A Longitudinal Study of Language Development in Two Children With Williams Syndrome

8/13/2019 A Longitudinal Study of Language Development in Two Children With Williams Syndrome

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A longitudinal study of language development in two

children with Williams syndrome*

Y O N A T A L E V Y

The Hebrew University

(Received7 May2002. Revised23 May2003)

A B S T R A C T

Williams syndrome (WS) is often cited as the prime example within

developmental disorders of the dissociation of language from other

cognitive skills, particularly from visuo-motor skills. This claimhas been responsible for the challenges posed by this population to

cognitive theories and to models of language acquisition. Two

Hebrew-speaking children with WS were followed longitudinally for

18 months, from the first occurrences of two word combinations. Y was

3;95;3 and BT was 4;25;8 during data collection. Both children

had an MLU of 1.82.8. The childrens linguistic profiles were

compared to the profiles of typically-developing (TD) children of

similar MLU as well as to the profiles of 11 children with a variety

of neurodevelopmental disorders (ND), matched on MLU. Theprofiles exhibited by the children with WS throughout the period of

the study differed from the profiles seen in both control groups.

I N T R O D U C T I O N

Williams syndrome (WS; Williams, Barratt-Boyes & Lowe, 1961) is a rare

autosomal genetic disorder (1:25 000 live births) characterized by typical

facial dysmorphology, renal and cardiovascular anomalies, statural defi-

ciencies, characteristic dental malformation and hypercalcemia (McKusick,1988). Most cases of WS are non-familial (but see recent findings, Osborne,

Pober, Chitayat, Bodurtha, Mandel, Costa, Grebe, Cox, Tsui & Scherer,

2001). A microdeletion on chromosome 7q11.23 has been identified in 98%

of the individuals with WS. The missing region typically includes the ELN

gene, which is hypothesized to account for the vascular and connective

tissue abnormalities. The other phenotypic characteristics are presumably

[*] This work was supported by the Israeli Science Foundation, Grant 795/97. I am grateful

to the Israeli Williams Syndrome Association for their help and enthusiasm. Addressfor correspondence: Yonata Levy, Psychology Department, The Hebrew University,Jerusalem, Israel 91905. fax : 972-2-5881159. e-mail: [email protected]

J. Child Lang.31 (2004), 287310. f 2004 Cambridge University Press

DOI: 10.1017/S0305000904006002 Printed in the United Kingdom


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linked to the adjacent 16 or more genes that are part of the standard deletion

in WS. IQ in individuals with WS is typically within the 5070 range.

Reliable linkages between specific gene deletions and details of the cognitive

profile of WS have not yet been found (Mervis, Morris, Bertrand &

Robinson, 1999; Tassabehji, Metcalfe, Karmiloff-Smith, Carette, Grant,Dennis, Reardon, Splitt, Read & Donnai, 1999).

The cognitive profile of individuals with WS has been characteristically

described as having spared auditory short term memory and spared

linguistic and face recognition abilities, in the face of serious deficits in

number, visuo-spatial cognition, motor behaviour, planning and problem

solving (Bellugi, Marks, Bihrle & Sabo, 1993; Gosch, Stading & Pankau,

1994; Udwin & Dennis, 1995; Mervis et al., 1999). A distinct behavioural

phenotype and a relatively well-understood genotype have made WS a

particularly good candidate for brain-behaviour studies and as such ithas attracted the interest of researchers in a number of domains. WS is

often cited as the prime example within developmental disorders, of the

dissociation of language from other cognitive skills, particularly from

visuo-motor skills.

In recent years research has focused on the exact nature of the linguistic

competence that individuals with WS exhibit. This work resulted in

controversial positions, with an increasing number of studies casting doubt

on the intactness of linguistic competence in individuals with WS. At the

focus of the current debate are studies of morpho-syntax and lexicalsemantics. In the review of the literature below we focus on the former since

this is the area of linguistic knowledge most relevant to the current study.

In her seminal work on the cognitive profile of adolescents and adults

with WS, Bellugi and colleagues (e.g. Bellugi, Bihrle, Neville, Doherty &

Jernigan, 1992 ; Bellugi et al., 1993) argued that the linguistic profile of

individuals with WS shows a sparing of syntax both in comprehension

and in production, which extends to tests of metalinguistic abilities as well.

Morphological markers are generally used correctly, including markers for

tense and aspect, and so are auxiliaries and articles (Bellugi et al., 1993). In

most of these studies participants with WS were school age children or

adolescents and their achievements were compared to those of individuals

with Down syndrome.

Udwin & Dennis (1995) are in agreement with the view expressed by

Bellugi and colleagues. They too conclude that mature individuals with WS

have an unusual command of language. Their comprehension is usually far

more limited than their expressive language, which tends to be grammati-

cally correct, complex and fluent at a superficial level but verbose and

pseudo-mature in its content.

Mervis et al. (1999) argued that a unique cognitive profile characterized

individuals with WS. Contrary to previous work (Bellugi et al., 1992, 1993)

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they concluded that the language abilities of individuals with WS as

measured on standardized tests were significantly delayed relative to CA

controls. Delay was evident on receptive vocabulary, receptive grammar,

semantic fluency and syntactic measures (see also Volterra, Capirci, Pezzini,

Sabbadini & Vicari, 1996 ; Karmiloff-Smith, Grant, Berthoud, Davies,Howlin & Udwin, 1997). Syntactic abilities as well as MLU were at the

expected level for mental age (MA). Furthermore, while achievements on

visuo-spatial tasks were significantly lower than scores on verbal tasks, a

correlation was found between achievements on these two types of tasks,

suggesting that language in individuals with WS was not independent of

other cognitive skills.

