I've been reading Steven Pinker's The Language Instinct, and his big subject seems to be language use by young children as evidence that the human brain is hardwired to receive and manipulate language. So I'm intrigued that he doesn't say anything about Baby Sign Language. Maybe he does, but somewhere else. Or maybe it just hasn't been studied much. I know some people think it's a symptom of overachieving parenthood, like trying to raise majestic superchildren by playing them Bach in the womb and so on. But I think it's intriguing.
The gist is that you can teach preverbal kids sign language, and there's a fledgling standard system that's partly related to ASL (why they don't simply use ASL, I don't quite get...) Anyway, you can get baby board books with signs for things like "more", "enough", "hurt", "drink", "cat", "bird" and "flower". My sister used these with her daughter, and I found it fascinating.
The biggest advantage for parents is that it allows kids to clearly express ideas like "I'm thirsty", "I'm full", "I'm still hungry", "I've had enough of this game" and "It hurts". My niece unequivocally used the signs to communicate these ideas well before her first birthday. In fact, it was during her first birthday party that she made her first identified sentence-like communication. My brother was playing the (questionably advisable) game of turning the oven light on and off for her amusement. At one point, he flicked the switch off, and she made the signs for "more" and "light" in succession.
Another thing I found interesting was that my niece used signs to "talk" to herself. We sometimes would watch her amusing herself with her toys while making signs that made sense in context (as in "Here's a kitty", "Here's a birdie").
Well before her first birthday, she clearly showed that she grasped the idea that a concept can be signified or made manifest in numerous ways. For instance, she would use the sign for "flower" to indicate different types of flowers, so she clearly reconized that a tulip, a dandelion and a rose are all "flowers", even though they don't look much alike. She also used it for pretend flowers, floral patterns on fabric, quite abstract illustrations and, on one occasion, for a whirligig on a stick.
The signs allowed windows into her personality that might otherwise have remained closed. Once she gestured inquiringly to an bandaid on my brother's finger. He said and signed that it was a hurt. The next day when he walked in, she approached him and made the hurt sign, indicating his hand, with a demeanor that seemed to suggest that she was asking, as an adult might, "How's your hurt finger"? Even if that interpretation reads too much into the situation, it's clear that she remembered the hurt the next day.
Somewhat related: I like gardens, and would frequently talk/sign to her about them. When I arrived for visits, she would often make the flower sign as soon as she saw me, showing at least that she recognized me as something like "the one who likes flowers" (I'm certain she didn't think I was a flower), and perhaps demonstrating the wish to communicate a much more sophisticated idea, like "So, Sarah, how's your garden doing?" or "Seen any nice flowers lately?"
Again, I'm no scientist, so I might well be reading too much into that interpretation – which is why I'd love to read some solid research by the Pinkers of this world on the subject.
(Photo by kahanaboy from Morguefile.)