phonologicalandlexicalcharacteristicsofsound ... 언어치료연구( 20 4 )제 권제호 the amount...

Phonological and Lexical Characteristics of Sound Productions by Typically Developing 87Children Versus Children with Phonological Delays

Abstract

Phonological and Lexical Characteristics of Sound

Productions by Typically Developing Children Versus

Children with Phonological Delays

Su Yeon Lee*(Department of Speech-Language-Hearing: Sciences &

Disorders, University of Kansas)

Holly L. Storkel**(Department of Speech-Language-Hearing: Sciences &

Disorders, University of Kansas)

This study explored the influences of phonological and lexical characteristics onproduction. Eighteen children were identified as either typically developing (TD) orphonologically delayed (PD). For each emerging target sound, segment average,word frequency, and neighborhood density were computed. The results showed thatthe TD group produced sounds more accurately in high phonotactic probability butrevealed no effect of phonotactic probability on production by the PD group.Turning to lexical properties, the results showed no effect of word frequency onproduction by the TD group but found that the PD group produced sounds moreaccurately in low frequency words. Lastly, both groups produced sounds moreaccurately in high density words, while the advantage was greater for TD children.These findings suggest that influences of phonological and lexical properties onproduction may vary across children.

Keywords : Sound production, phonotactic probability, frequency, neighborhood density,phonological delays

* 이수연 제 저자 교신저자 캔사스대학교 언어병리학과 박사과정( 1 , ) :([email protected])** 공동저자 캔사스대학교 언어병리학과 교수Holly L. Storkel( ) :

게재신청일 : 2011. 10. 28▶

수정제출일 : 2011. 12. 04▶

게재확정일 : 2011. 12. 23▶

86 언어치료연구 제 권 제 호( 20 4 )

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the amount of activation between representation of word forms and phonologicalsegments influence the speed and accuracy of producing words.An alternate account for the high density advantage is attributed to the more

phonologically detailed representations argued to be present in high densityneighborhoods. It has been suggested that neighborhood density may be associatedwith the level of detail in the lexical representation (Storkel & Gierut, 2002). Thehigher density words may have more segmentally detailed representations than thelower density words in order to prevent the occurrence of homonymy in thelanguage (Garlock, Walley, & Metsala, 2001). These segmentally detailedrepresentations may, in turn, facilitate the creation of an association between anexisting lexical representation and a new phonological representation (see alsoStorkel & Gierut, 2002). Thus, it can be predicted that the higher density wordsare more likely to be modified in children’s productions for both groups ofchildren.

4. Conclusion

The phonological and lexical characteristics of words appear to influence soundproduction and hold potential account for variation in phonological acquisition,particularly interword variability. This study revealed that interword variability inacquisition may be predictable by the phonological and lexical characteristic ofwords, proposing possible predications for accurate production of emerging sound inthe course of phonological acquisition. Particularly, it is predicted that highphonotactic probability and high neighborhood density may trigger early soundmodification in TD children’s production, with unclear frequency effect. On theother hand, low frequency and high neighborhood density may lead to accuratesound production for the PD group, with no clear effect of phonotactic probability.Conclusively, these findings from the present study suggest that phonological andlexical organization may influence the phonological development of both TD and PDgroups, yet with different patterns of effects across these two groups. Afollow-study with a larger number of participants is needed for generalization ofthe findings of the current study.


likely to show accurate production in less well practiced environments (i.e., lowfrequency environments) while TD children did not show the frequency effect. Itis possible that part of the delay for children with PD may be in their inability toattempt new sounds in a variety of phonological and lexical context.One possible account for low frequency effect may be related to the strength of

the underlying lexical representation (Storkel & Gierut, 2002). High frequencywords may have strict lexical representations associated with their existingphonological representations. In comparison, low frequency words may have flexiblerepresentations or may not have built strong associations between the lexicalrepresentations and the phonological representations. Therefore, low frequencywords may be easier for these children to modify their existing phonologicalrepresentations to newly acquired ones. This hypothesis is supported by data fromadult speech productions where infrequent words seem to be more likely to elicitspeech errors than frequent words, interpreted as temporary changes in soundproduction (Vitevitch, 1997).

