Parental Reports of SpokenLanguage Skills in ChildrenWith Down Syndrome

Eva BerglundDepartment of Psychology

Stockholm UniversityStockholm, Sweden

andCollege of Health and

Caring SciencesFalun, Sweden

andUppsala University Hospital

Uppsala, Sweden

M6rten ErikssonUniversity of Gavle

Gavle, Sweden

Ir6ne JohanssonUniversity of Karlstad

Karlstad, Sweden

- m. m = w m

Spoken language in children with Down syndrome and in children in a normativegroup was compared. Growth trends, individual variation, sex differences, andperformance on vocabulary, pragmatic, and grammar scales as well as MaxLU(maximum length of utterance) were explored. Subjects were 330 children withDown syndrome (age range: 1-5 years) and 336 children in a normative group(1;4-2;4 years;months). The Swedish Early Communicative DevelopmentInventory-words and sentences (SECDI-w&s) was employed. Performance ofchildren with Down syndrome at ages 3;0 and 4;0 was comparable with that ofchildren in the normative group at ages 1;4 and 1;8 respectively. In comparisonwith children in the normative group of similar vocabulary size, children withDown syndrome lagged slightly on pragmatic and grammar scales. The earlydevelopment proceeded in most cases with exponential or logistic growth. Thisstresses the great potential of early intervention.

KEY WORDS: Down syndrome, language, parental reports, normative group,SECDI

The aim of the present study was to examine growth trends andindividual variation in spoken-language development in a repre-sentative sample of Swedish children with Down syndrome.

Pueschel and Hopmann (1993) have commented on the great need toacquire "good normative studies of the communication and languageskills associated with Down syndrome, as helpful guidelines for bothparents and professionals" (p. 354). The current study is the first large-scale study of a national sample of children with Down syndrome inwhich normative data are provided. We also studied sex-related differ-ences in language among children with Down syndrome and children inthe normative group. The data included vocabulary size, pragmatic skills,grammar skills, and maximum length of utterance (MaxLU) from theSwedish Early Communicative Development Inventory-words and sen-tences (SECDI-w&s; see Berglund & Eriksson, 2000).

Only a few studies have produced general results regarding the com-municative development of children with Down syndrome. General find-ings concern the developmental timetable and the existence of consider-able variability across children. Some previous studies involved only afew subjects and can thus be regarded as case studies in the sense thatthey offer examples but present no normative data (e.g., Gillham, 1990).Although a number of the studies encompass groups of children observedat specific ages (e.g., Stroeminger, Winkler, & Cohen, 1984), most includeno information as to whether the children investigated were enrolled in

Journal of Speech, Language, and Hearing Research Vol. 44 * 179-191 * February 2001 * ©American Speech-Language-Hearing Association 1791092-4388/01/4401-0179

I

specific language-stimulation programs or if they hadadditional deficiencies. Children with Down syndromeoften suffer from eye disorders; cardiac disorders; asth-ma; allergies or immunologic diseases; impairment ofhearing; and various gastroenterological, neurological,orthopaedic, and endocrinological complaints.

Because there are very few studies describing com-municative development in children with Down syn-drome in terms of either general trends or variabilityacross children, our primary aim was to provide infor-mation relevant to researchers and clinicians in thisarea. The age at which children with Down syndromestart to talk and, in particular, when their first wordsare uttered was one focus of the study. Several studieshave shown that some children with Down syndromeutter their first words when they are 12 to 24 monthsold, though substantial individual variation exists. Otherstudies have noted, however, that it is not until age 3;9that some children with Down syndrome uttered theirfirst words (Gillham, 1990; Stroeminger. et al., 1984). Ingeneral, the development of a first vocabulary is ex-tremely slow in children with Down syndrome (Gillham,1990).

We also wished to describe individual variation inspoken-language development. Inasmuch as there isextensive variation in the age at which first spokenwords appear, there is also considerable variability inlater communicative development. Gillhaii's (1990) sub-jects reached the 50-word level between the ages of 3;6and 6;0. In their age 3;0 subjects, Stroeminger et al.(1984) found that vocabulary size ranged from 0 to 85words. There is also sizeable variation in the develop-ment of mean length of utterance (MLU; Brown, 1973).Caselli et al. (1998) found that children with Down syn-drome were severely delayed in reaching developmen-tal stages and that the children exhibited individualdifferences. Caselli et al. also found that children withDown syndrome were more advanced in lexical compre-hension and' gestures than in lexical production. AlsoChapman, Seung, Schwartz, and Kay-Raining Bird(1998) found a specific expressive language impairmentin their subjects. However, they found no evidence of acritical period for language development nor of a "syn-tactic ceiling" of MLU. In a longitudinal study, Fowler(1988) found that at age 4:0, the highest MLU scoresobtained by three children were 1.5, 2.2, 'and 2.2 (pp.236-238); at age 5;0 the highest.scores of five childrenwere 1.9, 2.2, 2.3, 3.7, and 3.8. One criterion for inclu-sion in Fowler's sample was that the child should pro-duce two-word utterances. Accordingly, performance inthe Fowler study is expected to be higher than the aver-age performance of children with Down syndrome. ,

In summary, the studies reviewed here indicate-thatthere is extensive individual variation in children with

Down syndrome, both in terms of age at onset of spokenlanguage and in later performance. To our knowledge,however, the magnitude of variation in relation to agehas never been the primary focus of previous studies.

