language Abilities In Williams Syndrome: A Critical...

Language abilities in Williams syndrome:A critical review

JON BROCKUniversity of Oxford, UK

AbstractWilliams syndrome is a rare genetic disorder in which, it is claimed, language abilities are relatively strong despitemild to moderate mental retardation. Such claims have, in turn, been interpreted as evidence either for modularpreservation of language or for atypical constraints on cognitive development. However, this review demonstratesthat there is, in fact, little evidence that syntax, morphology, phonology, or pragmatics are any better than predictedby nonverbal ability, although performance on receptive vocabulary tests is relatively good. Similarly, claims of animbalance between good phonology and impaired or atypical lexical semantics are without strong support. There is,nevertheless, consistent evidence for specific deficits in spatial language that mirror difficulties in nonverbal spatialcognition, as well as some tentative evidence that early language acquisition proceeds atypically. Implications formodular and neuroconstructivist accounts of language development are discussed.

In 1964, von Armin and Engel reported clini-cal observations of six children with infantilehypercalcemia, a developmental disorder thatwe now know as Williams syndrome. The au-thors noted that, despite suffering from severemental retardation, the children possessed “anunusual command of language” ~p. 367!. Fortyyears of research has done little to change thischaracterization of Williams syndrome. Morerecently, for example, Bellugi, Lichtenberger,Jones, Lai, and St. George ~2000, p. 12! statedthat “the general cognitive impairment seen inadolescents and adults with Williams syn-drome stands in stark contrast to their relativestrength in language, their facility and easein using sentences with complex syntax, not

generally characteristic of other mentally re-tarded groups.”

The potential theoretical importance of Wil-liams syndrome has not been lost on research-ers. In particular, the disorder has been widelycited as evidence for the “modularity” of lan-guage. However, the idea that individuals withWilliams syndrome have a “preserved” or “nor-mally developing” language module has beenchallenged by researchers arguing that the lan-guage acquisition process in Williams syn-drome is subtly different to that found in typicaldevelopment. In fact, the evidence to supportall of these claims is somewhat less clear cutthan is often portrayed. Key findings have notalways been replicated, and results are oftendependent on factors such as the choice ofcontrol group or comparison measure. The aimof this paper, therefore, is to provide a criticalreview of empirical findings concerning lan-guage in Williams syndrome and to considertheir implications for theories of languagedevelopment.

The paper begins with a brief overview ofWilliams syndrome, followed by an introduc-tion to the theoretical background and consid-

The preparation of this paper was supported by the Wil-liams Syndrome Foundation ~United Kingdom! and theMedical Research Council. I thank Courtenay Norburyand Kate Nation for comments on the manuscript andChris Jarrold, Jill Boucher, and Teresa McCormack formany useful discussions.

Address correspondence and reprint requests to: JonBrock, Department of Experimental Psychology, Univer-sity of Oxford, South Parks Road, Oxford OX1 3UD,United Kingdom; E-mail: [email protected].

Development and Psychopathology 19 ~2007!, 97–127Copyright © 2007 Cambridge University PressPrinted in the United States of AmericaDOI: 10.10170S095457940707006X

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eration of a number of important conceptualand methodological issues. The main body ofthe review is then divided into sections look-ing at studies of phonological, lexical–semantic, grammatical, and pragmatic skillsin Williams syndrome. The paper concludeswith a discussion of the theoretical implica-tions and directions for future research.

Williams Syndrome

Williams syndrome is a rare genetic disorder.Its prevalence is often quoted as being around1 in 20,000 live births ~Morris, Demsey, Leon-ard, Dilts, & Blackburn, 1988!, although amore recent study revised this estimate to 1 in7,500 ~Strømme, Bjørnstad, & Ramstad, 2002!.The genetic cause of Williams syndrome hasbeen traced to a submicroscopic deletion ofabout 25 genes in the 7q11.23 region of chro-mosome 7 ~Ewart et al., 1993; see Donnai &Karmiloff-Smith, 2000!. This deletion in-cludes the gene ELN, which codes for theprotein elastin ~Lowery et al., 1995! and afluorescent in situ hybridization test for thedeletion of ELN is now routinely used to con-firm clinical diagnoses. In isolation, the dele-tion of ELN is directly linked to the cardiacanomalies associated with Williams syn-drome ~see below!, but does not appear tohave any effects on cognitive development~Gray, Karmiloff-Smith, Funnell, & Tassa-behji, 2006!.

Clinical presentation

The syndrome was first recognized on the ba-sis of medical and physical features, includingcardiac anomalies and hypercalemia ~exces-sive blood calcium levels!, which occurred inassociation with developmental delay and anunusual “elfin” facial profile ~Bongiovanni,Eberlein, & Jones, 1957; Joseph & Parrott,1958; Williams, Barratt-Boyes, & Lowe, 1961;see Morris, 2006; Semel & Rosner, 2003, forrecent reviews!. Perhaps the most commonfeature of Williams syndrome, however, is anabnormal reaction to certain sounds ~Levitin,Cole, Lincoln, & Bellugi, 2005; Marriage,1996; van Borsel, Curfs, & Fryns, 1997!. This

is typically referred to as “auditory hyperacu-sis,” although, in fact, very few individualswith Williams syndrome show enhanced abil-ity to detect low amplitude sounds ~Levitinet al., 2005!. People with Williams syndromeare often described as being extremely friendlyor “hypersociable” ~e.g., Doyle, Bellugi, Koren-berg, & Graham, 2004; Jones et al., 2000!,and show enhanced emotional empathy rela-tive to individuals with other learning dis-abilities ~Tager-Flusberg & Sullivan, 2000!.However, their performance on social reason-ing tasks is no better than predicted by mentalage ~Tager-Flusberg & Sullivan, 2000!.

Neurophysiology

Overall brain volume is reduced in Williamssyndrome. However, when overall volume iscontrolled for, imaging studies have identifiedspecific reductions in parietal regions ~Eckertet al., 2005!, the corpus callosum ~Schmittet al., 2001!, and brainstem ~Reiss et al., 2000!,but a relatively large auditory area ~Holingeret al., 2005! and cerebellum ~Jones et al., 2002!.Recent studies have also identified increasedcortical gyrification and complexity ~Schmittet al., 2002; Thompson et al., 2005! and ab-normal hippocampal shape ~Meyer-Lindenberget al., 2005!. In addition, there is evidence foratypical neuron size and packing ~Galaburda& Bellugi, 2000; Galaburda et al., 2002!.

Overall and nonverbal cognition

The majority of individuals with Williams syn-drome are classified as having mild to moder-ate mental retardation ~e.g., Arnold, Yule, &Martin, 1985; Howlin, Davies, & Udwin, 1998;Mervis, Morris, Bertrand, & Robinson, 1999;Udwin, Yule, & Martin, 1987!. Studies typi-cally show a significant advantage for verbalIQ over performance IQ ~Grant et al., 1997;Howlin et al., 1998; Levy & Bechar 2003;Udwin & Yule 1990; see also Udwin & Yule,1991! or a nonsignificant trend in this direc-tion ~Dall’Oglio & Milani, 1995; Pagon, Ben-nett, LaVeck, Stewart, & Johnson, 1987!.However, the magnitude of this dissociation isrelatively small ~cf. Seashore, 1951!. For ex-ample, in the largest study to date, Howlin

98 J. Brock

et al. ~1998! reported mean verbal and perfor-mance IQs in adults with Williams syndromeof 64.5 and 60.8, respectively.

The verbal IQ advantage is driven, at leastin part, by exceptionally poor performance onvisuospatial construction subtests, in whichparticipants are required to reconstruct a two-dimensional pattern using colored blocks ~seeFarran & Jarrold, 2003!. Indeed, a number ofstudies have shown that visuospatial skills ingeneral are extremely poor in Williams syn-drome. For example, Farran, Jarrold, andGathercole ~2001, 2003! have reported thatperformance on visuospatial construction andmental rotation tasks is significantly poorerthan on the Ravens Colored Progressive Ma-trices, a measure of nonverbal reasoning~Raven, 1993!. Similarly, Mervis and col-leagues have noted that standard scores forthe spatial cluster of the Differential AbilitiesScale ~Elliot, 1990! are much poorer than forverbal or nonverbal scales ~Mervis, Robin-son, Rowe, Becerra, & Klein-Tasman, 2003!,and that these selective visuospatial difficul-ties are both highly specific and virtually uni-versal to Williams syndrome ~Mervis et al.,2000!. Difficulties with numerical cognitionare also frequently noted ~Ansari et al., 2003;Udwin, Davies, & Howlin, 1996!, and there issome evidence that, like visuospatial skills,numerical abilities are poorer than predictedby overall cognition ~Paterson, Girelli, Butter-worth, & Karmiloff-Smith, 2006!.

Theoretical Perspectives

The potential theoretical importance of Wil-liams syndrome was first highlighted by thework of Bellugi and colleagues ~e.g., Bellugi,Marks, Bihrle, & Sabo, 1988; see also Bel-lugi, Lichtenberger, Mills, Galaburda, & Ko-renberg, 1999!. According to the traditionalPiagetian view, language acquisition is predi-cated on cognitive development ~see, e.g.,Piaget, 1963; Shaffer & Ehri, 1980; Sinclairde Zwart, 1967!. However, Bellugi et al. ~1988!argued that Williams syndrome directly chal-lenges this account. In particular, they re-ported the cases of three children with Williamssyndrome, who produced language that was“complex in terms of morphological and syn-

tactic structures” ~p. 183! despite the fact thatthey lacked the supposed cognitive prerequi-sites as measured by performance on Piaget-ian conservation and seriation tasks. Since thispioneering work, Williams syndrome has fre-quently been cited as evidence that languageis independent of cognition or “modular” ~seeAnderson, 1998; Bickerton, 1997; Piatelli-Palmarini, 2001; Pinker, 1994, 1999; Rondal,1994; Temple & Clahsen, 2002!.

The principles of modularity were outlinedby Fodor ~1983, 2000!, who argued that thereare two main types of cognitive systems: non-modular central processing systems and spe-cialized modules that have evolved to handlespecific types of information. Following Chom-sky ~1965, 1988!, Fodor claimed that humanlanguage fits this definition of a module. Themost important characteristic of modules istheir impenetrability to general knowledge andinput from other modules, termed “informa-tion encapsulation.” If, as Bellugi and col-leagues have argued, language is preserved ordevelops normally in Williams syndrome inthe face of intellectual delay, this can be takenas strong evidence for information encapsula-tion and, hence, for the modularity of lan-guage ~cf. Moscovitch & Umilta, 1990!.

An important issue here is the level or“granularity” at which modularity appliesto language ~see Levy, 1996; Thomas &Karmiloff-Smith, 2005!. Fodor ~1983! im-plied that the language system in its broadestsense is modular. However, linguists often ap-ply a narrower definition of “language,” whichincludes only the abstract computational mech-anisms involved in syntax, morphology, andphonology ~see, e.g., Hauser, Chomsky, &Fitch, 2002!. According to Chomsky ~1980!,only these computational aspects of languagecould be considered to be modular. Other re-searchers have gone further, suggesting thatmodularity applies to specific aspects ofgrammar such as morphosyntactic rules ~see,e.g., Pinker, 1999!. Indeed, this confusionis reflected in the literature on Williams syn-drome. For example, Anderson ~1998! sug-gested that Williams syndrome may represent“a classic case in which @the language acqui-sition# module has been spared from the gen-eral brain damage caused by the genetic

Language in Williams syndrome 99

disorder” ~p. 168!, but also conceded that “se-lective sparing might take place . . . at a finergrain than the entire linguistic system” ~p. 169!.

