When SS#1 was a toddler, I asked the doctor to check his hearing. The doctor asked me to elaborate and I told him that SS#1 just didn't seem to acknowledge me when I spoke to him, even if I raised my voice. The doctor smiled kindly at me and said that he didn't think anything was wrong with my toddler's ears.
His diagnosis? Selective hearing. He assured me that ALL children developed this condition at some point. He was right. The Manimal has developed it as well.
Now, with SS#1 getting older, he seems to have developed brain damage. At least that's Bill Cosby's diagnosis.