Content coverage of single-word tests used to assess common phonological error patterns.

LSHSS

Research Article

Content Coverage of Single-Word Tests Used to Assess Common Phonological Error Patterns Cecilia Kirka and Laura Vigelanda

Purpose: This review evaluated whether 9 single-word tests of phonological error patterns provide adequate content coverage to accurately identify error patterns that are active in a child’s speech. Method: Tests in the current study were considered to display sufficient opportunities to assess common phonological error patterns if they provided at least 4 opportunities for each of 11 error patterns. The target phonemes for these error patterns had to occur as singletons (except for final consonant deletion and cluster reduction) and in stressed syllables (except for weak syllable deletion). Error patterns for which positional asymmetries have been documented

(velar fronting, stopping of fricatives and affricates, and cluster reduction) required 4 opportunities in both wordinitial and word-final position to meet the study’s criterion. Results: None of the tests provided 4 opportunities for every error pattern, the criterion level used in this study. Error patterns that tended to be underrepresented across tests included weak syllable deletion, reduction of wordfinal clusters, fronting of velars, gliding of liquids, and deaffrication. Conclusion: This review will allow clinicians to gain a deeper understanding of the methods used to assess phonological error patterns in single-word tests.

P

The long-term goal of phonological intervention is the correct production of speech sounds in connected speech. For this reason, it is recommended that clinicians engage the client in spontaneous conversation and use the resulting speech sample as the basis for identifying phonological error patterns (Morrison & Shriberg, 1992). For individuals with severe phonological problems, this method of elicitation can result in it being nearly impossible to determine the attempted target words. Furthermore, in spontaneous speech, it can be difficult to obtain a representative sample of all the phonemes of interest. An alternative to sampling connected speech that avoids these difficulties is provided by eliciting single words in citation form. However, because the production of single words does not always accurately predict how a child will say these words in connected speech, it is recommended that both types of samples be included in an assessment battery (Bernthal et al., 2013). Although both connected speech and single-word samples are useful for evaluating phonological error patterns, the remainder of this article focuses only on single-word testing. More specifically, the purpose of this study was to examine the relative content coverage of phonological error patterns across tests. Our study provides a complement to a study by Eisenberg and Hitchcock (2010) that considered the validity of using single-word production data from

honological error pattern analysis is recommended as part of a comprehensive phonological assessment for children with multiple speech sound errors (Bernthal, Bankson, & Flipsen, 2013). This type of analysis is based on the assumption that when children acquire the phonological system of their language, they often make errors that apply to classes of speech sounds rather than to individual phonemes. For example, some children systematically replace fricatives in adult target words with stops. Because phonological error pattern analysis recognizes that speech errors apply to classes of sounds, it has the potential to facilitate treatment efficiency. For example, rather than providing intervention for every fricative that a child stops, a clinician can establish the correct production of just one or two fricatives with the expectation that this will generalize to the correct production of fricatives that are not directly targeted (Geirut, Morrisette, Hughes, & Rowland, 1996; Tyler, Edwards, & Saxman, 1987).

a

University of Oregon, Eugene Correspondence to Cecilia Kirk: [email protected] Editor: Marilyn Nippold Associate Editor: Rebecca McCauley Received July 29, 2013 Revision received February 17, 2014 Accepted August 26, 2014 DOI: 10.1044/2014_LSHSS-13-0054

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Disclosure: The authors have declared that no competing interests existed at the time of publication.

Language, Speech, and Hearing Services in Schools • Vol. 46 • 14–29 • January 2015 • Copyright © 2014 American Speech-Language-Hearing Association

11 tests of articulation and phonology for the purpose of compiling a phonetic inventory. The majority of the tests reviewed in this article refer to phonological process analysis. However, we prefer the term phonological error pattern analysis for the following reasons. The label phonological process analysis is based on the theory that a child’s production of a word can be derived from the adult pronunciation by a series of rules or processes (Stampe, 1973). Thus, a child who pronounces key as [di] is said to apply the phonological process of velar fronting to convert /ki/ to /ti/ and then the process of prevocalic voicing to convert /ti/ to [di]. According to more recent phonological theory, there are no rules or serial derivations, and instead the child’s output form is decided by a set of constraints on the child’s phonological system that are evaluated in parallel (Barlow & Gierut, 1999; Smolensky, 1996). To avoid the implication that children’s error patterns are derivational rather than constraint-based, as well as to avoid confusion with the term phonological processing, we refer to phonological error patterns rather than phonological processes in the remainder of this article. Given that many clinicians use tests that measure phonological error patterns as one source of information for determining appropriate intervention targets, it is important that these tests provide a representative indication of the phonological error patterns that are displayed in a child’s speech. Some error patterns, such as velar fronting and stopping of fricatives, are much more prevalent in word-initial position than word-final position (e.g., Chiat, 1983, 1989; Dyson, 1986; McAllister Byun, 2012; Smit, 1993a). Thus, if the opportunities for velar fronting consist mostly of word-final velars, the error pattern of velar fronting may go unrecognized in a child who fronts velars in word-initial position only. An additional consideration is that some error patterns remove the opportunity for another error pattern to occur. For example, a child who reduces all consonant clusters to a singleton consonant is likely to remove opportunities for gliding of liquids in words such as blue and crab. In this instance, the total number of opportunities for gliding will need to be adjusted, or the percentage of occurrence for the error pattern of gliding will be misrepresented. Before we can determine whether single-word tests provide a sufficient number of opportunities to establish the various phonological error patterns in a child’s speech, it is necessary to come up with a set of core phonological error patterns and provide recommendations on the best way to evaluate each of them. The error patterns selected for this review include the 10 most common patterns produced by the 670 children between the ages of 2;0 (years;months) and 8;11 who were tested to create the American normative sample of the Diagnostic Evaluation of Articulation and Phonology (DEAP; Dodd, Huo, Crosbie, Holm, & Ozanne, 2006). However, we made two changes to the error patterns listed in the DEAP. We separated the error pattern of fronting into velar fronting and palatal fronting, and we did not examine the error pattern of vocalization. Instead, we eliminated the error pattern of vocalization of postvocalic /l/

and renamed vocalization of /r/ as derhoticization. Our rationales for these decisions are justified in the discussion that follows. Our selection of error patterns is also supported by a number of research studies that report that these errors are among the most frequently occurring errors in the speech of children learning to speak English (Haelsig & Madison, 1986; Hodson & Paden, 1981; James, 2001; Preisser, Hodson, & Paden, 1988; Roberts, Burchinal, & Footo, 1990).

Definitions of Phonological Error Patterns In the following section, we draw on phonological theory and empirical research to support the definitions of the error patterns that we used to evaluate the tests included in our review. We provide a summary of our definitions in Table 1. In our discussion of the various phonological error patterns, we point out some of the more common dialectal differences produced by speakers of American English, but our discussion of these differences is not comprehensive. It is the responsibility of speech-language pathologists working with children from culturally and linguistically diverse populations to familiarize themselves with the phonological features of the specific dialect spoken by their clients to avoid misdiagnosing phonological differences as a speech sound disorder (American Speech-LanguageHearing Association [ASHA], 2004).