Critics of this modular approach to lan-guage have argued that it ignores the pro-cess of development ~Karmiloff-Smith, 1992;Thomas, 2005a!, and should not, therefore, beapplied to disorders such as Williams syn-drome, which are fundamentally developmen-tal in nature ~see Abbeduto, Evans, & Dolan,2001; Bishop, 1997; Karmiloff-Smith, 1998!.According to the alternative “neuroconstruc-tivist” perspective, linguistic capabilities inWilliams syndrome should not be framed interms of intact ~or normally developed! mod-ules but rather as the product of altered con-straints on cognitive and linguistic development~see, e.g., Karmiloff-Smith, 1998; Karmiloff-Smith, Scerif, & Thomas, 2002!. The clearestevidence for atypical constraints on languagedevelopment is likely to come from studies ofearly language and its precursors in infancy,before compensatory processes can mask theunderlying difficulties ~Karmiloff-Smith &Thomas, 2003!. However, even when individ-uals are able to compensate for their originaldifficulties, residual abnormalities may be re-vealed by closer inspection of the languageprofile or the factors affecting performanceon particular tasks ~Thomas, 2005b!.

Thomas and Karmiloff-Smith ~2003! re-viewed a large body of evidence from studiesof Williams syndrome and put forward a suiteof hypotheses falling under the umbrella of an“imbalance” between phonological and seman-tic processing. Most prominent among thesewere the suggestion that language is overreli-ant on phonological short-term memory ~cf.Grant et al., 1997; Karmiloff & Karmiloff-Smith, 2001; Mervis et al., 1999; Vicari, Car-lesimo, Brizzolara, & Pezzini, 1996! and theclaim that lexical-semantic processing is some-how impaired or atypical ~cf. Rossen, Klima,Bellugi, Bihrle, & Jones, 1996; Temple, Alma-zan, & Sherwood, 2002!. These hypothe-ses were contrasted with what Thomas andKarmiloff-Smith ~2003! termed the “conser-vative hypothesis.” This is effectively a nullhypothesis representing the view that the lan-guage acquisition process is delayed but notfundamentally altered in Williams syndrome

~cf. Tager-Flusberg, Plesa-Skwerer, Faja, &Joseph, 2003!. According to this view, anyunique characteristics of language in Wil-liams syndrome are indirect consequences ofother nonlinguistic aspects of the disorder suchas a strong desire for social interaction andimpaired visuospatial cognition.

Methodological Issues

The aim of this review is to evaluate the em-pirical evidence relevant to the modular orneuroconstructivist accounts of language inWilliams syndrome. Unfortunately, many stud-ies have not reported any statistical analysesof their data, and sometimes have not evenprovided descriptive data. A number of stud-ies have only included data from individualswith Williams syndrome without reference torelevant comparison data, and some frequentlycited studies have not, in fact, ever been pub-lished. Other studies have simply looked atage-equivalent or mental age scores acrossstandardized tests, under the assumption thatsignificant differences in performance are nec-essarily an indication of an uneven cognitiveor linguistic profile. In fact, as Mervis andKlein-Tasman ~2004; see also Bishop, 1997!have forcefully argued, there are a number ofpsychometric reasons why this assumption isfalse. This review is therefore restricted topublished quantitative data that allow one tocompare results across studies and address thetheoretical issues discussed above. However,even within these studies, a wide range ofmethodologies have been adopted, often re-sulting in apparently conflicting findings. Be-fore reviewing the empirical evidence, it is,therefore, important to first consider a num-ber of methodological points.

Williams syndrome group characteristics

The first issue concerns the nature of the Wil-liams syndrome group. Many of the studiesreviewed in this paper have only included asmall sample of individuals with Williams syn-drome. The problem here is that in geneticdisorders, the phenotypic expression is not justthe product of the genetic anomaly. Rather, itis the product of an individual’s entire genetic

100 J. Brock

endowment, combined with their environ-ment, and the complex interaction betweenthe two ~Plomin & Rende, 1991!. On top ofthis genuine individual variation, performanceon a particular test at a particular time is animperfect measure of the underlying compe-tence, so there is also a substantial degree ofnoise in behavioral data ~Bishop, 1997!. Thisis nicely illustrated in a recent study by Porterand Coltheart ~2005!, who reported that indi-viduals with Williams syndrome ~N � 39; agerange � 5– 44 years! showed marked individ-ual variation in their cognitive strengths andweaknesses as measured by performance onvarious subtests of the Woodcock Johnson testbattery ~Woodcock & Johnson, 1990!. In thelight of such findings, case studies and studiesof small groups of individuals with Williamssyndrome should be treated with caution.

A further point to consider is the age rangeof the Williams syndrome group. In theory, itis possible that the cognitive profile in Wil-liams syndrome is different at different ages~see, e.g., Jarrold, Baddeley, & Hewes, 1998!.Unfortunately, however, practical issues in-volved in recruitment mean that large samplesof individuals with Williams syndrome are of-ten heterogeneous in terms of age and devel-opmental level, and this can potentially obscuredevelopmental changes in the cognitive pro-file ~Porter & Coltheart, 2005!. When evalu-ating the studies reviewed in this paper, it is,therefore, important to consider not only thesize of groups tested but also the age range ofthe participants.

Comparison data

The second main methodological issue con-cerns the source of the comparison data. Themajority of studies reviewed in this paper haveemployed a matched control design. The logichere is that, if groups are matched on onemeasure but not another, this suggests a selec-tive strength or weakness ~although see Strauss,2001!. However, the choice of comparisongroup may be critical. Typically developingchildren obviously provide the benchmark for“normal” cognitive profiles, but matchinggroups on any measure of ability introducespotentially confounding group differences in

both age and IQ ~Jarrold & Brock, 2004;Mervis & Klein-Tasman, 2004!. Moreover,some studies have recruited typically develop-ing control groups whose chronological agesmatch the mental ages of the Williams syn-drome group under the assumption thatgroups will be matched on mental age. Un-fortunately, mental age measures are not al-ways particularly accurate and, consequently,groups may not, in fact, be particularly closelymatched ~Bishop, 1997!.

An alternative approach is to include a con-trol group of individuals with other forms oflearning difficulties, who are matched to theWilliams syndrome group for both age andability ~and therefore IQ!. Often, these con-trols all have some other specific developmen-tal disorder such as Down syndrome, or lesscommonly, fragile X or Prader–Willi syn-drome. The concern here is that any groupdifferences could reflect patterns of strengthsand weaknesses in the comparison group asmuch as in the Williams syndrome group. Otherstudies have therefore included a group of in-dividuals with learning disabilities of hetero-geneous origin. In theory, any syndrome-specific profiles in the control group willaverage out, but the makeup of the group isoften opaque so comparison across studies isdifficult.

In sum, there is no obvious best practicewhen recruiting control groups. As such, onecan really only gain an accurate assessment oflanguage in Williams syndrome via the deploy-ment of multiple comparison groups ~cf. Bu-rack, Iarocci, Flanagan, & Bowler, 2004!.Unfortunately, few studies have done this, soone aim of this review is to bring togetherstudies employing various different controlgroups in order to get an idea of the “bigpicture.” With these methodological consider-ations in mind, I begin the review of languagein Williams syndrome by looking at phonology.

Phonology

Phonology refers to the processing of the soundsystem of a language, and is often consideredto be a relative strength in Williams syn-drome. In particular, it has been widely ar-gued that phonological short-term memory


skills represent a “peak ability” ~cf. Merviset al., 1999, 2003!. Studies have also investi-gated whether phonological processing mech-anisms develop atypically, with claims of areduced influence of long-term phonologicaland semantic knowledge on phonologicalshort-term memory.

Speech perception

At the age of 7–8 months, typically develop-ing children learning English appear to primar-ily segment the stream of incoming speech onthe basis of prosodic cues, showing greatersensitivity to strong–weak words ~e.g., “can-dle”! than to weak–strong words ~e.g., “gui-tar”!. By the age of 10–11 months, other cuessuch as the co-occurrence of syllables and pho-nemes in words become more prominent, en-abling children to identify weak–strong words~Jusczyk, Houston, & Newsome 1999; Mattys& Jusczyk, 2001!. However, Nazzi, Paterson,and Karmiloff-Smith ~2003! found that mucholder children with Williams syndrome ~N �17; 15– 48 months! appeared to remain depen-dent on prosodic cues, showing a familiarityeffect to strong–weak words but not to weak–strong words. This finding suggests that theearly development of phonological speech per-ception in Williams syndrome is severely de-layed. By contrast, Böhning, Campbell, andKarmiloff-Smith ~2002! reported that olderchildren and adults with Williams syndrome~N � 13; 10–51 years! performed as well asage-matched controls when required to repeatverb–consonant–verb ~VCV! syllables thatwere presented auditorily, despite the factthat neither group was at ceiling on thistask. Clearly, further research is required todetermine the developmental trajectory ofphonological speech perception in Williamssyndrome.

Speech production

Two small-scale observational studies of tod-dlers with Williams syndrome have investi-gated early speech production in relation tomotor development. In typical development,at approximately the same time that canonical~i.e., repetitive! babbling is first observed, tod-

dlers also demonstrate rhythmic hand banging~Locke, 1993!. This co-occurrence is assumedto signify the development of rhythmic motorcontrol required for both activities ~Ejiri &Masataka, 2001!. Mervis and Bertrand ~1997!reported data from two children with Wil-liams syndrome for whom the onset of bothbehaviors occurred within the same month ~ateither 7 or 8 months!. Similar results werereported by Masataka ~2001!, who followedeight children with Williams syndrome fromthe age of 6 months, and noted that the onsetof rhythmic banging preceded canonical bab-bling by between 0 and 8 months. In addition,there were significant correlations between on-sets of banging, babbling, and first words, butno significant correlations between these mea-sures and any other measures of motor con-trol. The available evidence therefore indicatesa normal relationship between speech produc-tion and motor development.

Clinical reports suggest that older indi-viduals with Williams syndrome have goodspeech, although they may have occasionalproblems with difficult multisyllabic words~Semel & Rosner, 2003!. Udwin and Yule~1990! reported that 84% of children with Wil-liams syndrome ~N � 43; 6–16 years! hadfluid, intelligent speech. Moreover, when 20of these children were compared with learn-ing disabled controls matched on age and ver-bal IQ, they produced a significantly greaterpercentage of utterances that were completeand intelligible. Studies using parental ques-tionnaires have also concluded that speechquality is significantly better among individu-als with Williams syndrome than among age-and nonverbal ability-matched individuals withnonspecific developmental disabilities ~Gosch,Städing, & Pankau, 1994; N � 25; 4–10 years!or age-matched individuals with Down syn-drome ~Laws & Bishop, 2004a; N � 19; 6–25years!.

