I did signing with my daughter, and as a result she had very advanced communication. I know this, because she was being observed by a local university baby lab at the time (for something different) and they told me
. By about 2, she had over 500 words and signs. I believe the average is 50? Again, I know this as I had to document it for the babylab.
I remember her frantically signing at about a year 'light' and we worked out her night wakings was due to her being scared of the dark. We had tried everything logical previously, but hadn't thought that she might be scared of the dark.
At 1, she would sign 'washing machine' to ask to go and watch someone's washing machine (bless her, she had an obsession with them, and used to like looking at them at different people's houses).
She would also ask for me to read a book, and then sign to tell me which one she wanted!
How many other just turned one year olds can ask for the light to be turned on, to go and see a washing machine, or to request a specific book? It gave her language far beyond her 'year', and I would certainly recommend it.