3. Consistent Neighborhood Density Effects

Children in both groups produced target sounds accurately in words with highneighborhood density. This high density advantage observed in both groups isconsistent with findings of the previous works which suggest that phonologicallysimilar words facilitate lexical retrieval rather than compete among each otherduring speech production (Vitevitch, 1997, 2002, Vitevitch & Sommers, 2003;Gordon & Dell, 2001). The results from these study can be accounted for bycurrent models of speech production (e.g., Dell, 1986; Stemberger, 1985).Specifically, in Dell’s interactive model, words would activate phonologically similarwords (i.e., neighbors) through the shared phonological segments, and the amountof activation interacting between representations of word forms and phonologicalsegments would differ by the numbers of neighbor. Accordingly, high densitywords would receive greater amounts of activation from the larger number ofneighbors than words with sparse neighborhoods, resulting in high density wordsbeing produced more rapidly and accurately than low density words with sparseneighborhoods. Thus, in interactive models of speech production, the difference in


sound sequence disadvantage), incompatible to the overall effect pattern of thegroup. Four children showed the common sound sequence advantage as did TDchildren, which can also be accounted for by the interactive model of speechproduction. In comparison, five children demonstrated the common sound sequencedisadvantage, which may be attributable to the similarity of common soundsequences to many other know words. This presents an implication of theirdifficulty distinguishing common sound sequence words from other similar forms,which has been shown in their lexical acquisition (Storkel, 2004). For thesechildren with PD, words with rare sound sequences are similar to fewer knownwords, and thus are easier to be distinguished from each other. In this way, therare sound sequences appear to be more attractive to these children and facilitatecreation an association between lexical and phonological representations.Alternately, their inability to use common sound sequence advantage, which wouldprovide more frequent environments to practice, may be related to the casualmechanism for their phonological delays. However, from this finding of variableeffect within the PD group, the pattern of effects of the phonotactic probability isnot clear in any direction.

2. Variable Frequency Effects

The results of this study showed different patterns of frequency effects acrosstwo groups. No frequency effect was observed in the TD group while lowfrequency effect was evidenced in the PD group. The overall direction offrequency effect in the TD group was on high frequency. Yet, this is unclear sincethe SEM criterion was not met. In addition, this high frequency effect wasobserved in fewer TD children: four out of nine showed this pattern. Thus, thefindings indicates no frequency effect in TD children, which does not support thefindings of Leonard and Ritterman (1971) in which children were more likely toproduce the target sound in frequent words more accurately than they did ininfrequent words.In the PD group, the overall direction of frequency effect was on low frequency:

accurate productions of these children were on lower frequency words whilemeeting both criteria. This findings suggests that children with PD may be more


. DiscussionⅣ

The purpose of this study was to examine the phonological and lexicalcharacteristics of sound production by typically developing (TD) children andchildren with phonological delays (PD). In summation, results of this study showeddifferent patterns of the phonological and lexical characteristics on soundproduction across the TD and PD groups. The interpretation of the differentpatterns and possible theoretic accounts for the differences will be discussedfurther in subsequent paragraphs.

1. Variable Phonotactic Probability Effects

In the present study, the effects of phonotactic probability on sound productionvaried across groups. The TD group showed a common sound sequence advantagemeeting both pre-determined criteria (SEM and individual subject criteria). Thisfinding is consistent with the previous studies in speech production and lexicalacquisition (Edward, Beckman, & Munson, 2004; Munson, Edward, & Beckman,2005; Storkel, 2004), which can be accounted for by interactive models of speechproduction (e.g., Dell, 1986; Stemberger, 1985). In Dell’s model, the commonsounds or sound sequences that occur in many words receive additional inputs asinterwined activation between representation of word forms and phonologicalsegments. The greater amounts of activation that common sounds or soundsequences with high phonotactic probability receive enable them to be retrievedmore rapidly and accurately than do rare sounds or sound sequences. Thisadditional activation may facilitate the creation of phonological representations forthe newly acquired phonemes and the formation of new associations with lexicalrepresentations.On the other hand, the PD group showed variable probability effects on sound

production. The mean probability difference (0.0018) was bigger than the SEM(0.0014), meeting the SEM criterion, yet the subject criterion was not met; onlyfour out of nine subjects showed the same pattern of common sound sequenceadvantage. Although it seems a fairly equal number, more children (five out ofnine) produced target sounds accurately in words with low probability (common


accurate and inaccurate production. For both groups, high neighborhood densityeffect was observed. Figure III.3 shows the pattern of neighborhood density effectfor the TD and PD group.

1) Neighborhood Density in the TD Group

High density advantage in production accuracy was observed in the TD group.The mean neighborhood density for accurate productions (M = 7.006) was higherthan inaccurate productions (M = 5.402). The mean difference (M = 1.604) wasbigger than the SEM (0.667). This high density effect was observed in themajority of subjects (Seven out of nine).

