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Chronological Age vs. Hearing Age

August 21st, 2008 by | Tags: , , , , , , , | 4 Comments »

CHRONOLOGICAL AGE:  How old a child actually is.  Time since the child was born.

HEARING AGE: Time since the child has been receiving auditory input through appropriate amplification.  Time since the child received hearing aids and/or cochlear implants.

For example:  “Susie” was born August 21, 2001.  Today is August 21, 2008.  Susie’s chronological age is 7-0 (seven years, zero months).  If Susie received a cochlear implant at 13 months of age (on September 21, 2002), her hearing age is 5-11 (five years, eleven months) or one year and one month less than her actual, chronological age.

BUT is this really the case?

Did you know that babies’ ears (the physical structures) start to develop around 18 weeks after conception?  The physical parts of the ears are fully formed around 25 weeks post-conception, but babies begin to HEAR only 18 weeks after being conceived!  So, by the time a child breathes its first breath after a typical 40 week pregnancy, that child already has 22 weeks, or over FIVE MONTHS, of hearing experience.  In the womb, a child can hear the mother’s blood circulating and the sounds of digestion, and also sounds from the outside world, like parents’ voices and music.  Unborn babies even begin to recognize their mothers’ voices around the 25th week of pregnancy.  (See HERE for these great facts and more about human development.)

Unborn babies come into the world with over five months of hearing experience, if they are able to hear.  This pre-exposure to the outside world, one that is loud and full of noises, helps hearing children with sensory integration (dealing with the overwhelming flood of sensory stimuli that are part of our world each day).  Think about it — as a hearing adult (or a deaf adult with listening and spoken language training) — you are able to attune to the sounds in your environment, to focus on the things that are important (speech) and block out the sounds that are unnecessary distractions (the washing machine humming in the background).  Hearing babies have a head start on learning to listen, and learning how NOT to listen.  They have already had five months to “practice” navigating the world of sound.

This is why early detection of hearing impairment is crucial, and early amplification is a MUST.  Babies can’t wait!  If a deaf baby is identified at 3 months and receives hearing aids by month 6, they have already missed out on ELEVEN months of hearing experience.  This is not to say that all hope is lost.  Obviously, children identified much, much later have been successful learning to listen and talk (think about the days before newborn hearing screening, digital hearing aids, and cochlear implants — deaf children learned to talk then, under much tougher circumstances), just to emphasize the importance of getting your deaf child access to sound as soon as possible.  The sooner you start working on listening and spoken language, the better chance you have of closing that gap!

TO LEARN MORE… Carol Flexer, Ph.D., is one of the biggest names in the field of auditory brain development, especially for deaf children learning to listen and speak.  HERE is her personal website, and HERE are some fantastic quotes, words of wisdom, and pieces of advice from her books and public speeches.

Written by

Elizabeth Rosenzweig MS CCC-SLP LSLS Cert. AVT is a Listening and Spoken Language Specialist Certified Auditory Verbal Therapist. She provides auditory verbal therapy, aural rehabilitation, IEP advocacy, consultation, and LSLS mentoring for clients around the world via teletherapy. You can learn more about Elizabeth's services on her Website or Facebook.

4 Comments

Julia

October 14, 2009 at 10:07 am

You misspelled “amplification” under HEARING AGE. Just thought you would want to know.

Elizabeth

October 14, 2009 at 4:48 pm

Thanks, Julia! I appreciate the extra set of eyes. It’s been corrected.

Missy

April 16, 2011 at 11:04 am

While I agree wholeheartedly that early identification, amplification & access to supportive services is crucial, I wonder about the science behind some of the other statements made in the article. Although we know that babies can hear in utero, I wonder about this affecting their ability to “filter out” unimportant noises at birth. While it has been documented that babies can recognize their mothers’ voices immediately after birth, I fail to see how a baby inside a womb can possibly have the context to determine which of the other noises it hears are worthy of attention. Furthermore, all newborns are pretty good at ignoring everything and sleeping through all sorts of sensory input.

One of my children was born deaf, and I wonder how the scientific community can determine that his prenatal experience was somehow less productive because he could not hear. Was this statement linked to a specific study? Since everything in there is underwater, perhaps deaf fetuses can still sense their mothers’ voices, digestive gurgles etc. through vibro-tactile or some other stimulation? In fact, how has it been determined that the affinity hearing children have for their mothers voices postpartum is because their previous exposure to her voice was through ONLY their sense of hearing?

Following this line of thought logically, does this mean that deaf babies have already spent 5 months honing their other senses, and already have a jump on their hearing peers in comprehending non-auditory sensory input?

If you are going to insinuate that deaf babies are disadvantaged even before birth, please cite some credible sources backing this.

Thanks & have a good day.

Elizabeth

April 17, 2011 at 9:08 pm

Missy, thank you for your comment. Here is a great article that explains fetal auditory development, including some information on how pre-term and term infants discriminate, or filter, auditory stimuli: Graven, S.N. and Browne, J.V. (2008). Auditory Development in the Fetus and Infant. Newborn and Infant Nursing Reviews, 8(4): 187-193. (http://www.wonderbabiesco.org/UserFiles/File/Graven%20and%20Browne%20Auditory%2008.pdf). You are right that it is impossible to determine if infants in utero (with or without hearing loss) are able to detect their mother’s voice through vibrotactile sensation — an experiment to test this theory would be lethal. However, I think it is a reasonable hypothesis to make, since infants who are tested after birth respond to their mothers’ voices preferentially in an auditory-only condition. If their experience was solely vibrotactile in the womb, it is doubtful that they would perform so well and so consistently in the auditory-only condition after birth. The infant response goes beyond discrimination, too. When exposed to their female voices just hours after birth, not only did infants show preferential reactions to their mothers’ voices, but they also showed activity in the left hemisphere of the cerebral cortex (the language-processing center). This article (http://www.montrealgazette.com/life/word+Montreal+team+finds+newborns+respond+uniquely+mother+voice/3989817/story.html) explains one such study, published in the journal Cerebral Cortex, conducted by researchers at the Universite de Montreal.

While it is possible that children who are prenatally deaf may have time to hone their other senses before birth (I am not aware of any studies demonstrating this, perhaps because Universal Newborn Hearing Screening is relatively new and, even then, it is impossible to definitively determine a hearing loss within hours of birth), I suppose it depends upon whether or that kind of cortical reorganization is viewed as a good thing. The brain — especially the infant and toddler brain — certainly changes based upon the input it receives. Deprived of auditory stimulation, those areas weaken. For parents who have chosen an auditory approach for their child(ren) with hearing loss, research suggests that, with good, early access to sound provided by cochlear implants (or hearing aids, as appropriate), auditory evoked cortical latency measures can “catch up” and resemble those of typical hearing peers (see work by Sharma and Dorman, e.g. http://journals.lww.com/neuroreport/Abstract/2002/07190/Rapid_development_of_cortical_auditory_evoked.30.aspx).

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