Phonological short-term memory

Most studies of phonology in Williams syn-drome have looked at performance on phono-logical short-term memory tasks such asimmediate serial recall ~digit and word span!or immediate repetition of polysyllabic non-

102 J. Brock

words ~nonword repetition!. As Table 1 dem-onstrates, individuals with Williams syndromeconsistently perform better on digit and wordspan tasks than individuals with Down syn-drome ~Jarrold, Baddeley, & Hewes, 1999;Klein & Mervis, 1999; Vicari et al., 2004;Wang & Bellugi, 1994!, despite similar orpoorer performance on analogous visuospa-tial memory tasks ~Corsi span!. However,Down syndrome is associated with severe def-icits in phonological short-term memory ~see,e.g., Brock & Jarrold, 2005!, so it may beunwise to treat these findings as evidence forphonological short-term memory strengths inWilliams syndrome. Indeed, the other studiessummarized in Table 1 show that individualswith Williams syndrome perform no better than~and sometimes worse than! typically devel-oping or learning disabled controls matchedon overall mental age, nonverbal ability, orreceptive vocabulary knowledge ~Brock, 2002;Brock, McCormack, & Boucher, 2005; Jar-rold, Cowan, Hewes, & Riby, 2004; Laing,Hulme, Grant, & Karmiloff-Smith, 2001; Ma-jerus, Barisnikov, Vuillemin, Poncelet, & vander Linden, 2003; Robinson, Mervis, & Rob-inson, 2003; Vicari et al., 1996, 2004!.

Performance on these tasks is, in fact, jointlydetermined by phonological short-term mem-ory and by long-term memory for word mean-ing and phonological structure ~see, e.g.,Majerus & van der Linden, 2003!. Studieslooking in more detail at phonological short-term memory have consistently failed to findevidence for atypical effects of “phonologi-cal” factors in Williams syndrome such as wordor nonword length and phonological similar-ity ~Brock, 2002; Grant et al., 1997; Lainget al., 2005; Vicari et al., 1996!. In contrast, anumber of studies have reported evidence forreduced effects of long-term word knowl-edge. Most prominently, Vicari et al. ~1996!observed a reduced effect of word frequencyin Williams syndrome, leading the authors topropose that individuals with Williams syn-drome are “hyperphonological,” relyingexcessively on phonological coding. Comple-mentary results were reported by Majerus et al.~2003!, who noted reduced effects of wordfrequency, lexical status, and phonotactic fre-quency ~the frequency of phoneme combi-

nations in the native language! on theperformance of some individuals with Wil-liams syndrome. Similar conclusions were alsoreached by Karmiloff-Smith et al. ~1997!, whoobserved that individuals with Williams syn-drome were less likely to misrepeat nonwordsas similar-sounding real words, suggesting areduced interfering effect of lexical knowl-edge. However, Brock et al. ~2005! noted anumber of confounds in these studies. For ex-ample, the magnitude of these effects is influ-enced by participants’ familiarity with thestimuli ~cf. Hulme, Maughan, & Brown, 1991!and by their level of overall performance ~cf.Logie, Della Salla, Laiacona, Chambers, &Wynn, 1996!. When these factors were con-trolled for, individuals with Williams syn-drome demonstrated entirely normal effectsof lexical knowledge on phonological short-term memory ~see also Brock, 2002; Grantet al., 1997; Laing et al., 2005!.

Phonological fluency and awareness

Table 2 summarizes the performance of indi-viduals with Williams syndrome on more ex-plicit measures of phonological knowledge.In phonological fluency tasks, participants arerequired to think of as many words as they canthat begin with a specified letter. Volterra, Ca-pirci, Pezzini, Sabbadini, and Vicari ~1996;see also Temple et al., 2002! reported thatchildren with Williams syndrome outper-formed controls on such a task, although theauthors suggested that this finding was prob-ably artifactual given group differences in ageand phonological instruction at school. Thisview is supported by a more recent study byLevy and Bechar ~2003!, who found that chil-dren with Williams syndrome and learning dis-abled controls matched on age as well as IQperformed comparably on a test of phonolog-ical fluency.

Table 2 also summarizes two studies look-ing at performance on tests of phonologicalawareness such as rhyme detection ~identify-ing word pairs that rhyme! and phoneme de-letion ~deleting the initial sound from a word!.Individuals with Williams syndrome actu-ally perform worse than reading ability- orvocabulary-matched typically developing con-


Table 1. Phonological short-term memory

Source N CA Matching Task Finding

Brock ~2002!,Brock et al.~2005!

14 10–17 Receptive vocabularyCA: WS � LD . TD

Digit spanWord span

Probedserial recall

Overall: WS � LD , TDOverall: WS � LD � TDWord-frequency effect:

WS � TD � LDOverall: WS � LD , TDLexicality effect:

WS � TD � LDLexicalization errors:

WS � TD � LDNonword

repetitionOverall: WS � LD � TDNonword length effect:

WS � LD � TDWordlikeness effect:

WS � LD � TDGrant et al.~1997!

15 8–35 Nonverbal reasoning Nonwordrepetition

Overall: WS � TDNonword length effect: WS � TDWordlikeness effect: WS � TD

Jarrold et al.~1999!

16 M � 16.9 Receptive vocabulary,visuospatial

Digit span Overall: WS � TD � LD . DS

constructionaCorsi span Overall: WS , TD, LD, DS

Jarrold et al.~2004!

Receptive vocabularyb Word span Overall: TD .WS, DS

Karmiloff-Smithet al. ~1997!

14 9–27 Receptive vocabulary:WS . TD

Receptive grammar:WS . TD

Nonwordrepetition

Overall: WS . TDLexicalization errors:

WS , TD

Klein & Mervis~1999!

13 9–10 CA, overall MA Digit spanWord span

Overall: WS . DSOverall: WS . DS

Laing et al.~2001!

15 9–28 Receptive vocabulary,nonverbal reasoning

Digit span Overall: WS , TDWord span Overall: WS � TDNonword

repetitionOverall:

WS � TDLaing et al.~2005!

14 11–52 Receptive vocabulary,digit span

Word span Concreteness effect: WS � TD

Majerus et al.~2003!

4c 10–13 Receptive vocabulary Word span Overall: WS , TDLexicality effect: WS � TDWord-frequency effect:

WS , TDPhonotactic frequency effect:

WS , TDRobinson et al.~2003!

39 5–17 Receptive grammar Digit span Overall: WS � TDNonverbal reasoning:

WS � TDNonword

repetitionOverall: WS � TD

Receptive vocabulary:WS . TD

Vicari et al.~1996!

12 M � 9.9 Nonverbal MAd Word span Overall: WS � TDWord length effect: WS � TDWord-frequency effect:

WS , TDVicari et al.~2004!

69 4–30 Overall MA Digit spanCorsi span

Overall: TD .WS . DSOverall: TD .WS � DS

Wang & Bellugi~1994!

10 M � 13.4 CA, full-scale IQ Digit spanCorsi span

Overall: WS . DSOverall: WS , DS

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; DS, Down syndrome; TD,typically developing; LD, learning disabled; CA, chronological age; MA, mental age.aMatching measures controlled for by analysis of covariance.bWord span performance standardized against vocabulary score.cMultiple case study design. All four participants showed normal lexicality effects but two showed a significantlyreduced word-frequency effect and two a reduced phonotactic frequency effect.dTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.

104 J. Brock

trols on such measures ~Laing et al., 2001;Majerus et al., 2003!. It is, however, unclearwhether these findings indicate a genuine pho-nological deficit or simply reflect difficultieswith the conceptual demands of these partic-ular tasks ~cf. Morton & Frith, 1993!.

Summary

Compared to other groups with developmen-tal delay, individuals with Williams syndromeappear to have relatively good speech produc-tion. Moreover, their phonological short-termmemory capabilities are better than those ofindividuals with Down syndrome, althoughthere is little consistent evidence for similarstrengths relative to well-matched typically de-veloping children or individuals with otherforms of learning disability. There is also littlecompelling evidence that phonological skillsare in any way atypical. Having said this, youngchildren with Williams syndrome appear tohave difficulty segmenting the speech streamand this intriguing finding clearly demandsfurther investigation. In addition, very little isknown about the effect of unusual auditoryperception ~hyperacusis! on speech process-

ing ~Majerus, 2004; although see Elsabbagh,Cohen, Cohen, Rosen, & Karmiloff-Smith,2006!.

Lexical Semantics

Lexical semantics refers to knowledge of themeaning of individual words. Vocabularyknowledge is often described as a peak abilityand, superficially at least, provides some ofthe best evidence for linguistic strengths inWilliams syndrome. A number of authors havealso remarked upon the use of unusual or low-frequency words in the everyday conversationof individuals with Williams syndrome ~Bel-lugi et al., 1988; Rossen et al., 1996; Udwinet al., 1987; Udwin & Yule, 1990!. These andother findings have led to the suggestion thatlexical-semantic processing is impaired or issomehow atypical ~see Rossen et al., 1996;Temple et al., 2002; Thomas & Karmiloff-Smith, 2003!.

Vocabulary knowledge in young children

The acquisition of first words is severely de-layed in Williams syndrome. For example,

Table 2. Phonological fluency and awareness

Source N CA Matching Finding

Laing et al. ~2001! 15 9–28 Receptive vocabulary,nonverbal reasoning,reading MA

Phoneme deletion: WS , TDRhyme detection: WS � TDRhyme production: WS � TDSpoonerisms: WS � TDSyllable identification: WS � TDPhoneme identification: WS � TD

Levy & Bechar ~2003! 7 7–15 CA, full-scale IQ Phonological fluency: WS � LDMajerus et al. ~2003!a 4 10–13 Receptive vocabulary Minimal pair discrimination:

WS , TDRhyme judgment: WS , TDPhoneme deletion: WS , TD

Temple et al. ~2002!b 4 11–15 Overall MAc Phonological fluency: WS . TDVolterra et al. ~1996! 17 5–15 Nonverbal MAc Phonological fluency: WS . TD

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; TD, typically developing; LD,learning disabled; CA, chronological age; MA, mental age.aMultiple case study design. All four participants showed significant impairments on minimal pair and rhyme tasks.Only three were impaired on phoneme deletion.bMultiple case study design. Three out of four participants showed significantly enhanced phonological fluencyrelative to controls.cTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.


Mervis et al. ~2003! reported that, whereastypically developing children acquire a 10-word vocabulary by around 12–13 months~Fenson et al., 1993!, this milestone is de-layed on average until 28 months in Williamssyndrome ~N � 13!. However, attempts toquantify early linguistic competence suggestthat the delay is no greater than one wouldpredict on the basis of global cognitive delay.For example, Paterson, Brown, Gsödl, John-son, and Karmiloff-Smith ~1999! found thattoddlers with Williams syndrome or Down syn-drome, and typically developing childrenmatched on mental age demonstrated compa-rable receptive vocabulary knowledge as in-dexed by their tendency to look at a namedobject.