Studies of Italian-speaking individuals with WS are of particular

relevance to the current work since Italian, like Hebrew, has complex

morphology. Pezzini, Vicari, Volterra, Milani & Ossella (1999) studiedthe cognitive profile of Italian children with WS. Children with WS ages

4;1015;3, with a mean MA of 5;4 were compared to TD children ages

3;87;6 (mean age 5;6). Within the linguistic domain, children with WS

performed better than their MA matched controls on phonological fluency.

They were poorer, however, on the Boston Naming Test. There were no

group differences on any of the other language tasks. As for the perceptual-

motor tasks, children with WS performed better than their MA controls on

face recognition and significantly poorer on the WISC-R block design.

There were no significant differences on any of the other perceptual-motortasks (see also Volterra et al., 1996). Interestingly, an examination of indi-

vidual profiles in the Pezzini et al. (1999) study revealed a large variability

in performance among the participants with WS including on variables that

distinguished the group as a whole from the typically-developing children.

The Italian study argues against Mervis et al. (1999) who report a

characteristic cognitive profile of individuals with WS. However, in a recent

study of the cognitive profile of Hebrew-speaking adolescents with WS we

replicated Mervis et al. (1999), both with respect to the group as a whole

and with respect to individual profiles (Levy & Bechar, 2003). There was no

evidence in the Hebrew data of the individual variability seen in the Italian

group. Note that Pezzini et al. (1999) and Volterra et al. (1996) are open

to the criticism raised by Mervis & Robinson (1999) concerning the need to

control for chronological age as well as for mental age when comparing

across subjects and across tasks.

Summarizing, performance of individuals with WS on standardized tests

yields an advantage of performance on verbal tasks over other tasks,

specifically over visuo-motor tasks. Yet, achievement on verbal tasks is not

superior in any sense. It varies considerably among individuals with WS

and typically is at MA level. Auditory memory for words seems preserved

and it may even reach the expected CA level.

A L O N G I T U D I N A L S T U D Y O F L A N G U A G E D E V E L O P M E N T


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Along with assessments on standardized tests, individuals with WS

have been tested on experimental, non-standardized tasks. Such tasks are

particularly important when claims concerning preserved linguistic abilities

are at stake. One of the central current debates concerns morpho-syntax in

English speaking individuals with WS, specifically, plurals and past tenseformation.

Clahsen & Almazan (1998, 2001) and Clahsen & Temple (2003) focused

on morphology and morpho-syntax in children with WS. Past tense

formation, noun plurals and compounding were investigated in four

English-speaking children with WS. Results showed that children with WS

over-regularize the past tense /-ed/, and the plural /-s/ significantly more

often than MA controls, whereas knowledge of irregular past and irregular

plural was relatively poor. The children over applied the /-s/ plural to the

internal nominal elements within lexical compounds (yielding, for example,the ungrammatical compound *rats-eater instead of rat-eaters). Simi-

larly, the children over applied the regular comparative affix /-er/ where a

comparative more was required. Clahsen and colleagues interpret these

findings as evidence of a preserved grammatical rule system, along with

considerable deficits in lexical knowledge such as is implicated in knowledge

of irregular forms. Zukowsky (2001) too found a regular/irregular asym-

metry in plural production in children with WS. The participants resisted

over-regularizations of plural /-s/ to irregulars and were eventually able to

produce the irregular forms. Consequently, their deficits were interpretedas evidence for problems in retrieval.

Thomas, Grant, Gsodl, Laing, Barham, Lakusta, Tyler, Grice, Patterson

& Karmiloff-Smith (2001) examined past tense formation in a group of 18

English-speaking individuals with WS. Contrary to Clahsen and colleagues,

they found no selective irregular verb deficit once differences in mental age

were controlled for. The study revealed a deficit in generalization of past

tense regularities to novel forms in the WS group.

In a study of Hebrew morpho-syntax, 10 participants with WS were

compared to TD children (Levy & Hermon, 2003). Given the variability in

IQ scores that characterized the WS group, averaging over participants IQ

was not attempted. Instead, participants were compared to two control

groups: a younger group age 5;7 (5;35;11), (which spanned the lower

end of the WS IQ scores), and an older group age 11; 7 (10 ; 312; 6),

(which was at the upper end of the WS IQ level). The participants with WS

were significantly worse than the older control group on most sub-tests, that

is, they did not score higher than their average-to-low MA.

Several studies considered the early phases of language development

in toddlers with WS. As far as precursors to language were concerned,

a reduction in pointing and impairments in triadic interactions were

found (Laing, Butterworth, Ansari, Gsodl, Longhi, Panagiotaki, Paterson

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& Karmiloff-Smith, 2002). Similar to all other populations with neuro-

developmental disorders, the onset of language is usually delayed in WS.

Singer-Harris, Bellugi, Bates, Jones & Rossen (1997) suggested that the

mean delay was of two years. Vocabulary growth in WS was not correlated

with joint attention (Mervis & Bertrand, 1997). In a preferential lookingtask, toddlers with WS did not outperform toddlers with Down syndrome

in matching words to pictures. Both groups performed at MA level and

were significantly worse than CA normal controls (Paterson, Brown, Gsodl,

Johnson & Karmiloff-Smith, 1999). As for expressive vocabulary, Mervis &

Robinson (2000) reported of an advantage of two-year-old toddlers with

WS over age-matched controls with Down syndrome. The expressive

vocabulary advantage was present even before any of the children began to

combine words.

Relatively little is known about the acquisitional course of language inyoung children with WS. To the best of my knowledge, Capirci, Sabbadini

& Volterra (1996) is the only published longitudinal follow-up of language

development in a child with WS. Observations of this Italian-speaking girl

began when she had about 20 words and no syntax. The study reports

similarities between the acquisitional course followed by this child and the

developmental course observed in normal children. However, some differ-

ences were noted as well. In particular, while the child had good vocabulary

and proficient syntax she made agreement errors and errors of pronominal-

ization of the kind not documented in normally developing Italian children.By the age of 4;10, the childs cognitive profile as measured on normative

tests, was typical of WS, with linguistic abilities better than visuo-spatial

ones, although the latter were less impaired than one often sees in children

with WS.

