I find that interesting too, because for my daughter I have been told that she will stop making oohs and so on after 4-6 months. She is 6 months now and everyday she continues to make new noises and sounds. The infant hearing program says that a deaf baby stops because she hasnt heard the noise to repeat it. And up until this point it is just natural for babies to make a few noises. Please let me know how it goes for your Grandson. Does he have a hearing aid right now? I have our first implant meeting this month, so far her other doctors believe she is a candidate for a straight implant opposed to curved since she has no cochlea. She does have a open cavity where the cochlea should be.