Think about how most people talk to babies: Slowly, simply, repetitively, and with an exaggerated tone. It’s one way children learn the uses and meanings of language.
Now scientists have found that some adult birds do that when singing to chicks — and it helps the baby birds better learn their song.
The subjects of the new study, published last week in the journal Proceedings of the National Academy of Sciences, were zebra finches. They’re good for this because they breed well in a lab environment, and “they’re just really great singers. They sing all the time,” said McGill University biologist and co-author Jon Sakata.
The males, he means — they’re the singers, and they do it for fun and when courting ladies, as well as around baby birds. Never mind that their melody is more “tinny,” according to Sakata, than pretty.
Birds in general are helpful for vocal acquisition studies because they, like humans, are among the few species that actually have to learn how to make their sounds, Sakata said. Cats, for example, are born knowing how to meow. But just as people pick up speech and bats learn their calls, birds also have to figure out how to sing their special songs.
Sakata and his colleagues were interested in how social interactions between adult zebra finches and chicks influences that learning process. Is face-to-face — or, as it may be, beak-to-beak — learning better? Does simply hearing an adult sing work as well as watching it do so? Do daydreaming baby birds learn as well as their more focused peers?
To test this, the researchers placed some male chicks of around 40 days old with adult male “tutors;” these chicks were called “socially-tutored.” Other male chicks were placed alone, with only a speaker that piped in the song of the adults working with the other chicks, and they were deemed “passively tutored.” All the baby birds had previously been raised by females and so were “essentially naive” about song, Sakata said.
Whether they got one day or five days of exposure to the song, the chicks interacting with adults learned it better than those that heard it through a speaker. That suggests that social interaction is key, Sakata said. Hear for yourself:
Listen here to an adult followed by a socially tutored young bird.
Listen here to an adult followed by a passively tutored young bird.
The researchers also found that the more juveniles paid attention to their tutors — by staying awake, being quiet and not goofing off by, say, eating or flying around — the better they learned the song. The birds who only listened to the song through a speaker, on the other hand, didn’t seem to be paying it much attention.
“That kind of makes sense,” Sakata said. “Kids that pay attention to the teacher when the teacher is saying something important tend to learn better. That wasn’t particularly surprising, but it was a really robust finding.”
And now for the good part. When the adult birds were actually directing their song at their pupils, as opposed to just singing for fun, they spaced out their phrases, repeated more of their introductory notes and “cleaned up their syllables,” Sakata said — and the juveniles paid more attention. Basically, they did birdy baby talk, and it’s the first time it’s been documented.
Listen here to an an adult just singing normally.
Listen here to an adult singing directly to a young bird.
“We liken that a little bit to how people slow down their speech when talking to infants,” Sakata said. “It’s kind of cute that other animals do something similar.”
Sakata said it could be evidence of intentional teaching, though more research is needed to conclude that. For example, he said, it would be helpful to test whether adults sing differently to more advanced and less advanced students.
The study also revealed something that might have implications for people with social and communicative disorders such as autism. The researchers saw that some neurons in two areas of the brain associated with attention were more active in baby birds that were interacting with a singing adult than those that only heard the song. That could be a hint that dysfunctions in those neurons in humans might contribute to such disorders, Sakata said, and that targeting those neurons with treatment might help. He’s now testing that idea in baby birds.