What Humans and Sparrows Have in Common: They Make Sense of Sound in the Same Way

What do humans and sparrows have in common? They both make sense of sound in the same way. Scientists have found that swamp sparrows are capable of processing the notes that make up their simple songs in more sophisticated ways than previously realized.

There are finite types of sounds that make up a stream of human speech. Yet people are able to create and make sense of an almost infinite number of words and sentences about the present, past and future, unconsciously and automatically. Not only that, but how humans perceive speech sounds in influenced by context.

In this case, the researchers wanted to see if this common aspect of understanding spoken language, called partial phonemic overlapping, could also be found in birds. That's why they recorded and analyzed the songs of 206 male swamp sparrows.

What did they find? It turns out that the short repeated syllables that made up each song consisted of subsets of roughly 10 types of notes. In two experiments, the researchers compared males' territorial responses to songs in which either the first note or the last note of each syllable was substituted with a note of a different type. They found that how the birds perceived a particular note depended on where it fell in a snippet of song.

This response from the swamp sparrows revealed that they're capable of far more advanced hearing than previously realized. The study also suggests that the ability to perceive speech sounds differently in different contexts could have arisen before, rather than after, other aspects of human language such as semantics and syntax.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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