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

Their collaborator Kazuo Okanoya, then at the Riken Brain Science Institute in Japan, observed the same effect in Bengalese finches, which are able to sing much more complex songs. These birds were living in a more natural environment, flying around in large aviaries full of other finches; this helped confirm that learning individual transitions is part of a natural developmental process.

Dr. Tchernichovski and Gary Marcus, who studies infant language learning at New York University and who helped design the study, discussed the results. Could the difficulty learning transitions in songbirds hold true for human infants?

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. That could help explain why children continue to babble even as they begin to understand language, making the gap between comprehension and speech a little less mysterious.

“This result changes what we think kids are doing while babbling,” Dr. Marcus said.

This high-profile study is also likely to rekindle a touchy debate between human language researchers and birdsong researchers: Can we really use birdsong to learn about human speech?

The two might seem to have little in common. Birds and humans are evolutionarily distant, and birds use song differently from the way we use language. But in recent years, researchers have found many surprising parallels.