When adult humans talk to baby humans, we tend to sound ridiculous. We babble repetitively, use simpler words and sentences, and adopt an exaggerated, singsong intonation. This baby talk is common in cultures around the world, and despite its apparent silliness, science has shown it can help babies learn to speak.
And not just baby humans. According to a new study, similar "baby talk" helps young songbirds learn to sing like their parents. Adult zebra finches alter their vocalizations when singing to juveniles, scientists report in the Proceedings of the National Academy of Sciences, and chicks who receive this "tutoring" get a major boost.
"Songbirds first listen to and memorize the sound of adult songs, and then undergo a period of vocal practice — in essence, babbling — to master the production of song," says lead author and McGill University neurobiologist Jon Sakata in a statement.
And just as human parents coach their babies by speaking slowly and repeating words more often, zebra finches offer their chicks an avian version of baby talk.
"We found that adult zebra finches similarly slow down their song by increasing the interval between song phrases," Sakata explains, "and repeat individual song elements more often when singing to juveniles."
Here's an example of an adult zebra finch song when it's not directed at a chick, followed by the directed "baby talk" version used in social tutoring:
Credit: Sakata Songbird Lab/McGill University
To reveal this phenomenon, Sakata and his colleagues studied two groups of young zebra finches, a social songbird species native to Australia. One group was allowed to interact directly with an adult zebra finch, while the others listened to adults' songs played through a speaker. After a brief tutoring period, all the chicks were housed individually so they could practice their new skills without interference.
Chicks who socialized with an adult showed "significantly enhanced vocal learning" months afterward, the researchers write, even if the tutoring had only lasted one day. Adult zebra finches modified their songs and directed them at chicks during these in-person tutoring sessions, prompting the chicks to be more attentive than they were to unmodified or undirected songs. The more closely a baby bird paid attention to its tutor, the study's authors note, the better it learned the song.
An adult female zebra finch with two juveniles in Australia's Blue Mountains. (Photo: Lip Kee Yap/Wikimedia Commons)
This discovery is interesting on its own, offering a relatable glimpse into the way adult songbirds pass knowledge to younger generations. But the study's authors also dug a little deeper, investigating the behavior of certain neurons in brain regions associated with attention. When chicks received social tutoring from an adult, more neurons that produce the neurotransmitters dopamine and norepinephrine were activated than when chicks merely listened to audio recordings.
And that, Sakata says, may teach us about more than just birds. "Our data suggest that dysfunctions in these neurons could contribute to social and communicative disorders in humans," he explains. "For example, children who suffer from autism spectrum disorders have difficulty processing social information and learning language, and these neurons might be potential targets for treating such disorders."
Now that we know what social learning can do for young birds, Sakata's next goal is to see if this educational effect can be simulated by raising dopamine and norepinephrine levels in the brain. In other words, he says, "We are testing whether we can 'trick' a bird's brain into thinking that the bird is being socially tutored."