Complementary findings come from stud-ies using the MacArthur Communication De-velopment Inventory ~MCDI; Fenson et al.,1993!, a questionnaire measure of early lin-guistic competence ~see Table 3!. Lexicalknowledge is assessed by asking parents tocomplete a checklist indicating words that theirchild understands or produces. Singer-Harris,Bellugi, Bates, Jones, and Rossen ~1997! notedthat age-matched toddlers with Williams syn-drome and Down syndrome produced and un-derstood similar numbers of words, althoughthis finding is problematic because childrenwho were at ceiling on this measure were ex-cluded from the analysis ~Mervis & Robin-son, 2000!. Subsequently, Mervis and Robinson~2000! reported slightly larger vocabularies inWilliams syndrome. However, when match-ing is undertaken on the basis of mental age,

studies have reported comparable vocabularyknowledge in children with Williams syn-drome, children with Down syndrome, andtypically developing children ~Laing et al.,2002; Vicari, Caselli, Gagliardi, Tonucci, &Volterra, 2002!. Singer-Harris et al. ~1997! alsoused normative data from typically develop-ing children to directly compare comprehen-sion and production. Interestingly, childrenwith Williams syndrome produced signifi-cantly more words than one would predict onthe basis of their comprehension, although asimilar trend was also found in the Down syn-drome group.

Factors influencing vocabulary acquisition

Typically developing children are able to usemultiple cues to determine the meanings ofwords ~see, e.g., Bloom, 2000!. For example,they often infer that when an adult names anobject, it refers to the object that they areattending to rather than any other ~e.g., Bald-win, 1991!. Györi, Lukács, and Pléh ~2004!reported that 12 out of 14 individuals withWilliams syndrome ~9–22 years! were able touse the direction of the experimenter’s eyegaze to determine which of two novel objectshad been named. However, two studies sug-gest that younger children with Williamssyndrome have difficulty achieving “joint at-tention.” Laing et al. ~2002! reported that, com-pared with mental age matched typicallydeveloping controls, toddlers with Williamssyndrome ~N �13; 17–55 months!were poorerat initiating joint attention, either by making

Table 3. Early vocabulary knowledge as indexed by the MacArthur CommunicationDevelopment Inventory

Source NCA

~months! Matching Finding

Vicari et al. ~2002! 12 M � 59 Nonverbal MA Production: WS � TD � DSMervis & Robinson ~2000! 24 24–36 CA Production: WS . DSLaing et al. ~2002! 13 17–55 Overall MA Comprehension: WS � TD

Production: WS � TDSinger-Harris et al. ~1997! 32 M � 34 CA Comprehension: WS � DS

Production: WS � DS

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; DS, Down syndrome; TD,typically developing; CA, chronological age; MA, mental age.

106 J. Brock

eye contact between the tester and a toy or bypointing. The Williams syndrome group alsoshowed fewer points to animated dolls andwere less able to follow the experimenter’spoints. Similarly, Mervis and Bertrand ~1997!found that children with Williams syndrome~N � 8! were unable to respond appropriatelyto pointing gestures from adults and, unliketypically developing infants ~cf. Messer, 1994!,did not use pointing before they labeled ob-jects verbally. However, the authors noted thatthe caregivers of toddlers with Williams syn-drome often compensated for their children’sdifficulties by establishing shared attention inanother way, either by physically touching theobject before naming it or by simply namingan object that the child was already attendingto.

Other studies of Williams syndrome havelooked at the relationship between vocabularyacquisition and cognitive development. In typ-ically developing children, there is a rapid in-crease in the rate of vocabulary learning ataround 18 months ~Nelson, 1973; althoughsee Ganger & Brent, 2004!. It has been sug-gested that this “vocabulary spurt” is accom-panied by fundamental changes in cognitiveprocesses underlying word learning ~Nazzi &Bertoncini, 2003!. For example, by the age ofapproximately 18 months, children can de-duce that a novel word refers to an object forwhich they do not already have a name, so-called “fast mapping” ~Mervis & Bertrand,1994!. They also begin to show “spontaneousexhaustive sorting,” organizing objects by cat-egory membership when asked to “fix themup” ~Gopnik & Meltzoff, 1987!. Finally, by20 months of age, typically developing chil-dren are able to form name-based categories,inferring that visually dissimilar novel objectsgo together if they are given the same name~Nazzi & Gopnik, 2001!. However, Mervisand Bertrand ~1997! noted that six of seventoddlers demonstrated neither fast mapping norspontaneous exhaustive sorting until after theonset of their vocabulary spurt ~defined as anincrease of at least 10 new words every twoweeks!. Similarly, Nazzi and Karmiloff-Smith~2005; see also Nazzi, Gopnik, & Karmiloff-Smith, 2005! noted that children with Wil-liams syndrome ~N �12; 33–82 months! were

unable to form name-based categories, de-spite having expressive vocabularies that weremuch larger than those of typically develop-ing 20-month-olds.

These findings have been interpreted as ev-idence for atypical language acquisition pro-cesses in Williams syndrome. Given that thereare multiple cues to word meaning ~Bloom,2000!, such a view appears overstated, al-though there may be a subtle shift in the bal-ance of factors that determine vocabularyacquisition in Williams syndrome. More im-portantly, these findings clearly challenge anystrong claims based on data from typicallydeveloping children that there are necessaryconditions for vocabulary development.

Vocabulary knowledge in older childrenand adults

Table 4 shows the performance of older chil-dren and adults on various measures of vocab-ulary knowledge. On receptive vocabularytests, participants are presented with sets offour pictures, and are required to indicate whichpicture corresponds to a spoken word. Studiesusing a range of control groups have almostuniversally found that individuals with Wil-liams syndrome perform better on such tasksthan would be expected on the basis of overallmental age, nonverbal reasoning abilities, orvisuospatial construction skills ~Bellugi, Bihrle,Jernigan, Trauner, & Doherty, 1990; Clahsen,Ring, & Temple, 2004; Jarrold et al., 1999;Robinson et al., 2003; Vicari et al., 2004; al-though see Klein & Mervis, 1999; Volterraet al., 1996!. This vocabulary advantage isnicely illustrated by data collected by Brock,Jarrold, Farran, and Laws ~2006!, who testedlarge groups of typically developing andlearning disabled children to map out the de-velopmental relationship between receptive vo-cabulary, age, and nonverbal reasoning ability.They were then able to show that the recep-tive vocabulary knowledge of adolescents withWilliams syndrome ~N � 21; 10–17 years!was better than predicted by their chronolog-ical age and nonverbal ability. In contrast,individuals with Down syndrome had signifi-cantly poorer receptive vocabulary scores thanpredicted.


It is noticeable, however, that this vocabu-lary advantage is less clear cut on other mea-sures of lexical knowledge. For example,although Udwin and Yule ~1990! found thatchildren with Williams syndrome were betterable than controls to give definitions for words,Bellugi et al. ~1990! found no group differ-ences. More compelling are the findings fromnaming tasks in which participants are simplyasked to provide the names of depicted ob-jects or actions. Individuals with Williams syn-drome perform no better than mental agematched controls ~Bello, Capirci, & Volterra,2004! and consistently perform worse than onreceptive vocabulary tests ~Clahsen et al., 2004;Lukács, Pléh, & Racsmány, 2004; Thomaset al., 2006; Vicari et al., 2004; Volterra et al.,1996!.

One possibility is that receptive vocabu-lary tests overestimate genuine word knowl-edge in Williams syndrome ~Temple et al.,2002!. Indeed, in a recent study, Clahsen et al.~2004! found that children with Williams syn-drome outperformed controls on a traditionalreceptive vocabulary test but performed worse

than controls on a modified vocabulary test inwhich the target and distracters on each trialwere drawn from the same semantic categoryand more fine-grained semantic knowledge wastherefore required. It is noteworthy, however,that receptive vocabulary tests also appear tobe relatively insensitive to language difficul-ties in other disorders such as Down syn-drome, specific language impairment, anddyslexia ~Laws & Bishop, 2004b; Snowling,van Wagtendonk, & Stafford, 1988!, althoughvocabulary knowledge is not usually betterthan predicted by mental age.

Vocabulary acquisition and phonologicalshort-term memory

Work by Baddeley and colleagues ~see, e.g.,Baddeley, Gathercole, & Papagno, 1998! showsthat phonological short-term memory is highlycorrelated with receptive vocabulary knowl-edge in children, and appears to play a criticalrole in the learning of phonological word forms.One suggestion, therefore, has been that chil-dren with Williams syndrome rely exces-

Table 4. Vocabulary knowledge

Source N CA Matching Results

Bello et al. ~2004! 10 9–13 Overall MA Naming: WS � TDBellugi et al. ~1990! 6 10–17 CA, full-scale IQ Receptive vocabulary: WS . DS

Definitions: WS � DSClahsen et al. ~2004! 7 10–16 Overall MAa Receptive vocabulary: WS . TD

Naming: WS , TDJarrold et al. ~1999! 16 M � 16.9 Visuospatial construction Receptive vocabulary: WS . LD, TDKlein & Mervis ~1999! 11 9–10 CA, overall MA Receptive vocabulary: WS � DSLukács et al. ~2004! 15 7–19 Receptive vocabulary Naming: WS , TDRobinson et al. ~2003! 39 5–17 Receptive grammar

Nonverbal reasoning:WS � TD

Receptive vocabulary: WS . TD

Temple et al. ~2002! 4 11–15 Overall MAa Naming: WS , TDb

Thomas et al. ~2006! 16 12–53 Receptive vocabulary Naming Accuracy: WS , TDNaming Speed: WS , TD

Udwin & Yule ~1990! 20 M � 10.3 Verbal IQ, CA Definitions: WS . LDVicari et al. ~2004! 69 4–30 Overall MA

Receptive grammar:WS � TD . DS

Receptive vocabulary: WS . TD � DSNaming: WS � DS , TD

Volterra et al. ~1996! 17 5–15 Nonverbal MAa Receptive vocabulary: WS � TDNaming: WS , TDReceptive grammar: WS , TD

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; DS, Down syndrome; TD,typically developing; LD, learning disabled; CA, chronological age; MA, mental age.aTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.bMultiple case study design. Two out of four children with Williams syndrome performed significantly worse thancontrols.

108 J. Brock

sively on phonological short-term memoryduring language acquisition ~Grant et al., 1997;Mervis et al., 1999, 2003; Vicari et al., 1996!.This could not only explain why receptive vo-cabulary is a relative strength but would alsobe consistent with the view that the meaningsof word are less well understood. However,as noted earlier, claims that phonologicalshort-term memory is particularly strong inWilliams syndrome appear to be withoutfoundation.

There is, in fact, relatively little direct ev-idence for an unusual relationship betweenvocabulary knowledge and phonological short-term memory in Williams syndrome. Barisni-kov, van der Linden, and Poncelet ~1996!reported the case of CS, a 20-year-old womanwith Williams syndrome, who performed aswell as age-matched controls on a nonwordlearning task that patients with acquired pho-nological short-term memory impairments areunable to complete ~cf. Baddeley, Papagno,& Vallar, 1988!. Subsequently, Grant et al.~1997! reported that the pattern of correla-tions between receptive vocabulary knowl-edge and nonword repetition in individualswith Williams syndrome ~N � 17; 8–35 years!was reminiscent of that found in typically de-veloping 4-year-olds who were argued to relyheavily on phonological short-term memoryto learn words ~Gathercole, 1995!. However,Brock ~2002; N � 14; 10–17 years! failed toreplicate this finding, and noted that compar-ing correlational patterns in typically devel-oping and developmentally delayed groups isproblematic given the very different ageranges.

