisyllabic words with clusters (multi cluster)
The preliminary results with typically developing children has found that both syllabicity and clusters add to word complexity, as measured by the percentage of correct consonants for each (PCC). This is demonstrated in Table 1 where the results of two children, Ian and Jennika, are presented for the categories in (2). Note that there is a noticeable range of PCC scores, with the mean around 40%.
These results have been replicated across a number of children.
The next phase of this line of research has explored the same analyses for children with SSD. It was found that one group of children with SSD showed a similar pattern to the typically developing children in that they showed a correlation between word complexity and PCC. These children were considered to be having a phonological delay. The results for two children from this group, Tim and Barry are given in Table 1. A second group, however, did not show a significant correlation. For these children, the lack of this effect was interpreted as an articulatory effect. That is, there were certain sounds that they could not make, regardless of a word’s complexity. These children were concluded to have an articulatory problem. The results for two children in this group, Alan and Danny, are given in Table 1. While preliminary, the range of PCC scores can be examined to see the difference. The range of scores for children with phonological delay are limited (around 10% or less), while those for children with delay are greater (means around 25%).
Table 1. PCC scores and word complexity Children Age Range Mono
Single
Multi Single
Mono Cluster
Multi Cluster Ian 1,9 33% 71% 53% 36% 38%
Jennika 1,11 30% 70% 56% 44% 40%
Tim 5,0 21% 26% 37% 16% 19%
Barry 8,9 31% 71% 68% 40% 40%
Alan 5,11 9% 18% 16% 20% 11%
Danny 5,6 14% 34% 26% 20% 30%
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Evidence for a spectrum
Observe that these preliminary results followed the categorical interpretation discussed earlier. Here we discuss two further analyses that led to the spectrum proposal. One is a case study of a child CS who was diagnosed with a SSD. We demonstrate that an analysis of CS speech sample demonstrated both articulatory and phonological influences. The second study is a longitudinal study conducted on the speech of 20 two-year-old children with repaired child lip/palate. The first samples from the children showed a wide range of atypical speech patterns. Analyses found that each child used their own phonological strategies to cope with their clefts. Samples taken approximately ten months later showed significant improvements and typical phonological acquisition.
CS
CS was diagnosed as having a SSD with multiple sound substitutions. To determine his phonological system, CS was given a phonological assessment with approximately 300 words by the second author.
It was determined that his consonant inventory consisted of two distinct consonant groups. There were 12 consonants that CS produced correctly with virtually 100% accuracy. These were /m, n, p, t, k, b, d, g, w, j, f, h/. At the other extreme, there were consonants that were produced with virtually 0%
accuracy. He had no correct fricatives except /f/, no affricates, and no liquids. In other words, his consonants were either completely correct or completely incorrect. A preliminary conclusion was that he has a particular problem with articulation since his percentage of correct consonant production was not influenced by word complexity.
A relational analysis was then conducted to determine his patterns of substitution. Given that he was diagnosed as having primarily an articulation problem, it was predicted that his substitutions would follow well known markedness relations. That is, it was anticipated that his substitutions would consist of sounds he could produce for those more marked sounds that he could not. These predictions are shown in Table 2 along with the actual substitutions.
Table 2. CS substitution patterns
Class Phonemes Predicted Actual Fricatives /s/, /ʃ/ [t] [θ]
/z/ [d] [ð]
/θ/ [f] [f]
/v/ [w] [w]
Affricates /tʃ/ [t] [t] or [θ]
/dʒ/ [d] [d] or [ð]
Liquids /r/, /l/ [w] [w]
The results only partially supported the predictions of markedness. The phonemes that met the predictions were the liquids, and the fricatives /θ/ and /v/. The affricates varied between the predicted
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stop consonants and the more marked dental fricatives. The lingual fricatives /s/, /ʃ/ and /z/ did not meet the predictions. CS substituted the more marked dental fricatives.
The more marked substitutions can be accounted for using the phonological predictions of maximal contrast as discussed above. First, notice that CS can make dental fricatives, e.g., /s/ to [θ], but he does not correctly use it for /θ/, where he replaces the target with [f]. If he were to replace the lingual fricatives with stops, he would lose the underlying distinction between stops and continuants. By using the more marked dental fricatives, the distinction is maintained. This phonological influence competes with the unmarked options in the affricates. That is, the affricates vary between the predicted stops and the marked dental fricatives as with the lingual fricatives. The liquids met the predictions, but note that the underlying feature distinction between obstruents and sonorants is maintained with the unmarked option. We conclude that CS is a child who is on the articulatory side of the phonological spectrum, but still shows the underlying influence of acquiring the English phonological system.
