Language and Down's Syndrome - An approach to the acquisition of grammar in the mentally retarded

Content

I. Introduction

II. Down Syndrome – An overview
i. What is Trisomy 21? –A brief history
ii. Physical and cognitive consequences

III. Language of children with Down syndrome
i. General problems in speech
ii. Suggestions for Individual differences

IV. Morphosyntax in Individuals with Down Syndrome
i. General morphosyntactic problems
ii. The acquisition of grammatical morphemes

V. Conclusion

VI. Bibliography

I. Introduction

The acquisition of language has been a field of study rather new to research, emerging only in the middle of the last century. Among scholars it has been of great interest how people acquire their first language and there have been a great number of controversies what some of the suggested hypotheses are concerned. Another fairly interesting issue, as opposed to normal language acquisition, is the study of people who acquire language even though they are faced with quite particular learning conditions. These people, precisely those who suffer from mental retardation, usually do acquire language; however, this language seems to diverge from the one acquired by typically developing individuals. The present paper will discuss the linguistic problems of individuals with Down syndrome (DS), a genetic disorder, occurring in groups of any social or educational level. It is considered to be the “most common cause of moderate to severe learning disability in childhood”. (Buckley 2000: 10) Approximately one in 700-900 babies is born with Trisomy 21 by mothers of any age. (cf. Buckley 2000: 9-10)

The study of Down syndrome children in particular, offers several advantages. Due to their physiognomy, subjects with Down syndrome are fairly easy to identify. In addition, language impairment in DS individuals represents a very prominent feature of this group. In this paper, a brief overview on some of the keyfacts shall be given first of all in order to understand the general problems typical of this genetic disorder. Second, the difficulties in speech production will be discussed in relation to physiological and cognitive consequences. The last chapter will deal with the acquisition of morphosyntax in DS individuals as opposed to the grammar in typically developing subjects and will, additionally, consider one particular approach as an account for the apparent differences – the Critical Period Hypothesis.

II. Down Syndrome – An overview

i. What is Trisomy 21? –A brief history

In 1866, a London physician, called John Langdon Down, started to make first steps in investigating a phenomenon, well-known today, under the term Down’s syndrome. Down, being the pioneer in this field of study, introduced the term Mongolism due to the fact that individuals suffering from this disorder seemed to resemble people from a specific region in Asia. (cf. Warkany 1975: 9-10) His research led to the wrong conclusion that patients were dealing with a form of racial deviation. Down suggested the syndrome to be an indicator for a putative regression towards an evolutionarily earlier form – a somehow primitive racial type. (cf. Tamm 1994: 12) In this paper, the term Mongolism will not be used due to political correctness. Instead, Down syndrome and Trisomy 21 will be used interchangeably.

In the following 93 years, several other theories with regard to Down’s syndrome became object of research by a number of scholars. Among them were many misconceptions such as Alcoholism, Syphilis and Tuberculosis, to name only a few, which were regarded as the determinants for the condition. Even social differences came into consideration until it could be proven that cases of Down’s syndrome occurred in any social class regardless of nationality, ethnicity etc. However, scholars realized quite quickly, that older women were more likely to give birth to a child with Down’s syndrome, than it was the case with the younger ones. Nevertheless, many misconceptions were drawn such as maternal worries, exhaustion by many pregnancies etc. (cf. Warkany 1975: 10-11) Finally, in 1959, Lejeune and his co-workers made an amazing observation, when analysing the tissue cultures of nine Down’s syndrome patients. To be more precise, they discovered that all of the subjects showed 47 chromosomes in their cells instead of the usual 46. (cf. Warkany 1975: 13)

Usually the nuclei of human body cells contain 46 chromosomes. Two of them are crucial for the determination of sex (XX for women, XY for men). Normally, the other 44 chromosomes form pairs of two, one chromosome coming from the mother and the other from the father. Individuals suffering from Down’s syndrome show a deviation in this aspect with reference to the chromosome 21. The genetic information of this particular chromosome is not only present in a pair as it is usually the case, but it turned out to be tripled in most or all body cells. Hence, this led to the denomination Trisomy 21. (cf. Tann 1994: 14) Even though Trisomy 21 is known as the by far most frequent type of Down’s syndrome, there are other forms of this disorder such as the Translocation Down’s syndrome and the Mosaicism. (cf. Donnel et al. 1975: 20,25) Nevertheless, the impact on learning development does not vary very much among these different types. (cf. Buckley 2000: 9) For further depth consult Donnel et al. (1975). However, even though a lot of research has been done until today, the causes for the occurrence of Trisomy 21 have not been found. Maternal age turned out to be a major factor but recent research has shown that also paternal age seems to have an impact on the condition. (cf. Tann 1994: 15)

