Learning birdsong Singing zebra finches could one day shed light on how some babies learn to talk faster and more accurately than others.
Findings from a new study today in the journal Proceedings of the Royal Society B could also improve understanding of communication problems in autism and schizophrenia.
Human babies learn speech by babbling and then slowly convert this into speech by imitating the sounds made by adults, says lead researcher neuroscientist Dr Thierry Lints of Texas A&M University.
In the same way, songbirds learn how to sing by babbling and then imitating the songs of adult birds.
Few animals, apart from birds, have this capacity for vocal learning, says Lints.
He says avian brain circuits involved in communication are similar in design to those involved in human communication, which makes birds a good model for studying such things as the aquisition of speech by babies.
While a fair bit is known about how birds recognise and produce a song, Lints says little is known about the "imitative memory" that allows them to accurately encode the details of an adult's song in their brain.
Lints says previous studies of imitative memory had exposed young birds to adults for around two months before testing their ability to replicate songs.
But he and colleagues wanted to find out how quickly birds can encode an adult's song and imitate it.
To investigate this, the researchers used male zebra finches, which are 'tutored' to sing by their fathers.
Chicks were raised in the absence of fathers before being placed in soundproof boxes where their baseline 'untutored' song was recorded.
Lints and colleagues then exposed the young finches to bursts of adult song totalling just 75 seconds over only a matter of hours.
They then continuously recorded the sounds made by the young birds for two months and then compared the vocal changes made by the birds each day to their final success in imitating the adult's song.
The researchers found some birds encoded the adult song rapidly.
"They can capture all the intricate details of the song in this little training session," says Lints.
He and colleagues found 10 per cent of the birds were able to take a perfect audio snapshot of the adult's song shortly after or during training, and reproduce it perfectly two months later.
The birds that produced the most rapid vocal changes during training ended up being the best at imitating adult songs, says Lints. In other words, the fastest learners were also the most accurate.
Other birds either matched only parts of the adult's song after two months or sang "completely aberrant" songs, as if they had had no training at all.
Lints and colleagues found the age at which the birds were exposed to training influenced their ability to acquire song. Birds that were able to imitate their father's song were trained at 35 or 45 days after hatching.
By comparison, those first exposed to adult song at 60 days performed no better than untrained birds at imitating.
"This is as in humans, where speech and language develops at a critical phase when acquisition is easiest," says Lints.
He would now like to find out what genes are associated with the speed and accuracy of learning in finches, as this may shed light on the genetic factors influencing different learning abilities of babies.
Lints says the study reveals an "interesting parallel" with findings that babies are best able to remember information if they are allowed to nap after being first exposed to it.
The bird study shows after the first burst of song, young finches that were able to imitate adult song had a nap. And, contrary to previous research, which suggested birds needed an overnight sleep to encode songs, these birds were able to make vocal changes on the same day.
"So this daytime napping may be an important part of the birds being able to respond in this way," says Lints.
Lints says the findings might also help improve understanding other communication problems in humans, including difficulties in learning non-verbal communication.
Here also, a baby must store an "internal model" of what an adult individual does and use that to shape their own behaviour. He point out that autism and schizophrenia have been linked to problems with establishing such models for behaviour.