by Mark McGowan
Toddlers fitted with cochlear implants take more time, on average, to process spoken words in their vocabulary than their normal-hearing peers, according to a study led by a professor from NIU.
Tina Grieco-Calub, who was a post-doctoral student at the University of Wisconsin-Madison during the time of the 2006-2008 study, said that those time delays – on the order of milliseconds – could impact how children with cochlear implants learn new words.
And, Grieco-Calub said, if these children are taking longer to process the words that they know, they might miss opportunities to learn new words and expand their vocabularies.
Published in the December 2009 issue of the Journal of Speech, Language and Hearing Research, the research funded by a National Institutes of Health grant gives clinicians and parents the understanding that children with cochlear implants need more time to process auditory information.
Cochlear implants are intended only for children who have severe to profound hearing loss or who are deaf.
“There are a number of published studies involving school-age children with cochlear implants that look at their language outcomes – standardized measures of spoken language performance, expressive or receptive – but they don’t tell us how these children are processing auditory information on a real-time basis,” Grieco-Calub said.
“This gives us insight into how children process language, particularly when their vocabularies are starting to emerge – right in the middle of the language explosion,” she added. “Even though their language appears to be developing, many children do not appear to be processing information as efficiently as children with normal hearing.”
Grieco-Calub and her co-researchers, Jenny Saffran and Ruth Litovsky, used video cameras and special software to digitally record eye movements and determine the length of reaction time from spoken cue to visual response.
Forty-six 2-year-old children participated, 26 of whom have cochlear implants.
Four objects – baby, ball, doggy and shoe – were chosen for the study. “We verified with their parents that those words were in their vocabularies,” she said.
Children were seated in a double-walled, sound-attenuated booth. As the researchers played recordings of questions regarding the test words – “look at the,” “where is the” and “can you find” – children turned their eyes toward the corresponding objects.
The toddlers were seated in infant seats or on the laps of caregivers, who were listening to music via earphones to eliminate the possibility that they might bias the children’s behavior during the experiment.
“On average, children with cochlear implants took longer to look at the target objects after hearing the target label,” Grieco-Calub said. “Some did perform similarly to their normal-hearing peers but others performed much poorer.”
Researchers also discovered that adding acoustic competition – a background noise of two-talker babble – further slowed the reaction time of both groups of children. The researchers believe this could have implications for children who need to comprehend language when there is considerable background noise.
Consequently, Grieco-Calub said, parents and teachers should strive to minimize background noise and provide visual cues.
Grieco-Calub is a professor in the School of Allied Health and Communicative Disorders, housed in the NIU College of Health and Human Sciences.