What might be the contribution of a documentation of the early stages of

language acquisition in WS to the theoretical debate surrounding the

linguistic abilities of individuals with this syndrome? Most of the work

that concerned mature linguistic competence in disordered populations has

not considered it theoretically necessary to relate the observations to the

developmental trajectories en route to mature competence. It may be argued,

however, that if there were normal onset and normal rate and course of

acquisition the claim for the relative sparing of language in individuals with

WS in the face of general cognitive deficits would be greatly enhanced.

Karmiloff-Smith and colleagues (Karmiloff-Smith, 1998 ; Karmiloff-

Smith, Scerif & Thomas, 2002), however, argue that an investigation of the

course of acquisition is bound to reveal atypical pathways. Thus, even if

there are behaviourally intact cognitive systems in the mature individual,

normalcy is only apparent and a fine-grained analysis is likely to discover

that the underlying knowledge base is in fact atypical. This is so since the

effects of anomalous genotypes are indirect and non-specific and likely to



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affect internal brain environment and the ways in which that environment

interacts with the input to achieve learning (Karmiloff-Smith, 1998).

Whether atypical brains in fact follow atypical developmental trajectories

is an empirical question. It is still possible that despite the disruption of

normal brain structures, compensatory mechanisms may provide for normallearning.1 Note that some of the studies summarized above bear upon these

issues. Data is still scant, however, with respect to early grammatical

development in WS.

The current work reports on a longitudinal follow up of two Hebrew-

speaking children with WS. The linguistic profiles of the children with WS

were compared to profiles of typically-developing (TD) children as well as

to children with other neurodevelopmental disorders of similar MLU

(Levy, Tennebaum & Ornoy, 2000, summarized in Table 3). Although we

used our own control group, the linguistic variables that were studied weremostly those that have been investigated in TD Hebrew-speaking children.

Below I give a short summary of the morphological and syntactic

phenomena in Hebrew that are relevant to the current study. Related

acquisitional facts, describing typical development are summarized as well.

A brief description of relevant aspects of Hebrew grammar

and related acquisitional facts

Hebrew has the characteristics of Semitic languages, i.e. words are com-posed of consonantal roots cast in vocalic word patterns. The roots are

usually tri-consonantal while the patterns are in the form of vocalic infixes,

prefixes and suffixes. There are seven verb patterns binyanim and about

three-dozen noun patterns mishkalim. All verbs are analysable into

root+pattern. With respect to nouns, however, this generalization is only

partial since some nouns do not have a recognizable root.

It is generally the case in Hebrew that the roots convey core meanings,

while the derivational paradigms may partially introduce meaning modu-

lations. While the formal paradigms are highly systematic and well-formed-

ness is clearly defined, the semantics that the derivational patterns convey is

only partially predictable from their forms.

Hebrew has a rich inflectional morphology. Generally, verbs are inflected

for tense, number, person and gender while nouns have gender and are

marked for plurality. Agreement with respect to gender, number and person

is obligatory between subjects and predicates as well as within noun

phrases. Nouncomplement constructions that are without verbs, tradition-

ally called nominal sentences, are well formed in Hebrew. An accusative

[1] For a discussion of the notion of compensatory mechanisms and brain plasticity and itsapplication to cases of congenital disorders, see Levy, 2003.

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marker /et/ is obligatory. Footnote 2 gives examples of agreement, verbless

clauses and the use of accusative /et/.2

The acquisition of Hebrew morphology has been studied extensively in

recent years. Berman (1985, 1994) investigated the development of verb

morphology. She argues that early verb use is rote learned and thus, itembased. Once the child begins to vary verb forms, each root will appear in

many patterns and with a variety of inflectional endings.3 Hebrew-speaking

children start out with SEMANTICALLY unanalysed forms of verbs yet at the

same period they can effectively control the necessary formal manipulations

of the various root+pattern combinations. It is only around age four, a long

time after they have been using most verb patterns productively, that chil-

drens errors indicate that they begin to appreciate the semantics of the

system (Berman, 1985, 1994).

Previous studies of the acquisition of gender in a variety of languages,including Hebrew, show that children master the formal-morphological

parts of this system relatively early (Mulford & Morgan, 1983; Smoczynska,

1985; Levy, 1988). Thus, even under age 3;0, errors of linguistic gender on

inanimate nouns, which mark gender morphologically, are rare. In cases of

animate nouns in which linguistic gender is determined by the semantic

notion of gender, errors are common and learning is a more protracted

[2] Examples 14 illustrate agreement patterns in Hebrew. Examples 57 demonstratenoun+complement constructions and the use of accusative et.

1. ha-yeled nixnas la- kita ha-xadashathe-boy entered-sg/m to(def)-class/f the-new/fThe boy entered the new class

2. ha-yalda nixnesa la- kit-ot ha- xadash-otthe-girl entered-sg/f to(def)-classes/f/pl the-new/f/plThe girl entered the new classes

3. ha-yeladim nixnesu la- xadarim ha-xadashimthe-boys entered-pl to(def)-room/m/pl the-new/m/plThe boys entered the new rooms

4. ha-yeladot nixnesu la- xadarim ha-xadashim

the-girls entered-pl to(def)-rooms/m the-new/pl/mThe girls entered the new rooms

5. ha-yeled xaxamthe-child clever The child (is) clever

6. ima ba- baytmother in(def)-homeMother (is) at home

7. ima raata et ha-yeledmother saw-past/f/sg (acc.marker) the(def)-boyMother saw the boy

[3] For example, the root G-D-L may appear in the childs speech in the following forms:GaDaL he grew up; hiGDiL he increased; GuDaL he was grown-passive; GiDeLhe grew-causative.