*1.6037

*0.6842

0.0000

0.5000

1.0000

1.5000

2.0000

2.5000

Mean Density Difference

<Figure III.3> Mean density difference between accurate versus

inaccurate production

2) Neighborhood Density in the PD Group

As shown in TD group, high density advantage in production accuracy wasobserved in the PD group. The mean neighborhood density for accurate productions(M = 0.684) was bigger than the SEM (0.667). This high density effect wasobserved in five out of nine subjects.


accurate productions (M = 3.157) was higher than inaccurate productions (M =3.036) but the mean difference (M = 0.121) was smaller than the SEM (0.138).Four children produced the target sounds accurately in high frequency words, whilefive children produced the target sounds accurately in low frequency words. Thus,these findings indicate no frequency effect in the TD group.

0.1214

*-0.1740

-0.4000

-0.3000

-0.2000

-0.1000

0.0000

0.1000

0.2000

0.3000

1

Mean Frequency Difference

<Figure III.2> Mean frequency difference between accurate

versus inaccurate production

2) Frequency in the PD Group

Low frequency effect was observed in the PD group. The mean frequency foraccurate productions (M = 2.9) was lower than inaccurate productions (M =3.074) yielding the mean difference (M = 0.174) which was bigger than the SEM(0.138). This low frequency effect was observed in majority of subjects (six outof nine) whose production accuracy was higher in low frequency words.

3. Neighborhood Density

Neighborhood density was computed to examine the lexical characteristic of


Variable phonotactic probability effect was observed in the PD group. The meansegment average of accurate productions (M = 0.0456) was higher than that ofinaccurate productions (M = .0438) which yielded the mean difference (0.0018)bigger than the SME (0.0014). However, the more subjects (five out of nine)produced target sounds accurately in words with low probability while the rest(four out of nine) showed more accurate productions for words with highprobability.

* 0.0023

*0.0018

-0.0020

-0.0010

0.0000

0.0010

0.0020

0.0030

0.0040

0.0050

0.0060

Mean Phonotactic Proability Difference

<Figure III.1> Mean phonotactic probability difference between

accurate and inaccurate production

2. Word Frequency

The lexical property of word frequency was computed for accurate andinaccurate production using the on-line child corpus calculator (Storkel & Hoover,2010). Different patterns of frequency effect were observed between the twogroups. Figure III.2 shows the pattern of frequency effect for the TD and PDgroup.

1) Frequency in the TD Group

No frequency effect was obtained from the TD group. The mean frequency for


criterion which relates to five out of nine subjects in the group show the sametrend such as low or high advantage for accurate production. Such criteria werechosen instead of statistical significance in the consideration of an exploratoryphase of the present study. This would allow exploring any possible influences orunique patterns of these variables on sound production and then open up forpotential line of investigation that warrants further evaluation.

5. Reliability

Consonant-to-consonant transcription reliability was computed for the PKPprobe of each child and was 96% (SD = 2). Scoring reliability for productionaccuracy was 100% and three measurements were 95%, 98%, and 94%.

. ResultsⅢ

1. Phonotactic Probability

Positional segment averages for accurate and inaccurate production werecomputed to measure the phonological property of phonotactic probability andrevealed different patterns for typically developing (TD) children and children withphonological delays (PD). Figure III.1 displays the pattern of phonotacticprobability for the TD and PD group.

1) Phonotactic Probability in the TD Group

High phonotactic probability effect was observed in the TD group. The meansegment average for accurate productions (M = 0.0448) was higher thaninaccurate productions (M = 0.0425). The mean difference (M = 0.0023) wasbigger than the SEM (0.0014). In addition, the majority of children (eight out ofnine) showed the high phonotactic probability effect: they produced the targetsounds accurately in words with high phonotactic probability.

2) Phonotactic Probability in the PD Group


For accurate and inaccurate production of each emerging sounds, phonotacticprobability, word frequency, and neighborhood density were computed using anon-line database called the Child Corpus Calculator (Storkel & Hoover, 2010).This database contains 4,834 of child corpus and calculates phonotactic probability,word frequency, word length, and neighborhood density.

1) Phonotactic Probability

Positional segment average was computed to measure phonotactic probability.Positional segment average refers to the mean likelihood that each sound occurs ina given word position (Storkel, 2008). The calculation methods using an on-linechild calculator (Storkel & Hoover, 2010) followed the procedures described inStorkel (2004). The positional segment averages for each word with accurateproduction were averaged separately from those with inaccurate production foreach group.

