It sounds like he is right on track. It is true that babies and toddler's brains generally focus on either the physical or the verbal skills- one at a time. Try to get a response out of Aidan by asking him questions, repeat words a lot, keep reading books with large pictures of objects, and teach him a few common sign langage words to help decrease frustration. My daughter (now 17 months) was walking well by her first birthday, and is an avid runner, climber, etc. (monkey, really), but she doesn't have the vocabulary I would have thought yet either. I know she understands things, and she does say certain words all the time (Mama, Daddy, Dad, all done, gone), and she babbles a lot, but a lot of the time she will say a new word once or twice and then she won't say it anymore. She said "milk" clear as day 2 times about 3 months ago, and hasn't said it since. The same thing happened with "grandma", "grandpa", "teeth", "more please", and plenty more I can't think of right now. One other thing I noticed with myself is that I sometimes didn't pick up on a word that she was saying until someone else heard it. Sometimes a little creativity is needed! =) Don't worry- he will catch up. The important thing is that he understands what you are saying and is babbling. If he doesn't start saying more words by the time he is 18 months, you may want to check in with the doctor. Happy talking!