Language researchers have long relied on participants suffering from language disorders as a means to better understand how language develops in healthy people. A new special issue of Applied Psycholinguistics covers the study of mental disorders that affect language development. Cognitive Daily will report on a couple of these articles in the coming weeks, so we thought it would be useful to first provide a general overview of some of these disorders, as Mabel L. Rice, Stephen F. Warren, and Stacy K. Betz of the University of Kansas do in their article “Language Symptoms of Developmental Language Disorders: A Overview of Autism, Down Syndrome, Fragile X, Specific Language Impairment, and Williams Syndrome” (Applied Psycholinguistics, 2005). The hope of Rice and her colleagues is that linguistic research about these conditions may help in diagnosis and treatment as well.
Rice et al. identify three major issues in identifying symptoms of language disorders. First is how the language ability itself is measured. Tests can be expressive (how well does the child speak?) or receptive (what does the child understand?). They can measure grammar or vocabulary. Different disorders will impact different aspects of language ability, and are best measured with different tests. Second is whether the symptom simply delays one or more aspects of language development, or whether it is truly deviant (permanently different from normal individuals). Finally, there is the question of whether the disorder is specific to language, or if it is accompanied by problems in other cognitive abilities. When I hear someone’s child has “Fragile X,” or “Autism,” I tend to think “what a shame,” but Rice et al.’s approach allows us to take a more positive perspective, and seek to gain a better understanding of how that child’s mind works.
SLI, or specific language impairment, lives up to its name. It is a condition where a child’s cognitive skills suggest they should be able to learn language, but they still have difficulty with language tasks. The impairment tends to be so specific that it does not affect speech, but only language ability, so kids pronounce words and sentences correctly, but don’t have normal vocabulary and grammar skills. The vocabulary problems appear to be merely delayed, but grammar ability tends to trail vocabulary ability so severely that it may be called a deviance rather than just a delay.
Autism spectrum disorders are a broad range of disorders that share some similar symptoms, mainly related to communication and interaction with others. However, autism can be combined with fragile X, severe mental retardation, and other conditions, or limited, in the case of Asperger syndrome, mainly to social interaction problems.
While some children with autism are nonverbal, recent research suggests that most have some communication skills. There is even a subgroup of children with autism who learn a set of words early in life, only to stop using them temporarily later on. In short, the language-related symptoms in autism patients varies from complete inability to communicate all the way up to nearly normal language development.
Fragile X syndrome is an inherited form of mental retardation carried on the X chromosome. Since boys only have one X chromosome, they tend to have more severe symptoms than girls. Up to 35 percent of children with fragile X also have autism (and this is the only known means of inheriting autism). Most children with fragile X have both language delays and general cognitive delays, suggesting that it is a very general condition. They tend to have more difficulty with expressive language skills than receptive skills. In addition, they also display speech problems: a “harsh vocal quality” and quick pace that makes speech difficult to understand.
Williams syndrome is another genetic disruption, which results in facial distortions, a hoarse voice, hyperfriendliness, and some mental retardation. Children with Williams syndrome seem to develop language a bit more slowly than normal kids but eventually develop full proficiency, while lagging behind in other cognitive measures. Contrast this to SLI, where kids have poor language ability and good other cognitive skills.
Down syndrome is the malady with a readily identifiable masklike facial deformation (though not what afflicted Cher’s son in Mask) and mental retardation. It is the most common genetic cause of retardation. Children with Down syndrome acquire language more slowly than their other cognitive abilities would suggest, but language acquisition is different for different tasks. They learn vocabulary about as fast as would be expected, but grammar and syntax come disproportionately slowly. Due to a deformed vocal tract and intermittent hearing loss, they also show speech difficulties.
It is important to remember that this is an incomplete list, focusing on language abilities, and even then giving only the highlights. However, it should serve to help differentiate between different conditions. Hopefully, research into the language ability of children with these conditions will help us not only understand language better, but also how best to help these kids live happy lives.