Cleft Lip/Palate
The second study providing evidence for a phonological spectrum approach to SSD concerns a recent study on the speech of children with cleft lip/palate (CLP) (Ingram & Scherer, 2015). The study examined the speech development of 20 two-year old children with repaired CLP using the Profiles of Early Expressive Phonology Skills (PEEPS) assessment test (Stoel-Gammon & Williams, 2013). The speech samples were then analyzed using a multidimensional approach (Ingram & Dubasik, 2011).
The analyses looked at whole word measures (Ingram, 2002), syllable shapes, and included relational and independent analyses.
Table 3. Atypical patterns in CLP Productions Percentage No Fricatives
Velar Fronting No Final Consonants
Voice Ahead of Place, e,g,, /b,p,t,d/
Glottal Compensation
Gross Inclusion, e.g. [d] /d, s, dʒ, k, g / 65%
50%
40%
30%
25%
10%
Other 75%
The children in the first samples showed a wide range in their PCC scores, 12% to 63% (x = 39%).
The relational analyses revealed that each child showed a mix of typical and atypical phonological patterns. While no consensus exists concerning what is considered an atypical pattern, we identified six such potential categories. Table 3 presents them along with the percentage of children who showed instances of each. The first two categories identify an inability to produce fricatives and velars in any word position. The third identifies a lack of any or no more than one final consonant.
Voice Ahead of Place is a pattern that emerges in some children who have a lack of velars. They proceed to acquire a voice distinction for lingual and/or coronal while this acquisition typically follows the acquisition of velars. Glottal compensation is an over reliance on glottals, a pattern discussed in the CLP literature. Gross Inclusion is a pattern discussed in Grunwell (1985) in which a single consonant, often [d], is used for a wide range of phonemes (at least four in our analyses). Other more idiosyncratic patterns were also noted and placed under the other category.
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It was also the case that the children all had at least one atypical pattern, and some as many as 6.
There were six children with 1 or 2, seven children with 3 or 4, and seven children with 5 or 6.
Ten children were selected for similar analyses taken approximately 10 months later. During this time, the children received 48 sessions of an early speech and language intervention that targeted lexical and speech sound production (primarily consonant production). There were great improvements for all the children at the second sample points. The mean PCC scores in sample 1 were 39%, and this doubled in the second samples to a mean of 80%. Relational analyses indicated that the atypical patterns of the earlier samples were no longer found. The children had by then acquired fricatives, velars and final consonants, and were only relying on gross inclusion. They has gone from showing patterns characteristic of phonological disorders to patterns more like those of younger typically developing children but delayed.
Summary
A child’s acquisition of their language’s phonological acquisition involves simultaneous acquisition of articulatory skills and phonological representations. During the process, there is an interaction between articulation limitations and the need to distinguish phonemes. A common way to cope with this problem is for the child to follow principles of markedness, that is, to express a phoneme not yet pronounceable by one that is less marked. This is a phonological phenomenon, but it can be seen as an articulatory limitation as well.
Children with speech sound disorders are children challenged with greater articulatory difficulties than typically developing children. In some cases, this appears to be a matter of delay. That is, the children appear to be following a typical course of acquisition, but they are older relative to their point of development. In other cases, their development is different looking, that is, atypical, and in these cases it is likely due to specifically more severe articulatory problems. Some of these are clearly identifiable as articulatory, such as in the case who lisps, or one who cannot make a /r/. Between these two types of development, there is a more complex situation, this being children who have a range of possible articulatory problems, and are compensating for them in phonological ways. In some instances we can see the interplay taking place between articulation and phonology in the form of substitution shifts, that is, instances where the child produces a sound, but as a substitution rather than for its phoneme equivalent.
We suggest that a way to better understand this more complex group showing what might be called a phonological disorder. The proposal is to distinguish the phonological patterns that appear to be more articulatory based (unmarked) from those that are phonological, and to see any particular child as following along a spectrum. Some may show primarily unmarked phonological processes that place them on the articulatory side. Others may make greater phonological compensations that can be identified as phonological. Children may also vary their place on this spectrum over time.
This proposal was demonstrated through the analysis of two different situations, one a case study of a child assessed as having a speech sound disorder, the other a group study of children with clefts. The consonants in the sample of the child in the case study divided into two clear groups, those that he could pronounce correctly and those that he could not. He appeared to be on the articulatory side of the spectrum, and showed predictable simplifications. It was also possible, however, to identify a clear instance where his substitutions were a substitution shift, driven by an effort to maintain maximal contrast. The group study on children with clefts also deals with an instance where articulation would be expected to be a major factor in assessment. These children at the same time would otherwise be expected to be typically developing, were they not having to deal with their clefts.
The result of this circumstance was their showing temporarily very atypical phonological patterns in their early stage of phonological development. Later assessment showed noticeable improvements and the disappearance of the atypical patterns.