The happy babbling that entertains parents as their babies try to mimic speech turns out to have a parallel in the animal world.
Baby birds babble away before mastering their adult song, researchers report in Friday's edition of the journal Science.
Michale S. Fee and colleagues at the Massachusetts Institute of Technology studied the brains of baby zebra finches as the little birds learned the unique song they would use as adults.
The baby birds practiced making sounds incessantly, the team reports in Friday's edition of the journal Science.
"Birds start out by babbling, just as humans do,'' Fee said, while the adult bird produces a very precise pattern of sound.
Like babies moving their limbs or trying to walk, babbling emphasizes the importance of play activities in learning.
"The parallels between human and bird language are indeed striking,'' said psychology professor Bob McMurray of the University of Iowa, though there are also important differences between the structure of human language and bird song.
"This work illustrates that language learning may operate by very general principles ... that can be seen across species as different as finches and humans,'' added McMurray, who was not part of Fee's team.
"However, when these somewhat simple principles are translated into neural tissue the results can be surprisingly complex,'' he added.
Indeed, Fee discovered that one part of the finch brain produces song, while the babbling is controlled by a different part of the brain.
A part of the finch brain known as the LMAN is used during the 30 to 45 days the young birds are babbling, the researchers found. But when the adult song is learned, that is controlled by the brain's high vocal center, or HVC, and the LMAN is inactive.
"In birds, the exploratory phase ends when learning is complete. But we humans can always call upon our equivalent of LMAN, the prefrontal cortex, to be innovative and learn new things,'' Fee noted.
When the researchers disabled the HVC in adult birds, the LMAN took over again and babbling resumed.
McMurray said such studies help illustrate some of the deeper developmental mechanisms that may underlie human language development.
"In this case we see hints of the remarkable ability of the brain to teach itself — one area of the brain creates a variable signal that presumably drives learning or reorganization in another,'' he said.
"We still need to understand the process of learning and the reorganization of brain tissue that goes with it, as well as the structure in the song and which aspects are selectively encoded as the bird develops,'' he said.
Fee's research was funded by the National Institutes of Health, the Hertz Foundation and Friends of the McGovern Institute for Brain Research at MIT.