Final Consonant Deletion The error pattern of final consonant deletion (FCD) occurs when the syllable coda in the target word is deleted. Most typically developing children produce final consonants by the age of 30 months (Preisser et al., 1988). Before this age, children have a preference for open syllables, and so they will often delete singleton consonants and consonant clusters in word-final position. However, the deletion of word-final clusters should not be classified as FCD, if that deletion is specific to clusters. For example, a child who produces the final consonant in bus and cake but deletes the entire cluster in desk displays the error pattern of cluster deletion, not FCD. This child has the ability to produce singleton coda consonants but is not able to produce all cluster types in syllable codas. Similarly, the deletion of the final consonant in a consonant cluster (e.g., hand → [hæn]) should be classified not as FCD but instead as cluster reduction. This is supported by the fact that most children who produce hand as [hæn] do not have difficulty producing the final consonant in bed. When assessing the production of word-final consonants, it is important that consonants with different manners and places of articulation be included. Nonetheless, we argue that neither the lateral liquid nor the rhotic liquid should be included as opportunities for the error pattern of FCD because postvocalic /l/ is often vocalized in adult speech and so does not provide a valid opportunity for assessing the production of word-final consonants (Schneider, Burridge, Kortman, Mesthrie, & Upton, 2004; Wells, 1992). Similarly, postvocalic /r/ is best analyzed as a rhoticized

Kirk & Vigeland: Assessment of Phonological Error Patterns

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Table 1. Summary of definitions used to evaluate opportunities for error patterns. Error pattern Final consonant deletion (FCD)

Weak syllable deletion (WSD)

Definition used to evaluate opportunities for error pattern The final consonant or the entire final consonant cluster of a word is deleted. Word-final /l/ and word-final /r/ are not included as opportunities for FCD. Note that the deletion of a single consonant from a cluster of two or three consonants is called cluster reduction, even if the deleted consonant is word-final. A nonfinal, unstressed syllable in a word is deleted.

Cluster reduction

A cluster of two consonants is reduced to one consonant, and a cluster of three consonants is reduced to either one or two consonants.

Prevocalic voicing

A word-initial voiceless consonant becomes voiced.

Postvocalic devoicing

A word-final voiced consonant becomes voiceless.

Velar fronting

Gliding of liquids

A consonant made with a constriction at the velum is replaced by a consonant made at the alveolar ridge. Words containing the present progressive morpheme –ing are not included as opportunities for velar fronting. A consonant made with a constriction at the hard palate is replaced by a consonant made at the alveolar ridge. A fricative or affricate is replaced with a stop consonant that shares the same or similar place of articulation (/f/ and /v/ are replaced with labial stops; /s/, /z/, /ʃ/, /ʒ/, /ʧ/, and /ʤ/ are replaced with alveolar stops). The interdental fricatives, /q/ and /ð/, and the phoneme /h/ are not included as opportunities for this error pattern. The liquids /r/ and /l/ are replaced by the glides [w] or [j].

Derhoticization

A rhoticized vowel loses its /r/ coloring.

Deaffrication

The voiceless affricate is replaced by the voiceless fricative at the same place of articulation.

Palatal fronting Stopping of fricatives and affricates

Examples food → [fu] beans → [bi]

tomato → [ˈmeɪɾoʊ] elephant → [ˈɛfǝnt] bread → [bɛd] splash → [blæʃ ] wasp → [wɑs] pig → [bɪg] sock → [zɑk] dog → [dɑk] nose → [noʊs] cow → [taʊ] sing → [sɪn] sheep → [sip] bridge → [brɪdz] four → [pɔɚ] sun → [tʌn] dish → [dɪt] ring → [wɪŋ] leaf → [jif] girl → [gɜl] star → [stɑʊ] chip → [ ʃɪp] cheese → [ ʃiz]

Note. Only singleton consonants (except for final consonant deletion and cluster reduction) in stressed syllables (except for weak syllable deletion) are considered valid opportunities for a given error pattern. Word-medial consonants are not considered valid opportunities for any error pattern.

vowel than as a consonant (Olive, Greenwood, & Coleman, 1993). Therefore, we recommend that word-final /l/ and /r/ should not be considered valid opportunities for the error pattern of FCD.

Weak Syllable Deletion Typically developing children under the age of 2 years often omit the final unstressed syllable in words like cracker and feather, but by 22–25 months, deletion of the unstressed syllable in these words is rare (Preisser et al., 1988). From the age of 3, even children with unintelligible speech are usually able to produce both syllables in two-syllable words with a strong–weak stress pattern (Hodson & Paden, 1981). However, children with and without a phonological disorder often find it difficult to accurately produce the initial unstressed syllable in words such as giraffe and policeman. Echols and Newport (1992) collected spontaneous productions in natural contexts from three English-speaking children at the one-word stage of language acquisition. They found that syllables in multisyllabic words that were both unstressed and nonfinal were omitted much more frequently than unstressed syllables in word-final position (51% vs. 11%). The tendency of American English-speaking children

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to omit unstressed, nonfinal syllables from their earliest productions has also been noted by Ingram (1978), Kehoe and Stoel-Gammon (1997), and Klein (1981). As discussed above, children with typical phonological development rarely delete unstressed syllables in word-final position. Therefore, we argue that words with word-final unstressed syllables, such as tiger and grasshopper, are not appropriate items to use for the purpose of identifying the occurrence of weak syllable deletion. Instead, we recommend that only unstressed, nonfinal syllables should be considered valid opportunities for evaluating weak syllable deletion (e.g., elephant, computer).

Cluster Reduction In the literature on the acquisition of consonant clusters, there is disagreement regarding the classification of errors involving clusters (Chin & Dinnsen, 1992; Grunwell, 1981b; Kirk, 2008; McLeod, van Doorn, & Reed, 2001b; Smit, 1993b). To help resolve these differences, we review three stages of cluster acquisition that occur before accurate production of clusters is achieved. We use this discussion to support recommendations as to what should be considered valid opportunities for the evaluation of cluster reduction.

Language, Speech, and Hearing Services in Schools • Vol. 46 • 14–29 • January 2015

Developmental Stages of Cluster Acquisition Consonant clusters are not typically mastered until after 3 years of age (Smit, 1993b), and mastery develops as children progress through a number of stages between their first attempts at consonant clusters and their correct productions. The various stages in the acquisition of clusters were first formalized for stop + liquid clusters by Greenlee (1974) and were later expanded by Elbert and McReynolds (1979) to include all cluster types. Cluster deletion. One of the earliest occurring cluster errors is the deletion of an entire cluster. However, cluster deletion should not be confused with the error patterns of initial consonant deletion and final consonant deletion. A child displaying final consonant deletion (or initial consonant deletion) will delete singleton consonants and consonant clusters in word-final (or word-initial) position. Cluster deletion, in contrast, reflects difficulty with consonant clusters. Cluster deletion, as defined here, occurs only rarely in the speech of young children. In a study investigating cluster production in typically developing, Englishspeaking children between the ages of 1;5 and 2;7, fewer than 1% of the total attempts at target words containing either a word-initial or a word-final cluster resulted in cluster deletion (Kirk, 2008). Cluster reduction. In the second stage of cluster development, children reduce target words containing two consonants in the syllable onset or syllable coda to a single consonant. They may also reduce target clusters with three consonants either to two consonants or to a single consonant. For example, snake might be produced as [neɪk] and splash as [blæS] or [bæS]. Coalescence is a specific type of cluster reduction that involves the merging of phonological features from each of the consonants in the target cluster to produce a new consonant. Spoon pronounced as [fun] is an instance of this type of cluster reduction. In this example, the [f ] preserves the continuancy of the /s/ as well as the labial place specification of the /p/ (Chin & Dinnsen, 1992; Pater & Barlow, 2003). Cluster reduction is one of the last phonological error patterns to disappear in the speech of typically developing children, and it is one of the most common difficulties for children with a speech sound disorder (e.g., Chin & Dinnsen, 1992; McLeod, van Doorn, & Reed, 1997). Cluster substitution. The third stage in cluster development is cluster substitution. This error pattern occurs when the correct number of consonants is produced, but one or more consonants are replaced by a different consonant. Two different types of cluster substitution errors have been identified (Kirk, 2008). One type of substitution error in clusters can be predicted from the child’s production of singleton consonants. Thus, if a child realizes leaf as [wif ] and slide as [swaɪd], then this would be considered a predictable substitution error. The second type of substitution error in clusters occurs when the substitution cannot be predicted from the child’s singleton production. For example, if a child pronounces block as [blAk], but blocks as [blAts], then this would be considered an unpredictable substitution error, yet one that is relatively common. A study of cluster

