M is now 15 months, and her receptive vocabulary is quite large. She knows her vehicles, body parts, and a remarkable number of animals (giraffe, hyena, etc.). Not coincidentally, we spend a large amount of our time together reading books about vehicles, body parts, and animals – at her initiation. Her productive language is also proceeding apace. As one friend astutely observed, she has a dozen words, nearly all of them "ba."*
I've noticed something very interesting over the last three months. Here's one example. When M first discovered the word "da," she used it for several days, with extreme enthusiasm, in a way that seemed like was identical to the word "dog." The form-function mapping was consistent and distinctive: it would be used for dogs and pictures of dogs, but nothing else. But then over the course of subsequent days, it felt like this word got "bleached" of meaning – it went from being "dog" to being "wow, cool!"
The same thing happened with her first extended experience with cats, at a visit to my parents' apartment. She started producing something that sounded like "tih" or "dih" – very clearly in response to the cats. But this vocalization then gradually became a noise of excitement that was seemingly applied to things that were completely different. Perhaps not coincidentally, our visit was over and we didn't have any cat-oriented books with us, so she couldn't use the word referentially. Now that we're back in the land of cat books, the word is back to having a "real" meaning.
This looks to me to be a lot like the phenomenon of "semantic bleaching," where words' meanings get gradually broadened to incorporate other meanings (like the loss of the "annus" – year – part of the meaning of anniversary). This kind of bleaching typically happens over a much longer timescale as part of grammaticalization, the process by which content words can become particles or affixes (e.g. as in the content verb "go" becoming a particle you can use to describe things in the future like "going to X"). But maybe it is happening very quickly due to the intense communicative pressure on M's extremely small lexicon?
The idea here would be that M only has a very small handful of words. If they don't fit the current situation, she adapts them. But mostly the communicative context she's adapting to is, "hey, look at that!" or "let me grab that!" So the process of bleaching words out from "dog" to something more like "cool!" could actually be a very adaptive strategy.
I've checked the research literature and haven't found anything like this described. Any readers know more?
* It's really more like ball ("ba"), balloon ("ba", but possibly just a ball), bus ("ba"), perhaps baby ("ba") and bottle ("ba") as well, dog ("da"), yes ("dah"), cat/kittie ("dih"), truck ("duh"), daddy ("dada"), yum ("mum-mum"), more ("muh"), hi ("ha-e"), and bye ("ba-e"). Some of these are speculative, but I think this is a pretty good estimate.