Semantic fluency

Motivated by observations of unusual worduse of people with Williams syndrome, Bel-lugi et al. ~1990! investigated lexical-semanticprocessing by means of a semantic fluencytask. When asked to provide as many exam-ples as they could of a given category ~in thiscase, animals!, children with Williams syn-drome produced more responses than childrenwith Down syndrome. The authors also notedthat children with Williams syndrome gavemore atypical responses. This finding has been

widely cited but, although a number of exam-ples were given ~e.g., “chihuahua,” “ibex”!,the authors did not include any formal analy-ses of the frequency or typicality of responses.Moreover, as Table 5 shows, most subsequentstudies have found comparable levels of over-all performance in individuals with Williamssyndrome and, where reported, there is no ev-idence for group differences in the typicalityor frequency of responses ~Jarrold, Hartley,Phillips, & Baddeley, 2000; Johnson & Carey,1998; Levy & Bechar, 2003; Lukács et al.,2004; Rossen et al., 1996; Scott et al., 1995;Volterra et al., 1996!. Interestingly, individu-als with Williams syndrome appear to pro-duce more repetitions than controls ~Jarroldet al., 2000; Lukács et al., 2004!, indicatingthat they may have difficulties monitoring orinhibiting previous responses. If anything, thishighlights the difficulty of using a task withclear strategic and executive components as ameasure of underlying semantic processing ~seeJarrold et al., 2000!.

Homonym processing

A second study widely cited as evidence foratypical semantic processing in Williams syn-drome was conducted by Rossen et al. ~1996!,who investigated processing of ambiguouswords. Participants were presented with threewords: a target homonym ~e.g., “bank”! andtwo words related to its two different mean-ings ~e.g., “money” and “river”!. They werethen asked to decide which two words wenttogether. Compared with typically developingcontrols, children with Williams syndrome~N � 6; 10–18 years! showed a reduced biastoward pairing the homonym with its morecommon associate. The authors interpreted thisfinding in terms of atypical activation of itemsin the lexicon. However, group-matching pro-cedures are unclear, and it is possible that thechildren with Williams syndrome simply hadgreater knowledge of the alternative mean-ings ~cf. Norbury, 2005!. Indeed, Rossen et al.reported that, when asked for definitions ofthe words and then prompted for a secondmeaning, the children with Williams syn-drome were more able than controls to pro-duce the second definition.


Semantic priming

Neville, Mills, and Bellugi ~1994! investi-gated semantic processing in Williams syn-drome using event-related potentials ~ERPs!.Participants heard or read sentences that wereeither congruent or contained an anomalousfinal word. Compared with normative datafrom typically developing individuals, thosewith Williams syndrome ~N � 7; 10–20 years!showed increased late positive ERP responsesto auditorily presented words that were con-gruent with the preceding sentence. In all otherconditions, their ERPs were apparently nor-mal. The authors interpreted their results asevidence for increased semantic priming inthe auditory modality. Unfortunately, how-ever, no formal statistical analyses were re-ported, so it is difficult to be sure how reliablethese findings are and, to this author’s knowl-edge, no published studies have attempted toreplicate these findings. In a subsequent be-

havioral study, Tyler et al. ~1997! reportedthat individuals with Williams syndrome ~N �12; 14–30 years! showed normal semanticpriming effects. Responses were significantlyfaster to words that were preceded by a func-tionally related word ~e.g., “sweater, warm”!or a categorically related word ~e.g., “mouse,hamster”! than they were when the precedingword was unrelated.

Summary

Research on semantic knowledge and process-ing in Williams syndrome paints a somewhatconfusing picture. Overall, the available evi-dence suggests that young children with Wil-liams syndrome have vocabularies that are nobetter or worse than one would expect basedon their nonverbal abilities. By adolescence,however, performance on receptive vocabu-lary tests is a definite strength. Although this

Table 5. Performance on semantic fluency tasks

Source N CA Matching Category Findings

Bellugi et al. ~1990! 6 10–17 CA, full-scale IQ Animals Total: WS . DSJohnson & Carey ~1998! 10 11–32 Receptive vocabulary Animals Total: WS � TDJarrold et al. ~2000! 13 8–28 Receptive vocabulary Animals,

body partsTotal: WS � LDTypicality: WS � LDFrequency: WS � LDRepetitions: WS . LD

Levy & Bechar ~2003! 7 7–15 CA, full-scale IQ Animals,kitchen items

Total: WS � LD

Lukács et al. ~2004! 12 7–19 Receptive vocabulary Animals,clothes, drink,food, furniture,musicalinstruments,occupations,reading material

Total: WS � TDTypicality: WS � TDFrequency: WS � TDRepetitions: WS . TD

Rossen et al. ~1996! 6 10–18 CA, full-scale IQ Animals, food Total: WS . DSFrequency: WS � DS

Scott et al. ~1995! 11 9–10 CA, full-scale IQ Animals Total: WS � DSTypicality: WS � DSFrequency: WS � DS

Temple et al. ~2002! 4 11–15 Overall MAa AnimalsThings in a house

Total: WS � TDTotal: WS . TDb

Vicari et al. ~2004! 69 4–30 Overall MA Animals, clothing,food

Total: WS � TD � DS

Volterra et al. ~1996! 17 5–15 Nonverbal MAa NA Total: WS � TD

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; DS, Down syndrome; TD,typically developing; LD, learning disabled; CA, chronological age; MA, mental age; NA, not available.aTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.bMultiple case study design. Three out of four children with Williams syndrome performed significantly better thancontrols.

110 J. Brock

provides the first evidence consistent withclaims that language in Williams syndrome isrelatively good, it is important to note that thisadvantage is not found on other measures ofvocabulary knowledge. Researchers have at-tempted to explain why naming abilities arerelatively poor but, arguably, a more pertinent~and still unanswered! question is why recep-tive vocabulary is a strength.

Studies of young children with Williamssuggest that they have difficulty achieving jointattention and are unaware of various princi-ples of word use and category membership.Consequently, they may have to rely moreheavily on other cues to word meaning. How-ever, studies of semantic processing in olderindividuals has failed to find convincing evi-dence of any residual abnormalities resultingfrom compensatory strategies. This, of course,leaves unexplained why so many authors haveremarked upon unusual word usage in every-day conversations. One suggestion that de-serves further investigation is that unusualwords are a pragmatic device, used by indi-viduals with Williams syndrome as a tool togain attention and mediate social interactions~Thomas et al., 2006!.

Grammatical Abilities

Grammatical abilities can be broadly dividedinto syntax and morphology. Syntax refers tothe rules of the language system that specifythe combination of words in sentences, whereasmorphology denotes the use of grammaticalaffixes that mark, for example, tense, number,and ~in some languages! gender. Individualswith Williams syndrome are often describedas having “perfect” syntax and morphology~e.g., Bickerton, 1997; Piatelli-Palmarini, 2001;Pinker, 1999!. However, such claims are lessremarkable when one considers that typicallydeveloping children have mastered most syn-tactic structures by the age of 3 to 4 years ~cf.Crain & Pietroski, 2002; Pinker, 1994! andthat, by adolescence, most individuals withWilliams syndrome have mental ages wellabove this level ~cf. Karmiloff-Smith, 1998!.Critical to this debate, then, are studies look-ing at the emergence of grammatical com-petence in young children with Williams

syndrome and studies of more complex syn-tax in older individuals with Williams syn-drome. A further issue addressed in this sectionis whether or not syntax and morphology areacquired normally. In particular, it has beensuggested that superficially good grammati-cal abilities in Williams syndrome may be aconsequence of good auditory memory androte learning as opposed to intact grammaticalskills ~e.g., Karmiloff & Karmiloff-Smith,2001; Karmiloff-Smith et al., 1997!.

Early grammatical development

Surprisingly few studies have looked at earlygrammatical development in Williams syn-drome. Of these, most have used the Wordsand Sentences Scale of the MCDI ~Fensonet al., 1993!, which assesses the grammaticalcomplexity of children’s utterances by askingparents to indicate which of two phrases bestresembles their child’s output ~e.g., “Medi-cine, no!” or “I don’t want any medicine”!.The most comprehensive of these studies wasconducted by Vicari et al. ~2002!, who tested12 Italian-speaking children with Williams syn-drome ~mean age � 4.9 years!, 12 youngertypically developing children, and 12 slightlyolder children with Down syndrome. The threegroups were matched on nonverbal mental ageand, according to the MCDI, had comparablevocabularies. However, the children with Wil-liams syndrome and the typically developingcontrols produced utterances of comparablecomplexity, whereas individuals with Downsyndrome produced somewhat simpler utter-ances. These findings were corroborated by anumber of laboratory-based measures of gram-matical competence including estimated meanlength of utterances, verbal comprehension,and repetition of sentences.

Comparable results have been reported instudies of English-speaking children. Singer-Harris et al. ~1997! used normative data forthe MCDI to show that children with Wil-liams syndrome ~N � 27; mean age � 45months! demonstrated a normal relationshipbetween the number of different words theyused and the complexity of sentences they pro-duced. In contrast, the grammatical complex-ity of children with Down syndrome was much


poorer than predicted by their lexical reper-toire. Similar results were also reported byMervis et al. ~2003!, who followed 22 chil-dren with Williams syndrome longitudinally,starting on average at 26 months. Finally,Mervis et al. ~1999! coded the utterances of39 2- to 12-year-olds with Williams syndromeusing the Index of Productive Syntax ~Scar-borough, 1990!. In contrast to children withDown syndrome, fragile X, or autism ~Scar-borough, Rescorla, Tager-Flusberg, Fowler, &Sudhalter, 1991!, those with Williams syn-drome showed a normal relationship betweensyntactic complexity and mean length ofutterances.

In sum, the available evidence suggests that,in contrast to other developmental disorders,the early stages of language development inWilliams syndrome are characterized by a nor-mal relationship between grammatical com-plexity, vocabulary knowledge and mental age.However, there is no evidence that syntaxemerges any earlier than would be predictedon the basis of general cognitive and lexicaldevelopment.

Comprehension of grammar

A number of studies have shown that adoles-cents and adults with Williams syndrome per-

form at or close to ceiling on tests evaluatingthe comprehension of syntactic structures suchas binding ~e.g., “Is Mowgli tickling him-self?”! and passives ~e.g., “The teddy ismended by the girl”; Bellugi et al., 1990; Clah-sen & Almazan, 1998; Ring & Clahsen, 2005;see Table 6!. This is in stark contrast to theperformance of individuals with Down syn-drome. However, where studies have includedtypically developing children of similar men-tal age to those with Williams syndrome, thesecontrols have also been close to ceiling onthese tests. It is therefore difficult to draw anyfirm conclusions from these studies regardinggrammatical strengths or weaknesses in Wil-liams syndrome.