production in 11 typically developing, English-speaking children between the ages of 1;5 and 2;7 found that almost one third of substitution errors in clusters could not be predicted from singleton production (Kirk, 2008). In the majority of cases, these unpredictable substitution errors could be accounted for by assimilation of place or manner. When children are at the stage of cluster development where they preserve the correct number of consonants in the target cluster, a common error pattern is the insertion of schwa between two consonants in a cluster (Smit, 1993b). An example of this type of vowel insertion occurs when the target word slide is produced as [səˈlaɪd]. Smit (1993b) noted that although schwa epenthesis is common for word-initial clusters consisting of a consonant followed by an /r/ or /l/, it is rare for word-initial /s/ + stop clusters. This led Smit (1993b) to suggest that schwa epenthesis may represent a lengthened transition into the liquid rather than true vowel insertion. For this reason, she considered schwa epenthesis in clusters to be an acceptable production of the target cluster, and we follow her recommendation. The evidence reviewed above suggests that errors involving cluster substitution and vowel epenthesis are more advanced stages in the development of clusters than the error pattern of cluster reduction. Therefore, we do not recommend collapsing these error patterns with the error pattern of cluster reduction.

Word-Initial Clusters and Word-Final Clusters Any valid measure of the error pattern of cluster reduction should sample both word-initial clusters and wordfinal clusters because only by comparing the production of words such as blocks and box can we determine whether a child’s inability to say the final cluster in these words is due to a phonological impairment or to an impairment in grammatical morphology. Previous work on the acquisition of consonant clusters by typically developing 2-year-olds showed a tendency for word-final clusters to be acquired before word-initial clusters (Kirk & Demuth, 2005). However, in that study, not all word-final clusters were produced more accurately than word-initial clusters, and all participants had considerable difficulty with the correct production of word-final /s/ + stop clusters. Other researchers have also reported that 2-year-old children learning English tend to produce CVCC words before CCVC words (Paul & Jennings, 1992; Watson & Scukanec, 1997), although no breakdown of cluster accuracy according to the segmental content of those clusters was provided. Researchers have also reported that different cluster types (e.g., word-initial obstruent + /r/ clusters vs. wordinitial /s/ + stop clusters) may undergo different types of errors (e.g., cluster reduction vs. cluster substitution) at a given stage in a child’s phonological development (Kirk, 2008; Kirk & Demuth, 2005; McLeod, van Doorn, & Reed, 2001a, 2001b; Smit, 1993b). Furthermore, a child who reduces all clusters to singletons will sometimes show different reduction patterns depending on the sonority of the phonemes that comprise those clusters (Greenlee, 1974;


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Ohala, 1999; Pater & Barlow, 2003), as exemplified by a child who pronounces stop as [tAp] and snake as [seɪk]. In order to provide speech-language pathologists with a clinically useful overview of a child’s consonant cluster development, we recommend that a test of phonological error patterns should include items that represent each of the following cluster types: word-initial /s/ + stop, word initial /s/ + nasal, word-initial obstruent + /l/, word-initial obstruent + /r/, word-initial consonant + glide, word-final nasal + /z/, word-final stop + /s, z/, word-final nasal + stop, wordfinal /s/ + stop, word-final stop + stop, and word-final fricative + fricative. Word-Medial Clusters Blevins (1995) argued that the intervocalic cluster in words such as telescope is syllabified as the onset of the following syllable because the stressed vowel draws in as many of the preceding consonants as are phonotactically legal. The syllabic affiliation of other medial clusters is less clear. For example, there is no consensus on the syllabification of words such as candy, which, according to the phontactics of English, can be syllabified as either [ˈkæn.di] or [ˈkænd.i]. The word basket provides an even greater range of possible syllabifications: [ˈbæ.skət], [ˈbæs.kət], or [ˈbæsk.ət]. Given that word-medial consonant sequences do not represent a cohesive set of phonological structures, we recommend that they should not be examined for the error pattern of cluster reduction.

Prevocalic Voicing The error pattern of prevocalic voicing occurs when a word-initial voiceless consonant is replaced by a voiced consonant. In general, this change in voicing occurs without affecting manner or place; thus, cup becomes [gÃp] and fish becomes [vɪS], although a speaker may display additional error patterns that alter manner and/or place. Prevocalic voicing appears to be motivated by the anticipation of the following (voiced) vowel and so occurs much more frequently than devoicing of word-initial voiced consonants (Weiner, 1979). Word-initial /s/ + stop clusters are not helpful for deciding whether a voicing error has occurred. In English, voiced and voiceless stops in word-initial stressed syllables are not distinguished by the presence versus absence of voicing during the stop closure, because both lack voicing. Instead, they are distinguished by the duration between the stop burst and the initiation of voicing, which is called voice onset time (VOT). The VOT of the stop immediately following word-initial /s/, as in spoon, is very similar to that of a voiced stop, whereas the VOT of an aspirated voiceless stop is longer (Olive et al., 1993). Thus, for English listeners, the stop in a word like spoon sounds more like the initial phoneme in [bun] than in [phun], and this can be easily verified by recording the word spoon and splicing off the /s/ phoneme. Therefore, /s/ + stop clusters should not be used as evidence that a child voices prevocalic consonants. Furthermore, when other cluster types undergo cluster

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reduction, it may be that changes in the voicing of the remaining consonant(s) are due to coalescence with an adjacent liquid or nasal, as in clock becoming [gAk]. Therefore, we recommend that only singleton consonants should be considered when determining voicing errors.

Postvocalic Devoicing The error pattern of postvocalic devoicing occurs when a word-final voiced consonant is replaced by a voiceless consonant. It should be noted that for many adult speakers of English, the final consonant in words such as tub and nose are phonetically almost completely voiceless (Klatt, 1976). The primary acoustic cue to postvocalic voicing in English is the consonant–vowel ratio rather than the presence versus absence of voicing during the obstruent following the vowel (Denes, 1955; Port & Dalby, 1982). Thus, a fricative or stop is heard as voiceless when it is about the same duration as the vowel that precedes it, and a fricative or stop is heard as voiced when it is much shorter than the preceding vowel. Children learning word-final voicing contrasts in English, such as the difference between bus and buzz, must learn the appropriate consonant–vowel ratio.

