EVANSTON, Ill. --- One of every 12 school-age children who is otherwise normal has difficulty understanding and expressing spoken language. Children with this condition, called specific language impairment (SLI), have difficulty distinguishing individual sounds of normal speech. Many but not all children who have reading problems fall into this category.
"Children with SLI have trouble understanding spoken language even in the quietest environment," said Beverly Wright, assistant professor of communication sciences and disorders at Northwestern University. "This condition interferes with the academic progress of millions of schoolchildren."
Recently, Wright and her colleagues at the University of California, San Francisco, and the University of Florida, Gainesville, observed that children with SLI had marked deficits in auditory perception for sounds other than speech.
In laboratory tests, they observed clear and distinct difference between the ability of children with SLI to process brief tones in special sound contexts as compared with that of normal children. The differences depended on where the tones were placed in time in relation to other sounds as well as on the frequencies, or pitches, of the tones in relation to the frequencies of other sounds.
Children enrolled in the study listened for brief tones that were presented either before, during or after special "masking" sounds. The intensity of the tones was increased until the children could detect them.
Long tones were used first to train the children to the task. Wright noted that the children with SLI performed equally with their normal peers when the tone was long. But differences were observed when the tone was short, indicating that the length of the tone was a factor in their ability to process the sounds.
"When the tone was short, the children with SLI performed more poorly in all test conditions compared with the normal children," Wright said. "In addition, the task was easiest for the normal children when the tone was presented just before the noise, whereas the children with SLI experienced the most difficulty under this condition."
The unimpaired children could hear a tone occurring before the noise at 45 decibels -- a sound level equivalent to that in a quiet room. But before the children with SLI could hear the tone, it had to be elevated to 90 decibels -- a sound level equivalent to that at the side of a superhighway.
Wright said that the deficits of the children with SLI are so huge that her group's test easily could be used as a diagnostic tool. What's more, there is evidence that these are deficits can be reduced by training.
Wright's study was published in the May 8, 1997, issue of the journal Nature. She and her colleagues are continuing research on auditory processing difficulties and their possible remediation. They are seeking school-aged participants preferably between the ages of 7 and 9, with and without SLI, and children and adults with dyslexia.
For information, call (847) 491-2453.