We're doing this with our second child now. It removes a lot of frustration from the parents and the kids when the child can actually communicate about what they want, see, hear, think, etc. It seems to cut down on fits, and definitely helps us communicate. As one of the other commenters said kids' language apparatus is fully functioning before they have the fine motor skills necessary to make all the speech sounds they need to say words, so it's a nice hack :) Teach them sign language which they have enough fine motor skills to use until their mouth control gets to the point that they can speak.
Our first kid is now 5 and doesn't really remember any signs, but he said sentences and told stories even in sign language before he could speak well.
> As one of the other commenters said kids' language apparatus is fully functioning before they have the fine motor skills necessary to make all the speech sounds they need to say words
To add to this: My son is 30 months, and his speech is coming along well, but one really fascinating part is how he will construct sentences that are far more elaborate than what he can say, and substitute "missing" words for with a specific sound.
It is clear these aren't "just" sounds from how he'll repeat phrases with the right number of "words", just some of them are padded out because he doesn't know how to say them yet, and then gradually more words will get added to the various phrases as he figures out how to pronounce them.
Our first kid is now 5 and doesn't really remember any signs, but he said sentences and told stories even in sign language before he could speak well.