The songs produced by birds share similarities with the structure of human language, a study shows.

An international team of researchers have uncovered a previously undetected structure in the birdsong of Bengalese Finches that has the same statistical patterns found in human languages.

The songbirds – famous for their complex, learned songs – organize their songs using the same mathematical formula found in human speech – a trait that has developed over time which makes complex communication easier to learn and pass from one generation to the next.

The findings build on the team's previous discovery that humpback whales also rely on the similar systematic structure.

Language has long been considered a uniquely human trait, with features that mark it out as distinct from the communication of all other species.

The findings suggests that some of language's most fundamental building blocks may not be uniquely human after all, but a universal feature of learned communication, the researchers say.

The research suggests that like human language the communication processes for songbirds and humpback whales are an evolutionary solution with them being transmitted culturally, meaning that they learn their communication systems from each other.

The team, led by researchers from the University of Edinburgh, the Hebrew University of Jerusalem and Teikyo University in Japan used methods inspired by how babies discover words in speech, and applied them to song data collected from Bengalese Finches in Japan.

The team observed the Finch songs contained statistically coherent sequences of notes, the avian equivalent of "words", and these sequences followed the same patterns observed in human language where a few words are used very frequently and others are used more rarely – known as a Zipfian distribution.

Data was collected across the various stage of development of the birds and the patterns were already present during the birds' earliest attempts at singing, suggesting they emerge naturally as part of the learning process.

The young song birds listen to the sounds around them to unconsciously learn the statistical patterns of the sounds and organise their songs – similar to how babies figure out where one word ends and the next begins by recognising which sounds frequently occur together, the research found.

This statistical process is thought to make language easier to learn, helping infants identify recurring "chunks" of speech within the continuous stream of sounds they hear every day. 

Recently, the lead researchers of this study, together with Dr. Ellen Garland from the University of St. Andrews, found similar statistical patterns in the songs of humpback whales.

The teams says the new findings suggest that some of the fundamental building blocks that make language learnable can emerge wherever communication is learned and passed from one generation to the next – even in the songs of small birds.

Professor Simon Kirby of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, who co-led the research said: "We have become used to the idea that language is unique in the natural world. But by using insights from how babies learn language we've been able to take a closer look at birdsong, and have discovered a surprising commonality between these species separated by more than 300 million years of evolution. Both humans and songbirds pass on their communication through culture, and this is what creates the patterns that language and birdsong share. We humans are the only species with language, but we share the planet with several others who also have culturally evolving communication, and this may make us more similar to one another than we previously thought."

Scientists have long known that songbirds learn their songs by listening to adult birds, much as children learn language from the people around them.

This study goes a step further by showing that the songs themselves are organised according to the same statistical principles that help human babies learn spoken language.

Together with recent discoveries in humpback whales, the findings suggest that evolution may repeatedly arrive at the same solution whenever complex communication must be learned and transmitted across generations, the researchers say.

The study is published in the journal Science Advances. Link to study: www.science.org/doi/10.1126/sciadv.aea3015.

The research is co-led by Professor Simon Kirby of the University of Edinburgh, Professor Inbal Arnon of the Hebrew University of Jerusalem, and Professor Kazuo Okanoya of the Advanced Comprehensive Research Institute, Teikyo University, Japan.

Professor Inbal Arnon, a Leverhulme Trust Visiting Professor at the University of Edinburgh and of the Hebrew University of Jerusalem, said: "People often think language is what makes humans unique. Our findings suggest that some of the fundamental properties that make language what it is can emerge wherever communication is learned and passed from one generation to the next – and that this happens across evolutionarily distant species (humans, Bengalese Finches, humpback whales). This does not mean that human language is not special in other ways, but it gets us closer to understanding what it shares, and does not, with other communication systems in nature. For me, it is really exciting to see how ideas from child language learning can reveal new insights about language evolution and animal communication"

Professor Kazuo Okanoya of the Advanced Comprehensive Research Institute, Teikyo University, Japan, said: "I have studied Bengalese finch song for many years and thought I knew it rather well. It was therefore a pleasant surprise to discover, through this international collaboration, that it shares yet another property with whale song and human language: frequently used chunks of syllables tend to be shorter, while less frequently used chunks tend to be longer – a pattern known as Zipf's law."

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