Children with Down syndrome have often beenmatched with unaffected children in terms of nonverbalmental age (see Chapman, 1995). When such matchinghas been used, the large variability in the groups of chil-dren with Down syndrome has proven to be similar toor greater than the variability among unaffected chil-dren. Yet, there is also considerable variation in the per-formance of unaffected children (Bates, Dale, & Thal,1995; Berglund & Eriksson, 2000; Eriksson & Berglund,1999; Fenson et al., 1994). Miller, Sedley, Miolo, Rosin,and Murray-Branch (1991, cited in Chapman, 1995)found that when spoken and signed words were addedchildren with Down syndrome who used manual signsobtained vocabulary scores similar to those of their un-affected peers matched on mental age. When vocabu-laries increased in miagnitude, the child mostly addedspoken words.

To identify the ages at which the performance ofchildren with Down syndrome parallels the performanceof unaffected children was a further aim of this study.Mervis (1990), for example, compared the performanceof children with Down syndrome at age 3;0 to that ofunaffected children at age 1;6, suggesting similar quali-tative aspects of conceptual development but slowervocabulary development in children with Down syn-drome. In a study by Mundy, Sigman, Kasari, andYirmiya (1988) children with Down syndrome with amean age of 3;8 obtained expressive language scorescomparable to those of unaffected children at age 1;6.Bates et al. (1995) found that infants with Down syn-drome lagged several months or years behind unaffectedinfants in communicative abilities, measured by theAmerican Communicative Development Inventories:Infant version (CDI: Infants; see Fenson et al., 1993).In the period covered by CDI: Toddlers (Fenson et al.,1993), the delay was found to be approximately 2 years(Bates et al., 1995). Smith, von Tetzchner, and Michalsen(1988) found that about half of their subjects with Downsyndrome at age 5;0 had scores comparable to those ofunaffected children at age 2;6 on the McCarthy scalesof children's abilities, whereas the remaining childrenwith Down syndrome had lower scores. Delay was morepronounced with regard to language skills as opposedto their general cognitive functioning among childrenwith Down syndrome. Interestingly, the delay waspresent in nonverbal communication as well as in speech,suggesting that the language problems among childrenwith Down syndrome are not merely articulatory innature. Miller (1995) found a language-specific delay ina comparison of children with Down syndrome and un-affected children matched on mental age. He reported

180 Journal of Speech, Language, and Hearing Research * Vol.44 * 179-191 * February 2001

that 65% of children with Down syndrome performed atvocabulary levels below the 1 0i percentile of unaffectedchildren (i.e., the performance of the lowest scoring 10%of the unaffected children); the rate of vocabulary learn-ing was slower than general cognitive developmentamong children with Down syndrome. Harris (1983)found that children with Down syndrome between theages of 2;6 and 6;9 performed comparably to unaffectedchildren between the ages of 1;5 and 2;5 on MLU. Fi-nally, Fowler's (1988) subject, Rebecca, reached the age2;4 MLU level of Brown's (1973) subjects (Adam andSarah) at about age 5;0.

The evidence strongly suggests developmental de-lay among children with Down syndrome. Whereas thefirst spoken words may appear at the expected time,spoken language development proceeds.at a slower pace.The age 1;6 level is reached at about ages 3;0 to 3;8 bychildren with Down syndrome. Further, there is largeindividual variation with respect to onset of languageand later performance.

In the studies thus far reviewed a variety of lan-guage measures, such as size of vocabulary, MLU, theMcCarthy Scale, and expressive language scores, wereemployed. Some findings suggest that there are irregu-larities in the development of language skills. From sev-eral studies, there are reports of specific limitations inthe development of syntax (both production and com-prehension) but no such deficiencies in vocabulary(Beeghly, Weiss-Perry, & Chapman, 1995; Chapman,Schwartz, & Kay-Raining Bird, 1991; Cicchetti, 1990;Miller, 1995). Bates et al. (1995), for instance, reporteddissociation between grammar scores and vocabularyin children with Down syndrome (i.e., children withDown syndrome had lower grammar scores than theirunaffected peers despite matching vocabulary). However,it was not clear whether the difference in rate of devel-opment between vocabulary and syntax (grammar) wasalready present at the first stages of development. Inour study, therefore, we regarded it as crucial to exam-ine differences between children with Down syndromeand unaffected children on pragmatic skills, grammarskills, andmaximum length of utterance (MaxLU) whenvocabulary was treated as a covariate.

Few studies have documented sex-related languagedifferences in children with Down syndrome. Nonethe-less, evidence of sex differences in language abilities inchildren with Down syndrome was noted in the resultsfrom a parental questionnaire study (Buckley & Sacks,1987). In children under the age of 14, 70% of the girlsand 46% of the boys used sentences of five or more words,whereas in children over the age of 14, 77% of the girlsand 70% of the boys used such sentences. To our knowl-edge, the only study directly addressing the issue of sexdifferences in language skills is that of Beeghly et al.(1990). Those authors reported that girls tended toprogress more rapidly than boys did.

AimsThe primary aim of this study was to describe the

spoken-language development of children in a nation-wide sample of Swedish children with Down syndromeand then to compare their development with that ofunaffected children in a normative group. The studyaddressed three target problems: (1) growth trends andindividual variation in language performance, (2) sexdifferences in language performance, and (3) differencesbetween children in the normative group and childrenwith Down syndrome.

MethodParticipantsGroup With Down Syndrome

The group with Down syndrome comprised 330 chil-dren (124 girls and 206 boys) between the ages of 1 and5;6 (see Table 1). The subjects constituted approximately45% of all children with Down syndrome born in Swe-den during 1991-1995. (The percentage is based on datafrom Sweden's Medical Birth Register.) Our subjectsconstitute an even larger proportion of the actual popu-lation because perinatal mortality among children withDown syndrome is very high (as high as 10% tol5%over the first 5 years of life). For 102 of the children(31%), parents indicated that their child had additional

Table 1. Number of children with Down syndrome as a function of age, gender, additional deficiencies, and use of manual signs.

