Most people recognize that birth defects, infections, blockages, eardrum punctures, tinnitus from loud noises, and various other things can adversely affect the middle and inner ear, important parts of the hearing equation. But a lot can also go wrong during a sound's journey along the eighth cranial nerve through the relay stations and inside the auditory cortex. APD is a condition that affects that interior trip to the auditory cortex and the processing stage that transforms hearing into listening within the cortex itself.
THE DEVELOPMENTAL LADDER
Since we don't yet know what causes APD and can't predict at what age it may develop, it's important to understand the typical developmental milestones common to most young children. These developmental milestones are a loose guide. They can help you to zero in on your child's listening development. If your child's listening and speaking skills don't come anywhere near the trajectory I describe, APD may be the problem. Keep in mind that the ideas, observations, and indications that follow are not one-size-fits-all. A child's journey to developmental maturity is a ladder of many rungs. Your son or daughter can pause on one rung longer than another child the same age, skip one, or even go back a few and still be well within the range of "normal." Always keep in mind that variation and individual timing is the natural order of things when it comes to growing children.
Birth to Three Months
• Newborns listen to sounds that are close to them.
In the first ninety days of life, a newborn infant is fully occupied by the basic needs for comfort, food, rest, hygiene, and love. During these first beautiful months your baby spends most of his or her day sleeping and being kept clean, fed, and adored. At the same time that your baby begins to develop a sense of touch she also begins to respond to the trust and warmth she soaks up from the people who care for her. By the third month your baby begins to grasp and hold things such as rattles and stuffed animals, and fully expects that her comfort and contact needs will be met. Initially your baby communicates by crying. You and the other adults around her begin to read her signals and recognize that the specific cry for being hungry is different from the cry for being wet. Soon she will start making other sounds and playing with her growing ability to vocalize; she will repeat sounds that get your attention and approval.
Three to Six Months