A number of studies have looked at perfor-mance on the Test for Reception of Grammar~TROG; Bishop, 1989! or the Grammar Com-prehension Test ~Rustioni, 1994; see Table 6!,in which participants are presented with fourpictures and are simply required to point tothe one that corresponds to a spoken phrase.Despite the absence of ceiling effects, perfor-mance is still no better ~and sometimes poorer!than predicted by nonverbal or overall mentalage and is significantly poorer than receptivevocabulary knowledge ~Robinson et al., 2003;Vicari et al., 2004; Volterra et al., 1996;Zukowski, 2001!. Nevertheless, individuals

Table 6. Comprehension and production of grammar

Source N CA Matching Finding

Bellugi et al. ~1990! 6 10–17 CA, full-scale IQ Comprehension of passives: WS . DSComprehension of negation: WS . DSComprehension of conditionals: WS . DSSentence completion: WS . DSSentence correction: WS . DS

Grant et al. ~2002! 14 8–31 Receptive vocabulary:WS . TD

Repetition of relative clause sentences:WS , TD

Ring & Clahsen ~2005! 10 M � 12.6 Overall MAa Comprehension of actives: WS � TDComprehension of passives: WS � TD

Robinson et al. ~2003! 39 5–17 Receptive grammar Receptive vocabulary: WS . TDNonverbal reasoning: WS � TD

Vicari et al. ~2004! 69 4–30 Overall MA Receptive grammar: TD � WS . DSSentence repetition: TD .WS . DS

Volterra et al. ~1996! 17 5–15 Nonverbal MAa Receptive grammar: WS , TDZukowski ~2001, 2004! 10 10–16 Overall MA Receptive grammar: WS , TD

Elicited production of relative clauses:WS , TD

Elicited production of questions: WS � TD

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; DS, Down syndrome; TD,typically developing; CA, chronological age; MA, mental age; NA, not available.aTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.

112 J. Brock

with Williams syndrome again outperformthose with Down syndrome ~Vicari et al.,2004!.

Karmiloff-Smith et al. ~1997! suggestedthat individuals with Williams syndromehad particular difficulties with blocks of theTROG testing complex embedded clauses.However, these items are also most difficultfor typically developing children ~Bishop,1989!. Indeed, Phillips, Jarrold, Baddeley,Grant, and Karmiloff-Smith ~2004! foundthat individuals with Williams syndrome~N � 32; 8–38 years! performed no worsethan typically developing children andlearning disabled controls on these blocks ofthe TROG despite being matched on overallperformance.

Some authors have argued that tests suchas the TROG underestimate grammatical com-prehension in Williams syndrome because per-formance is influenced by other factors suchas word-retrieval and memory capabilities~e.g., Clahsen & Almazan, 1998; Schaner-Wolles, 2004!. Karmiloff-Smith et al. ~1998!attempted to address these concerns using an“on-line” test of syntactic processing in whichparticipants were asked to simply monitor spo-ken sentences for a target word. Like adultcontrols, individuals with Williams syndrome~N � 8; 15–35 years! showed slower reactiontimes when the target word was preceded bya violation of word order ~e.g., “new the test”!or auxiliary markers ~e.g., “was have themilk”!. However, only the control adults weresensitive to violations of subcategory struc-ture ~e.g., “struggle the dog”!. Although thisstudy highlights the potential utility of on-line tests of grammatical competence, few con-clusions can be drawn because it is unclearwhether language- or mental age matchedcontrols would show the same pattern ofperformance.

Productive grammar

Productive grammar is often evaluated by ask-ing participants to repeat sentences that varyin syntactic complexity. Grant, Valian, andKarmiloff-Smith ~2002! found that individu-als with Williams syndrome performed worsethan typically developing 6-year-olds when

required to repeat complex relative clause sen-tences, despite having higher receptive vocab-ulary scores. Subsequently, Vicari et al. ~2004!reported that individuals with Williams syn-drome performed more poorly than mental agematched typically developing controls on asentence repetition task, although both groupsoutperformed individuals with Down syn-drome. Unfortunately, in these studies, it isdifficult to rule out the possibility that poorperformance is a consequence of verbal mem-ory difficulties rather than a specific syntacticdeficit.

Volterra et al. ~1996! used a sentence rep-etition test with 17 Italian children ~5–15years!. Only 9 were able to complete thetask, but these children produced a number ofunusual syntactic and morphological errors.Similar findings were reported by Capirci,Sabbadini, and Volterra ~1996! in a case studyof a young Italian girl with Williams syn-drome. No quantitative analyses were re-ported in either study, but the authors notedthat the errors were unlike those produced byyounger typically developing children. Con-sequently, these two studies have frequentlybeen cited as prime evidence that languagedoes not develop normally in Williams syn-drome. Given their potential theoretical impor-tance, it is surprising that they have not beenfollowed up in studies with larger groups ofindividuals with Williams syndrome and othercomparison groups.

Finally, Zukowski ~2004! investigated pro-ductive syntax in two studies using scenariosdesigned to elicit the relevant syntactic struc-tures. Relative clause production was evalu-ated by requiring participants to identify oneof two similar objects ~e.g., “the cow that theboy is pointing to”!. Children with Williamssyndrome made more errors than mental agematched typically developing controls. How-ever, 9 of the 10 participants were able toproduce at least one correct relative clausesentence, suggesting that the structures werein their grammatical repertoire but their im-plementation was often disrupted. In thesecond study, Zukowski ~2004! prompted par-ticipants to conduct a telephone interview witha pretend celebrity. Children with Williamssyndrome and typically developing controls


were able to ask affirmative questions, butshowed similarly poor overall performancewhen prompted to ask negative questions.Moreover, error patterns for negative ques-tions were similar across groups. For exam-ple, both groups made auxiliary-doubling errors~e.g., “Who did you didn’t invite to the party?”!but never doubled the wh- phrase ~e.g., “Whodidn’t you invite who to the party?”!. Zukowski~2004! noted that, because there are few nat-urally occurring situations requiring such neg-ative questions, neither correct nor erroneousresponses could have been learned by rote.This, she argued, provided evidence that syn-tax develops normally in Williams syndromeand is not excessively reliant on rote learning~cf. Karmiloff & Karmiloff-Smith, 2001!.

Production of grammatical gender

The idea that individuals with Williams syn-drome have “intact” language was challengedby Karmiloff-Smith et al. ~1997! in a study ofFrench gender assignment. Cues to the genderof known and unknown objects were providedby the article ~un or une! or the phonologicalendings of words ~e.g., words ending in -inare typically masculine whereas those endingin -ine are usually feminine!. Participants wereprompted to produce the definite article andcolor adjective ~both of which are marked forgender! and, across all conditions, individualswith Williams syndrome ~N �14; 9–27 years!performed worse than typically developingcontrols, despite having higher scores for vo-cabulary and grammatical comprehension.Their difficulties were particularly marked onnovel objects, leading Karmiloff-Smith et al.~1997! to suggest that, unlike typically devel-oping children, they have difficulty extractingthe underlying morphological system and relyon rote learning of article0noun pairs. How-ever, the authors also noted that difficultiesmay arise because phonological cues are notcompletely reliable ~see also Clahsen & Alma-zan, 1998!. To address this issue, Levy andHermon ~2003! conducted similar studies inHebrew, in which gender marking is more reg-ular than in French. Unfortunately, neither par-ticipants with Williams syndrome nor controlswere able to comply with task demands.

Regular and irregular morphology

Most studies of morphology in Williams syn-drome have focused on the distinction be-tween regular and irregular morphology,typically by asking participants to completesentences such as “Every day I go to the park.Yesterday I . . .” According to current linguis-tic theories ~e.g., Pinker & Ullman, 2002!,regular morphology involves the use of rules~e.g., add the -ed suffix to create the pasttense of a verb!, whereas irregular morphol-ogy ~e.g., the past tense of “go” is “went”!requires the use of specific lexical knowl-edge. Table 7 summarizes studies of regularand irregular morphology in Williams syn-drome. A first key point to note is that indi-viduals with Williams syndrome have neverbeen found to perform significantly better thanmental age matched controls, either on regu-lars or irregulars. Some studies have foundthat they perform better on regulars than ir-regulars ~Bromberg, Ullman, Marcus, Kelly,& Levine, 1995; Clahsen et al., 2004; Pléh,Lukács, & Racsmány, 2003! or show signifi-cant impairments relative to controls on irreg-ulars but not on regulars ~Clahsen & Almazan,1998; Penke & Krause, 2004; Zukowski,2005!, suggesting a dissociation between in-tact rule use and impaired lexical knowledge~e.g., Clahsen & Almazan, 1998; Pinker, 1999!.However, studies large enough to employmixed designs have found no evidence for aninteraction between group and regularity~Thomas et al., 2001; Zukowski, 2005!. More-over, all of the studies in Table 7 are subjectto ceiling effects, with almost all participantsperforming at or close to 100% on regulars.Significant group differences for regulars arethus virtually impossible, so it is inappropriateto talk of selective impairments for irregulars~or, alternatively, to rule out this possibility;see Bishop, 1997; Strauss, 2001!. Further re-search with younger participants whose per-formance is not subject to ceiling effects isthe only way to address this issue.

A number of these studies have also lookedat the ability to apply morphological rules tonovel words, but the results have been ex-tremely varied. In their past tense studies,Clahsen and colleagues ~Clahsen & Almazan,

114 J. Brock

1998; Clahsen et al., 2004! reported that, whenconfronted with novel verbs that rhymed withexisting irregulars ~e.g., “crive,” which rhymeswith “drive”!, children with Williams syn-drome were significantly more likely than con-trols to regularize the past tense, suggesting atendency to over apply morphological rules.Thomas et al. ~2001! attempted to replicate thesefindings but found that, rather than overregu-larizing the novel verbs, individuals with Wil-liams syndrome tended to leave novel verbsunmarked. Finally, Zukowski ~2005! found nosignificant group differences in the ability toproduce plurals for novel “regular” nouns.

Spatial grammar

The contrast between the language abilities ofindividuals with Williams syndrome and their

visuospatial construction skills is often por-trayed as evidence for a dissociation betweenlanguage and cognition. However, visuospa-tial deficits in Williams syndrome appear tobe mirrored by specific difficulties with gram-matical constructs involving spatial or rela-tional terms. For example, Lukács et al. ~2004!found that Hungarian children with Williamssyndrome ~N � 12; 7–19 years! performedworse than typically developing controls on atest of spatial morphology, despite outperform-ing controls on nonspatial morphology. Simi-larly, Landau and Zukowski ~2003! askedindividuals with Williams syndrome ~N � 12;7–14 years! and mental age matched controlsto describe a series of brief video scenes in-volving moving objects such as a cup jumpingonto a frog’s head. Although there were noreliable group differences in describing the

Table 7. Regular and irregular inflectional morphology

Source N CA Matching Task Findings

Bromberg et al. ~1995! 4 M � 18 NA English plurals WS: regulars . irregularsWS: regulars . irregulars

English past tense WS: regulars . irregularsWS: regulars . irregulars

Clahsen & Almazan ~1998!,Clahsen et al. ~2004!