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process. These findings hold across all languages studied so far, among

them Hebrew (Levy, 1988).

In a cross-sectional survey of productive syntax in Israeli children aged

1;05;6, Dromi & Berman (1986) found an increase in the use of polyclause

utterances and a decrease in the use of one-clause utterances, documentedup to age 4;0. A decrease was observed in the production of nominal and

copular clauses as well, along with an increase in the use of clauses with

finite verbs. This is in line with the view that an increase in the use of

sentences with finite verbs characterizes more advanced grammatical stages

(Berman, 1994; Rice & Wexler, 1996).

Previous studies have shown that at or around MLU 3, children control

agreement and errors become minimal. Crucial parts of the verb morphology

are likewise acquired around this stage. A reduction in errors of morphology

along with a wealth of derivational and inflectional forms suggests thatthe core structures of Hebrew morphology have been acquired at this

developmental stage.4

At about the same time, use of accusative marker -/et/- is almost error

free and the proportion of complex clauses increases (Berman, 1985; Dromi

& Berman, 1986; Levy, 1988). However, unlike errors of morphology, the

number of errors of syntax and meaning at this stage does not decrease

in a similar fashion. In other words, while morphology has been largely

mastered, the childs syntactic and lexical repertoires grow richer and more

complex but her performance with respect to those aspects is not as yeterror free (Levy et al., 2000).

In sum, research in the acquisition of Hebrew as well as of other

languages has uncovered developmental trajectories and in some cases

suggested theoretical motivation for the simultaneous emergence of specific

linguistic features in the childs repertoire. Thus, it was suggested that

agreement is conditioned upon the emergence of functional categories. Most

clearly, agreement is part and parcel of verb finiteness (Hyams & Wexler,

1993; Rice & Wexler, 1996 among many). The present study does not

discuss these theoretical perspectives but focuses instead on the develop-

mental trajectories observed in toddlers with WS and the way they compare

with normal development. Consequently, the variables that entered the

linguistic profiles presented in the current study were chosen according to

the following : similar to other languages, in Hebrew, increased use of

tensed verbs indicates that functional categories have developed. Less use of

verbless clauses that are a common grammatical construction in Hebrew,

along with increase in the use of complex clauses signal improved syntax.

Gender marking on inanimate nouns is a formal morphological marker that

[4] The full derivational system of Hebrew is not mastered by children until they are wellinto the school years.

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is acquired prior to or around MLU 3. Agreement is a syntactic operation

that children master when MLU is about 3 and the Hebrew accusative

marker /et/ is likewise acquired at that time.

T H E S T U D Y

Participants and method of data collection

One girl, BT, and one boy, Y, were studied in naturalistic play situations in

their respective homes. The children had a confirmed genetic diagnosis of

WS (FISH; Mervis et al., 1999). In both cases pregnancy and birth were

uneventful. WS was diagnosed during the first months of the childs life.

The children are from middle class, well-educated families. Data collection

started when the children were beginning to combine two words.5

Approximately every three to five months three one-hour sessions wereheld with Y and BT. All three sessions took place in the course of 7 to 10

days. The experimenter was instructed to interact with the child in a natural

way, focusing on activities that encouraged conversation. Child and exper-

imenter played together, had meals, read books and engaged in other home

activities. Specific manipulations were not attempted. The sessions were

audio-recorded and later transcribed by the person who collected the data.

The same experimenter saw both children for the whole period of data

collection. The analysis below is based on 18 hours of recorded conver-

sations with Y and BT, divided into five periods covering the duration ofthe study.

Y was 3;95;3 during data collection and BT was 4;25;8. MLU for

both children was 1.82.8. MLU was calculated according to the system

adapted for Hebrew by Dromi & Berman (1982) and revised by Levy

(1995). In addition to matching on MLU at the beginning and end of the

study, the children were matched on proportion of utterances with MLU

longer than 5. This procedure is necessary to control for potential biases

that are inherent in central measures such as the mean. For Y the

proportion of utterances of length 5 and above was 7.716

.8%. For BT thisproportion was 618.7%. Table 1 gives ages, number of analysed utterances,

MLU and percent of utterances of length 5 and above for Y and BT for the

duration of the study.

Twenty TD children, aged 2;02; 4, MLU 2.22.8 (mean=2 : 6 ;

S.D.=0 :16) served as controls. The range of MLU and of percent of

utterances of length 5 and above in the controls was the same as it was for

Y and BT during the periods of the study. The range of utterances of

[5] In fact, the experimenter visited the children for nearly 6 monthspriorto the first sessionreported here. During that time there were no word combinations and the children spokeonly single words. These sessions are therefore not included in the current report.



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length 5 and above in the controls was 8.415%. This percentage is higher

than that reported in Dromi & Berman (1986) for their sample of Hebrew-

speaking two-year-olds. Note that the lowest MLU in the control children is

higher than MLU in Y and BTs earliest recordings. Thus, the controls are

matched to Y and BT on MLU for period IIV, yet not for period I. This

is due to the fact that we could not find children with MLU under 2 who

could also be matched to Y and BT on percent of sentences longer than 5.

Similar to Y and BT the children came from middle-class, educated

homes. Each control child was seen twice on consecutive days, for a total of11:30 hours. A similar procedure for obtaining speech samples to those

described above was applied. Altogether 3523 utterances were analysed for

the controls.

Although the control data was cross-sectional rather than longitudinal, it

was drawn from a group of children whose MLU and percent of sentences

longer than 5 covered most of the period of data collection from Y and BT.

Furthermore, the comparisons involved the distribution around the mean

rather than a single mean value (see next section) and thus spanned most of

the developmental phase studied in Y and BT.