A diagnosis like Down syndrome brings along a number of physical and cognitive consequences for the individual. These will be dealt with in the following section, in order to understand possible problems which may interfere with the process of language acquisition in these subjects.

ii. Physical and cognitive consequences

Down syndrome individuals are fairly easy to differentiate from normally developing children what their physiognomy is concerned. Nevertheless, one has to bear in mind that the effects of Trisomy 21 can differ very much when it comes to mental and physical development. Buckley (2000) mentions possible congenital heart defects which happen to occur in approximately 50% of all individuals with Down syndrome but do not arise in the other 50. (cf. Buckley 2000: 9) Still, there are some features that are very typical of this particular condition, for example, the fairly small skull as well as the prominent forehead of Down syndrome subjects. In addition, the flat and rather short nose and the particular angled shape of the eyes are further features this genetic disorder brings along. The ears of persons with Trisomy 21 are usually small and deformed. Further malformations include the jaws, the tongue and the teeth. This often results in a protrusion of the tongue, which is mainly due to its reasonable size and the small oral cavity. (cf. Sanger 1975: 33-38) Besides, Down’s syndrome individuals often have to face middle-ear infections which may lead to permanent hearing loss. (cf. Miller 1987: 233) Vision is also often affected by the genetic disorder. DS subjects are often short or long sighted, which can be corrected by the use of glasses or surgery. What their motor skills are concerned, a number of babies with Trisomy 21 suffer from hypotonia which causes their muscles to be limp and has a great impact on their further motor development. (cf. Buckley 2000: 20-21) Very often, Trisomy 21 is accompanied by further health problems, namely respiratory diseases and leukaemia. Whereas only half of the children born with Down syndrome managed to survive infancy in the 1950s, nowadays, a lot of them reach the age of 50 years or more. (cf. Wishart 1988: 8)

The mental development of people suffering from Down syndrome is a field of study rather new to research. The majority of DS-IQ scores happen to vary between 45 and 55, nevertheless, IQs of near normal level as well as of severe retardation may also be found among individuals. (cf. Tager-Flusberg 1999: 312-313) When analysing the Intelligence Quotient (IQ) of children and adults with Down syndrome, many scholars have shown that DS-IQs decreased with increasing age. Buckley (2000) does not deny these findings; nevertheless, she states that such results may lead to misinterpretations with regard to improvement. Progress does take place, but at a slower pace than of normally developing controls. Cognitive development in individuals with Down syndrome has to be regarded as a slow-motion version of the normal development. In addition, Buckley argues that language problems in individuals with Down syndrome generally cause the decreasing IQ. (cf. Buckley 2000: 17)

Among the mentally retarded, it is a common fact that communication skills as well as language faculties do not progress as it is the case in typically developing individuals. However, it is important to see that these subjects do not make use of strange linguistic forms. (cf. Miller 1988: 168) Are language-problems always present in Trisomy 21 patients? What kind of problems are these? What are the possible causes? The next section is supposed to find answers to these questions as well as give an insight into the problems children have to put up with in the process of language acquisition.

III. Language of children with Down syndrome

i. General problems in speech

The difference between the development of language compared to the motor and cognitive progress in Down syndrome children is very strong. Addressing this particular problem of language acquisition in DS subjects, Fowler (1990) states as follows:

“Language consistently develops more slowly in children with Down syndrome than do other aspects of motor and cognitive development; this lag is evident in infancy and grows wider as the children with Down syndrome become older.”

(Fowler 1990: 322)

In general, mentally retarded children develop competence in productive speech and comprehension at a much slower pace than normally developing children of the same chronological age (CA). This delay becomes apparent as soon as children reach the initiation age of word production. (cf. Miller 1988: 168/182) Some scholars (i.e. Rondal 1997) believe that brain differences are mainly responsible, in particular, for the morphosyntactic delay in DS subjects. Nevertheless, up to date research in neurology does not yet happen to account for a direct link between neurological structures and differences in language function. (Rondal 1997: 183, Fowler 1990: 320)

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