2) Word Frequency

Word frequency was determined from word counts using the on-line childcorpus calculator (Storkel & Hoover, 2010). Children-based frequency counts ofeach word were summed and averaged for accurate and inaccurate production.

3) Neighborhood Density

Using the Child Corpus Calculator, neighborhood density was computed for eachword by counting the number of words in the dictionary that differed from a targetword by a one sound substitution, addition or deletion in any word position.Density for each word was then averaged for each production type (accurate vs.inaccurate).

4. Criteria for significance

Two criteria had been established in order to validate interpretation ofsignificance of effects and make interpretation stronger. One was a SEM criterionwhich was related to mean difference between accurate and inaccurate productiongreater than SEM (standard error of measurement). The other was a subject


Dunn & Dunn, 1997) and Expressive Vocabulary Test (EVT; Williams, 1997), (3)no history of cognitive, social, motor, visual, or major medical disorder reported byparent, and (4) residence in monolingual English-speaking homes. Table .1Ⅱdisplays descriptive information.

<Table II.1> Demographic data for TD and PD children

TD PD

M SD M SD

Age 44 5.2 58 8.5

GFTA-21percentile 39 10.2 9.7 3.7

PPVT-III2percentile 60 14 62 21

EVT3percentile 44 22 62 27

Note. TD = Children with typically development; PD = Children with phonological delays.1Goldman-Fristoe Test of Articulation-2 (GFTA-2, Goldman & Firstoe, 2000)2PeabodyPictureVocabularyTest-III PPVT-III;Dunn&Dunn,1997)3ExpressiveVocabularyTest EVT;Williams,1997).

2. Procedures

Independent phonological analyses on a child’s spontaneous word productionsusing the Phonological Knowledge Protocol (PKP; Gierut, Elbert, & Dinnsen, 1987)were examined to identify emerging sounds that were produced with someaccuracy but less than 50% accuracy. The PKP is a picture-naming task to elicitsingle-word productions of all target consonants of English in at least fivedifferent words in each relevant sound position (Gierut, Elbert, & Dinnsen, 1987).Each production of a target sound was scored as accurate or inaccurate andcomputed for accuracy for each sound. Accessing the accuracy of each soundidentified six emerging sounds (f, ð, , ʃ, ʤ, l) which were produced within rangeθ

of 17 to 45% accuracy from nine children with PD. Then, the child in the PDgroup was matched on accuracy of that sound to a TD child. For those emergingsounds, phonological and lexical characteristics of accurate and inaccurateproduction were examined.

3. Measurements


probability, frequency and neighborhood density on accurate production of emergingsounds in real words by the two groups. This study was to examine thephonological and lexical characteristics of accurately produced words; conversely,interword variability can be predicable by the phonological and lexicalcharacteristics of words. Several predications emerge from different types ofavailable date.More specifically, within the interactive models, accurate production resided in

words with common sound sequences, high frequency, and high neighborhooddensity across two groups. An alternate predication emerges from the findings ofsound change; that is, accurate production resided in words with high frequencyand low neighborhood density, with the effects of phonotactic probability as yetundetermined. A third possible prediction derives from the lexical acquisition data;that is, the effects of phonotactic probability on sound production vary acrossgroups, with each group showing a different pattern of the effects.

. MethodsⅡ

1. Participants

Eighteen participants were drawn from a large study on word learning researchat the University of Kansas. Nine (5 boys, 4 girls) of them were from the groupof children with phonological delays (PD), aged 3;9 (years; months) to 5;8 (M =4;8). The rest were from the group of typically developing (TD) children betweenthe ages of 3;2 and 4;4 (M = 3;7). Groups were defined based on performance onthe Goldman-Fristoe Test of Articulation-2 (GFTA-2, Goldman & Fristoe, 2000).Children with PD scored at or below the 10th percentile on the GFTA-2 whilechildren with TD scored above the 10th percentile.All participants met the following inclusion criteria: (1) normal hearing as

determined by passing a hearing screening at 20 dB at 1000, 2000, and 4000 Hz(American Speech-Language Hearing Association [ASHA], 1997), (2)age-appropriate vocabulary, expressive and receptive language abilities asevidenced by performance on Peabody Picture Vocabulary Test-III (PPVT-III;