Coding and analysis

The complete corpora were coded twice, by two independent coders. Child

utterances were coded according to the CHILDES system (MacWhinney,

1995), supplemented by a special coding system for Hebrew texts (Levy,

1995). Excluded from the coding were imitations, repetitions, game-like

utterances as well as utterances in which there were problems of articu-

lation. The files were later compared and disagreements over coding were

resolved by discussion. Utterances for which agreement could not be

reached were discarded from the analysis. Those constituted 0.8% of Ys

T A B L E 1. Age, number of analysed utterances, MLU and % of utterances

of length 5 and above for Y and BT

Period

AGE

Number of

analysedutterances MLU % utterances5 and longer

Y BT Y BT Y BT Y BT

I 4 ;3.26 3 ;10.20 601 652 1.8 1.8 7.7 6II 4 ;8.05 4 ;2.04 532 407 2.4 2.2 13.5 9.8III 4 ;10.28 4 ;7.01 509 642 2.4 2.1 13.9 11.2IV 5 ;3.16 5 ;0 486 646 2.5 2.3 14.4 10.7V 5 ;8.03 5 ;4.02 604 438 2.8 2.8 16.8 18.7

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and 0.6% of BTs entire corpus. Thus the analysis presented below is based

on instances for which there were complete agreement between the coders.

Coding referred to correct usage as well as to errors and concerned

aspects of morphology, syntax, lexical choices and pragmatics. The coding

of grammatical errors is problematic because of the nonstandard use thatmay be found in colloquial speech and the central role that extralinguistic

context plays in the interpetation of utterances within discourse. Since the

level of education of the childrens parents was comparable to that of the

researchers who did the coding, the coders standards of colloquial speech

were adopted as the baseline for coding decisions.

The errors found in the childrens productions were divided into three

main categories: syntactic, morphological and meaning. This broad division

offered a first-pass impression of the childrens performance, although

dividing errors into these three categories involved some controversialdecisions since certain errors related to more than just one linguistic aspect.

Syntactic errors related to diverse syntactic phenomena such as subordinate

constructions and the relevant functors, agreement, use of accusative

marker /et/, prepositions and ungrammatical subject omissions which are

cases of omissions of third person as well as of subject pronouns with

present tense verbs.6 Errors of morphology included formal errors involving

root consonants, word patterns and inflections. Recall that in Hebrew one

can often distinguish formal morphological from semantic errors.

Errors of meaning related to lexical, semantic and pragmatic aspects ofutterances. For example, errors in word choice, use of incompatible terms and

problems of reference were considered as tapping lexical-semantic prob-

lems. Utterances in which the child used a negative term and immediately

contradicted it by using a positive term that reversed the meaning of the

statement, or instances in which reference could not be determined from

what was actually said were coded as meaning problems. Errors of gender

marking on animate nouns, inappropriate marking of tense, person and

number, and lack of definite marker when definiteness was required, were

likewise counted among the meaning errors. Errors of tense, number,

person and gender were coded as meaning errors when the focus was on the

correct marking of the semantic concept rather than on agreement or on

problems of morphological form.

As for the specific variables, those were chosen from among the variables

studied in TD children, as summarized in the section on Hebrew. Based on

that, the following 12 variables were investigated: error types and percent of

use of Hebrew verbless clauses, percentage of complex sentences, correct

[6] Hebrew has a mixed pattern of subject omission. While subjects can be freely omittedin 1st and 2nd person past and future, omission is ungrammatical in 3rd person past andfuture as well as in all persons in the present tense.



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syntactic agreement, correct use of accusative marker, errors in gender

marking on inanimate nouns, errors of gender on animate nouns, use of past

tense verbs, errors of word choice and pragmatic infelicity.7 While gender

marking on animate nouns, errors of word-choice and pragmatic infelicity

as well as the combined count of meaning errors code for semantic andpragmatic aspects of the childrens speech, the other variables are more

clearly formal-grammatical. Note that the specific variables also count

among the errors in the general categories: the syntactic, morphological and

semantic errors. However, the overlap in the count of errors that result

from this is small, since the broader categories include many more errors of

the relevant types.

Percentages were calculated in the following way: percent of the different

error types was calculated out of the total number of errors committed by

the child; percent of verbless and complex clauses were calculated out of thetotal number of coded utterances for each child. Percent of use of accusative

marker and of agreement were calculated relative to obligatory contexts of

usage. That is, use of /et/ was calculated relative to the number of utter-

ances in which an accusative marker was required, while agreement was

calculated relative to instances of noun (or pronoun)verb combinations.8

Errors of gender on animate and inanimate nouns were calculated out of the

total number of errors of morphology. Percent of past tense was calculated

[7] Pragmatic infelicity relates to cases in which the childs choice of words or constructionwas such that, had the GENERAL CONTEXT been different, that same word or constructionwould have been appropriate. Discourse exchanges in which the child does not respondto the investigators questions and changes the topic inappropriately, exchanges inwhich the childs response indicates lack of understanding of the requirements of theconversation are likewise coded as pragmatically inappropriate.

The following are examples of pragmatically appropriate and inappropriate uses:

Ch : ve-ima ve-aba yiknu lanuand-mom and-dad will buy-pl.3rd to-usAnd mom and dad will buy us

Res: ma?

what?Omission of the direct object results in a grammatical, yet, referentially opaque and thuspragmatically unacceptable sentence.

The following is an example of a pragmatically appropriate exchange:Ch : tavi li uga kazot

bring-3rd, fem.sg me cake like-thisget me a piece of this cake

Res: ze nigmar, mictaeretIts finished, sorry

Ch: az kazotithen like-this, fem.sg.so, like this one

[8] In Hebrew, adjectives and certain prepositions likewise agree with the head noun.However, there were no such instances in the childrens productions.

L E V Y


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out of the total number of verbs used by the child. Errors of word-choice

and errors of pragmatics were calculated out of the total number of errors of

meaning committed by the child.

The mean and standard deviation (S.D.) of the control group provide

measures of the performance and the variance seen in TD children from

period II through V. Y and BT were considered similar to the controls with

respect to a given variable if their achievements were within one S.D. from

the normal mean. In such cases Y and BTs performance was marked y.

