What is CAPD?
Children and adults who have central auditory processing disorder (CAPD) are a heterogeneous group of people who have difficulty using auditory information to communicate and learn. CAPD is not a specific problem or disease; rather it is a set of problems that occur in different kinds of listening tasks. Often children with CAPD are first diagnosed with attention deficit hyperactivity disorder (ADHD) or learning disabilities. Later, an audiologist may render a diagnosis of CAPD. To audiologists, CAPD includes problems with one or more of the following auditory tasks (ASHA CAPD Task Force, 1996):
Sound localization and lateralization
Auditory pattern recognition
Temporal aspects of audition (resolution, masking, integration, ordering)
Auditory performance decrements with competing acoustic signals
Auditory performance with degraded acoustic signals
Audiologists make the diagnosis using standardized tests of these skills administered in carefully controlled acoustic environments with very sophisticated calibrated equipment. Because the American Speech Language Hearing Association has determined that diagnosis of CAPD falls under the scope of practice of audiology, it is important to understand what the audiological diagnosis means.
Sound localization and lateralization refers to the ability of a child or adult to know where a sound has occurred in space. This is an important survival skill; localization is used to identify a source of sound, like a moving vehicle or barking dog.
Auditory discrimination refers to the ability to distinguish one sound from another. The term is most often used for distinguishing speech sounds, such as phoneme /p/ from phoneme /b/.
Auditory pattern recognition refers to the ability to determine similarities and differences in patterns of sounds.
Temporal aspects of auditory processing refers to the ability to sequence sounds, integrate a sequence of sounds into words or other meaningful combinations, and perceive sounds as separate when they quickly follow one another.
Auditory performance decrements refers to the ability to perceive speech or other sounds when another signal is present. The other signal might be noise or another similar speech signal, and the competing signal might be soft or loud.
Auditory performance with degraded acoustic signals refers to the ability to perceive a signal in which some of the information is missing. A degraded signal might be one where parts of the sound spectrum have been deleted, the highest or lowest frequency components of the sound are removed, or where the sound is compressed in time.
How does CAPD differ from “auditory processing disorders” described by other professionals?
CAPD is clearly recognized as a problem for many children and adults—as it affects language learning and contributes to reading disorder and dyslexia—and is well documented in research.
Often children diagnosed with CAPD may have received another diagnosis before being seen by an audiologist. The disorder can be confusing for parents, educators, and other professionals working with these children. For this reason, Dr. Jay Hall has stated that identifying the CAPD population requires the combined efforts of speech-language pathologists and audiologists. Often psychologists, physicians, and educators need to be included in the assessment and treatment team as well.
In previous diagnoses, speech-language pathologists may have referred to auditory- or language-processing disorders, which often have to do with weaknesses in auditory sequencing, auditory memory, and auditory closure.