Fronting of Velars The error pattern of velar fronting occurs when a velar phoneme is replaced by an alveolar phoneme. Although some researchers (e.g., Inkelas & Rose, 2007; McAllister Byun, 2012) have defined velar fronting as occurring when a velar consonant is replaced by a coronal consonant (alveolars and interdentals), the examples discussed in both these studies involve the replacement of velars by alveolars only. We follow researchers who have adopted a stricter definition of velar fronting such that velars are replaced by alveolars only (e.g., Dunn & Davis, 1983; Dyson, 1986; Grunwell, 1981b; James, 2001; Lowe, Knutson, & Monson, 1985; McReynolds & Elbert, 1981; Stoel-Gammon & Dunn, 1985). We also recommend that words with the present progressive suffix (e.g., fishing, swimming, and jumping) not be included as opportunities for velar fronting, given that adult speakers of many dialects of American English frequently substitute [n] for /ŋ/ in the present progressive, particularly in casual speech (Gordon, 2004a; Schneider, 2004). Positional asymmetries in the fronting of velars to alveolars have been well documented in the literature. Specifically, it has been found that fronting of word-initial velars is much more common than fronting of word-final velars. The majority of these studies report on typically developing children (Chiat, 1983; Dyson, 1986; Ingram, 1974; Inkelas & Rose, 2007; Smit, 1993a), but positional asymmetries have also been documented in the speech of children with phonological disorders (McAllister Byun, 2012; Morrisette, Dinnsen, & Gierut, 2003). The fact that word-initial velars are fronted more commonly than word-final velars should be taken into consideration when evaluating the number of opportunities for this error pattern to occur in a child’s speech. Given this asymmetry, it is important that a test


contains sufficient opportunities for evaluating word-initial velars.

Fronting of Palatals The error pattern of palatal fronting occurs when a palatal phoneme is replaced by an alveolar phoneme. We recommend that the fronting of palatals be assessed independently from the fronting of velars, given that velar fronting resolves earlier than palatal fronting in typically developing children (Stoel-Gammon & Dunn, 1985). Empirical support for the different age of acquisition for velars and palatals is provided by Vihman and Greenlee (1987), who found a higher incidence of palatal fronting than velar fronting in 11 typically developing children at 36 months. Two of the 3-year-olds tested by Vihman and Greenlee fronted both velars and palatals, while six children fronted only palatals. The two remaining children in the study did not front either velars or palatals. Similar results have been reported for typically developing 2-year-olds (Dyson & Paden, 1983). The positional asymmetry found for the fronting of velars does not appear to hold for palatals. Smit (1993a) reported that fronting of palatals (with manner preserved) occurs frequently in both the word-initial position and the word-final position, suggesting that opportunities for testing this error pattern are likely to be equally represented in either position.

Stopping of Fricatives and Affricates The error pattern of stopping occurs when a fricative or affricate is replaced by a stop consonant that shares the same place of articulation. If there is no homorganic stop, then replacement is by a stop at the nearest place of articulation. Thus, labio-dental fricatives (/f/ and /v/) are replaced by labial stops ([p] and [b]), while interdental fricatives (/q/ and /ð/), alveolar fricatives (/s/ and /z/), and palatal fricatives or affricates (/S/, /Z/, /tS/, and /dZ/) are all replaced by alveolar stops ([t] and [d]). Words with the phoneme /h/ should not be considered as opportunities for stopping because the phoneme /h/ is different from other fricatives in that the constriction is at the glottis rather than in the vocal tract. Because the production of /h/ does not involve the articulators (tongue, teeth, lips), this allows the vocal tract to take on the configuration of adjacent phonemes. For this reason, it has been suggested that /h/ in English might be better classified as a voiceless vowel (Ladefoged & Maddison, 1996). Other researchers have classified /h/ as a glide along with /j/ and /w/ (Smit, 1993a). We do not intend to resolve the classification of /h/ here, but it is important to note that /h/ is rarely replaced by a stop in the speech of young children (Smit, 1993a). Similarly, the replacement of a fricative or affricate by a glottal stop should not be classified as stopping. Given that glottal stop replacement affects a much wider class of consonants than just fricatives and affricates (Grunwell, 1981b; James, 2001; Smit, 1993a), we see no viable justification for

classifying the replacement of fricatives and affricates by glottal stops as stopping. The interdental fricatives as potential targets for stopping require special mention because the phoneme /ð/ is particularly prone to being produced as a stop for an extended period, often until a child is 6 years old or older (Grunwell, 1981a; Snow, 1963). Conversely, /q/ rarely undergoes stopping, and the two most common errors for /q/ are replacement by [f] or variants of [s] (Smit, 1993a; Vihman & Greenlee, 1987). However, for both of these consonants, care must be taken to determine an acceptable production for each individual child because these consonants are particularly susceptible to variant pronunciations depending on the dialect of English spoken in the child’s speech community (Goldstein, 2001; Pearson, Velleman, Bryant, & Charko, 2009). Combining fricatives where stopping is resolved early and fricatives where stopping is not resolved until much later (or which rarely undergo stopping) as a single error pattern may lead to incorrect identification of stopping as a pattern that is active in a child’s phonological system. Some researchers have acknowledged that there are two different types of stopping by separating the error pattern of stopping into early stopping and later stopping (McLeod & Bleile, 2003; Watson & Scukanec, 1997). We recommend that the interdental fricatives not be included as opportunities for the error pattern of (early) stopping and suggest that the accuracy with which these consonants are produced would be better examined as part of an articulation test. Positional asymmetries have been reported for the stopping of fricatives and affricates such that stopping is more common for word-initial fricatives and affricates than for word-final fricatives and affricates (Chiat, 1989; Smit, 1993a). Smit (1993a) reported that this asymmetry does not hold for /v/, which is just as likely to be replaced by [b] in word-final position as word-initial position. Given the positional asymmetries for stopping of fricatives and affricates, it is important that sufficient opportunities are provided for evaluating these phonemes in word-initial position.

Gliding of Liquids The error pattern of gliding occurs when a glide (/w/ or /j/) replaces a liquid (/r/ or /l/). Although other consonants are sometimes replaced by glides, this occurs very infrequently in the speech of children with typical phonological development as well as those with a phonological disorder (Grunwell, 1981a; Hodson & Paden, 1981; Ingram, 1989; Smit, 1993a). Therefore, consonants other than liquids do not provide reasonable opportunities for this error pattern to occur. In addition, liquids in consonant clusters similarly do not provide a reliable context for evaluating the error pattern of gliding because consonant clusters very commonly undergo reduction to a singleton consonant, in the speech both of typically developing children and of children with a phonological disorder. For word-initial clusters that contain a liquid, it is the liquid consonant that is most often


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deleted (Greenlee, 1974; Pater & Barlow, 2003). Wordmedial intervocalic liquids are also prone to deletion, which makes them unreliable contexts for evaluating whether gliding has occurred. Weak syllable deletion, in particular, can result in word-medial liquids being deleted, as in common pronunciations of words such as balloon → [bun], telephone → [ˈtɛfoOn], and giraffe → [dæf ] (Grunwell, 1981a; Pater, 1997). For most children, gliding of /l/ resolves earlier than gliding of /r/ (Smit, 1993a). For this reason, any test of phonological error patterns should provide sufficient opportunities for both /l/ and /r/.