If Y and BTs error rates were above one S.D. or their correct performancewas below one S.D., they were considered below the level of the controls,

marked asx. If their performance was above one S.D. and their error rates

were below one S.D., they were considered better than the average normal

child and their performance was marked+. A similar analysis was adopted

in Levy et al. (2000) in which language in children with various neuro-

developmental syndromes was compared to the profile of TD controls.

Conti-Ramsden (1998) and Johnson & Carey (1998) use a comparable

approach in their respective studies. Note that our focus is on a childs

whole profile and the way it compares with the profiles of the controls,rather than on performance on individual variables. By selecting a range of

possible values around the group mean we are picking up the variance

across TD children within the same language levels as Y and BT through-

out the period of the study, correcting for the fact that data from the

controls was cross-sectional, rather than longitudinal.

Findings

Growth in MLU for BT and for Y over the period of the study is presented

in Figure 1. Both children show an increase in MLU of about 1 point

on average during the 18 months of the study, reaching MLU 2.8 in

1.5

1.9

2.3

2.7

3.1

54321

Y

BT

Fig. 1. MLU for Y and BT for periods IV.



14/25

the final session. This level of MLU is achieved by TD children in the

first half of their third year, in other words, about 23 years sooner than Y

and BT.

Note that MLU for the first period of the study for both Y and BT is 1.8,

which is outside the range of the MLU of the TD controls. A comparison

can therefore be drawn between Y and BT and the TD controls in relation

to four out of the five periods of the study.

Table 2 gives the performance of Y on the 12 variables for each of the five

periods of the study along with the means and S.D. of the control group.

Table 3 gives the scores achieved by BT. Appendix 1 gives raw data for

both children. A dividing line is drawn in Tables 2 and 3, between the eight

grammatical variables and the last four variables, which are primarily

T A B L E 2. Language profiles of Y measured on 12 linguistic variables and

their status relative to the mean performance of typically developing controls

Periods 1 2 3 4 5

VariablesControlsmean %

Globalmeasures

Syntactic errors 29.5S.D.=9.56

22.9y

17.9+

17.9+

17.9+

31.5y

Morphology errors 13.6S.D.=8.64

20.5y

12.8y

11.9y

11.0y

8.5y

Specificmeasures

Verbless clauses 12.3S.D.=6.8

14.1y

6.6y

6.2y

6.0y

6.8y

Complex sentences 5.5S.D.=4.9

4.2y

3.3y

5.5y

7.7y

13.5+

Past tense verbs 21.4S.D.=7.65

3

x

30

+

21

y

13

x

16

y

Correct accusative /et/ 6.6S.D.=2.2

6.1y

11.1x

11.8x

12.5x

3.3+

Gender errors animates 3.1S.D.=2.3

0+

0.5+

0.4+

0.4+

1.5y

Agreement errors 8.5S.D.=4.04

16.7x

0+

0+

0+

7.9y

Globalmeasures

Meaning errors 58.2S.D.=11.2

56.6y

69.4y

70.2x

71.1x

60.1y

Specific

measures

Gender errors

inanimates

10.6

S.D.=5.4

7

y

5.4

y

4.9

+

4.4

+

0.7

+

Word choice errors 3.7S.D.=1.2

2.4+

10.2x

11.3x

12.4x

9.7x

Pragmatic errors 8.9S.D.=3.1

17.1x

14.3x

11.0y

7.8y

12.1y

y, within one S.D. from the mean.x, worse than the controls (below/above one S.D. from the mean of TD controls).+, better than the controls (below/above one S.D. from the mean of TD controls).

L E V Y


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semantic. The latter are likely to be affected by the childrens lower than

normal IQ.

Since period 1 is outside the range of MLU of the controls, the com-

parison will focus on periods IIV with occasional reference to period I. For

periods I through IV, Y and BT have a similar percent of verbless clauses as

well as a similar percent of complex clauses as do the controls. This suggests

that the combined measure of MLU along with percent of sentences longer

than MLU 5 is not just measuring length but in fact captures knowledge of

syntax as it is reflected in the use of sentence types. In period V complex

clauses in both children EXCEED the percent seen in the controls.

A consideration of the eight grammatical variables in Table 2 reveal

+ orx signs for Y in 50% of the cells. Table 2 shows 47.5% of the cells for

T A B L E3. Language profiles of BT measured on12 linguistic variables and their

status relative to the mean performance of typically developing controls

Periods 1 2 3 4 5

VariablesControlsmean %

Globalmeasures


15.9+

40.4x

17.4+

18.5+

19.6+

Morphology errors 13.6S.D.=8.64

12.7y

27.9x

13.2y

10.2y

10.1y

Specificmeasures


13.9y

5.1+

8.1y

6.3y

6.9y


2.4y

3.1y

4.2y

5y

10.8+


24

y

22

y

13

x

17

y

26

y

Correct accusative /et/ 6.6S.D.=2.2

11.8x

8.7y

10.5x

0+

0+


0.5+

0+

0+

0.4+

0.9y


0+

7.7y

3.9+

0+

10.2y

Globalmeasures

Meaning errors 58.2S.D.=11.2

71.3x

31.7+

69.4y

71.4x

70.3x

Specificmeasures

Gender errors inanimates 10.6S.D.=5.4

2.9+

7.3y

2.6+

3.2+

1.8+


11.5x

4.8y

15.6x

17x

15.9x


15.3x

5.8y

15x

12.1y

12.3y




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T A B L E 4. Performance of children with ND on 13 linguistic variables and t