Age in years;months

1 1;6 2 2;6 3 3;6 4 4;6 5 5;6 Total

Girls 12 14 15 8 11 19 11 15 11 8 124Boys 29 17 15 15 20 17 37 21 19 16 206Additional deficiencies 9 11 5 6 6 12 15 17 11 10 102Manual signs 30 26 27 20 28 30 45 34 26 22 288Total number of children 41 31 30 23 31 36 48 36 30 24 330

t Berglund et al.: Language in Children With Down Syndrome 1 81

deficiencies: 14% had cardiac disorders, 7% had ear com-plaints or frequent otitis media, 15% had eye disorders,and 5% had neurological or orthopedic problems.

Most of the children were enrolled in language-stimulation programs where speech and manual signswere used simultaneously (n = 288, 87%). Among one-year-olds, 73% used manual signs, whereas in the olderage groups the proportions varied between 83% and 94%.Parents did not indicate which words their child signed.Other communication aids were letters, used by 32 ofthe children (10%), and computers, used by 28 (8%); bothmethods wvere used more commonly by older children.Parents did not give more detailed descriptions of howtheir children used letters or computers. Seven chil-dren used pictograms (2%), and one child used BLISSsymbols.

Offices from all regions of Sweden responsible forservices for children who are mentally delayed recruitedthe subjects. Criteria for inclusion were specified agerange (preschool age).and diagnosis of Down syndrome.The local offices distributed the SECDI to parents, whothen returned the completed inventory to the researchgroup. If necessary, reminders were sent to parents bythe local offices. Because we did not make a special re-quest for medical records, the data of children with suchconditions as translocation or mosaicism are not reportedseparately.

Before data collection, staff members at the localoffices were contacted by telephone in order to obtaininformation on the number of potential subjects in therelevant ages. During data collection, approximate re-gionalresponse rates were recorded. Ib examine whetherthere was any general effect of differential response rateson language and communicative skills, we comparedchildren from regions with a response rate over 60% withthose from regions with a lower response rate. For thiscomparison, we employed data on vocabulary perfor-mance in that this is a measure of the earliest develop-ing language skill of the measures used in the presentstudy. A two-way ANOVA (age by response group) wasconducted, where children were divided into five groupsaccording to age. Whereas the age effect was significant(p < 0.01), indicating that older children obtained higherscores, the response rate by region was not (p = 0.91).Thus, we aggregated the scores of children from regionswith different response Tates in subsequent analyses.

The Normative GroupThe children with Down syndrome were compared

with a representative sample of unaffected children be-tween the ages of 1;4 and 2;4. The sample was drawnfrom the SwedishBirth Register andincluded two thirdsof all Swedish children born on two specific days. Thedata, which were derived from Berglund and Eriksson

(2000), comprised 900 reports on 336 children from twocohorts. Each child was measured on one-to three occa-sions. The children were followed over 6 months: Paren-tal reports were requested three times during this period.The chief inclusion criterion was that the child should beable to speak Swedish. A few children who lived abroadand were recently internationally adopted or who' werediagnosed as developmentally delayed were excluded. Aresponse rate of 88% was obtained. In total, 476 reportson girls and 424 reports on boys were collected.

Instrument and ProcedureThe SECDI-w&s, as described in Berglund and

Eriksson (2000), was used to obtain scores for vocabu-lary, pragmatic skills, and grammar skills. The vocabu-lary score was computed from all words the parents hadindicated their child produced from a 710-item check-list containing words from 21 semantic categories. De-viation from standard pronunciation was accepted.Pragmatic skills is here used in a restricted sense todenote the ability to communicate about future or pastevents, about absent objects or persons, and to expressownership, disregarding linguistic form. These achieve-ments increase the child's competence "to do things withwords" but do not themselves reflect different commu-nicative functions. The parents answered five questionsabout their child's pragmatic skills. Two measures ofgrammar were employed. The grammar score was cal-culated from questions about whether the child com-bined words and whether he or she used morphologicalmarkers for the possessive form, definite singular, defi-nite plural, plural marking of nouns, and past-tense ofverbs. The child received a score of 1 on items in thepragmatic and grammar scales if the parent reportedthat the child occasionally performed the target behav-ior and a score of 2 if this occurred often. The MaxLUscore is a MLU count (in morphemes) of examples ofthree long utterances the parents recently had heardtheir child produce. Reliability scores for vocabulary,pragmatic, and grammar were examined previously inthe normative group. Intra-individual test-retest scores(i.e., percentage of items the child performed with asimilar or larger score 3 months later) were calculatedfor the normative group (Berglund & Eriksson, 2000).The test-retest reliability scores for the 197-22 monthinterval in children in the normative group are givenin Table 2 for each language skill measure. Also, theCronbach alpha scores for 22-month-old children (n =311) are specified.

Additional information on the validity and reliabil-ity measures in relation to the SECDI-w&s was reportedin Berglund and Eriksson (in press). The use of paren-tal reports on language of mentally delayed children wasdiscussed in Berglund (1992) and in Miller,; Sedley, and

182 Journal of Speech, Language, and Hearing Research * Vol, 44 *, I179-191 * February2001

Table 2. Description of scales and measures. Reliability scores wereintra-individual test-retest scores in the 19-22 month interval inchildren in the normative group. Cronbach alpha was calculated in22-month-old children.

