Baby birds are like baby humans on at least one score: they both babble. But as songbirds grow up, they make the switch from babbling to singing by flipping to a different brain circuit, new research finds, suggesting a new view of human infant behavior.
We should toss out the idea that babbling is an undeveloped adult behavior, said study leader Dmitriy Aronov of MIT. "Maybe we should think of these behaviors as being the presence of exploration … of creativity," he told LiveScience.
Some scientists have thought that a single brain pathway matures to produce song in birds. In the study detailed in the May 2 issue of the journal Science, however, male zebra finches were found to use one circuit for babbling as juveniles and another for singing as adults.
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In terms of brain regions, babbling was not just undeveloped singing.
Male songbirds learn to sing by exploring their vocalizations. Human babies may be doing the same thing when they babble, said Ofer Tchernichovski, a neuroscientist who has studied bird song at City College of New York and was not associated with the study.
Aronov's team studied songbirds as a model to reveal the brains behind complex behaviors, such as singing, for which there are analogous human behaviors, such as speaking.
To understand the transition to singing in birds' brains, Aronov and his MIT colleagues, including fellow graduate student Aaron Andalman, studied male zebra finches, small birds native to Australia and Indonesia.
The researchers turned off parts of the birds' brains using chemicals or surgery. When the part of the brain devoted to adult singing was knocked out, the baby birds kept babbling and never advanced to singing. This meant another circuit was responsible.
Interestingly, when the researchers did the same thing to adult birds — disabled the area for adult song — the full-grown birds babbled like babies. This violates the use-it-or-lose-it rule: Babbling circuitry was not lost as the finches reached adulthood. So, the finches may use both circuits, but one or the other dominates at different times in their lives, the researchers think.
When the finches learn their songs, their exploration or creativity is complete, said team member Michale Fee, "but we humans can always call upon our equivalent of [the birds' babbling center], the prefrontal cortex, to be innovative and learn new things."
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