Language Impairments: Causes and Prevention
Researchers work hard to find factors that cause specific disabilities because finding a cause often makes it possible to take preventive measures. Unfortunately, as with so many disability areas, the causes for most cases of speech or language impairments are unknown. Consequently, ways to prevent them from occurring in the first place have not yet been identified. The causes of certain conditions, however, are well known. For some of those conditions, impairments are preventable or can be treated to reduce or eliminate the challenges they present. The known causes of speech impairments tend to differ from the known causes of language impairments. We will first consider speech impairments and then turn our attention to language impairments.
Speech impairments can result from many different conditions, including brain damage, malfunction of the respiratory or speech mechanisms, and malformation of the articulators. Some children make articulation errors because they do not use the right motor responses to form sounds correctly. They make errors because of the way they use the speech mechanisms—tongue, lips, teeth, mandible (jaw), and/or palate—to form the speech sounds. For others, the cause may be a physical or organic problem, such as a cleft palate, where an opening exists in the roof of the mouth, or a cleft lip, where the upper lip isn't connected, resulting in an inability to form some speech sounds.
A cleft lip or palate affects the ability to produce speech. Its incidence varies by race/ethnicity: about 1 of every 500 live births for Asian Americans, about 1 of 750 for Whites, and about 1 of 2,000 for African Americans (McWilliams & Witzel, 1998). The proportions of cleft lips and palates tend to be consistent; about 25 percent involve only the lip, 50 percent involve the lip and the palate, and the remaining 25 percent involve the palate alone. Most cleft lips can be repaired through plastic surgery and do not have a long-term effect on articulation. A cleft palate, however, can present continual problems because the opening of the palate (the roof of the mouth) allows excessive air and sound waves to flow through the nasal cavities. The result is a very nasal-sounding voice and difficulty in producing some speech sounds, such as s and z. A cleft palate is one physical cause of a speech impairment that requires the intensive work of many specialists. Plastic surgeons, orthodontists, and SLPs often join forces to help individuals overcome the speech disability that results from cleft lips and palates.
Although professionals can describe stuttering, they are unable to pinpoint or agree on a single cause for the problem (Ratner, 2005). Experts do believe, however, that stuttering episodes are related to stress, particularly when the conversational situation is very complex or unpredictable (Hall, Oyer, & Haas, 2001). Dysfluencies are more likely to occur and reoccur when the situation is challenging or confusing.
Voice problems, which are less common in schoolchildren, can be symptomatic of a medical problem. For example, conditions that interfere with muscular activity, such as juvenile arthritis, can result in a vocal disturbance. Voice problems also can be caused by the way the voice is used: Undue abuse of the voice by screaming, shouting, and straining can damage the vocal folds and result in a voice disorder. Rock singers frequently strain their voices so much that they develop nodules (calluses) on the vocal folds, become chronically hoarse, and must stop singing or have the nodules removed surgically. Teachers who notice changes in children's voices that are not associated with puberty should refer the student to an SLP.
Language impairments have many causes. Brain injury can result in conditions such as aphasia, which interferes with language production. Genetic causes are implicated when members of both the immediate family and the extended family exhibit language impairments (Owens, Metz, & Haas, 2003). The environment, especially the lack of experiences that stimulate language development, is also a major factor contributing to language impairments.
Clearly, then, heredity does not explain all language impairments. The quality and quantity of early language input has a definite effect on vocabulary development and language development (Harwood, Warren, & Yoder, 2002). Inability to benefit from language models can also contribute to inefficient or delayed language acquisition. For example, chronic otitis media, or middle ear infection, can cause children to miss hearing and imitating others' language during key developmental periods and may result in difficulties with language development (Roberts & Zeisel, 2002). Poor language development can be caused by environmental factors, including lack of stimulation and of the proper experiences for cognitive development and learning language. Some children do not develop language because they have no appropriate role models. Some are left alone too often; others are not spoken to frequently. Some are punished for speaking or are ignored when they try to communicate. Many of these children have no reason to speak; they have nothing to talk about and few experiences to share. Such youngsters are definitely at risk for developing significant language impairments.
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