shown that these children exhibit different patterns to phonological lexical variablesof language, which may reflect a causal mechanism in their phonological delays.Munson, Edward, and Beckman (2005) suggest that the difficulty seen in childrenwith PD on nonword repetition tasks is different from the types of difficulty thatare encountered by TD children, although the common sound sequence advantageswere observed in both groups. It was proposed that production difficulty associatedwith rare sound sequence in TD children was related to their difficulty buildingcategorical phonemic representations that link among acoustic, perceptual, andlexical representations to each other. As children’s vocabularies expand, childrenare thought to develop robust phonemic representations. Nevertheless, theproduction difficulty associated with children with PD was presumably more relatedto difficulties developing strong representations of the acoustic-auditory andarticulatory characteristics of speech. This assumption was based on their loweraccuracy with no greater effect of phonotactic probability in children with PD.In the line of lexical acquisition research, the direction of the effect of

phonotactic probability has shown to vary across groups (Storkel, 2004). Resultsfrom Storkel’s study (2004) showed that children with PD learned nonwordscomposed of rare sound sequences more rapidly than common sound sequences,whereas TD children showed the opposite pattern. It was hypothesized that thedifferent effects of phonotactic probability across groups was attributable to theeffect of phonological similarity. In the hypothesis, the children with PD may havedifficulty forming lexical representations and associates between lexical andsemantic representations for common sound sequences due to similarity to manyother known words. Conversely, novel rare sound sequences seem to facilitatecreation of a unique lexical representation in children with PD in that these raresound sequences are similar to few other know words. By contrast, novel commonsound sequences, which are similar to many other known words, seem to facilitatephonological processing and thus establishing associations with many other knowwords for TD children.This opposite direction of the phonotactic probability effect on lexical acquisition

across TD and PD groups implies a potentially different pattern of the effects ofphonological and lexical variables on other realms of language and phonologicaldevelopment. Of particular interest in this study was the effect of phonotactic


the differential generalization in children’s sound system proposed by Morrisetteand Gierut (2001). They found that high frequency as input in treatment resultedin the greatest sound changes across the children’s sound system, whereas highneighborhood density did not generally or consistently induced sound change. Takentogether, it was suggested that high frequency words and low density words asinput in treatment promote sound change. Conversely, it is possible that the lexicalcharacteristics of frequency and sparse neighborhoods facilitate the formation ofassociation between phonological representation and lexical representation, therebyleading to sound change.Alternately, another line of research has examined the influence of the lexical

properties on the accuracy of children’s output (Gierut & Storkel, 2002;Morrisette, 1999; Storkel & Gierut, 2002). These studies compared the frequencyand density of the words that change from incorrect to correct to those otherwords that do not undergo sound change. Storkel and Gierut (2002) found thatinfrequency words were more likely to undergo sound change than frequent words.In terms of neighborhood density, sound changes occurred more often on wordsfrom dense neighborhoods than words from sparse neighborhoods (see also Gierut& Storkel, 2002; Morrisette, 1999). From the observed results, it was predictedthat low frequency and high density words are more likely to undergo soundchange as a result of treatment. However, it has not reported whether children’sinitial productions are more or less accurate on low or high frequency words.Thus far, two separate lines of investigation have shown which words trigger

change in treatment and which words actually undergo change as a result of thattreatment. Nevertheless, it is unclear that the same pattern would occur in thenatural course of lexical diffusion (i.e., sound change) since the results weredrawn from children with phonological delays after phonological treatment. In fact,recent research has shown differential effects of phonological and lexical variableswith typically developing children (TD) and children with phonological delays (PD),which may hold potential insight for the differential effects of these variables onsound production.Children with PD may demonstrate a variety of speech-production errors

experiencing delays in the phonology acquisition without any obvious medical,social, cognitive, sensory, or motor deficits (Storkel, 2004). Current research has


lexical organization of the words and phonological structure in the course of soundlearning (see Geirut & Morrisette, 1998; Gierut, Morrisette, & Champion, 1999;Gierut & Storkel, 2002; Morrisette & Gierut, 2001).To date, the phonological characteristics of phonotactic probability have not yet

been attested for its potential effects directly on sound production in real words.However, with regard to developing systems, there is one relevant study examiningthe effects of phonotactic probability on children’s production of coda consonants(Zamuner, Gerken, & Hammond, 2004). In Zamuner et al.’s study, children weremore likely to produce the same coda in nonwords composed of common soundsequences than rare sound sequences, supporting phonotactic probability as apredictor of coda production. The common sound sequence advantage wasaccounted for by the similarity of nonwords to acquired production templates. Thatis, nonwords composed of common sound sequences are more similar to children’sacquired production templates and have more detailed representations so that theycan be accessed faster and more accurately than other non-words that might nothave as detailed representations.In terms of lexical variables, high frequency words have long been thought to