Vocalization of Liquids In what follows, we provide evidence to suggest that vocalization of /l/ should not be considered an error pattern. We then go on to argue that vocalization of /r/ is more aptly described as derhoticization (loss of rhotic quality). Vocalization of /l/ Vocalization of postvocalic /l/ is widespread in the speech of adult speakers of many American English dialects (Schneider et al., 2004). It is particularly common in Pennsylvania, New England, and the South, where it is often realized as either a vowel or a velar glide or is deleted altogether (Gordon, 2004a, 2004b; Schneider, 2004; Wells, 1992). The frequency with which vocalization occurs depends on the phonetic context, with vocalization more likely to occur in non-prevocalic environments (e.g., sell, sells, sold, but not selling; Wells, 1992). The incidence of /l/ vocalization in American English by educated speakers of many dialects has also been documented as increasing (Kretzschmar, 2004). As a further rationale for our recommendation that vocalization not be considered an error pattern, we note that auditory judgments of vocalization as distinct from nonvocalization tend to be unreliable. For example, the authors of the DEAP (Dodd et al., 2006) reported a low interrater reliability coefficient for the transcription of /l/ across all word positions. They suggested that this low reliability is likely due to the difficulty in accurately evaluating the production of /l/ in words such as girl and school. Because auditory judgments are not always reliable, instrumental techniques such as cinefluorography and electropalatography (EPG) have been used by researchers to provide an objective indication of vocalization versus nonvocalization. In these studies, vocalization is defined as a lack of alveolar– lingual contact. Cinefluorographic data from a study by Giles and Moll (1975) showed that postvocalic /l/ is often vocalized in American English, typically in faster speech rates and in consonant clusters where the consonant following the /l/ does not share the alveolar place of articulation. According to an EPG study by Scobbie and Wrench (2003), /l/ vocalization in both British and American English takes place more frequently before a pause and before consonants than prevocalically.

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Examining the spectrogram of postvocalic liquids can also provide an objective indication of vocalization. Spectrographic data from Olive et al. (1993) showed that after the vowels /æ/, //, /u/, and /Ã /, the boundary between the vowel region and the /l/ region is not visibly differentiated. They suggested that the sounds in these spectrograms should be interpreted as /l/-colored vowels rather than instances of two distinct phonemes. In summary, evidence from the fields of sociolinguistics and phonetics suggests that vocalization of postvocalic /l/ by adult speakers of American English is pervasive, although there is some variability depending on the dialect spoken and the phonetic context. Given that /l/ is so often vocalized by adult speakers, we suggest that it is not appropriate to consider vocalization of /l/ a worthwhile intervention target. Vocalization of /r/ (Derhoticization) The replacement of postvocalic /r/ with a vowel (e.g., star → [stAO], zipper → [ˈzɪpoO], bird → [bÎd], feather → [ˈfɛðə]) is sometimes labeled vocalization of /r/ (e.g., StoelGammon & Dunn, 1985; Weiner, 1979). However, given that the difference between the target word and the child’s production across all these examples is loss of the /r/ quality, we argue that this error pattern is more accurately described as derhoticization.

Deaffrication The error pattern of deaffrication is defined as occurring when an affricate is replaced by a fricative at the same place of articulation. When an affricate is replaced by a fricative at any place of articulation, for example, cheese → [siz] or chair → [qɛɚ], these errors are better explained as palatal fronting or dentalization that occurs in addition to deaffrication. Given that deaffrication occurs so rarely for the voiced affricate /u/ (Smit, 1993a), the inclusion of /u/ as an opportunity for deaffrication may lead to underestimating the percentage of occurrence of this error pattern. For this reason, we recommend including only instances where the voiceless affricate /^/ is replaced with [S] as valid opportunities for deaffrication.

Effect of Lexical Stress on Production Accuracy A number of studies have shown that the production accuracy of a consonant is affected by whether that consonant occurs in a stressed syllable, with stressed syllables associated with more accurate productions (Kirk & Demuth, 2006; Klein, 1981; Zamuner & Gerken, 1998). For example, Kirk and Demuth (2006) asked 15 typically developing 2-year-olds to imitate novel words of different phonological shapes (e.g., /ˈgɛpnək/ vs. /gəpˈnæk/). Their results showed that coda consonants were more accurately produced in stressed syllables than in unstressed syllables in both wordmedial and word-final position. Similar findings have been reported for the production of real words by young children


(Klein, 1981). Given these results, we recommend that only target phonemes and clusters that appear in stressed syllables should be considered valid opportunities for assessing the occurrence of phonological error patterns. For example, because the final consonant in the word glasses occurs in an unstressed syllable, it would not be considered to be a valid opportunity for the error patterns of final consonant deletion or postvocalic devoicing. Along similar lines, the word-final consonant cluster in elephant occurs in an unstressed syllable and so would not be considered a valid opportunity for evaluating cluster reduction.

Choosing a Criterion for Number of Opportunities For a phoneme to be attributed to a child’s phonemic inventory in conversational speech, some researchers have required that this phoneme be produced correctly relative to the adult target at least twice in a given word position (Ingram & Ingram, 2001; Stokes, Klee, Carson, & Carson, 2005). However, there is currently no research indicating what constitutes a sufficient number of opportunities for concluding that a child’s speech displays a particular phonological error pattern. Because error patterns necessarily involve classes of sounds, such as fricatives or consonant clusters, it seems reasonable that more than two opportunities should be required. In the interest of balancing comprehensiveness with the time constraints of clinical practice, we follow McReynolds and Elbert’s (1981) recommendation that a test include at least four exemplars of a given error pattern in order for that error pattern to be considered active in a child’s phonological system. The requirement that a test provide at least four opportunities for each phonological error pattern is obviously arbitrary, a point acknowledged by McReynolds and Elbert. This cutoff is probably too low for some types of errors, such as cluster reduction and final consonant deletion, which have the potential to affect a large number of consonants. However, until we have empirical data that identify the optimal number of opportunities required to provide a representative sample for individual error patterns, four opportunities seem to constitute a reasonable criterion.

Method Inclusion Criteria To select the tests included in this review, we initially consulted the list of phonological and articulation tests that are provided online by ASHA (n.d.). Tests that met the following criteria were selected for further review: (a) The test examined phonological error patterns using single-word production, (b) the test was published in or after 1990, (c) the test provided standardized instructions for administration and scoring (although normative data were not required), and (d) the test could be obtained for purchase

from the publisher or author. Only nine tests met these inclusion criteria: 1.

Arizona Articulation Proficiency Scale, Fourth Edition (AAPS–4; Fudala, n.d.)

2.

Bankson-Bernthal Test of Phonology (BBTOP; Bankson & Bernthal, 1990)

3.

Clinical Assessment of Articulation and Phonology, Second Edition (CAAP–2; Secord & Donohue, 2014)

4.

Diagnostic Evaluation of Articulation and Phonology (DEAP; Dodd et al., 2006)

5.

Hodson Assessment of Phonological Patterns, Third Edition (HAAP–3; Hodson, 2004)

6.

Khan-Lewis Phonological Analysis, Second Edition (KLPA–2; Khan & Lewis, 2002)

7.

Phonological Screening Assessment (PSA; Stevens & Isles, 2001)

8.

Rules Phonological Evaluation (RPE; Webb & Duckett, 1990)

9.

Structured Photographic Articulation Test II featuring Dudsberry (SPAT–D II; Dawson & Tattersall, 2001)

All tests included in the current review, except the PSA, are one component of a test with multiple subtests designed to assess various aspects of articulation and phonology. The current review focuses only on the subtest designed to assess phonological error patterns in single-word productions. Five tests (AAPS–4, CAAP–2, DEAP, RPE, SPAT–D II) provide opportunities for eliciting production of a selection of test items in connected speech. With the exception of the PSA, all tests include scoring information for an articulation subtest in addition to a subtest that evaluates phonological error patterns. Two of the tests (CAAP–2, RPE) group together a set number of opportunities for each error pattern on their respective response form, and this results in some test items being elicited more than once. For example, the word pig occurs three times on the response form for the CAAP–2, one time for each of final consonant deletion, prevocalic voicing, and postvocalic voicing. For tests where the same test item was listed more than once, the phonemes in the repeated test items contributed only once to our analysis. A comprehensive examination of the psychometric properties of six of the tests included in this review (BBTOP, CAAP–2, DEAP, HAPP–3, KLPA–2, SPAT–D II) is provided in Kirk and Vigeland (2014). The test manuals of the RPE and the PSA do not provide any information on the psychometric properties of their respective tests. The RPE does, however, provide the percentage of occurrence of the error patterns examined on the basis of data from 181 children between the ages of 3;0 and 6;11. The test manual for the AAPS–4 has not yet been published, although the response form and definitions of the phonological error patterns are available as part of a standardization study that is currently under way.