(+/x S.D.) of typically-developing co

Children with ND A Mi M B E

Variables

Controls

mean %

Globalmeasures


24y

20y

20y

37y

2y

Morpho errors 13.6S.D.=8.6

7y

19y

24x

8y

1y

Specificmeasures


23.4x

12y

18.8y

15y

5y


1.4y

3.1y

2.3y

7.6y

2y


19y

17y

20y

21y

1x

Correct accusative /et/ 93.4S.D.=12

100y

100y

92.3y

85.7y

9y


4.7y

0y

5.6x

0y

0y


100+

100+

88.2y

100+

10+

Globalmeasures

Meaning errors 58.2S.D.=11

69y

60y

56y

55y

5y

Specificmeasures

Gender errorsinanimates

10.6S.D.=5.4

28.6x

10y

5.6y

6.7y

0+


1.5+

3.4y

3.7y

7.4x

1+


24x

16x

13x

17.2x

8y


302


17/25

BT with+ orx signs. That is, the grammatical profiles of Y and BT differ

from profiles of language matched, TD controls on approximately 50% of

the variables points. Interestingly, 37.5% and 32.5% of the cells respect-

ively, are marked as+, that is, Y and BT were doing ABOVE one S.D. of the

performance of the TD children in over one third of the cases examined.Note that the+/x signs are not confined to certain profiles. However, both

children do not have a single x sign in the final period of the study in any

of the grammatical variables, and BT does not have x signs in the period

IV either.

Within the 8 grammatical variables, accusative /et/, gender of inanimate

nouns and agreement are strictly formal and do not involve semantics to the

extent that, for example, marking past tense does. Throughout the period of

the study the children are either within one S.D. or above the performance

of the controls on those variables, except Y whose errors on accusative /et/exceed one S.D., during periods IIIV.

The differences between the profiles of Y and BT and the controls

were recalculated relative to an interval of 112

S.D. This interval is more

traditionally used to define non-normative performance (Leonard, 1998).

For Y, 22.5% of the cells are still outside the normal range, with 10% being

above the performance of the controls. For BT too, 22.5% of the cells are

outside the normal range, with 12.5% above the performance of the controls

and 10% under.

How does the developmental course of Y and BT compare with profilesof children with other neurodevelopmental disorders (ND)? Table 4 gives

individual linguistic profiles of children with a variety of neurodevelop-

mental disorders and compares them to the profiles of the TD controls. The

data in Table 4 reproduces in part Levy et al. (2000) findings, to which

three more subjects were added (Ta, R and Si). Altogether 11 profiles are

presented. Appendix 2 gives a summary of the childrens neurological

conditions, their IQ levels, their MLU and the number of analysed utter-

ances. Individual profiles are presented and there is no attempt to average

over the group. The range of MLU is 2.22.9 and percent of utterances of

MLU 5 and above is 6.817.3%. Thus the children with ND match Y and

BT in periods II through V.

Similar to Tables 2 and 3, Table 4 divides between the eight grammatical

variables and the four semantic ones. However, unlike Y and BT, when the

first eight variables are considered the performance of the children with

ND, for its most part, is within one S.D. of the mean of the controls. Of the

grammatical variables 19% received either + or x for the 1 S.D. criterion.

The scores that depart from the mean of the controls are found all over the

table and do not characterize specific children. No more than 8% of the cells

that depart from the mean of the TD children received a + sign. Unlike Y

and BT, the children with ND are within one S.D. of the controls on all the



18/25

grammatical variables except agreement, which is the only formal variable

on which five children with ND score better than the TD controls.

Are the linguistic profiles of children with ND more similar to the

profiles of the TD controls than the linguistic profiles of Y and BT? In

order to draw such a comparison, each child with ND was given a scorewhich is the sum of the cells for which there is a y sign for that child. A

maximum score a child could obtain on the full profile was 12. A maximum

score on the grammatical profile was 8. A similar scoring procedure was

applied to profiles IIV for Y and BT. Their overall score was divided

by 4, to obtain the mean number ofy across the periods of the study. The

scores obtained by the children with ND were compared to the mean

scores of Y and BT (MannWhitney, Statistica, release 4.0, Statsoft, Inc).

Both comparisons yielded statistically significant differences (Full profile,

z=2.48 ; p


19/25

phase (as measured by MLU and percent of sentences longer than 5), the

profiles of Y and BT are similar to profiles of TD children. We are interested

in the entire profile rather than in individual variables.

The findings suggest that in periods IIV the profiles of Y and BT

differed on average from the profiles of the controls in 50% of the variablesmeasured at various points in time. Recalculating the differences with

respect to 112

S.D. resulted in a difference in performance on 22% of the

measured variables. The differences are outstanding especially in view of

the far greater similarity to the normal that is seen in the profiles of children

with ND of equivalent MLU, and the statistically significant differences

between the profiles of Y and BT and profiles of children with other ND,

overall, as well as with respect to the grammatical variables.

Does growth in MLU predict grammatical development in Y and BT? In

the first recordings, MLU in Y and BT was lower than that of the controls.However, percent of verbless clauses and complex clauses was within the

normal range for Y and BT during that first period, and performance

on most of the variables was either within or above the range seen in the

controls. While the differences in performance between the children with

WS and the controls in periods IIV are in both directions, the children

outperform the normal controls on 35% of the variables, whereas they are

poorer on just 15% of the variables. Marking gender on inanimate nouns

and agreement, which are formal-grammatical variables, are among the ones

that Y and BT perform the best on. These data suggest that MLU mayunderestimate the childrens grammatical development. This is particularly

suggestive given how similar to the normal are the profiles of children with

other ND.

This conclusion does not hold, however, for the linguistic variables that

are semantic-conceptual where higher than normal error rates have been

observed. This is not surprising given the childrens general cognitive

handicaps. The increased number of errors in word choice is nevertheless

unexpected in view of the reported good vocabularies in children with WS

(Mervis & Robinson, 2000). It is possible that these conflicting results are

due to the different methodologies used. Mervis & Robinson are based on

parental reports, which, while noting usage, are presumably less sensitive to

the accuracy and appropriateness in context of the words that the children

use. When correct usage is the focus of the analysis, the data show that

children with WS perform less well than language matched normal controls.

