Baby sign language has been shown to improve vocabulary skills, if not just directly but also towards recognition and understanding, so it helps give another form of communication and lessens tantrums because they can't get their message across.

DD1 had learnt about 10 signs by 14 months, 40 signs by the time she was 18 months, her actually vocab was only about 10. In the next couple of months her signs peaked at about 50, but her speech exploded to about 100. I what great in the mean time for her to be able to communicate.

Another consideration is that children's actual jaw structure changes about the ages of 18mths-2 1/2, apparently its thought to cause discomfort and some pain, so it can affect many things like speech, and behaviour, thought to be linked to the terrible 2's.

Before you know it, he will be chatting his head off.