21

Conventions for Transcribing Test Items The tests included in this review all followed slightly different conventions for transcribing test items. To allow comparisons across tests, we made the following decisions regarding the transcription of liquids and nasals. Postvocalic /r/ was always transcribed as a rhoticized vowel. Thus, the words car, ear, and fire were transcribed as /kAɚ/, /iɚ/, and /faɪɚ/, respectively. The final vowel in words with a strong– weak stress pattern, such as feather and tiger, was transcribed as rhoticized schwa. Word-final /l/ and word-final nasals, as in the words apple and wagon, were considered to be consonants in unstressed syllables (rather than syllabic consonants). The second vowel in words like basket and carrot was transcribed as schwa, not /ɪ/, and was therefore analyzed as an unstressed syllable.

Summary of Criteria for Evaluating Content Coverage Tests in the current study were considered to have met our criterion for adequate content coverage if they provided at least four opportunities for each of the 11 common phonological error patterns listed in Table 1. The target phonemes for these error patterns had to occur as singletons (except for the error patterns of final consonant deletion and cluster reduction) and in stressed syllables (except for weak syllable deletion). Error patterns for which positional asymmetries have been documented (i.e., velar fronting, stopping of fricatives and affricates, and cluster reduction) required four opportunities in both word-initial and wordfinal position to meet the criterion. Gliding of /l/ was assessed separately from gliding of /r/. Word-medial consonants were not considered valid opportunities for any error pattern because it is not clear whether these consonants should be syllabified as syllable onsets, syllable codas, or ambisyllabic (Rvachew & Andrews, 2002; Stoel-Gammon, 2002), and as we have argued earlier, the syllabic affiliation of a phoneme can affect the accuracy with which it is produced.

Interrater Reliability Both authors independently examined each test item from the nine tests under review to identify the number of opportunities for each error pattern. The number of opportunities provided by each test was determined according to the criteria discussed in the previous section and not according to the definitions laid out in the relevant test manuals. For example, the initial phoneme in the word cat provides an opportunity for the error pattern of velar fronting in word-initial position, but the initial phoneme in the word clown does not. Point-to-point agreement was calculated for a total of 7,545 rating judgments (503 total test items for each of 11 error patterns, with three error patterns evaluated separately by position within the word and gliding evaluated separately for /l/ and /r/). The percentage of agreement between the two scorers was 99.8%.

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Disagreements were resolved through discussion until consensus was reached.

Results The number of opportunities provided by each test for the 11 core error patterns is shown in Table 2, with opportunities calculated using the criteria in Table 1 rather than the definitions set out in the test manuals. The final column in Table 2 provides the total number of error patterns for which a given test provided at least four opportunities. Note that the possible total for this column is 15 because some error patterns required four opportunities in both word-initial and word-final position to meet criterion, and gliding of /l/ was assessed separately from gliding of /r/. Table 3 summarizes the definitions supplied by the test manuals of each reviewed test. All nine tests provided at least four opportunities for the error patterns of final consonant deletion, cluster reduction in word-initial position, prevocalic voicing, postvocalic devoicing, palatal fronting, and stopping of fricatives and affricates. Only five of the nine tests provided sufficient opportunities for assessing weak syllable deletion (AAPS–4, BBTOP, CAAP–2, DEAP, KLPA–2). Only the HAPP–3 and RPE provided at least four opportunities for cluster reduction in word-final position. All tests, except the SPAT–D II, provided sufficient opportunities for assessing velar fronting in word-final position, but only five tests (AAPS–4, BBTOP, KLPA–2, RPE, SPAT–D II) provided sufficient opportunities for wordinitial velar fronting. The lack of opportunities for evaluating velar fronting in word-initial position is of concern because, as discussed above, many children front velars only in wordinitial position. Only the RPE provided sufficient opportunities for assessing gliding of the lateral liquid /l/, and only two tests (BBTOP, RPE) provided adequate opportunities for assessing gliding of the rhotic liquid /r/. Six tests (AAPS–4, BBTOP, HAAP–3, KLPA–2, PSA, RPE) provided sufficient opportunities for assessing derhoticization. Finally, only the BBTOP provided sufficient opportunities for assessing deaffrication. In summary, none of the tests that we reviewed provided at least four opportunities for all of the phonological error patterns discussed above. However, both the BBTOP and the RPE came close to meeting our criteria for adequate coverage. The BBTOP failed to reach criterion on the error patterns of cluster reduction in word-final position and gliding of /l/. The RPE failed to reach criterion on the error patterns of weak syllable deletion and deaffrication.

Discussion This review evaluated content coverage for nine single-word tests assessing 11 common phonological error patterns. When we began this evaluation process, it quickly became evident that not all tests assessed the same set of error patterns and that these error patterns were defined


Table 2. Number of opportunities for phonological error patterns. Cluster reduction Test


AAPS–4 BBTOP CAAP–2 DEAP HAAP–3 KLPA–2 PSA RPE SPAT–D II Total tests

FCD WSD Initial Final 36 51 27 24 32 25 34 61 22 9

4 9 8 5 1 4 0 0 2 5

7 10 9 15 20 16 28 15 10 9

2 3 0 1 5 2 0 5 1 2

Velar fronting

Prevocalic voicing

Postvocalic voicing

Initial

Final

Palatal Fronting

18 25 10 12 12 13 7 25 14 9

12 16 11 7 4 4 9 19 6 9

7 12 3 1 3 4 2 6 4 5

5 8 8 7 7 4 10 14 3 8

8 14 7 5 7 5 7 4 7 9

Stopping of fricatives and affricates

Gliding of liquids

Initial

Final

/l/

Total error /r/ Derhoticization Deaffrication patterns

10 16 8 8 9 10 7 12 9 9

14 16 10 8 9 7 10 16 10 9

1 3 2 1 1 1 1 5 2 1

2 4 2 1 1 2 1 7 1 2

7 5 2 1 5 4 6 6 1 6

3 5 2 1 2 2 2 0 2 1

11 13 9 9 10 11 9 13 8

Note. Initial = word-initial position; Final = word-final position; Total error patterns = total number of error patterns for which a test provided at least four opportunities; AAPS–4 = Arizona Articulation Proficiency Scale, Fourth Edition; BBTOP = Bankson-Bernthal Test of Phonology; CAAP–2 = Clinical Assessment of Articulation and Phonology, Second Edition; DEAP = Diagnostic Evaluation of Articulation and Phonology; HAAP–3 = Hodson Assessment of Phonological Patterns, Third Edition; KLPA–2 = Khan-Lewis Phonological Analysis, Second Edition; PSA = Phonological Screening Assessment; RPE = Rules Phonological Evaluation; SPAT–D II = Structured Photographic Articulation Test II featuring Dudsberry; Total tests = total number of tests that provided at least four opportunities for a specified error pattern.

