When would you be concerned?

mrssunshine12

My cousin has a 16 month old son. At his one year appointment her pediatrician said she should be taking him to a specialist because at that point he was only really making babbling sounds. Obviously my cousin was pretty upset about this and came home crying. My mom and our aunts told her she shouldn't be worried, every kid does things at their own pace. 

Almost four months later and he's made a little progress but not much. He'll say "yeah" to pretty much everything, but other than that lots of noises and no words. Other than talking he's doing really well- he's healthy, running, jumping, dancing, listens well, he's even got pretty good rhythm with the wooden spoon and pots and pans. 

My mom watches him during the week and she's started to become concerned. He communicates what he wants really well nonverbally though. I was just curious to see if anyone else has experienced something like this and at what point you would get worried.