No. Max Cronbachitems score Reliability alpha

Vocabulary 710 710 92% 0.99Pragmatic skills 5 10 88% 0.81Grammar skills 6 12 93% 0.83MaxLU 3

Note. MaxW was MW calculated over 1-3 long utterances writtendown by parents. A score oF 0 was given if children did not use anywords. A score of 1 was given if the parent had not given anyexamples of long sentences and the child had a vocabulary of 1-100words (indicated in the vocabulary section). The MaxW score wascoded as missing if the parent had not given any examples of longsentences and had indicated that the child combined words (item 6 -grammar skills) or if the parent had not given any examples of longsentences and the child had a vocabulary of more than 100 words(indicated in the vocabulary section).

Miolo (1995). Parents of children with Down syndromeare able to describe the language skills oftheir childrenand are as competent as parents of unaffected children.

Statistical ProceduresThe children with Down syndrome were divided into

10 age groups. These half-year groups were used fordescriptions of developmental trends and individualvariations on the four language measures. Number andsex of children in each age group are given in Table 1.Developmental trends and individual variation weredescribed by median values and first and third quartilefor all language measures (vocabulary size, pragmaticskills, grammar score, and MaxLU). In addition, the 1 0 th

and 9g0 h percentiles are also given for vocabulary size,the scale with the greatest variation. For the five agegroups representing whole years, proportions of childrenusing more than 1, 2, 10, and 50 words were reported.The same age groups were used to test age and sex ef-fects in the ANOVAs for each of the language measures.

We also sought to determine which equation-lin-ear, exponential, or logistic-best fit the data. Of course,linguistic skills cannot proceed exponentially in the longrun. Proficient users acquire by definition few new fea-tures. Hence, logistic equations have greater face valid-ity than exponential functions in early language devel-opment. However, logistic growth curves in the presentstages of language development might reflect ceilingeffects of the employed scales rather than a genuinepattern of language acquisition. Therefore, we modelboth logistic and exponential equations as well as lin-ear equations. In this analysis all data of children in

the normative group between the ages of 16 and 25months were used, as well as all data of children withDown syndrome. To make the analysis feasible, scoresof zero in vocabulary, pragmatic skills, and grammarskills were changed to 0.01. Language development, inmeasures yielding significant sex effects, were modelledby using the best-fitting equations for each sex sepa-rately. To describe development in measures withoutsignificant sex effects, the total scores were used.

ResultsThe results of the growth trend and individual varia-

tion in language performance are reported separatelyfor each of the four language measures. Next, we ex-plore age and sex differences in language skills. Anevaluation of which regression functions best repre-sented the language skills of children was also under-taken. Finally, we present the development of the prag-matic and grammar scales in children with Downsyndrome as they compare with those of children in thenormative group matched for vocabulary size or MaxLU.

Developmental TrendsVocabulary Scores

Some of the children with Down syndrome utteredtheir first spoken words by their first birthday. Propor-tions of children passing the milestones of 1, 2, 10, and50 spoken words at various ages are shown in Table 3,together with maximum language scores for each agegroup. A majority of the children 'used more than 10words at age 2. The 50-word milestone was passed bymore than half of the children at about age 4.

Median vocabulary scores (50th percentile) increasedsteadily with age: 0 words in 1-year-olds, 10.5 words in2-year-olds, 16 words in 3-year-olds, 53 words in 4-year-olds, and 198 words in 5-year-olds (see Figure 1). To il-lustrate the large individual differences, in each age

Table 3. Percentage of children passing the 1 -word, 2-word, 1 0-word, and 50-word milestones and the maximum number of wordsreported for the best-performing child in each age group.

Age in years

1 2 3 4 5

l word 12 80 90 98 942 words 7 77 90 98 9210 words 3 53 81 88 9150 words 0 3 23 54 73

Maximum number 11 71 165 668 655of words

Berglund et al.: Language in Children With Down Syndrome 183

Figure 1. Developmental trends in vocabulary among children withDown syndrome: I010% 25%h 50th,. 7 5I, and 9 0 ih percentiles.

700

600

X 500

c( 4000

> 300

2 200

,100

1;0 1;6 2;0 2;6 3;0 3;6 4;0 4;6 5;0 5;6

Age in years;months

Figure 2. Developmental trends in pragmatic skills among childrenwith Down syndrome 25I, 5 0th, and 75th percentiles.

109-

8

2 7.0cn6

5.I

4.-3.-

2

I1.0

0

E0)ED.

1;6 2;0 2;6 3;0 3;6 4;0 4;6 5;0 5;6

Abe in years;months

Figure 3. Developmental trends in grammar skills among childrenwith Down syndrome: 25%, 50th, and 75 'h percentiles.

12

10

00mco

E2(D

8

6

4

2

0

group there were children who did not use any words atall, and'there were also a number of older children whohad a vocabulary of more than 600 words.

Pragmatic SkillsPragmatic skills were measured using five items

from the SECDI (maximum score 10 points). Thereseems to be a ceiling effect for pragmatic scores, wherebythe 7 5 th percentile lies close to the maximum score be-yond age 4;6 (see Figure 2). Yet, 19% of the parents ofthe 5-year-olds did not indicate that their children per-formed any of the pragmatic activities. The pragmaticskills section of the SECDI contains one item indicatingwhether a child understands when the parent talksabout absent persons or objects. This was the first prag-matic skill developed in most of the children and wasmastered by 19% of the children at age 1;6, by 40% atage 2, 62% at age 3, 81% at age 4, and 79% at age 5.

Grammar ScoreThe grammar score section of the SECDI comprises

six items, yielding a maximum score of 12 points. Therewere examples of children who combined words (13%o)or used morphological markers (3%) at age 2, thoughthe overall median score for grammar skills did not riseabove 0 until after age 3;6 (see Figure 3).