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Table 3. Definitions of error patterns provided by the test manuals. Error pattern Final consonant deletion Deletion of word-final singleton consonant Deletion of word-final consonant cluster Deletion of final consonant in word-final cluster Postvocalic /l/ included Postvocalic /r/ included Weak syllable deletion Deletion of an unstressed, nonfinal syllable only Deletion of any unstressed syllable Deletion of any syllable (stressed, unstressed, initial, medial, final) Cluster reduction Tautosyllabic CC → C; CCC → CC or C Substitution of one or more consonants in a cluster by a different consonant Schwa inserted between two consonants Heterosyllabic CC → C; CCC → CC or C Deletion of a consonant cluster Prevocalic voicing Word-initial voiceless consonant replaced by a voiced consonant Word-initial consonant cluster replaced by a voiced consonant cluster Postvocalic devoicing Word-final voiced consonant replaced by a voiceless consonant Word-final consonant cluster replaced by a voiceless consonant cluster Velar fronting Velar replaced by an alveolar only Velar replaced by any “front” sound, usually an alveolar [ŋ] is replaced with [n] in –ing suffix Palatal fronting Palatal replaced by an alveolar only Palatal replaced by any “front” sound, usually an alveolar Palatal fronting assessed separately from velar fronting Stopping of fricatives and affricates Fricative or affricate replaced by a stop Fricative but not affricate replaced by a stop /h/ replaced by a stop Fricative (and affricate) replaced by /?/ Gliding of liquids Liquid replaced by a glide Stop, nasal, or liquid replaced by a glide Liquid or glide replaced by a glide Any consonant replaced by a glide Derhoticization Loss of /r/ coloring for full vowels only Loss of /r/ coloring for any vowel Deaffrication /t ʃ / replaced by [ ʃ ] Affricate replaced by a fricative at the same PoA Affricate replaced by a fricative at any PoA Affricate replaced by any continuant or stop

AAPS–4 BBTOP CAAP–2 DEAP HAAP–3 KLPA–2 PSA RPE SPAT–D II √ ✗ ✗ √ ✗

√ ✗ ✗ √ ✗

√ √ ✗ √* √*

√ √ ✗ √ ✗

√ NS NS ✗ ✗

√ √ ✗ √ ✗

√ NS NS √ ✗

√ NS NS ✗ ✗

√ NS √ √ √

✗ ✗ √

✗ ✗ √*

✗ ✗ √

✗ √* ✗

✗ ✗ √

✗ ✗ √

✗ √ ✗

Ø Ø Ø

✗ ✗ √

√ ✗

√ √

√ ✗

√ ✗

√ ✗

√ ✗

√ ✗

√ ✗

√ ✗

✗ ✗ √

✗ ✗ √

✗ ✗ ✗

✗ ✗ ✗

✗ √ ✗

√ ✗ ✗

✗ ✗ ✗

✗ ✗ ✗

✗ ✗ ✗

√

Ø

√

√

√

√

√

√

Ø

√

Ø

✗

√

NS

√

NS

✗

Ø

√

Ø

√

√

√

√

√

√

Ø

√

Ø

✗

√

NS

√

NS

✗

Ø

√ ✗ √

✗ √ ✗

✗ √ ✗

√ ✗ ✗

✗ √ ✗

✗ √* √

√ ✗ ✗

✗ √ ✗

√ ✗ √

√ ✗ ✗

Ø Ø ✗

✗ √ ✗

√ ✗ ✗

✗ √ ✗

✗ √ √

Ø Ø ✗

✗ √ ✗

√ ✗ ✗

√ ✗ ✗ NS

√ ✗ ✗ NS

√ ✗ ✗ NS

✗ ✗ ✗ ✗

✗ √ ✗ ✗

√ ✗ ✗ ✗

✗ √ ✗ NS

✗ √ ✗ NS

√ ✗ √ NS

✗ ✗ √ ✗

√ ✗ ✗ ✗

√ ✗ ✗ ✗

✗ √ ✗ ✗

✗ ✗ ✗ √

√ ✗ ✗ ✗

√ ✗ ✗ ✗

√ ✗ ✗ ✗

√ ✗ ✗ ✗

✗ √

✗ √

✗ √

✗ √

Ø Ø

✗ √

Ø Ø

Ø Ø

Ø Ø

✗ √ ✗ ✗

✗ ✗ √ ✗

✗ √ ✗ ✗

✗ ✗ √ ✗

✗ ✗ ✗ √

✗ ✗ √ ✗

Ø Ø Ø Ø

Ø Ø Ø Ø

Ø Ø Ø Ø

Note. Italics indicate the definition of the error pattern used in this review to calculate the number of opportunities; √ = this definition was provided in the test manual; ✗ = this definition was explicitly rejected by the test manual; NS = no information about this definition was specified in the test manual; Ø = this error pattern was not included in the test; * = discrepancy between test manual and response form but was scored according to details provided in the test manual; PoA = place of articulation.

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differently across tests. To allow comparison across tests, we proposed a set of core phonological error patterns. We justified our selection and definition of these error patterns by referring to phonological theory and empirical research. In redefining this core set of error patterns, we narrowed the definition of some types of errors, specifically syllable deletion and fronting. We also drew attention to the fact that the frequency with which some errors occur depends on the position of the target phoneme within the word. Thus, the error patterns of velar fronting, stopping, and cluster reduction all show positional asymmetries in their frequency of occurrence. In addition, we argued that it would be best to eliminate some of the errors that have traditionally been included in tests of phonological error patterns, such as the reduction of medial clusters and vocalization of /l/. Six of the nine tests we reviewed (CAAP–2, DEAP, HAAP–3, KLPA–2, RPE, SPAT–D II) recommend calculating percentage of occurrence for each of the error patterns listed on their response forms. The percentage of occurrence is used to identify those error patterns that are active in the phonological system of the child being tested, with the active error patterns serving as potential targets for intervention. For each of these six tests, the response form lists the total number of opportunities for each error pattern. This is useful, however, only if the number of opportunities provided on the response form represent realistic opportunities for the particular pattern to occur. For those tests where the clinician is required to examine every item for all possible phonological error patterns, the design of the response form makes it easy to underestimate the percentage of occurrence of a given error pattern. Phonological error patterns that involve a deleted consonant or syllable can cause scoring errors by removing the opportunity for another error pattern to surface. For example, opportunities for gliding are likely to be removed if cluster reduction or weak syllable deletion occurs in the same word. To adjust for this, the clinician must continually update the total number of opportunities on the response form, which is time-consuming and prone to error. An alternative to having the clinician update the total number of opportunities on the response form is to eliminate test items that are unlikely to elicit a given error pattern. In our review of these nine tests of phonological error patterns, we did not follow the scoring suggested in the test manuals. Instead, we counted as opportunities only those phonemes that provided a reliable opportunity for a given error pattern to surface. For this reason, we considered only phonemes that occurred as singletons (except for cluster reduction) and in stressed syllables (except for weak syllable deletion). Using only these stable phonetic contexts, we found that none of the tests met the criterion of providing at least four opportunities for all eleven error patterns. The error patterns that tended to be underrepresented across tests included weak syllable deletion, reduction of wordfinal clusters, fronting of velars in word-initial position, gliding of liquids, and deaffrication.

