DS children's language, which could indeed be interpreted as their language development being different, not sinply delayed, conflicts with much of the vork in this area, although it must be emphasised that this present study eiployed a fairly small sanple size which necessarily tempers any conclusions drawn frcm comparisons of these results with those of other studies. However, the work of Jean Fondai (1978, 1980) has offered substantial, although not exclusive,
support in favour of the Delay hypothesis, at least insofar as DS language development is concerned. His studies have involved matching DS and "normal" children on the basis of MLU (measured in morphemes rather than words) and then comparing other aspects of their syntactic and semantic language. He and his colleagues found many similarities between the 2 groups both in syntactic and semantic development. Ryan (1975) too, in her sample of MLU matched "normal" and DS children likewise found many striking similarities, and more recently, studies by CXvens and MacDonald (1982) and Ctoggins and his associates (Coggins, 1979; Coggins and Morrison, 1981; Coggins and Stoel-Gaimcxi, 1981; Coggins, Carpenter and Owings, 1983) all of which matched DS and nonhandicapped children on the basis of MLU, found few differences between the 2 groups of children and thus lend support to the Delay hypothesis. Fondai concludes in his studies that the similarities in the language of MLU-matched DS and "normal" children attest to the validity of MLU as a measure of language development in ES as in "normal” development.
Nevertheless, both Fondai and Ryan observe that MLU matched "norml" and ES children differ on one variable: that of vocabulary, and in the case of both researchers, the DS children in their
their "normal" controls. This Fondai explains as being due to the DS children being older and having thus had more time to learn vocabulary. Ryan too argues that it is because DS children spend longer at the one word stage and/or because single words are perhaps easier for DS children to learn than syntax.
Neither researcher thus interprets DS children's greater vocabulary abilities over their syntactic abilities - a gap of a magnitude not found in "normal" development - as a difference in development. However it is argued here that it is not sufficient to explain this as due to their increased CA, if this increased CA has not also resulted in better syntactical skills. As Ellis and Cavalier (1982) argue, for the developmental position to hold, resting as it does on the assumption that persons of equal Ml are equal in cognitive level it would have to "posit a trade off between organic maturation and environmental experience. " Given moreover, these aspects of language appear to develop in synchrony in "normal" children, there is little evidence for saying that vocabulary is more easily learned than syntax; and if this is the case in DS children, then this suggests in itself a difference, not merely a delay, in development.
It should be noted that a study by Bririker and Bricker (1980) also examined the relationships amongst component language skills, but in a mixed sample of both nonhandicapped and handicapped preschoolers (the latter having IQs ranging frcm 24 to 69, their retardation being unspxecified by the researchers ). .. This study, like the present one, examined both receptive and expressive abilities for a set of nouns, and receptive abilities for a set of verbs, and
objects (i.e. receptive syntax). Measures also included an 'assessment of subjects' MLU. Using a multiple linear regression analysis to examine their results, these researchers found that whilst MA appeared to account for very little of the variation in MLU, a significant proportion of this could be predicted by the measure of receptive syntax, and vice versa. Of even more interest insofar as this present study is concerned. Drinker and Bricker also report that receptive and productive abilities for verbs did not have any significant predictive value for MLU, although they did so for receptive syntax. In other words, as in this present study, MLU and vocabulary skills seem largely unrelated. Bririker and Bricker' s study, however, involves a very different subject sanple frcm that reported here and indeed, insofar as the results cited here are concerned, Bririker and Bricker ' s study does not differentiate between the developmentally delayed and the nondelayed children in the sanple.
Of more specific interest to the present results is a study by Harris (1983). This study casts further doubt both on the use of MLU to equate DS and "normal" children and on the "Delay" standpoint. In this study vherein DS and "normal" preschoolers were matched on MLU, Harris found not only that the DS children showed a greater variety of vocabulary in their single word utterances (as Fondai's work also shewed) but also that the patterns of correlations between MLU and other measures of leinguage ability were different in the 2 groups of children (a finding to seme extent replicated in this present experiment). Specifically, Harris found that DS children's MLU was positively correlated with linkages of the primary semantic
semantic relations. In contrast, insofar as the norihandicapped children are concerned, he found that MLU positively correlated with the relations of specific locations and with interrogatives and negatives. In other words, the DS and "normal" children in his study appear to be approaching the task of sentence construction in different ways, although they have been equated on the basis of MLU. Thus Harris concluded that MLU does not represent the same linguistic skills for "noriml" and DS children.
It should be noted that Harris does not propose, on the basis of his results, that DS children's language development is different, but rather that it is:
" . . . similar to that of normal children, but with variations in the extent to vhich the different linguistic sub-skills are co-ordinated and synchronised over time"
(Harris, 1983)
Hill and McCune-Nicolich (1980), in studying patterns of DS children ' s symbolic plan and language also comment on their showing greater horizontal and vertical variability (rather than a difference) on Piagetian-type tasks than do "normal" children. This, it will be observed, raises the issue of what precisely constitutes a "difference" in development. Hcurris argues that the asynchrony he observes (and vhich is observed in this present stuiy) cannot be described as "linguistic deviance" and thus cannot support
a Difference position. Spitz (1983) in a critique of the
Developmental (or Delay) position, however, points to the problem in defining "a difference":
". . . It is in fact difficult to imagine vhat a qualitatively different performance wauld look like, since retarded individuals
retarded persons] take in responding to a mentally challenging situation would surely be found scmevhere in the range of human development, even if one had to go back to very early childhood. " Whilst it is not proposed to more fully review the Delay-Difference arguments over this and other similar points (but see, for exanple Zigler and Balia, 1982; Spitz, 1983) it is nevertheless evident that asynchrony of development, as found in this present study and that of Harris (1983), within the perimeters inposed by the present small sample size, casts some doubt on the efficacy of MLU as a DS - "normal" language equating device. Moreover, if as this present study suggests, this asynchrony is partial, with some linguistic sub-skills being correlated as "normal" and others being out of step, then insofar as the Delay-Difference debate is concerned it will be observed that equating children on MLU eind looking at a particular set of these sub-skills may well reveal a Delay finding (as in Rondal's work, for exanple), but if the same sub-skills were examined with "normal" and DS children first being equated on say noun ratio, (a device vhich Goldin-Meadcw et al argue could be used instead of MLU as a gross language measure with young "normal" children), then the results would indicate a Difference. Indeed, insofar as this theoretical debate is concerned, the results here serve to enphasise the need to define more specifically vhat is meant by a Difference between DS and "normal" children before any effective examination of the Delay vs Difference hypotheses can take place.
In sunrnary, therefore, this study provides no evidence of a specific receptive-productive deficit in DS language development, insofar as receptive and productive vocabulary skills are concerned. In comparing it with Goldin-Meadcw* s work on "normal" children, however, it does illustrate a striking asynchrony in development betvreen the different sub-skills of DS children's language, in a way not found in norihandicapped children. This in turn raises the issue of the use of MLU, both as a measure of DS children's linguistic progress and as a language equatdLng device for the matching of DS
and "normal" children. Furthermore, this also questions the
conclusions that can be drawn frcm the many studies using MLU in
investigations of the Delay-Difference debate. Perhaps most
inportantly, however, the findings here enphasise the ocmplexity of the task of adequately assessing the language of the DS child and the risks of the under- or over-estimations of her ability that might result from the use of single, gross measure assessment tools such as MLU or indeed noun ratio. If language intervention is to be effective with IS children then, the evidence here suggests, it must be founded on more complex assessments than those vhich are used for the norihandicapped child.