First word?

(The somewhat cubist Brown Bear that may or may not have been the referent of M's first word.) 

M appears to have had a first word. As someone who studies word learning, I suppose I should have been prepared. But as excited as I was, I still found the whole thing very surprising. Let me explain.

M has been babbling ba, da, and ma for quite a while now. But at about 10.5 months, she started producing a very characteristic sequence: "BAba." This sequence showed up in the presence of "Brown Bear, Brown Bear, What Do You See," a board book by Eric Carle that she loves and that she reads often both at daycare and at home.

I was initially skeptical that this form was really a word, but three things convinced me:

1. Consistency of form. The intonation was descending, the stress was on the first syllable, and there was a hint of rounding ("B(r)Ab(r)a"). It felt very word-y.
2. Consistency of context. We heard this again and again when we would bring the book to her. 
3. Low frequency in other contexts. We pretty much only heard it when "Brown Bear" was present, with the exception of one or two potential false alarms when another book was present.

Even sillier, M stopped using it around 3 weeks later. Now we think she's got "mama" and "dada" roughly associated with us, but we haven't heard "BAba" in a while, even with repeated prompting. 

This whole trajectory highlights a feature of  development that I find fascinating: its non-linearity. M's growth – physically, motorically, and cognitively – proceeds in fits and starts, rather than continuously. We see new developments, and then a period of consolidation. We may even see what appears to be regression. 

It's easy to read about non-linearities in development. But observing one myself made me think again about the importance of microgenetic studies, where you sample a single child's development in depth across a particular transition point for the behavior you're interested in. As readers of the developmental literature, we forget this kind of thing sometimes; as parents, we are the original microgeneticists.