MaxLUA score of 1 on the MaxLU indicates that a child

uses single words only, and at least 25% of the childrenin all age groups had a score of 1 (or did not use anywords). As a consequence the 25ti percentile is not dis-played in Figure 4. A higher score indicates that a childuses at least two-word expressions (or two-morphemeutterances). Most of the children age 4 and over com-bined words; nonetheless, there were over 25% who did

Figure 4. Developmental trends in Maximum Length of Utteranceamong children with Down syndrome' 50h and 75,h percenfiles.

5 -

a)

oa 4 -

c

p

a)

rm 3.~0

m 2 -

xCa 1-.

2;0 2;6 3;0 3;6 4;0 4;6 5;0 5;6

Age in years;months

3;0 3;6 4;0 4;6 5;0 5;6

Age in years;months

184 JournalofSpeech,Language,andHearingResearch * Vol.44 * 179-191 . February2001

-75%

---50%

- -25%

-/ \

/7' -

IF

Table 4. Results of two-way ANOVAs (age by sex) performed onthe four communicative and language measures.

Age groups F Df p

Vocabulary score 1, 2, 3, 4, 5Age 23.79 4 <01Sex 4.49 1 <.05AgexSex 1.15 4 ns

Pragmatic score 2, 3, 4, 5Age 15.54 3 <.01Sex 7.48 1 <01Age x Sex .46 3 ns

Grammar score 3, 4, 5Age 14.52 2 <.01Sex 2.17 1 nsAge x Sex 1.55 2 ns

MaxLU score 3, 4, 5Age 14.02 2 <.01Sex 1.57 1 nsAge x Sex .49 2 ns

not combine words, even among those age 5;6. Mediangroup scores for maximum length of utterances suggestthat there are wide plateaus in the syntax developmentof children with Down syndrome. It should be noted,however, that a few children performed at quite ad-vanced levels.

Effects of Age and SexTo examine whether there were any effects of age

and sex on the various language measures, two-wayANOVAs (age by sex) were performed. For vocabulary(the earliest developing skill), performance at ages 1, 2,3, 4, and 5 was examined. Pragmatic skills (developingslightly after the first utterances) were analyzed for theage 2, 3, 4, and 5 groups. For analyses of grammar andMaxLU scores (late-developing skills), the age 3, 4, and5 groups were considered. All analyses revealed signifi-cant effects of age. The age effects were further exploredby one-wayANOVAs and Tukey post hoc tests (p < .05).In the case of vocabulary, 1-, 2-, and 3-year-olds did notdiffer significantly, yet 4-year-olds produced significantlyhigher scores than the younger children, and 5-year-oldsproduced significantly higher scores than 4-year-olds.In pragmatic skills, the scores of 2-, 3-, and 4-year oldsdiffered significantly, yet 4- and 5-year-olds did not dif-fer significantly (close to ceiling). The grammar scoresof 3-, 4-, and 5-year-olds differed significantly. Finally,in MaxLU, 3-year-olds produced significantly shorterutterances than 4- and 5-year-olds, who did not differsignificantly.

The effects of sex for vocabulary and pragmatic skills-were significant. Girls scored higher than boys did. Noage-by-sex interaction was revealed (see Table 4).

Developmental Comparisons for theDifferent Language Measures

We examined the R2 values to evaluate which func-tions were most efficient in representing the differentdistributions. Three kinds of function (linear, exponen-tial, and logistic) were examined for each language mea-sure in both groups of children (see Table 5). The expo-nential and logistic growth curves yielded identicalvalues and had the highestR2 values for vocabulary size,grammar skills, and MaxLU, regardless of group. Fur-ther, linear functions yielded the best fit for pragmaticskills, regardless of group. The ages when children withDown syndrome and children in the normative groupperformed similarly are illustrated in Figure 5, eachpanel of which illustrates either a linear or exponentialregression plot depending on which type yielded thehighest explained variance.

Table 5. The statistic characteristics for three kinds of regressionequation representing the growth (i.e., by age) factor for the fourcommunicative and language measures.

Group -Measure Equation R2 B constant

DS - Vocabulary Linear .315 7.490 -194.05Exponential .414 .0825 1.186Logistic .414 .921 .843

Pragmatic skills Linear .379 .146 -2.105Exponential .307 .094 .023Logistic .307 .910 43.463

Grammar skills Linear .251 .105 -2.819Exponential .382 .127 .0005Logistic .382 .880 1837.40

MaxLU Linear .314 .075 -.878Exponential .373 .030 .503Logistic .373 .970 1.987

NG - Vocabulary Linear .347 30.806 -485.11Exponential .414 .298 .150Logistic .414 .742 6.666

Pragmatic skills Linear .375 .589 -6.942Exponential .159 .230 .025Logistic .159 .794 39.858

Grammar skills Linear .315 .538 -8.714Exponential .366 .556 3.4 x 10-Logistic .366 .574 296057

MaxLU Linear .347 .344 -4.427Exponential .393 .135 .132Logistic .393 .874 7.584

Note. For Vocabulary, Pragmatic, and Grammar skills a score of 0 wasaltered to a score of 0.01 to make possible the examination of logisficand exponential functions. Children with Down syndrome (DS) age 1-5years and children in the normative group (NG) age 16, 19, 22, and25 months were included in the analysis.

Berglund et al.: Language in Children With Down Syndrome 185

Figure 5. A. Estimated vocabularydevelopment in girls and boys from the normative group (NG) and in children with Down syndrome (DS):exponential growth. B. Estimated development of pragmatic skills in girls and boys from the NG group and in children with DS: lineargrowth. C Estimated development of grammar for children in the NG group and in children with DS: exponential growth. D. Estimateddevelopment of MaxLU in children from the NG group and in children with DS: exponential growth.

