Testing for Central Auditory Processing Disorders (CAPD)
Parents often ask us whether we think their child has an auditory processing disorder. Central auditory processing is defined as how the brain interprets what the ear hears. A central auditory processing disorder (CAPD) is diagnosed by an audiologist, although a deficit in auditory processing is not the same thing as a hearing loss. In addition, it specifically precludes higher order cognitive disorders such as mental retardation, or specific language impairments.
Children are generally referred for CAPD testing for specific behaviors that are noted by parents, teachers or speech-language pathologists while performing an evaluation. These children often have difficulty hearing with background noise, as in a noisy classroom. They may have difficulty discriminating one sound or word from another. Following directions, especially multi-step directions may be difficult. Even though there is no hearing loss, difficulty with sound discrimination may result in frequent requests for repetition ('huh?'). Academic difficulties, especially in the area of phonics, as well as other aspects of reading, may be observed. Interestingly, some children with auditory processing impairments have no obvious deficits at all. This points to the fact that auditory processing is not any one thing; there are numerous auditory processes. Here is a list of some auditory processes:
- The ability to localize or lateralize sound; that is, to be able to tell where the sound is coming from. Think about children in school having to focus on their teachers' voices, while tuning out the voices of their classmates.
- Auditory discrimination: the ability to differentiate similar sounding phonemes, such at file and pile or zoo and shoe. In the school setting, as well as in other settings, children, especially during the language and literacy learning years, must internalize an accurate and undistorted message.
- Auditory processing with a degraded signal. A good example of this would be talking on a cellular phone. Even though many frequencies are filtered out, most of us still understand the message. It is important that as language users, we fill in the missing bits of sound and perceive the message correctly.
- Dichotic listening, which is the ability to hear a signal in both ears, even if they are different from other. An individual with CAPD might hear 9-3 in the right ear while simultaneously hearing 6-4 in the other, and then be unable to repeat all four digits correctly. Or they might be asked to state what they heard in one ear or the other, and not be able to do so.
Testing to discern all of the above processes is performed by an audiologist. If any area is deficient, that will generally equate with a specific difficulty in the school setting.
During a speech/language evaluation, the tester may perform screening tests to determine the need for more in-depth testing by an audiologist. One test is the Differential Screening Test for Processing, by Gail Richards and Jeanane Ferre. This test is given using a computer and headsets. One of the subtests presents two numbers in one ear and two different numbers in the other ear and the student has to name all four numbers. Another subtest requires students to repeat a nonsense word that is being heard in the presence of background noise. This testing is similar to what the audiologist does but results in a pass/fail score and merely points to the need to more in-depth testing by an audiologist.
If the CAPD test results are positive, there are a number of treatment modalities that can be utilized. One, that many of our parents are familiar with, is an FM Unit. An FM unit amplifies the teacher's voice and directs it into the student's ear. This is most helpful in the student who is unable to tune out background noise.
It is also very helpful for the child to be given preferential seating in school. It would be most helpful if the teacher would break down complex directions into smaller parts. Perhaps, the teacher could say, 'First, I want you to ...' Then,…. And finally, …'
It is also extremely important that the student him/herself know how to ask for what is needed in order to be able to understand the teacher and follow directions in the classroom. This is probably one of the most important things we can teach our students: to figure what they need to function well and then ask for whatever it is.
Speech/Language Pathologists work with students with CAPD, both before and after the diagnosis is made. There are a variety of activities that are done in therapy to enable these students to function most effectively in the school setting. We work to strengthen the skills the students already have, while increasing the repertoire of skills that are required to function in a world filled with sound.
For parents, whose children have received this diagnosis, Like Sound Through Water: A Mother's Journey Through Auditory Processing Disorder, by Karen Foli, may be helpful to read. When the Brain Can't Hear : Unraveling the Mystery of Auditory Processing Disorder, by Teri Bellis, may also be interesting and informative.