Language Development in Children with Down Syndrome
Down syndrome, or trisomy 21, is a genetic disorder. To understand how down syndrome happens, it is important to understand a little about chromosomes. Chromosomes are structures within each cell that are made up of genes; genes provide the information that determine everything about a person. A baby receives half of their chromosomes from their mother and half from their father. In a typical child, there are 23 pairs of chromosomes, for a total of 46. In a child born with down syndrome, there is an additional, or third, copy of their 21st chromosome, leaving them with 47 total chromosomes instead of 46. This additional copy leads to complications in the development of the brain and physical features of the child. Because 1 in 700 children in the United States are born with down syndrome, it is the most common genetic disorder; it is also the main genetic cause of intellectual disability, with language being the most impaired area of function in down syndrome (Martin, Klusek, Estigarribia, & Roberts, 2009, p. 2) Although each child with down syndrome is unique and has unique deficits, language, specifically expressive language, is consistently the most impaired area of function in children with down syndrome (Martin et. al., p. 1). The language of children with down syndrome is particularly weak in the areas of vocabulary, pragmatics, literacy, and syntax, but it is interesting to see how they communicate by using gestures and augmentative and alternative communication (AAC) in the form of sign language.
In the area of vocabulary, there is conflicting data about whether or not children with down syndrome comprehend vocabulary at the same time as typically developing children, but there is uniform data stating that children with down syndrome are delayed in their expressive vocabulary. The first spoken word in children with down syndrome is delayed when compared to a typically developing child, and the continuing growth of their lexicon is slower than a typically developing child. In the area of pragmatics, children with down syndrome do produce the same variety of communicative functions, with the exception of requests, that typically developing children do. For example, children with down syndrome do produce comments, answers, and protests. Children with down syndrome can stay on topic for the same amount of exchanges that a typically developing child can, but they do not initiate or expand topics as well as a child that is typically developing. In the area of literacy, there is not much consistency among children with down syndrome. While some children with down syndrome master reading, many do not (Martin et. al., p. 1-2, 4-8).
Although children with down syndrome have deficits in a variety of areas of language, their greatest weakness is in the area of syntax. In the area of syntax, children with down syndrome are more impaired than they are with vocabulary, pragmatics, and literacy. In children with down syndrome, syntax skills fall far below that of a typically developing child. Syntax skills in children with down syndrome are slower developing and can even decline in late adolescence. Children with down syndrome are delayed in producing two-word combinations compared to a typically developing child, and they consistently produce less complex utterances than typically developing children. Children with down syndrome show deficits in the area of expressive syntax during narratives, conversation, and repetition tasks. Children with down syndrome frequently omit necessary sentence elements or make morphological errors. The mastery and use of syntax in children with down syndrome continues well into the adolescent years. Children with down syndrome have a reduced mean length of utterance (MLU). They have been described to have telegraphic speech, omitting many words. The most noticed omission is that of verbs. “For example, when asked what one does during free time, and individual with DS might respond ‘cookies,’ whereas an individual who is TD might say, ‘(I) bake cookies.'” (Michael, Ratner, & Newman, 2012, p. 1737). In children with down syndrome, main verbs and auxiliary verbs are typically omitted the most. Children with down syndrome do not produce fewer different verbs; they actually produce a greater variety of main verbs than some children who are typically developing. Although children with down syndrome do appear to have a wide variety of verbs in their mental lexicon, they have difficulty accessing them during communication. Research shows that children with down syndrome consistently perform below that of typically developing children when carrying out tasks that involve syntactic processing, specifically the ability to retrieve and comprehend verbs. One study was done that consisted of 9 children with down syndrome and 9 children with and age equivalent receptive vocabulary; the study investigated the ability to retrieve and comprehend verbs in the children with down syndrome compared to the typically developing children. In all situations, individuals with down syndromes were significantly weaker in areas that involved syntax skills (Michael et. al., 2012, p. 1736-1737, 1744).