A B

350-

300

250

200

150

100

50-

16.0 (36) 17.5 (40) 19.0 (44) 20.5 (48) 22.0 (52) 23.5 (56) 25.0 (60)

Age of NG children (DS children) in months

C

0- NG children

10 - L - DS children

8-

6

4,

2

0 D .

16.0 (36) 17.5 (40) 19.0 (44) 20.5 (48) 22.0 (52) 23.5 (56) 25.0 (60)

Age of NG children (DS children) in months

00

a

(102

0

E01wil

16.0 (36) 17.5 (40) 19.0 (44) 20.5 (48) 22.0 (52) 23.5 (56) 25.0 (60)

Age of NG children (DS children) in months

D0 -

-o-NG childrenI - - DS children

4-

3 ---

2

- .

16.0 I16.0(36) `17.5(40) 19.0(44) 20.5(48) 22.0(52) 23.5(56) 25.0(60)

0

-xCU

Age of NG children (DS children) in months

Furthermore, we wanted to explore whether theearly word growth could be described by a growth func-tion other than an exponential one. To test this possibil-ity we performed an analysis inwhich only children withvocabularies of 50 or fewer words were included. (Thisis before the vocabulary spurt is expected to occur.) Thelinear function (R2 = 0.181) and exponentiai and logisticfunctions yielded close results (R2 = 0.174). Hence, itseems that linear, exponential, and logistic functions il-lustrate the growth of the small vocabularies (<50 words)about equally well.

Data for boys and girls are plotted separately in Fig-ure 5 (A and B), illustrating the developmental trends,-matched for age, for the skills with significant sex differ-ences (vocabulary size and pragmatic skills). In the vo-cabulary plot (A) we used exponential regression, and inthe pragmatic plot (B) we used linear regression because

these kinds of functions yielded highest explained vari-ance. The girls scored higher than the boys in bothgroups of children, and the differences between girls withDown syndrome and boys with Down syndrome werelarger than the differences between girls and boys inthe normative group for both vocabulary size and prag-matic skills.

Developmental Differences: PragmaticScale, Grammar Scale, and MaxLU

Three stepwise regression analyses (with enteringcriterion of F < .05 and removal criterion of F > .10)were computed to explore differences between childrenwith Down syndrome and children in the normativegroup on the pragmatic scale, on the grammar scale,and on MaxLU. Vocabulary size and sex were added tothe models in addition to group (children with Down

186 JournalofSpeech,Language,andHearingResearch * Vol.44 * 179-191 * February.2001

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syndrome and children in the normative group) to con-trol the possible influences from these variables. Vocabu-lary size entered first in all three equations, explainingmost of the variance. Group entered all equations in thesecond step. Although always significant, the increasein explained variance caused by group was small: .036for the pragmatic scale, .004 for MaxLU, and .002 forthe grammar scale. Children in the normative groupwith vocabulary equal to that of children with Downsyndrome generally scored slightly higher on a ll threescales. Sex never entered the models (see Table 6).

Developmental Differences on SingleSkills for Subjects Matched forVocabulary

The order of development of single pragmatic skillswas strikingly similar between children, regardless ofgroup, when matched on vocabulary size. The main or-der was the following: "understood when parent talkedabout absent objects," 'talked about absent owner," "talkedabout absent object," "talked about future events," and"talked about past events." Also the order in develop-ment of grammatical markers was strikingly similarbetween children with Down syndrome and children inthe normative group. Children first started to combinewords; thereafter they used genitive markers; and useof definite singulars, definite plurals, and indefinite plu-rals appeared before the use of past tense. Children alsostarted to combine words at similar percentages overthe different vocabulary size.

Table 6. Stepwise regression analyses (vocabulary, group, andsex) on MaxlU, the Grammar scale, and the Pragmatic scalesignificant variables.

Variable Df SE B b RI

Pragmatic scale (model) 1221 .58Vocabulary .00 .69Group .12 .20

Grammar scale (model) 1102 .88Vocabulary .00 .87Group .12 .04

MaxLU (model) 1108 .59Vocabulary .00 .75Group .10 .07

To further explore the differences between childrenwith Down syndrome and children in the normative group,logistic regressions were computed for the individual itemsof the pragmatic scale and the grammar scale. Vocabu-lary size, MaxLU, and sex were included in the modelsas covariates. These analyses revealed that children inthe normative group more often than children with Downsyndrome with a similar vocabulary size talked aboutownership, talked about missing things, and understoodtalk about missing things. Further, children in the nor-mative group more often than children with Down syn-drome marked genitives and the definite and indefiniteforms in singular. Boys spoke slightly more about pasttimes than girls did (see Table 7).

Table 7. Results of logistic regressions, with different kinds of single skills as dependent variables, and sizeof vocabulary, MaxlU, sex, and group (Down syndrome vs. normative group) as covariates. Method:forward entering-Wald.

Vocabulary MaxLU Sex Group

Wald R Wald R Wald R Wald R

Pragmatic skillsSpeaks about

passed time 138.42 .30 26.42 .13 4.75 .04B NEfuture 103.92 .26 39.18 .16 NE NEmissing things 78.54 .23 17.56 .10 NE 11.55 .08NG

Understands talk aboutmissingthings 61.18 .23 NE NE 74.10 .26NG

Speaks about owners 59.64 .20 16.90 .10 NE 22.69 .12NG

Grammar skillsGenitive markers 147.24 .33 17.82 .11 NE 5.33 05NGDefinite singular 268.33 .47 NE NE 9.05 .08 NG

Definite plural 130.39 .37 4.26 .05 NE NEIndefinite singular 131.70 .36 15.46 .11 NE 7.62 *07NG

Pasttense 117.80 .36 12.24 .11 NE NECombines words 69.99 .23 89.80 .26 NE NE

Note. NE = not in equafion. Boys highest. ir = Children from the normative group highest.

