Monday, July 1, 2013

Infants Learn to Babble Like Birds Learn to Sing

From the NYTimes:
Researchers who focus on infant language and those who specialize in birdsong have teamed up in a new study suggesting that learning the transitions between syllables — from “da” to “do” and “do” to “da” — is the crucial bottleneck between babbling and speaking...

He and Dr. Lipkind were teaching young zebra finches living in soundproof boxes to switch the order of syllables in their songs. Birdsong is composed of discrete song syllables (“chirp A,” “chirp B”) similar to syllables in human speech. The researchers piped in the song of an adult male zebra finch to teach young birds one song (A-B-C), then piped in a new song that required the birds to use the same syllables in a different order (A-C-B).

The birds could learn the new song only after a huge effort — by practicing thousands of times a day over many weeks. The fact that the new song simply required the birds to switch syllables around suggested that the roadblock was learning the transitions...

By analyzing an existing data set of recordings of infant babbling, they found that as babies introduce a new syllable into their repertory, they first tend to repeat it (“do-do-do”). Then, like the birds, they begin appending it to the beginning or end of syllable strings (“do-da-da” or “da-da-do”), eventually inserting it between other syllables (“da-do-da”).

As with the birds, learning the transitions between new syllables and old syllables is a painstaking process for babies.
Language Log weighs in HERE. The research has been published in Nature:

Dina Lipkind, Gary F. Marcus, Douglas K. Bemis, Kazutoshi Sasahara, Nori Jacoby, Miki Takahasi, Kenta Suzuki, Olga Feher, Primoz Ravbar, Kazuo Okanoya & Ofer Tchernichovski

Nature 498, 104–108 (06 June 2013) doi:10.1038/nature12173

Human language, as well as birdsong, relies on the ability to arrange vocal elements in new sequences. However, little is known about the ontogenetic origin of this capacity. Here we track the development of vocal combinatorial capacity in three species of vocal learners, combining an experimental approach in zebra finches (Taeniopygia guttata) with an analysis of natural development of vocal transitions in Bengalese finches (Lonchura striata domestica) and pre-lingual human infants. We find a common, stepwise pattern of acquiring vocal transitions across species. In our first study, juvenile zebra finches were trained to perform one song and then the training target was altered, prompting the birds to swap syllable order, or insert a new syllable into a string. All birds solved these permutation tasks in a series of steps, gradually approximating the target sequence by acquiring new pairwise syllable transitions, sometimes too slowly to accomplish the task fully. Similarly, in the more complex songs of Bengalese finches, branching points and bidirectional transitions in song syntax were acquired in a stepwise fashion, starting from a more restrictive set of vocal transitions. The babbling of pre-lingual human infants showed a similar pattern: instead of a single developmental shift from reduplicated to variegated babbling (that is, from repetitive to diverse sequences), we observed multiple shifts, where each new syllable type slowly acquired a diversity of pairwise transitions, asynchronously over development. Collectively, these results point to a common generative process that is conserved across species, suggesting that the long-noted gap between perceptual versus motor combinatorial capabilities in human infants may arise partly from the challenges in constructing new pairwise vocal transitions.

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