Did our study uncover atypical trajectories en route to mature linguistic

performance, as predicted by Karmiloff-Smith (1998)? Throughout the

period of data collection, no unusual error types of the kind that are never

encountered in TD children were committed by either Y or BT. The

longitudinal follow up revealed asynchrony between MLU and grammatical

complexity in the first 2 years of the development of grammar. MLU,



20/25

proportion of shorter vs. longer utterances in discourse and amount of

errors and correct use of specific variables were not synchronized in Y and

BT in the same way that they were in TD children.

A possible interpretation of asynchrony is that it signals deviance.

However, issues of timing that are related to the developmental paceof various components of language are so common in neurodevelopmental

disorders (Tager-Flusberg, 1999), and asychrony may be too weak a case to

argue for atypicality. For example, disorders of timing are most clearly seen

in the overall delay in the onset of language which is common in WS as

well as in other neurodevelopmental disorders (Singer-Harris et al., 1997;

Levy et al., 2000). This phenomenon is not considered sufficient evidence

for a deviant trajectory. I suggest that the asynchrony that has been

documented in the current study with respect to individual variables is of

the same nature, involving a unique developmental pace rather than adeviant trajectory.

Support for this view comes from the commonality of atypical timing in

the language of WS at various developmental points. Thomas et al. (2001)

report an overall delay in the acquisition of past tense which is seen in

regular as well as irregular verbs. Paterson et al. (1999) study showed a lack

of advantage for toddlers with WS in word learning over MLU matched

children with Down syndrome who are typically delayed in word acqui-

sition. These unexpected findings reflect an issue of timing of vocabulary

development relative to the expected WS linguistic phenotype.Finally, Jarrold, Baddeley & Hewes (1998) argued that verbal abilities

in WS develop at a higher rate than visual-perceptual abilities and this

difference in rate of development predicted that differences in performance

between those abilities will be seen in older persons and in particular, in

individuals who have reached a higher level of verbal abilities. Differences

among various sub-tests are minimal in individuals with WS who have low

levels of achievements. This conclusion has recently received support in a

longitudinal study of the individuals in Jarrold et al.s (1998) original study

(Jarrold, Baddeley, Hewes & Phillips, 2001).

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A P P E N D I X 1

R A W D A T A F O R T A B L E S 1 A N D 2

Table 1: Raw data for Y

Variables Y 1 Y 2 Y 3 Y 4 Y 5

Syntactic errors 47/205 35/196 37/207 39/218 78/248Morphology errors 42/205 25/196 25/207 24/218 21/248Verbless clauses 116/205 136/196 146/207 155/218 149/248Complex sentences 27/191 14/212 14/224 14/236 20/296Past tense verbs 8/191 5/212 8/224 18/236 40/296Correct accusative /et/ 2/33 4/36 3/22 1/8 1/30Gender errors animates 2/12 0/20 0/23 0/25 3/38Agreement errors 0/68 1/78 1/76 1/74 4/76Meaning errors 13/68 12/78 12/76 11/74 2/76Gender errors inanimates 5/205 80/196 49/207 17/218 24/248Word choice errors 35/205 28/196 28/207 27/218 30/248Pragmatic errors 3/91 39/129 28/136 17/143 31/204

Table 2: Raw data for BT

Variables BT 1 BT 2 BT 3 BT 4 BT 5

Syntactic errors 25/157 42/104 29/167 38/206 27/138

Morphology errors 20/157 29/104 22/167 21/206 14/138Verbless clauses 112/157 33/104 116/167 147/206 97/138Complex sentences 35/252 8/157 19/235 19/300 16/233Past tense verbs 6/252 5/157 10/235 13/300 25/233Correct accusative /et/ 4/34 2/23 2/19 0/19 0/7Gender errors animates 0/29 1/13 1/26 0/56 6/59Agreement errors 1/53 0/60 0/48 1/41 2/43Meaning errors 6/53 14/60 6/48 9/41 4/43Gender errors inanimates 18/157 6/104 26/167 35/206 22/138Word choice errors 24/157 6/104 25/167 25/206 17/138Pragmatic errors 28/117 23/104 16/127 34/191 39/150



24/25

A P P E N D I X 2

T Y P E O F S Y N D R O M E, I Q, M L U, C A A N D S I Z E O F C O R P O R A A N A L Y S E D

F O R T H E C H I L D R E N W I T H N D*

A, B, and Ta have fragile X syndrome; Mi has Sotos syndrome; M and Ehave hydrocephalus; Av and R have left hemisphere infarct; S and Si have

enlarged ventricles and T has left hemiatrophy

child syndrome IQ MLU agetotal

utterances

A fraX **GCI=48verbal=23

2.2 4 ; 8 383

Mi Sotos GCI=50verbal=24

2.5 6 ; 10 376

M Hydroc GCI=

63verbal=35 2.5 3 ; 3 587

B fraX IQ=70verbal=70

2.9 3 ; 5 365

E Hydroc Leiter=58 2.8 3 ; 5 739Av LHInfarct Leiter=60 2.3 4 ;4 530T Left Hemiatrop IQ=69

verbal=752.8 3 ;6 536

S EnlargV Bayley=74 2.4 3 ;6 533Ta fraX Bayley=73 2 :1 2 ;10 564R LHInfarct IQ=70 2 :7 3 ;4 433Si EnlargV Bayley=69 2 :6 3 523

* A, Mi, and M were tested on the McCarthy (1972). B, T and R were tested on theStanford-Binet (1960). E and Av were tested on the Leiter (1969) and S, Ta and Si weretested on the Bayley (1969).** Verbal scores for the McCarthy (1972) have a mean of 50 (S.D.=10) while the GCI has amean of 100 (S.D.=15).

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