Berglund et al.: Language in Children With Down Syndrome 187

DiscussionGrowth Trends and Individual Variationsin Language Performance

We found that the first word appears approximatelyone year after birth in about 10% of the children withDown syndrome and that after 2 years 80% had begunto talk. Furthermore, some children with Down syn-drome start to talk at about the same age as children inthe normative group (cf. Eriksson & Berglund, 1999).In this respect, we agree with Chapman (1995) that therate of acquisition is slower in most children but notnecessarily the onset of lexical acquisition. However,between 10% and 20% of the children with Down syn-drome had less than 10 words in their spoken vocabu-laries when they were 3 to 5 years old, and there weresome children who had not started to talk at all, regard-less of age.

The 50-word milestone was achieved by about 25%of the children with Down syndrome at age 3, by about50% at age 4, and about 75% at age 5. Thus, a substan-tial proportion of the children in our study attained thislevel at an earlier age than Gillham's (1990) subjects.At age 3;0 our subjects had an average vocabulary of36.0 words (range: 0-165 words), which can be comparedwith the Stroeminger et, al. (1984) finding of a mean of18.5 words (range: 0-85 words). The discrepancy partlymight be explained by the use of different languagemeasures in the two studies.

The majority (87%) of children in this study usedspeech and manual signs simultaneously. Therefore, thechildren with Down syndrome with the smallest spo-ken vocabularies are slightly underestimated in termsof the size of their "total" vocabularies in relation to chil-dren in the normative group. However, when the vocabu-laries increase in size, children with Down syndromemostly add spoken words to their repertoire (Miller etal., 1991, cited in Chapman, 1995). Hence, the highervocabulary scores in the present study should be closeto the total vocabularies of children with Down syn-drome. However, it would be expedient of future studiesin this area to assess the children's manual vocabular-ies as well.

Our language predictions from linear regression andexponential equations indicate that the performance of36-month-old children with Down syndrome parallelsthe performance of unaffected children at about 16months old (see Figure 5[A-D]). This finding confirmsthe result of Mervis (1990) that, on average, 3-year-oldchildren with Down syndrome perform similarly to un-affected children at age 1;6.

We noted that 48-month-old children with Downsyndrome performed at a level approaching that of

20-month-old unaffected children. Mundy et al. (1988)compared children with Down syndrome at age 3;8 withunaffected children at age 1;6, thus making a compari-son between groups that we found had matching resultsin this study. Bates et al. (1995) reported-that childrenwith Down syndrome lagged approximately 2 years be-hind unaffected subjects over the period covered by CDI:'Ibddlers, and our results are also in line with this find-ing. In our study, 3-year-olds lagged by about 20 monthsand 4-year-olds by about 28 months.

Smith et al. (1988) obtained similar results for 5-year-old children with Down syndrome and unaffectedchildren at age 2;6 in terms of performance on theMcCarthy scales of children's abilities. However, theyfound that delay in language skills of children with Downsyndrome was even more prolonged. This finding seemscomparable to our result regarding magnitude of delay.Harris (1983) found the MLU of children with Downsyndrome between ages 2;6 and 6;9 years was compa-rable to that of unaffected children between ages 1;5and 2;5. Our results indicate that about 5% to 10% ofchildren with Down syndrome combine words in theperiod from age 2 to 2;6 and that about 70% do so at age5;6. In this respect, Harris's findings are in accord withours.

In the comparison of different growth functions, weobserved almost identical patterns in the children withDown syndrome and -the children in the normativegroup, suggesting common growth patterns across chil-dren independent of the presence of dysfunction. An ex-ponential or a logistic curve y'ielded the highest ex-plained variance (R2 ) in three of the measures, whereasthe development of pragmatic skills was better describedby a linear equation. That the pragmatic scale was dif-ferent from the other scales suggests that the develop-ment measured by the pragmatic scale may be governedby other cognitive or linguistic principles. However, moredata on the development of pragmatic skills and theirrelations to other measures are needed before this issuecan be settled conclusively.

Robinson and Mervis (1998) have explored indi-vidual growth curves of vocabularies in children withWilliams or Down syndrome. They found that a logisticgrowth curve was most typical and that growth rate wasnegatively correlated with a linear fit. However, in 3 ofthe 5 children with Down syndrome in the Robinson andMervis study, language development was best charac-terized by linear growth. In the present study, we foundthat several of the measures are best described by expo-nential or logistic curves. As we have shown here, lin-ear, exponential, and logistic equations yield about thesame explained variance before the 50-word milestoneis reached. Thus, it seems that the Robinson and Mervisfindings are compatible with our group data.

188 Journal of Speech, Language, and Hearing Research * Vol. 44 * 179-191 . February 2001

The Significance of Sex Differencesin Language Skill

Our study confirms earlier findings of sex differencesin language skills of children with Down syndrome(Beeghly et al., 1990; Buckley & Sacks, 1987). Signifi-cant sex differences in our study were found for bothvocabulary and pragmatic skills, on which girls on av-erage perform better than boys do. However, in contrastto Fenson et al. (1994) among others who reported smallbut consistent differences between unaffected boys andgirls, Berglund and Eriksson (2000) and Eriksson andBerglund (1999) found no differences between boys andgirls among unaffected Swedish-speaking children. Ittherefore becomes important to ask if there are factorsassociated with Down syndrome that are responsible forthe superior language performance of girls as comparedto boys among children with Down syndrome. One suchset of factors would be if boys with Down syndrome hadmore additional deficiencies than girls with Down syn-drome. Yet, in analyzing additional deficiencies in thepresent study group, Berglund (1998) found no differ-ence in the distribution between boys and girls. We there-fore suggest that more research should be devoted toexplaining the sex differences in language skills amongchildren with Down syndrome.