Even though all children with down syndrome do not have a uniform way of life, they do have the increased use of gestures in common. Since children with down syndrome are diagnosed before birth or shortly after, early intervention is possible. A key factor in the early intervention of down syndrome is the encouragement of gestures and sign language. Research shows that children with down syndrome exhibit more gesture use than that of a typically developing child. Gesture use in children with down syndrome is particularly important in parent-child interaction because it is a channel by which they can translate their gestures into spoken words. The reaction of a parent to the gestures a child makes allows the child to place a word onto the gesture. Expressive language of a child with down syndrome is comprised mostly of gestures for far longer than it is in a typically developing child. Gestures are important for a typically developing child as well, but the use of gestures is usually transitioned into spoken words before 2 years of age. In children with down syndrome, the use of spoken words takes much longer to develop, so they rely on the use of gestures for much longer. It is imperative that a mother of a child with down syndrome respond to the child’s use of gestures in order for them to develop language. One study was done to examine the difference between gesture use in children with down syndrome and typically developing children. Understanding gesture use in children between the ages of 2 and 5 is important because typically developing children begin to depend less on gestures than children with down syndrome. The study consisted of 22 children with down syndrome being examined by a therapist as they participated in three activities totaling to 21 minutes with their mothers, and they were compared to typically developing children in the same scenario. The children with down syndrome were examined to use an average of 82.59 gestures during the 21 minutes of activity, and the typically developing children were examined to use an average of 51.18 gesture during the 21 minutes of activity (Lorang, Sterling, ; Schroeder, 2018, p. 1018-1020, 1023-1024). This study further emphasizes the importance of maternal responsiveness to gesture use in children with down syndrome; they very much depend on it to communicate.
Beyond gestures is sign language, which is a vital part of communication in children with down syndrome. In order to teach children with down syndrome how to communicate with sign language, it is important to incorporate the sign intervention into naturalistic language teaching, joint attention, and symbolic play. As mentioned earlier, children with down syndrome exhibit many deficits, but a specific deficit common to most children with down syndrome is the ability to use spoken language in correspondence with their mental age. The intervention of augmentative and alternative communication (AAC) can be very beneficial in helping children with down syndrome communicate. Specifically, the forms of AAC used in children with down syndrome are gestures and sign language. Because children with down syndrome use gestures far longer than typically developing children, having strong gesture use can allow them to combine their use of signs with spoken language to communicate effectively. Research has shown that combining signs with spoken language is more effective in teaching children with down syndrome than just teaching spoken words alone (Wright, Kaiser, Reikowsky, ; Roberts, 2013, p. 1-2).
Not only should children with down syndrome be taught to communicate by combining signs and spoken words, but they should be taught in a naturalistic way; studies show that this is the most effective. Naturalistic teaching is the most effective way to teach sign language because it builds on specific social strengths that children with down syndrome already have. This type of teaching is used by caregivers and teachers, and it is incorporated into play and daily routines. Naturalistic teaching is also effective because it encourages the child to initiate conversation while the adult focuses on responding to the child. Naturalistic teaching encourages the child to engage and participate in routines, which allows the child more opportunities to engage and participate in conversation. Studies have shown that naturalistic language intervention is very effective in teaching children with down syndrome. In one study, four children with down syndrome were evaluated to examine the effectiveness of Milieu Teaching in teaching sign language and spoken words to children with down syndrome. During the study, a therapist implemented the signs to the four children. All four of the children had an increase in their rate of signing and their variety of signs; they each acquired between 10 and 21 new signs and between 3 and 9 new words during the intervention. Also, the four children generalized their new signs and words to a new location, such as their home (Wright, et. al., p. 1-2).
Overall, it is clear to see that children with down syndrome struggle with a variety of areas of language. They have difficulties with vocabulary, pragmatics, literacy, and syntax, with the greatest area of difficulty being syntax. In the area of syntax, children with down syndrome have more difficulty than they do with vocabulary, pragmatics, or literacy. Children with down syndrome rely heavily on gestures and sign language to communicate with the people around them, especially their mothers. All children with down syndrome have the increased use of gestures in common, which is why it is so important for mothers to respond to these gestures; this allows the children to label their gestures with spoken words. When teaching children with down syndrome to use gestures and sign language effectively, it should be done in a naturalistic way. This will encourage the child to engage in conversation during their everyday routine.
Language Development in Children with Down Syndrome