Study shows hearing loss affects infant babble
Parents all over the world look forward to their babies’ first adorable coos, squeals and babbles. Other than crying to express a need or discomfort, these initial vocalizations are the first step toward a lifetime of communication for babies.
But what, exactly, propels infants to start to “goo-goo” and “ma-ma” in the first place? A new study done at the University of Missouri and published in the Journal of Experimental Child Psychology suggests that babies babble because of their ability to hear their own speech, and that babies with profound hearing loss didn’t make the same sounds with the same frequency as those babies with typical hearing.
The research is especially significant due to the fact that approximately 1.4 out of 1,000 newborns have a hearing loss. The good news is that most states now have mandatory newborn hearing screening, so it is possible to detect hearing loss earlier. However, it is important to remember that a diagnosis is only the first step; following up with early treatment or intervention is critical to language development.
“Hearing is a critical aspect of infants’ motivation to make early sounds,” says Mary Fagan, an assistant professor of communication science and disorders in the MU School of Health Professions. “The fact that they attend to and learn from their own behaviors, especially in speech, highlights how infants’ own experiences help their language, social and cognitive development. They are actively engaged in their own developmental process.”
Make no mistake; the language that babies hear from others is important as well. One study of pre-term infants showed that those infants whose parents and nurses spoke to their babies in the NICU fared better in language development when tested at 18 months of age than those infants who merely heard others talk about them and their ongoing care. This latest research shows that infants have a part to play as well, proving that they are not just passive recipients of language but are very important players in their own language development.
Babbling is normal among hearing 8 month olds. But in looking at 16 infants with profound hearing loss and 27 infants with typical hearing, the researchers at the University of Missouri found that babies with profound hearing loss rarely make the repetitive vowel sounds, “da-da”, “ma-ma” and “ga-ga”, for example, that are common among babies without hearing loss.
The good news, however, is that the MU researchers found that once the infants received cochlear implants they began babbling with the same frequency as typically hearing infants within just a few months. Cochlear implants are small electronic devices embedded behind the ear that serve to replace some functions of the impaired inner ear. Researchers noted that not only was there an increase in vocalizations with repetitive syllables, but that the number of repetitions in the string also increased.
Any vocalizations your baby makes are communication. "Babies show they can also express themselves with squeals, vowels and growls in the first months of life,” says Dr. D. Kimbrough Oller, Ph.D., professor of Audiology and speech-language pathology at the University of Memphis. Those early vocalizations also help babies learn to modulate vocal tone and volume. Crying is first, followed by vowel sounds such as “ooh” and “ahh”. Between 5 and 7 months, the consonant sounds begin to be added.
It is important to remember, however, that all babies develop differently. Just because your friend’s baby is babbling excessively by 6 months and yours isn’t doesn’t necessarily mean there is a problem. As a matter of fact, language is the most common developmental delay. However, if your baby isn’t cooing by 4 months, or isn’t babbling by 10 months, or if you notice that receptive language is lacking (meaning your baby doesn’t respond when you speak or say familiar words) you might want to run it by your pediatrician. There could be any number of reasons for the delay, most of which don’t warrant serious concern. At some point your pediatrician might decide a hearing test is in order. If it does turn out that your baby has a hearing loss, finding out early is the best thing.
The University of Missouri research isn’t the first indication that early intervention is crucial to language development. Previous research, such as a study done at the University of Colorado Boulder and published by the American Academy of Pediatrics, have also showed that early identified hearing impaired children have significant advantages over later identified children when it comes to language development. Across the board, research agrees that early intervention for hearing loss, whether that comes in the form of hearing aids or cochlear implants, allows babies and children to catch up to their hearing peers in terms of speech.
Fagan stresses that although there is not just one course of action for treatment or intervention in the event of hearing loss, any action taken should be done quickly as time is of the essence when it comes to language development.
“Many parents elect to have their children with profound hearing loss receive cochlear implants, and that’s a decision parents alone can make,” Fagan said. “Whatever decision the parents make, the data strongly show that if parents are going to choose a cochlear implant, the sooner the better. Studies like mine show how rapidly babies with hearing loss respond to cochlear implants, often minimizing the impact on their speech, language and vocabulary development.”