associate with productive sound change due to the importance of distinctness incommunication (Gierut, Morrisette, & Champion, 1999). Children may attend tohigh frequency words to understand other’s message and may articulate highfrequency words most accurately to deliver their message to others. An earlywork by Leonard and Ritterman (1971) examined the frequency effects on soundproduction by 7-year-old children and revealed that children had better productionaccuracy of target sounds in high frequency words than low frequency words (butsee Moore, Burke, & Adams, 1976). It appears that frequent words are morelikely to establish association with the target sound first, supporting that thelexical variable of frequency may facilitate the formation of new associationsbetween lexical representations and phonological representations.More recent studies have examined the role of lexical variables in longitudinal

sound change by children with functional phonological delays. Gierut, Morristte, andChampion (1999) reveled that treatment using high frequency words as inputinduced the greatest change in production accuracy of sounds while treatment usinghigh density words resulted in the least change. These results were comparable to


These effects of phonological and lexical variables on speech production havebeen accounted for by interactive models of speech production (e.g., Dell, 1986;Stemberger, 1985; MacKay, 1987; Rapp & Goldrick, 2000). In the process ofspoken language within interactive models, semantic representation activates allrelated lexical representations (E.g., ‘cat’ ‘dog,’ ‘meow’ etc. in the course ofnaming a ‘cat’). Once the lexical representation ‘cat’ is activated, the word formactivates its corresponding phonological representations that constitute the wordform (e.g., /k/, / /, /t/). The activated phonological representations in turn feedӕback activation to all lexical representations (referred to the neighbors) thatcontain those phonemes similar to the target word (e.g., ‘cat,’ ‘cap,’ ‘pat,’ etc).These activated neighbors, then, send activation back to the phonological nodes,which increase the amount of activation of the shared phonological nodes. Thus, itis assumed that words with dense neighborhoods would receive greater amount ofactivation from the shared phonological nodes than words with sparseneighborhoods, hence leading to faster access to dense neighborhoods (Vitevitch,2002). Moreover, the influence of phonotactic probability can be accounted for bya specific interactive model of Dell who described, “the model produces this effectbecause phonemes that are present in many words, particularly in common words,receive additional input as activation reverberates between words and phonemes”(Dell, 1988, pp. 34). It appears that the additional input or amounts of activationthat common sounds receive facilitate the access and retrieval of them morerapidly and accurately. Thus, the amount of activation between lexical andphonological representations is assumed to affect the retrieval process duringspeech production. In terms of frequency effect, high frequency words have higheractivation levels and spread more activation to their corresponding phonemes thanlower frequency words, which may facilitate retrieval process of speech production.

2. Evidence from Sound Change

The effects of phonological and lexical variables on speech production describedabove have been examined with adults and children with fully-developed orage-appropriate phonological development. Relatively fewer studies have examinedthese effects on phonological acquisition, suggesting the interaction between the


2002). Findings from children studies parallel this contradictory pattern of adults.Children recognize and repeat high-density words more slowly and less accuratelythan low density words (e.g., Garlock, Walley, & Metsala, 2001; Munson,Swenson, & Manthei, 2005), yet name high density words more accurately thanlow density words (German & Newman, 2004; but see Newman & German, 2002,2005). Despite the debate regarding the influence of neighborhood density, itseems that more research supports the perspective that high neighborhood densityfacilitates the process of spoken language.

2) Nonword repetition tasks

Studies of nonword repetition tasks have revealed that adults repeated nonwordscomposed of common sound sequences more rapidly and more accurately than raresound sequences (e.g., Vitevitch, 2003; Vitevitch & Luce, 1998 1999) and recallnonwords with common sound sequences more accurately than nonwords with raresound sequences (Thorn & Frankis, 2005).The common sound sequences advantages on speech production have been also

evidenced in children’s performance. Similar to adults, children repeated nonwordscomposed of common sound sequences more accurately and more rapidly than onescomposed of rare sound sequences (e.g., Beckman & Edwards, 2000; Edwards,Beckman, & Munson, 2004; Munson, 2001; Munson, Edward, & Beckman, 2005;Munson, Kurtz, & Windsor, 2005; Munson, Swenson, & Manthei, 2005). Moreover,Zamuner (2004) found that children were more likely to produce the codaconsonants of nonwords in common sound sequences than in rare sound sequences.In a serial recall task, Gathercole, Frankis, Pickering, and Peaker (1999) foundthat children recall more nonwords from a list which contains common soundsequences than ones from a list containing rare sound sequences.Turning to another lexical variable of neighborhood density, facilitative effects of

high neighborhood density have been evidenced in both adults’ and children’sproduction. For example, adults recall high density nonwords more accurately thanlow density nonwords (Roodenrys & Hinton, 2002). Children are also more likelyto produce and remember high density nonwords in repetition tasks (Gathercole,Willis, Emslie, & Baddeley, 1991) and immediate serial recall tasks (Gathercole,Frnakis, Pickering, & Peaker, 1999).


