Scientists from the University of Exeter in the UK and the University of Zurich in Switzerland have discovered that humans are not the only ones who can string together meaningless sounds to create language signals—their collaborative study shows that babbler birds are also able to communicate in this way.
The researchers discovered that the chestnut-crowned babbler—a highly social bird—has the ability to convey meaning by rearranging meaningless sounds in its calls. This babbler bird communication is reminiscent of the way humans form words. The research findings, which appear in an article in the June 29, 2015 edition of the journal PLOS Biology, reveal keys to the origins of human language systems.
“Although previous studies indicate that animals, particularly birds, are capable of stringing different sounds together as part of a complex song, these songs generally lack a specific meaning and changing the arrangement of sounds within a song does not seem to alter its overall message,” said lead author Sabrina Engesser from the University of Zurich. “In contrast to most songbirds, chestnut-crowned babblers do not sing. Instead, their extensive vocal repertoire is characterized by discrete calls made up of smaller acoustically distinct individual sounds.”
“We think that babbler birds may choose to rearrange sounds to code new meaning because doing so through combining two existing sounds is quicker than evolving a new sound altogether,” said co-author Andy Russell, PhD, from the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus who has been studying the babblers since 2004.
According to their article, the researchers noticed that chestnut-crowned babblers reused two sounds “A” and “B” in different arrangements when performing specific behaviors. When flying, the birds produced a flight call “AB,” but when feeding chicks in the nest they emitted “BAB” prompt calls.
When the researchers played the sounds back, the listening birds showed they were capable of discriminating between the different call types by looking at the nests when they heard a feeding prompt call, and by looking out for incoming birds when they heard a flight call. This was also the case when the researchers switched elements between the two calls: making flight calls from prompt elements and prompt calls from flight elements, indicating that the two calls were indeed generated from rearrangements of the same sounds.
Co-author Simon Townsend, PhD, from the University of Zurich explained that this is the first time that the capacity to generate new meaning from rearranging meaningless elements has been shown to exist beyond humans. “Although the two babbler bird calls are structurally very similar, they are produced in totally different behavioral contexts and listening birds are capable of picking up on this,” said Townsend.
According to the authors, the chestnut-crowned babbler produces the first sound element “B,” which appears to differentiate the meaning between flight and prompt vocalizations. This is akin to “cat” and “at” in English, where the “c” represents the differentiating element, or phoneme.
“Although this so-called phoneme structuring is of a very simple kind, it might help us understand how the ability to generate new meaning initially evolved in humans,” explained Townsend. “It could be that when phoneme structuring first got off the ground in our hominid ancestors, this is the form it initially took.”
Source: University of Exeter
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