What is Specific Language Impairment?
SLI is characterized by limitations in language functioning that can’t be attributed to insufficiencies in hearing, oral structure and function, or general intelligence. That means, this category of language impairment has no obvious cause and seems not to affect or be affected by anatomical, physical or intellectual deficits. Clinical identification of such children is hard and is normally based on absence of other contributing factors.
Children with SLI may be delayed in one aspect of language, and they do not catch up with age matched peers without intervention.
Criteria for diagnosing SLI –
- Nonverbal/performance IQ above 85
- Low verbal IQ
- Expression significantly poorer than Receptive Language ( understanding) skills
- Deficits in a variety of cognitive tasks including manipulating mental images, haptic/touch recognition, knowing that quantity remains the same across changes unless quantity is subtracted
- Poor visuo spatial short term memory and working memory
Around 10-15% of children may be “late bloomers” who do not achieve 50 single words and two-worded utterances by 24 months of age. Most of the late bloomers outgrow their delay, but around 20-50% of them have language problems that persist into pre school and school age. These children form the core of those with SLI.
Around 7.4 % of kindergarten children may have SLI. Even though this condition gets better with age, two thirds of all children grow up to have language difficulties in adolescence. E.g – At age 15, children with SLI have slower response time in language tasks than typical aged peers.
Children with SLI are perceived more negatively by teachers and peers. Young children manifest behavioural problems, which decrease with age. In elementary school, these kids show poor cooperative learning skills, contribute little, have lesser negotiating strategies than their language abilities. By middle school they develop poor self-esteem, scholastic incompetence and poor behaviour conduct.
Since children with SLI have poor working memory, they get easily overwhelmed by new information. They show lack of attention, and slow rates of vocabulary learning.
What are the causes of SLI?
Following have been identified as some causes for SLI
1. Biological Factors- Possible neurological factors have been suggested. These include
- Brain asymmetry ( Language functions are located in different areas from those found in people)
- Delayed myelination
- Evidence of greater reliance on Right Hemisphere of the brain. ( Language processing is concentrated on the Left hemisphere)
- Different pattern of brain region activiation and coordination as identified by MRI studies
- Reduced activation of those brain areas which are essential for language processing.
Strong inheritance patterns have also been identified in individuals with SLI. 60% of children with SLI have an affected family member, 38 % have an affected parent. Also research suggests that babies born pre term are at higher risk of SLI
2. Social Environmental Factors – Interaction of parents with children with SLI also is suggested to have an influence on the language learning of the children. Parents tend to correct the speech in ways in which the delayed children find difficult to cope with.
3. Processing Factors – Children with SLI tend to ignore active strategies to store and retrieve knowledge. Areas like information processing, memory and problem solving are affected which hinder in communication. Also some children with SLI may have poor cognitive skills and slow rate of response.