neighborhood of such words like sit which has many neighbors is considered densewhereas the neighborhood of the words with fewer neighbors is considered sparse.Thus, words with dense neighborhoods are said to be high density words whilewords with sparse neighborhoods are said to be low density words. Thecharacteristics of these phonological and lexical variables have been shown toinfluence the spoken language process across a variety of experimentalmethodologies.

1. Evidence from Speech Production

1) Real word naming tasks

Empirical studies have shown the positive effects of high phonotactic probabilitysound sequences on speech production. For example, adults name pictures of wordswith high-probability (common) sound sequences more rapidly thanlow-probability (rare) sound sequences (Vitevitch, Armbruster, & Chu, 2004).Moreover, adults are more likely to name words with common sound sequencesthan words with rare sound sequences (Levelt & Wheeldon, 1994). In children,however, no studies have examined the effects of phonotactic probability on realword production, which has motivated the current study.Turning to the lexical variables, experimental evidence has shown the positive

effects of high frequency on speech production by both adults and children.Specifically, in adults, high frequency words are produced more rapidly (Jescheniak& Level, 1994), and are less likely to be produced in error (Dell, 1988, Vitevitch,1997, 2002). Both children with typically developing phonology and children withword-finding difficulties have been shown to be more successful naming frequentwords than infrequent words (German, 1984; Newman & German, 2002).In terms of neighborhood density, there has been a contradictory pattern of

effects on speech production. For example, Vitevitch and Luce (1998, 1999) foundthat real words with high neighborhood density were repeated more slowly thanwords with low neighborhood density. In contrast, adults produce high densitywords more rapidly and accurately than low density words in naturally occurringmalapropisms (Vitevitch, 1997), elicited speech errors and picture naming(Vitevitch, 2002; Vitevitch & Sommers, 2003), and cases of aphasia (Gordon,


produced correctly first while others are still incorrectly produced. This impliesthat certain lexical representations will establish associations with the newphonological representation before others do. Thus, the purpose of the presentstudy was to explore the characteristics of accurately produced words whichpresumably appear to establish associations with the newly acquired sound.Recent literature suggests that the phonological lexical properties of a language

influence the process of spoken language. Particular interest has focused on aphonological variable of phonotactic probability and two lexical variables of wordfrequency and neighborhood density. Phonotactic probability refers to the likelihoodof sound occurrence in the language (Jusczyk, Luce, & Charles-Luce, 1994). Ithas been observed that certain sounds or sound sequences occur more frequentlythan others in the lexicon of a given language, and the frequency of soundoccurrence influences speech production (Storkel & Morrisette, 2002). Anindividual sound or sound sequences that occur in many words of the ambientlanguage in the same word position is considered to ha e high phonotacticprobability and, thus, refers to a common sound sequence. For example, the soundpattern of sit is a common sound sequence in English in that the individual sounds/s/, /ɪ/, /t/ in their given word positions and sound combinations (/sɪ/, /ɪt/)frequently occur in many other words of the language. By contrast, the soundpattern of these is a rare sound sequence, having low phonotactic probability forindividual sounds (/ð/, /ɪ/, /z/) and sound sequences (/ðɪ/, /ɪz/) that occur lesscommonly in English.Turning to the lexical variables, word frequency is the number of occurrences of

a word in the language (Kucera & Francis 1967). Certain words occur more oftenthan others. For example, the word these occurs much more frequently than theword sit: these occurs 1,573 while sit occurs only 67 times in an adult’s writtensample of 1 million words (Kucera & Francis, 1967). Neighborhood density isdefined as the number of words in a language that differ from a given word by aone phoneme substitution, deletion or addition (Luce & Pisoni, 1998). Thesephonologically similar words are referred to as neighbors. For example neighborsof the word sit include sip, sat, hit, it, and spit, among others. The word sit has alarge number of neighbors, in total of 36 in English, while the word these hasrelatively fewer neighbors of only nine such as those, tease, and ease. The


