Babbling is a key stage in language acquisition. We can see where it fits into the overall progression in the following “very rough” table taken from Jean Aitchison’s The Articulate Mammal: An Introduction to Psycholinguistics:
Rare or complex constructions
After the cooing or gurgling phase from which it develops, babbling has a distinctly speech-like quality because it features “sounds that are chopped up rhythmically by oral articulations into syllable-like sequences”, as Mark Liberman describes it.
The sounds most associated with babbling are mama, papa, dada, nana and slight variations thereon — as for example in the well-known video of twin babies repeating dada (and dadadadada, etc.) to each other.
This is true of a great many languages from different language families and parts of the world. The remarkable correspondence can be seen in a list included in Larry Trask’s “Where do mama/papa words come from?”, about which more below:
Some of you will have seen these videos already: Sam and Ren, fraternal twins, engaged in a conversation of very animated babbling. Regardless of your tolerance for cute-baby videos, the chat is great fun and quite fascinating to watch – especially the second video, which has been watched many millions of times in just a few weeks:
The boys’ mother is a twin herself, and she shares her family’s adventures here. (After the footage went viral, it wasn’t long before parodies popped up, but I’ve yet to see one worth linking to.) Some of the mediacoverage suggests the possibility that the twins have a “secret language”, but this is improbable. As Mark Liberman writes in a comment at Language Log,
It seems unlikely that material as phonetically unmodulated as this recording actually contains any communicated lexical material (as opposed to acting out conversational interaction without any propositional content). The “private languages” of siblings are not like this, for an obvious reason: it’s hard to develop an effective human spoken language with only one syllable. . . . It’s possible that variations in timing and pitch are carrying some quasi-lexical information here . . . but I rather doubt it.
Sam and Ren’s discussion might be minimal in its selection of syllables, but the twins show great range of tone, timing, and gesture. They deploy all sorts of conversational skills, and the fact that they are twins means each has a peer at a similar level of development with whom he can practise.
Many of their vocalisations take the form of reduplicated or reduplicative babbling (e.g., da-da-da), but there’s far more communication taking place than just repetition of simple utterances. Hope Dickinson, of the Speech-Language Pathology Program at Children’s Hospital Boston, says the twins are
demonstrating great mimicking of multiple aspects of conversation. . . . One thing they are using wonderfully is turn taking, as in first one “talks” and then pauses and the other responds. . . . There is fantastic rise and fall to their pitch and tones. Sentences or exclamations end loudly and emphatically, and there is also some questioning (rising) intonation. They are using gestures to supplement their talking, much like adults do. Their body distance is even very appropriate for most Americans; not too close, but not too far either.
Already, these twins have a greater command of turn-taking than some adults I’ve encountered, to say nothing of their infectious enthusiasm for, and delight in, simple conversation. Or not so simple. As the great computer intelligence Golem remarked, in Stanisław Lem’s Imaginary Magnitude, “Babble can be highly complex!”
We can’t say if the twins at that stage of development really can understand that the behavior they are practicing is language which communicates a very specific meaning. It may very well be that they are simply mimicking the entire behavior – intonation pattern, gestures, and turn-taking – and gaining an understanding that these actions and sounds produce certain results or behaviors when these large, lumbering adult creatures in the house perform them, and maybe they should learn to do the same.