Clinical Implications Our findings have important clinical implications for the developers of tests of phonological error patterns because it is important that the percentage of occurrence of an error pattern can be calculated both accurately and efficiently by test users. To achieve this goal, test developers need to carefully consider which error patterns to include in their tests and provide justification for their choices. In many instances, the definitions of these error patterns need to be updated so that they are informed by the most recent research in phonological acquisition. Furthermore, test developers must include sufficient opportunities for each error pattern to be displayed in the speech of the child being tested. Although we suggested that test developers provide at least four opportunities for a given error pattern, setting a higher cutoff value would likely be more informative, especially for patterns that involve a large number of different consonants, such as stopping of fricatives and affricates. Given that some types of consonant clusters are acquired earlier than others (e.g., Kirk & Demuth, 2005), it would be clinically useful to include a wider range of cluster types in both word-initial and word-final positions than is currently represented in the tests we reviewed. In addition to expanding the number of opportunities for some error patterns, test developers should consider eliminating error patterns that are unlikely to be helpful in determining appropriate intervention targets. For example, the error pattern of deaffrication usually affects only a single phoneme (Smit, 1993a). Because of the limited distribution of this error, it might be best to evaluate the production accuracy of this phoneme in a test of articulation rather than in a test of phonological error patterns. Similarly, if the purpose of phonological intervention is to help children to approximate the phonological system of adults from the same social and regional background, then vocalization of /l/ should also be removed from tests of phonological error patterns in communities where /l/-vocalization is a commonly observed phenomenon. Future test developers should also consider including backing and medial glottal stop replacement as error patterns that contribute to the total error score. Although few tests list either backing or glottal stop replacement as an error pattern, these errors are reported to occur more frequently among children with a phonological disorder than among younger, typically developing children (Hodson & Paden, 1981). Because one of the stated purposes of tests of phonological error patterns is the diagnosis of a phonological disorder, the inclusion of these error patterns may help to more accurately identify children who would benefit from intervention. We hope that test developers will take these recommendations into consideration when developing new tests and when next updating current tests of phonological error patterns. The recommendations we have provided in this review also have important implications for clinicians. If a phonological approach to intervention is adopted, then it is


25

critical for the clinician implementing that intervention to have a thorough understanding of phonological error pattern analysis. Our discussion of phonological error patterns and how these patterns are sometimes misinterpreted will help clinicians to gain a deeper understanding of the various types of phonological errors. This deeper understanding has the potential to help clinicians select more effective intervention targets.

Study Limitations and Future Research In the interest of helping clinicians to accurately and efficiently score tests of phonological error patterns, we have recommended that phonetically simple words be used to assess phonological error patterns. However, this recommendation could be criticized on the grounds that it does not provide a complete picture of a child’s phonological system. Research shows that error patterns in the speech of older children are more likely to show up in words consisting of three or more syllables than in shorter words (e.g., James, 2001; James, van Doorn, & McLeod, 2008). Therefore, limiting the phonotactic shape of the test items included in these types of tests may fail to capture the subtleties of the speech of school-age children. When testing older children, the data collected from tests of error patterns will need to be supplemented with speech probes that contain longer words with more complex syllable structure and stress patterns. In this article, we have made a number of recommendations regarding the best way to evaluate a core set of phonological error patterns in the speech of young children. A logical extension of the current study would be to compare the results of the tests included in our review as scored in two different ways: (a) according to our recommendations and (b) according to the instructions provided in the individual test manuals. This would involve identifying a number of children who display a variety of phonological error patterns, testing each child on all nine of the tests included in our analysis, and then scoring the results according to both methods listed above. Such an undertaking is clearly beyond the scope of the current study. However, we will provide a few examples of how the two methods of scoring could result in different outcomes for children with specific error patterns. Some error patterns remove the opportunity for another error pattern to occur, which may have the effect of seriously underestimating whether an error pattern is active in a child’s speech. For a child who reduces word-initial consonant + liquid clusters (e.g., bread → [bɛd]) and deletes weak syllables (e.g., elephant → [ˈɛfənt]), the opportunity for gliding will be removed in a large number of words. For example, the response form for the DEAP lists 21 opportunities for gliding. However, only two opportunities occur in wordinitial singleton consonants, with the majority of opportunities occurring either in word-initial clusters (n = 10) or word medially (n = 9). If the DEAP is scored according to the recommendations in the test manual, for a child who consistently glides liquids but also reduces word-initial liquid clusters and deletes weak syllables, the percentage of

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occurrence for the error pattern of gliding will be 10%. This clearly underestimates the prevalence of gliding in this child’s speech, which if scored according to the criteria suggested in the current article would be 100%. Error patterns that are much more prevalent in wordinitial position than word-final position may also contribute to underestimating whether an error pattern is active in a child’s speech. For a child who fronts velars only in wordinitial position, the error pattern of velar fronting may go unrecognized. We illustrate this with a specific example from the KLPA–2 response form. This test lists 19 opportunities for velar fronting. Four of these opportunities occur in word-initial singleton consonants, while the remaining opportunities occur in word-initial clusters (n = 4), wordmedial position (n = 3), and word-final position (n = 8). If the KLPA–2 is scored according to the recommendations provided in the test manual, for a child who consistently fronts word-initial velars but never fronts velars in other word positions, the percentage of occurrence of velar fronting will be 21%, which is unlikely to be high enough to warrant selection of velar fronting as an intervention target. However, if scored according to the criteria suggested in the current article, it would quickly become apparent that velar fronting in word-initial position would likely be an appropriate target for this child. It should be noted that although we use the DEAP and the KLPA–2 to provide specific examples of some of the differences between our method of scoring and that provided in the test manuals, similar discrepancies can be found with the other tests. In addition to providing accurate measures of the phonological error patterns displayed in children’s speech, these tests must also be efficient to score. As mentioned earlier, the response forms for the tests included in this review are organized in one of two ways. Tests either group together all opportunities for a particular error pattern on the response form, or the clinician is expected to examine every item for all possible phonological error patterns. This second method of scoring would appear to be more timeconsuming than the first as well as more prone to scoring error. However, further research is needed to determine whether scoring tests using a checklist format really is more accurate and/or efficient. There are currently no empirical studies that investigate the number of opportunities required to provide a representative sample of the various error patterns displayed in a child’s speech. Although we recommended that a test should include at least four opportunities for each error pattern, we acknowledge that this cutoff is probably too low for errors that have the potential to affect a large number of consonants, such as cluster reduction and final consonant deletion. There is clearly a need for further investigation into the optimal number of test items required to accurately identify each of the various error patterns. One obvious concern is that the inclusion of more opportunities has the potential to increase the time required to administer a test. However, if test scoring can be streamlined, perhaps by using a checklist format as suggested above, then this would free up more time for eliciting test items.


A number of previous studies have investigated the frequency with which children typically demonstrate specific phonological error patterns at specific ages (e.g., Haelsig & Madison, 1986; Preisser et al., 1988; Roberts et al., 1990; Smit, 1993a). The focus of the majority of these studies has been the phonological development of children with typical speech and language development. Relatively little is known about how and when these error patterns resolve for children with a phonological disorder. Although it is generally assumed that the speech errors produced by children with phonological difficulties are similar to those of younger, typically developing children, there is evidence to suggest that this may not always be the case. For example, Hodson and Paden (1981) found differences between children with a speech sound disorder and younger children with typical development regarding the types and frequency of some phonological errors. In summary, there is an obvious need for additional research that compares how phonological error patterns resolve for children both with and without a phonological disorder. Longitudinal studies, in particular, would help to clarify how these error patterns resolve over time in a given child. To make interpretation of these studies meaningful, it will be essential to carefully and comprehensively define the phonological error patterns used to analyze the speech of the study participants. In previous studies, the error patterns are often not clearly defined because researchers assume that the definitions are standard, but as we have shown in this review, there is a decided lack of agreement on this matter.

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