9 10–16 Overall MAa English past tense Regulars: WS � TDIrregulars: WS , TDNovel regulars: WS � TDNovel irregulars: WS , TD

Penke & Krause ~2004!,Krause & Penke ~2002!

5 15–19 Verbal MAa German past tense Regulars: WS � TDIrregulars: WS , TD

German plurals Regulars: WS � TDIrregulars: WS , TDb

Pléh et al. ~2003! 14 6–20 Receptivevocabularya

Hungarian plurals WS: regulars . irregularsTD: regulars . irregulars

Thomas et al. ~2001! 18 11–53 Verbal MAa,c English past tense Overall: WS , TDNo significant group by

regularity interactiond

Novel regulars andirregulars: WS , TD

Zukowski ~2001, 2005! 12 8–16 Overall MA English MA: WS � TDRegular plurals: WS � TDIrregular plurals: WS , TDNo significant group by

regularity interactionNovel regulars: WS � TD

Note: N, the number of participants with Williams syndrome; WS, Williams syndrome; TD, typically developing; CA,chronological age; MA, mental age, NA, not available.aTypically developing children’s chronological ages matched the mental ages of those with Williams syndrome.bThis result was only significant when two participants who performed well on irregulars were removed from theanalysis.cMatching variable controlled for by covariation.dClahsen and Temple ~2003! reanalyzed this data, noting that individuals with Williams syndrome performed signif-icantly worse on irregular past tense than typically developing 6-year-olds. They argued that this was evidence for aspecific deficit in irregulars. However, they failed to report that, on this analysis, the individuals with Williamssyndrome were also impaired on regulars ~Michael Thomas, personal communication!.


type of motion ~e.g., “fall,” “hop”!, individu-als with Williams syndrome were more likelyto omit the ground object and had more diffi-culty describing the path of the figure object.

Phillips et al. ~2004! found that individu-als with Williams syndrome ~N � 32; 8–38years! made more errors than typically devel-oping and learning disabled controls on blocksof the TROG involving spatial terms, despitebeing matched on overall performance. In afollow-up experiment, these authors used amodified version of the TROG containingmany more spatial terms. The groups wereclosely matched on nonspatial terms, but in-dividuals with Williams syndrome showed sig-nificantly poorer comprehension of spatialitems. Intriguingly, however, those with Wil-liams syndrome also had difficulties on non-spatial items that involved comparatives ~e.g.,“The frog is darker than the hen”!. Phillipset al. ~2004! therefore suggested that difficul-ties with spatial terms and with nonspatialcomparatives may reflect an underlying dif-ficulty in mapping language onto mentalmodels.

Summary

The grammatical skills of individuals with Wil-liams syndrome have received a great deal ofattention in recent years, perhaps because sup-posed strengths and weaknesses in syntax andmorphology speak most directly to modulartheories of language. However, although thereis evidence that individuals with Williams syn-drome have better grammatical comprehen-sion skills than those with Down syndrome,comparison with data from typically develop-ing children indicates that their grammaticalabilities are no better than one would predicton the basis of overall cognitive abilities ~atany stage of development!. This is true whetherone considers composite measures of gram-matical abilities such as the TROG or focusesonly on specific tests of syntax or morpholog-ical rules. As such, there really is no basis forciting Williams syndrome as evidence for themodularity of syntax or morphology. Indeed,far from showing that language and generalcognition can develop independently, the evi-dence for parallel deficits in visuospatial cog-

nition and language arguably demonstrate theprecise opposite.

In general, there is also very little evidencethat syntax or morphology develop atypically.Studies of young children with Williams syn-drome suggest a normal relationship betweensentence complexity and both lexical reper-toire and mean length of utterance. There isalso little firm evidence to support the claimthat individuals with Williams syndrome relyexcessively on rote learning when acquiringgrammatical structures. Having said that, thereare reports that Italian children with Williamssyndrome produce grammatical errors thatare extremely rare in typical development,and these findings clearly demand furtherinvestigation.

Pragmatics

The final linguistic domain considered in thisreview is pragmatics, which can be broadlydefined as the use of language within a socialcontext. Included under the umbrella of prag-matics are, for example, the ability to workout what a communicative partner knows orneeds to know, knowledge and adherence torules of conversational engagement, and theability to communicate nonverbally. In theirseminal paper, von Arnim and Engel ~1964!reported remarkably good pragmatic skillsamong children with Williams syndrome. Sim-ilarly, Karmiloff-Smith, Klima, Bellugi, Grant,and Baron-Cohen ~1995! noted that indi-viduals with Williams syndrome performedrelatively well on tests of pragmatic skills.However, other researchers have noted an “old-fashioned and formal style of speech,” a ten-dency to talk incessantly about irrelevant topicsand ask persistent questions, poor turn takingand topic maintenance, and failure to provideadequate information in responses ~Meyerson& Frank, 1987; Semel & Rosner, 2003; Sto-janovik, Perkins, & Howard, 2001; Udwinet al., 1987!.

Conversational and narrative skills

In a recent study, Laws and Bishop ~2004a!gave the Children’s Communication Check-

116 J. Brock

list ~CCC; Bishop, 1998! to the parents of 19children and young adults with Williams syn-drome ~6–25 years!. Pragmatic skills were re-ported to be much poorer than in a comparisongroup of younger typically developing chil-dren, despite the fact that both groups wererated as having similar syntactic abilities. Infact, inspection of standardized scores re-vealed significant impairments on all five ofthe pragmatic subscales of the CCC: coher-ence, stereotyped conversation, inappropriateinitiation, conversational context, and devel-opment of conversational rapport. Moreover,when compared to individuals with Down syn-drome or specific language impairment, thosewith Williams syndrome showed significantlybetter syntax but significantly greater impair-ments on the stereotyped conversation and in-appropriate initiation subscales.

Similar pragmatic anomalies have beennoted in laboratory-based studies looking atlanguage production either during conversa-tions or during narrative tasks, in which par-ticipants are required to describe a storypresented in a picture book ~see Table 8!. Twostudies ~Reilly, Losh, Bellugi, & Wulfeck,

2004; Stojanovik, Perkins, & Howard, 2004!have found that, when compared with chil-dren with specific language impairment, thosewith Williams syndrome are impaired on mea-sures of narrative and integration: this de-spite having similar structural language.Another consistent finding is that children withWilliams syndrome make fewer inferences ofmotivations and mental states than controls~Reilly et al., 2004! but make greater use ofsocial engagement devices and inferences ofemotions ~Reilly, Harrison, & Klima, 1995;Reilly et al., 2004; see also Jones et al.,2000!.

Udwin and Yule ~1990! argued that a sub-stantial minority of individuals with Williamssyndrome can be classified as producing“cocktail party speech,” a term often used todescribe children with spina bifida and hydro-cephalus ~Swisher & Pinkser, 1971!. Criteriafor cocktail party speech includes fluentspeech, an overfamiliar manner, and a ten-dency to introduce irrelevant personal experi-ences, use social phrases, fillers, or commitperseverations to a noticeable degree. In a sam-ple of 43 children with Williams syndrome

Table 8. Performance on measures of narrative and conversation

Source N CA Matching Task Findings

Reilly et al.~1995!

10 M � 15.8 CA, overall IQ Biographicalinterview

Affective states: WS . DSEmphatic markers: WS . DSEvaluative comments: WS . DSCharacter speech: WS . DS

Reilly et al.~2004!

36 5–13 CA Narrative Story length: WS � SLI , TDMorphological errors: WS � SLI , TDSyntax complexity: WS � SLI , TDThematic maintenance: WS , TD � SLISocial engagement: WS . SLI . TDCognitive inferences: WS , SLI � TD

Stojanoviket al. ~2004!

5 7–12 Verbal MA Narrative Grammatical markers: WS � SLISyntax complexity: WS � SLIConjunctive ties: WS , SLI

Udwin & Yule~1990!

20 10.3 ~2.6! CA, verbal IQ Conversation Range of communicative functions:WS � LD

Frequency of different language functions:WS � LD

Repetitiveness: WS � LDStereotypy: WS � LDIdioms: WS . LDSocial phrases: WS . LDFillers: WS . LD

Note:N, thenumberofparticipantswithWilliamssyndrome;WS,Williamssyndrome;DS,Downsyndrome;TD, typicallydeveloping; LD, learning disabled; SLI, specific language impairment; CA, chronological age; MA, mental age.


~6–16 years!, Udwin and Yule ~1990! reportedthat around 30% met these criteria, a similarpercentage to that found in children with hy-drocephalus ~Anderson & Spain, 1977!. More-over, compared with children with other formsof developmental disorder, those with Wil-liams syndrome were more likely to fulfillthese criteria ~see Table 8!.

Comprehension of figurative language

Understanding figurative or nonliteral lan-guage can be considered a pragmatic skill be-cause it requires an appreciation of the contextin which an utterance is made ~see, e.g., Nor-bury, 2004!. Semel and Rosner ~2003! sug-gested that many children with Williamssyndrome are able to appreciate and use anal-ogies, metaphors, similes, and idioms. Unfor-tunately, only one study of figurative languagecomprehension in Williams syndrome hasincluded relevant comparison data: Sullivan,Winner, and Tager-Flusberg ~2003! compared16 children with Williams syndrome ~8–17years!, Prader–Willi syndrome, or nonspe-cific learning difficulties. Groups werematched on chronological age, and had sim-ilar receptive vocabulary and nonverbal abil-ities. Participants heard stories in which theprotagonist made a false statement, but fewchildren in any group were able to differen-tiate between lies and jokes, with almost allfalse statements considered to be lies. Ofgreater interest, children with Williams syn-drome made significantly fewer references tomental states in justifying their responses. Theyalso showed a trend toward poorer perfor-mance on second-order knowledge questions~e.g., “Does Frank know that his grandfatherknows that he did not clean up the dishes?”!.These findings are clearly preliminary, andthere could be several explanations for poorperformance on these linguistically demand-ing tasks. Nevertheless, they appear to pro-vide further evidence for pragmatic difficultiesassociated with Williams syndrome.

Gestures and body language

Children with Williams syndrome are de-scribed as being sensitive to nonverbal cues

such as gestures, facial expressions, and bodylanguage. They are also reported to give fre-quent nonverbal feedback such as smiling,nodding the head, and using gestures to ex-press their reactions ~Semel & Rosner, 2003!.Again, however, few studies have actuallylooked directly at the use of gestures in Wil-liams syndrome. Singer-Harris et al. ~1997!reported that young children with Williamssyndrome produced significantly fewer ges-tures than those with Down syndrome, de-spite having similar oral vocabularies ~N �32; mean age � 34 months!. In contrast, Belloet al. ~2004! reported that slightly older chil-dren with Williams syndrome ~N � 10; 9–13years! made more use of gestures during apicture-naming task than either chronological-or mental age matched typically developingchildren.

