Sparrow Songs Shed Light on How Humans Perceive Sound

Sparrows, known for their melodic, whistling songs, are shedding light on how humans perceive sound and when this ability arose over the course of human evolution, according to new research.

Swamp sparrows are a grey-breasted bird found in wetlands across North America, known for their simple melodious trill that they repeat over and over again. But what do they have to do with human language and sound? Well, despite our unique complex cognitive skills, it turns out that certain songbirds like the sparrow also boast an understanding of speech sounds.

This is after a recent study found that birdsong and human speech are driven by the same genes.

Described in the journal Proceedings of the National Academy of Sciences, swamp sparrows can actually process the notes that make up their simple songs, making these birds more sophisticated than scientists previously realized.

Humans are able to create and make sense of almost an infinite number of words and sentences referring to the present, past and future, both unconsciously and automatically. For example, we can distinguish between the "t" in "city" and the "d" in "ready," even those these words are very similar and pronounced the same. This ability is called partial phonemic overlapping, or the understanding of spoken language.

In this study, Duke University scientists Nowicki and Robert Lachlan wanted to see if the same could be said for birds.

To find out, they recorded and analyzed the songs of 206 male swamp sparrows near Pymatuning Lake in Pennsylvania. Through statistical analysis they found that each syllable in each type of song had about 10 different kinds of notes. Researchers then simulated the songs of these songbirds, substituting either the first or last note of each syllable with a note of a different type - either short, intermediate or long.

It turns out this simple modification resulted in an even more aggressive territorial display among male sparrows, at least when the note was substituted in one position in the song, whereas substituting in another position actually made their territorial display weaker. This suggests that birds can perceive speech sounds differently in different contexts - a skill that humans need to be able to recognize speech.

According to the researchers, if birds can perceive speech, then it's possible that this ability developed in humans before, and not after, other aspects of human language such as semantics and syntax developed.

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