Language Skills Among ChildrenWith Down Syndrome and Childrenin the Normative Group

The order of development of single items on thegrammar and the pragmatic scales was strikingly simi-lar on the part of children with Down syndrome andchildren in the normative group. However, when matchedon vocabulary size, children with Down syndrome laggedbehind children in the normative group on the pragmaticscale, on the grammar scale, and on MaxLU. This effectwas small but was probably somewhat underestimatedbecause only the spoken vocabularies of children withDown syndrome were counted. Their total vocabular-ies with manual signs included would have been larger,thus emphasizing the lag (cf. the results on lexical com-prehension and gestures by Caselli et al., 1998). A lagin grammar skills is in accord with the findings of Miller,Miolo, Sedey, and Murray-Branch (1993, cited inChapman, 1995) and Wiegel-Crump (1981). The lag inpragmatic skills among children with Down syndromeas compared with children in the normative groupmatched on vocabulary size was actually greater thanthe lag in grammar skills. A lag in pragmatic skills isrelated to the often-cited restriction among childrenwith Down syndrome to "talk about here and now" (cf.Layton & Sharifi, 1978; Leudar, Fraser, & Jeeves, 1981;Rondal, 1978, all citedin Chapman, 1995). However, thepresent findings do not suggest an inability on the part

of children with Down syndrome to talk about absentobjects, owners, and past and future situations. Theyjust did it a little later than the children in the norma-tive group.

Limitations of the StudyBecause the study used a parental questionnaire, in-

formation dealing with nonverbal mental age could notbe obtained. For children who have small spoken vocabu-laries and who use signs to facilitate communication, theirtrue vocabularies might have been underestimated.

Another limitation is that because we used paren-tal questionnaires for the whole population of preschoolchildren with Down syndrome in Sweden, it was not fea-sible to obtain medical records. Thus, such importantinformation as hearing status was not available. None-theless, we did ask parents a global question about thehealth conditions of their child. Berglund (1998) ana-lyzed the potential detrimental effects that additionaldeficiencies have on vocabulary scores. If a child hadear disorders or a hearing impairment, this was signifi-cantly associated with increased risk for low vocabularyscores, but only when the child had other deficiencies(e.g., eye disorders, cardiac disorders, or neurological ororthopaedic problems). Having an ear or hearing disor-ders alone did not yield a significantly increased rela-tive risk for low vocabulary scores. Obviously, these find-ings suggest that medical records on hearing or screeningof hearing status (and the presence of other deficien-cies) should be included in language studies of childrenwith Down syndrome.

Implications of Findings on LanguageTherapy in Children With DownSyndrome

The timetables from this study on the developmentof language skills in children with Down syndrome areclinically useful. Using timetables makes it possible togive parents a reasonable idea about the language de-lay in their child and what to expect in the developmentof spoken vocabulary. Because of significant sex differ-ences in language skills, parents need to be informedabout how this affects their child. According to the mea-sures used here, children with Down syndrome are mainlydelayed and only marginally deviant in their languageskills. However, the vocabulary develops slightly aheadof pragmatic and grammar skills. Therefore, it seemsimportant that language stimulation programs pay spe-cial attention to pragmatic and grammar skills.

The form of the developmental function for variouslinguistic skills also has possible implications for lan-guage stimulation programs. Other things being equal,a small improvement in a skill with an exponential orlogistic function yields a higher later payoff than an

Berglund et al.: Language in Children With Down Syndrome 189

improvement of equivalent size in a linearly developingskill. Taken together with the argument above and thepresent finding of a linear development of pragmaticskills a good case can be made for developing programsdirected at stimulating grammar skills in children withDown syndrome. However, other things are rarely equal,and there are probably causal links between differentlinguistic skills. For example, it seems reasonable thata basic categorization of the world in the past, in thepresent, and in the future, as assessed by the pragmaticscale, is necessary before the particular grammaticalform that marks these categories in language can beacquired. If this is true, training programs should focuson the pragmatic skills before tackling grammar skills.A lexicon-driven model for the acquisition of gramniaris also consistent with the present findings. However,such a model must explain why children with Down syn-drome in general need a somewhat larger vocabularythan children in the normal group to reach a correspond-ing level of grammar. A likely explanation would be interms of weaker representational or computational re-sources in children with Down syndrome.

AcknowledgmentsThe research in this paper was supported by grants

from the Centre for Caring Sciences, Uppsala University;the Dalarna Research Institute; the Mayflower Foundation;the Research and Development Department of GavleborgCounty Council; Falun College of Health and CaringSciences; and the department of Caring Sciences at GavleUniversity. The authors are indebted to Professor HakanStattin at the Department of Psychology, Orebro University,for valuable methodological advice and comments on themanuscript. Professor Gunilla Preisler at the Department ofPsychology, Stockholm University, also provided usefulcomments on the manuscript; and Professor Lennart Bodin,Orebro University, helped with the statistics. IbmasBerglund, Gothenburg University, helped with coding ofthe data.

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Received March 17, 1999

Accepted October 20, 2000

DOI: 10.1044/1092-4388(2001/016)

Contact author: Eva Berglund, PhD, Uppsala UniversityHospital, Department of Nursing Research and Develop-ment, S-751 85, Uppsala, Sweden.Email: eva.berglund@adm.uas.lul.se

Bergiund et al.: Language in Children With Dawn Syndrome 1 91

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