Summary

Compared with other aspects of language, therehas been relatively little research on pragmat-ics in Williams syndrome, so the conclusionsreached here are necessarily tentative. Never-theless, there is converging evidence suggest-ing that children with Williams syndromeexhibit a number of pragmatic anomalies dur-ing conversational interactions. As noted ear-lier, individuals with Williams syndrome areoften described as being extremely sociableand affectionate, and social communication isclearly important for them. This is perhapsreflected, not only in the amount of speechproduced, but also in the excessive use of eval-uative and emotional terms and engagementdevices. Individuals with Williams also ap-pear to have difficulties understanding theinformational requirements of their conversa-tional partner. This may reflect greater diffi-culties in more “cognitive” social situations~cf. Tager-Flusberg & Sullivan, 2000!. In-deed, studies reviewed in this section also pointto relative difficulties in inferring mental states,both during narrative tasks and when interpret-ing nonliteral language.

In some ways, the pragmatic difficulties ofindividuals with Williams syndrome are rem-iniscent of those encountered by people withindividuals with autism ~see, e.g., Lord & Paul,

118 J. Brock

1997!. However, although there are interest-ing parallels between autism and Williams syn-drome, it is clear that most individuals withWilliams syndrome are not autistic, and it isimportant to point out that there is currentlyno evidence for specific impairments in socialcognition in Williams syndrome. Neverthe-less, further research is clearly required intothe links between the pragmatic skills andsocial cognition of people with Williamssyndrome.

General Discussion

Summary

Williams syndrome has played an importantrole in theoretical debates concerning lan-guage and language development. Unfortu-nately, as this review has illustrated, theempirical evidence to support many of theclaims made about Williams syndrome is lessthan straightforward. Having said this, it isstill possible to draw a number of relativelydefinitive conclusions about language devel-opment in Williams syndrome.

Looking first at early language develop-ment, it is certainly true to say that the emer-gence of language is severely delayed, butthere is no evidence to suggest that this delayis any greater than expected on the basis ofgeneral cognitive delay. Moreover, the avail-able evidence suggests that grammatical de-velopment proceeds in accordance with lexicaldevelopment, a contrast to the relative delayin the emergence of complex grammar in Downsyndrome. There is, nevertheless, some evi-dence to suggest that early language develop-ment is not entirely normal. Infants withWilliams syndrome are able to acquirevocabulary despite deficits in joint attentionand without possessing supposedly necessarycategory-based reasoning abilities. In addi-tion, there is some tentative evidence that in-fants with Williams syndrome have difficultieswith aspects of speech discrimination, and thatyoung Italian children with Williams syn-drome make somewhat atypical syntactic andmorphological errors.

Studies of adolescents and adults with Wil-liams syndrome reveal a similar pattern of

overall performance to that found earlier indevelopment. Individuals with Williams syn-drome consistently outperform controls withDown syndrome on tests of phonology andsyntax. However, studies with typically de-veloping or learning disabled controls sug-gest that language as a whole in Williamssyndrome is broadly in line with overall ornonverbal mental age. There are, however, anumber of exceptions to this general rule of“normal” mental age-appropriate language.First, across studies with different controlgroups and matching measures, individualswith Williams syndrome consistently outper-form controls on receptive vocabulary tests.Second, comprehension and production of spa-tial language is extremely poor. Third, prag-matic skills are unusual: individuals withWilliams syndrome are often verbose, makeexcessive use of evaluative language, havedifficulties providing the correct amount ofinformation, and appear to find nonliteral lan-guage problematic.

Theoretical implications

The supposed linguistic strengths of individ-uals with Williams syndrome have often beenused as evidence for the modularity of lan-guage. However, as the summary above sug-gests, there is actually very little evidence toshow that language is even a relative strength.The single exception here is receptive vocab-ulary knowledge, but it is important to recog-nize that this finding is inconsistent with anymodular account of language: either all lan-guage abilities should be relatively good, orcomputational aspects ~syntax, phonology butnot vocabulary! should be preserved. It hasalso been argued that Williams syndrome ischaracterized by modular preservation of mor-phological and syntactic rules. However, in-dividuals with Williams syndrome have neverbeen found to perform better than typicallydeveloping controls of comparable mental ageon any tests of syntax or morphology, nor isthere any convincing evidence for a dissoci-ation between lexical and rule-based gram-mar. In sum, there is precisely no sustainableevidence for a “preserved” language module


in Williams syndrome at any level of speci-ficity or “granularity.” Until such evidence isuncovered, researchers should refrain from cit-ing Williams syndrome as evidence for themodularity of language.

In contrast to modular accounts, neurocon-structivists have attempted to explain appar-ent linguistic strengths in Williams syndromein terms of atypical constraints on develop-ment as opposed to selectively preserved mod-ules. The absence of any evidence for suchlinguistic strengths means that this accountrequires some revision. Nevertheless, it is, ofcourse, still possible that language abilities inWilliams syndrome develop in an atypicalfashion without being particularly strong. Asnoted above, there is some evidence for atyp-ical early language development, especiallyfrom studies looking at joint attention andcategory-based reasoning abilities. However,there is little evidence that the “end state” oflanguage development is abnormal. In par-ticular, there is scant support for Thomasand Karmiloff-Smith’s ~2003! “phonology–semantics imbalance” hypothesis in any ofits guises. Instead, the available evidence ap-pears to be broadly consistent with the “con-servative hypothesis.” In other words, anyunusual characteristics of language such aspoor spatial language and pragmatic difficul-ties can be explained as indirect conse-quences of other nonlinguistic features of thedisorder.

Somewhat remarkably then, despite grossabnormalities of brain structure, severe delaysin language acquisition, and possible abnor-malities of early language development, theend state of language in Williams syndrome~at least in the narrow sense! appears to berelatively normal. Seen in this light, the sig-nificance of Williams syndrome is not that itdemonstrates how language can develop inde-pendently of cognition, or that it provides anexample of a radical departure from normallanguage development. Rather, Williams syn-drome illustrates quite how robust the lan-guage acquisition process is. In any complexsystem ~including language!, robustness isachieved through redundancy, ensuring thatsubtle malfunctioning of a component is notcatastrophic for the system ~Kauffman, 1995!.

Thus, for example, the fact that there are mul-tiple cues to word meaning ~cf. Bloom, 2000!means that, even if young children with Wil-liams syndrome appear unable to use one ormore of these cues, this does not prevent themacquiring language.

Although this view of language devel-opment in Williams syndrome differs fromboth the modular and neuroconstructivist ac-counts, it is perhaps consistent with a com-promise proposal recently put forward byThomas and Richardson ~2006! that unitesthese two perspectives. These authors sug-gested that the emergence of the modular lan-guage system in adults is the product ofdevelopment ~cf. Karmiloff-Smith, 1992!.However, they conceded the possibility thatthe constraints guiding emergence may notbe fundamentally altered by the kinds of ge-netic mutations found in developmental dis-orders such as Williams syndrome ~cf. Temple& Clahsen, 2002!.

Directions for future research

Throughout this paper I have suggested a num-ber of potentially interesting avenues for fu-ture research, investigating specific issues forwhich the available data are not yet conclu-sive. For instance, further research is war-ranted into issues related to the developmentof speech perception and the possible effectsof atypical auditory perception ~“hyperacu-sis”! and the emergence of syntax. Perhapsmost importantly, the development of prag-matic skills in Williams syndrome remains farfrom understood.

I have also pointed out a number of meth-odological pitfalls that future studies shouldattempt to avoid. These include, for example,concerns with ceiling effects, small samplesizes, broad age ranges, and reliance on men-tal age scores. Many of these difficulties stemfrom practical considerations involved in con-ducting research in a relatively rare disorder.However, given the increasing awareness ofWilliams syndrome among practitioners andthe consequent greater availability of partici-pants, these methodological concerns shouldnow be easier to avoid. In addition, the use ofstatistical approaches such as “developmental

120 J. Brock

regression” ~see Jarrold & Brock, 2004;Karmiloff-Smith et al., 2004! can, in theory,allow the researcher to test relatively hetero-geneous groups and at the same time deter-mine the extent to which factors such asage and overall ability contribute to taskperformance.

More generally, a recurring theme in thispaper has been the need for research directlycomparing different developmental dis-orders. Many studies have compared indi-viduals with Williams syndrome and Downsyndrome, but an obvious and importantquestion that remains unanswered is whylanguage ~narrowly defined! appears to de-velop relatively normally in Williams syn-drome but is severely impaired in Downsyndrome. These group differences are par-ticularly salient in studies of phonology andsyntax, although it is unclear whether there isany causal relationship between these twoareas of difficulty ~Jarrold, Purser, & Brock,2006!. Addressing these issues should pro-vide important insights into the factors influ-encing both typical and atypical languagedevelopment.

Researchers have tended to look for differ-ences between developmental disorders, butsimilarities may also be informative ~Bishop,1997!. Earlier, I touched upon similarities be-tween the pragmatic difficulties faced by in-dividuals with Williams syndrome and thoseassociated with autism. Other researchers haveargued that, like individuals with Williams syn-drome, those with nonverbal learning disabil-ity ~Karmiloff-Smith & Thomas, 2003; seeRourke, 1987!, Velocardiofacial0Di Georgesyndrome ~Bearden, Wang, & Simon, 2002!,and fragile X syndrome ~see, e.g., Cornish,Munir, & Cross, 1999! also show a disso-ciation between language and visuospatialcognition. Future research looking at the cor-respondences as well as subtle differences be-tween these different syndromes ~cf. Scerif,Cornish, Wilding, Driver, & Karmiloff-Smith,2004! may help tease apart the causal factorsthat lead to comparable behavioral manifesta-tions of very different genetic and neurologi-cal abnormalities.

A final issue that has not really beentouched upon thus far is the nature of indi-

vidual differences within Williams syndrome.As Dykens ~1995, p. 523! has pointed out,the behavioral consequences of genetic abnor-malities are probabilistic and simply repre-sent “the heightened probability or likelihoodthat people with a given syndrome will ex-hibit certain behavioral and developmentalsequelae relative to those without the syn-drome.” Much of the individual variation incognitive and linguistic studies is genuinenoise, representing random fluctuations in, forexample, attention, motivation, or knowledgeof particular stimuli that are being used at aparticular time. However, there is also likelyto be genuine individual variation, not just inoverall performance across tasks but in rela-tive strengths and weaknesses across do-mains ~cf. Porter & Coltheart, 2005!. Byignoring individual variation, one passes upon the opportunity to investigate why someindividuals with Williams syndrome show aparticular profile of abilities, whereas otherswith the same deletion do not. Put anotherway, the fact that an individual has Williamssyndrome needs to be treated as but one of anumber of factors that may or may not influ-ence their performance on the particular mea-sure of interest.

Conclusions

To conclude, it appears that many of the claimsmade concerning language abilities in Wil-liams syndrome have been somewhat over-stated. There is currently little evidence forselective preservation of linguistic skills inWilliams syndrome. Similarly, claims of un-usual patterns of linguistic strengths and weak-nesses in older children and adults appear tobe largely without foundation, although stud-ies of young children with Williams syn-drome provide some tentative evidence foratypical language acquisition processes. Nev-ertheless, Williams syndrome remains a fas-cinating condition that can provide importantinsights into the processes of language andcognitive development, particularly when seenin the broader context of other developmen-tal disorders.


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