Is baby talk benefit a child?

I'm a speech and language pathologist and I have to say that I disagree. I feel that "baby talk" has a place when used appropriately. When you are talking to your baby about something, such as what they can see, what they're doing, when you're playing with a toy etc, THEN it's most appropriate to use short, simple sentences to describe what's happening, e.g. "Drinking milk", "round it goes", "up up up!" etc. However at quieter times when there's less going on I think it can be helpful to engage in reciprocal "babble" at the level your baby is at. For example, if they're about 9 months old and are babbling things like "bababa", you might repeat back to them "bababa". They find this so rewarding! It's teaching them the art of conversation at a level they can manage. I would be very surprised if they didn't say "bababa" back to you again straight away, at least most of the time. Then you might change it up and say "mamama" or "dadada" or "ahgooo" or something like that and see if they are able to imitate. If they do - lots of smiles and praise! In this way you are also expanding their repetiore of sounds and teaching them that oh-so-crucial skill of imitation.