different rates and in different orders. For a newly acquired sound, a given childmay start using it correctly in certain words or in certain positions, but not in allwords. This type of variation refers to interword variability since a child producesa target sound in different ways across words and context (Gierut, Morrisett, &Champion, 1999). Gradually, the child generalizes the newly acquired sound to avariety of phonological and lexical contexts. This implementation process of soundchange on a word-by-word refers to lexical diffusion (Gierut & Storkel, 2002).The questions, then, arise which words trigger accurate production in the firstplace? Or what are the characteristics of the words that are produced correctly?Past research has attended to the functional attributes of a child as contributing

to the variation in phonological acquisition such as child’s unique learningstrategies, preferences for or avoidances of certain sounds, word shapes, orarticulatory routines (Macken & Ferguson, 1983). Recently, attention has shiftedto the words themselves as the factors that may influence acquisition process (i.e.,lexical diffusion). This line of study has focused on examining the properties oflexical structure and the interface between the phonology and lexicon inacquisition.Recent models of spoken language processing posit that three types of

information are represented and entailed in the processing of spoken language:phonological segments, whole words, and semantic information (Vitevitch,Armbruster, & Chu, 2004). Knowledge of phonological segments (i.e., individualsounds) forms phonological representations, whereas knowledge of whole wordsforms lexical representations in mental lexicon. Semantic information, that is themeaning or referent of a word, corresponds to semantic representations. In orderto produce a word, all of these representations are activated and thus there is aninteraction among these representations influencing each other as suggested byinteractive models of speech production (e.g., Dell, 1986; Stemberger, 1985; Rapp& Goldrick, 2000).Applying to sound change, when a child learns a new sound, he or she may not

yet have ambient, or adult-like, phonological representation for the target soundbut eventually they will acquire an adult-like phonological representation. The newphonological representation then must form associations with lexicalrepresentations. In the process of phonology acquisition, certain words are

언어치료연구 , 제 권 제 호20 4━━━━━━━━━━━━━━━━━━━Journal of Speech-Language & Hearing Disorders2011, Vol.20, No.4, 63 87～

Phonological and Lexical Characteristicsof Sound Productions by TypicallyDeveloping Children Versus Children

with Phonological Delays

이 수 연 캔사스대학교 언어병리학과( )

Holly L. Storkel 캔사스대학교 언어병리학과( )

요 약< >아동이 특정 언어의 말소리를 습득하는 과정을 살펴보면 아동은 일부 단어에서 새로 습,득하기 시작한 말소리를 정확히 산출하고 그 밖의 단어들에서는 오류를 보인다 그 후.점차적으로 음소를 정확히 산출하는 단어들이 늘어나고 비로서 완전한 말소리를 습득하,게 된다 이러한 과정에서 아동이 우선적으로 음소를 정확히 산출하는 단어들의 특성을. ,살펴보고자 한다 일반아동 명과 조음음운장애 아동 명을 대상으로 영어의 모든 말소. 9 9 ,리 중 의 정확성을 보이는 말소리를 조사한 후 그 말소리들을 정확히 산출한 단17 45% ,–

어들과 오류를 보인 단어들의 음운적 특성과 어휘적 특성을 살펴보았다 음운적 특성으.로 음소배열확률을 비교 분석하였고 어휘적 특성으로 어휘빈도와 근접어휘밀도를 비교,분석하였다 일반아동이 정확히 산출한 단어들의 음소배열확률은 오류를 보인 단어들의.음소배열확률 보다 높은 것으로 나타났다 고빈도 음소배열확률 효과 조음음운장애 아( ).동의 경우 뚜렷한 음소배열확률 효과가 나타나지 않았다 어휘빈도의 효과를 살펴보면, . ,일반아동은 어휘빈도 효과를 보이지 않았고 조음음운장애 아동집단은 빈도가 낮은 단어,들을 빈도가 높은 단어들 보다 정확히 산출하였다 저빈도 효과 근접어휘밀도의 효과( ).는 두 집단 모두 근접어휘밀도가 높은 단어들을 더 정확히 산출하였다 본 연구 결과는. ,단어의 음운적 특성과 어휘적 특성이 말소리 산출에 영향을 미칠 수 있다는 것을 시사하

며 아동의 조음발달 상태에 따라 다르게 나타날 수 있다는 것을 밝히고 있다, .

검색어 말소리 산출 음소배열확률 어휘빈도 근접어휘밀도 조음장애아동< > , , , ,

. IntroductionⅠ

In phonological acquisition, there is phonological variability within and acrosschildren. When a child learns sounds of a language, he or she acquires sounds at

phonologicalandlexicalcharacteristicsofsound ... 언어치료연구( 20 4 )제 권제호 the amount...

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