Little is known about baby's talk and just as little is known about how babies perceive and process words and sounds from adults and the world around them. It is through understanding how infants and toddlers develop life-long language skills that researchers at the Indiana University School of Medicine hope to help deaf infants with cochlear implants understand the audible world around them.
The Infant Language Lab at the James Whitcomb Riley Hospital for Children is studying language development of hearing infants and toddlers to establish a yardstick for toddlers who have received cochlear implants.
Among the answers the IU otolaryngology researchers seek: What do normal hearing babies actually comprehend? Can a child with a cochlear implant discriminate sound in the same manner as normal hearing infants? How do infants learn to process what they hear in relation to what they see?
With answers to these questions, researchers can track the progress of infants who use cochlear implants and provide speech therapists a means to assess the progress of individual infants and their language perception.
"Working with infants and toddlers presents unique challenges," said Derek M. Houston, Ph.D., Infant Language Lab director and assistant professor of otolaryngology-head and neck surgery. "Progress has been made in developing techniques to evaluate language perception in children over the age of two. Measuring these skills in infants too young to follow instruction requires the development of innovative testing techniques."
Dr. Houston and his colleague Tonya R. Bergeson, Ph.D., assistant professor of otolaryngology and co-director of the Infant Language Lab, are developing new techniques for evaluating language perception in an age group where "goo-ing" and "ga-ing" are intense communication.
"Since this was the first lab in the world to research speech and language development in hearing-impaired infants with cochlear implants, we have paved the way for much of the ongoing research," said Dr. Bergeson. "We are constantly striving to improve our methods and are in the process of developing a laboratory setting that has equipment capable of following the eye movements of the children. This will enhance our data collection tremendously."
By recording how the babies respond to different stimuli, researchers are able to evaluate how they differentiate and respond to sounds and learn language. Much of the response is based on when or how long the child looks at a particular object.
The testing appears simple; a parent and child sit in a small, darkened room facing a large-screen television set. Hidden above the TV is a video camera that records the movements and attention span of the youngsters involved in the studies.
For example, in one of the studies, 5- to 13-month-old infants see a duplicate image of a woman's face and each is mouthing a different word. The woman on the left says "judge" while the one on the right says "back." After the infants have seen the each woman "speak," the audio track changes and plays only one of the words. What researchers want to know is if the infant will match the audible word with the correct lip movement. The answer is in the baby's eyes.
In another test, the length of time an infant focuses on a red and white checkerboard pattern while hearing various words or hearing no sounds tells researchers that normal-hearing infants are interested in speech sounds and can discriminate between sounds. The same test administered to young children with cochlear implants indicated they show the same discrimination in speech after only one month of cochlear implant use.
Using varying images, sounds and stimuli, the researchers hope to gain a more in-depth understanding of how language is learned and why children who hear from birth respond differently to noises and speech from children who were born with severe hearing impairments.
"When a normal hearing infant hears a sharp, sudden noise, the baby looks in the direction the sound came from," said Dr. Houston. "Children born deaf who receive cochlear implants do not respond to sound in the same way - the same sudden noise may not produce a response of any kind. We want to understand issues like this, as well as how infants learn speech."
How much influence parents have on infant speech perception is another area of study at the Infant Language Lab. "In one of our projects, we are trying to determine why mothers instinctively talk baby talk to infants," said Dr. Bergeson. "Interestingly, we are finding that mothers of children with cochlear implants adjust their pattern of talking to the hearing age of the child." The hearing age is determined by how long the child has had a cochlear implant, so a 20-month-old who received an implant 12 months prior would have the "hearing age" of a one-year-old.
Through their research, Drs. Houston and Bergeson are listening intently to what infants and toddlers have to say. They want to tell the world what they learn because, as they both know, it's much more than just baby talk.