Research by Duke University in North Carolina studied parrot speech. It had been thought that the size of their brains was the key. But the study found it was due to the structure of their brains. They were found to have controlled vocal learning centres called ‘shells' (shown)
The research was conducted by scientists from Duke University in North Carolina.
Dr Mukta Chakraborty of Duke University said: 'This finding opens up a huge avenue of research in parrots, in trying to understand how parrots are processing the information necessary to copy novel sounds and what are the mechanisms that underlie imitation of human speech sounds.'
Parrots are one of the few animals considered ‘vocal learners’, meaning they can imitate sounds.
But why some birds are better than others has until now remained a mystery.
One explanation had been brain size, but by examining gene expression patterns, the new study published in Plos One found that parrot brains are structured differently than the brains of songbirds and hummingbirds, which also exhibit vocal learning.
In addition to having defined centres in the brain that control vocal learning called ‘cores,’ parrots have what the scientists call ‘shells,’ or outer rings, which are also involved in vocal learning.
The shells are relatively bigger in species of parrots that are well known for their ability to imitate human speech, the group found.
Previous research has only looked at the budgerigar, but the new study examined the brains of eight other parrot species including conures, cockatiels, lovebirds, two species of Amazon parrots, a blue and gold macaw, a kea and an African Grey parrot.
The researchers looked for specific gene markers that are known to have specialised activity in the brains of humans and song-learning birds.
They compared the resulting gene expression patterns in all the parrot brains with neural tracing experiments in budgerigars.
It found the most ancient parrot - the kea of New Zealand - has a rudimentary shell structure, suggesting the populations of neurons in the shells probably arose at least 29 million years ago.
Previous research has only looked at the budgerigar, but the new study examined the brains of eight other parrot species including conures, cockatiels (pictured), lovebirds, two species of Amazon parrots, a blue and gold macaw, a kea and an African Grey parrot
It had been assumed the regions surrounding the cores had nothing to do with vocal learning, but the findings support the group’s hypothesis that in humans and other song-learning animals, the ability to imitate arose by brain pathway duplication.
Most of the bird's vocal learning brain regions are tucked into areas that also control movement.
These areas in parrots also show some special patterns of gene expression, which the scientists speculate might explain why some parrots are also able to learn to dance to music.
Dr Chakraborty added: 'It takes significant brain power to process auditory information and produce the movements necessary for mimicking sounds of another species.
'The question is, how specialised are these parrot brains, and in what ways? Is it just a select group of specialised genes, or is it some specific projections that we haven’t discovered yet?'
Further studies will examine whether the shells give parrots a greater ability to imitate human speech.