Cochlear implants can allow profoundly deaf infants to hear speech - giving them the chance to eventually learn spoken language. However, a new study shows that the children receiving the implants don't automatically know how to listen when people speak to them.
Research presented this week at the Acoustical Society of America research meeting, showed that deaf babies with cochlear implants spent the same amount of time "listening" as normal-hearing infants of the same age. However, these children with implants spent less time than younger normal-hearing infants who had the same amount of hearing experience.
Cognitive psychologist Derek M. Houston, Ph.D., associate professor of otolaryngology and Philip F. Holton Scholar at Indiana University School of Medicine, said the insight would have implications for therapy for children receiving cochlear implants.
"When infants are born deaf, their development is shaped by a silent world. They learn to tune into the sights, smells, and touches that are relevant to them in their environment - but not the sounds," said Dr. Houston. "When they receive a cochlear implant, their world changes and are filled with sounds. But for these infants who have already begun to adapt to their silent environment, sounds may not - at least at first - be perceived as relevant to them."
In other words, they may hear the sounds around them but not have any motivation to focus on them, which slows their ability to learn speech and can be traced for years through word recognition testing.
Children with cochlear implants and normal-hearing children were tested in a sound-proof lab at Riley Hospital for Children at IU Health.
"It has been well-established that infants will look longer at a simple display - the checkerboard pattern - when hearing something they are interested in," Dr. Houston explained. "I measured their 'looking time' at the pattern when it was paired with a repeating speech sound, and compared that to the looking time at the same pattern with no sound."
Children with cochlear implants spent less time looking at the checkerboard pattern than children who could hear from birth. Furthermore, two years after implantation, children who were less attentive to speech early-on performed more poorly on a word recognition task.
An abstract of his research is available at http://asa.aip.org/web2/asa/abstracts/search.may11/asa220.html
Source: Indiana University