Putting Music to the Words

The forest is flush with sound, as wildlife fills the airwaves with songs and calls. Some species sing and some make word-like utterances, but only humans put the words and music together.

In many songbird species, males sing to defend territory and attract mates. As youngsters, they memorize snippets of melodies from neighboring older males. Then as adults, they link these melodies together to improvise new songs, just like a jazz musician.

Jazz may feel “free form,” but its tunes are far from random. The same is true for birdsong. Both the saxophonist and the sparrow have internalized a set of rules for stringing melodic patterns into larger sequences of music that are familiar but never exactly the same.

Male songbirds show off their singing skills to impress the ladies and to chase off the competition. But birdsong doesn’t mean anything, in the sense that some particular sound sequence stands for some object or event in the world. That is, songbirds have music but no words.

There are over four thousand species of songbirds, but singing is far less common in mammals. Among the primates, only our distant cousin the gibbon is a crooner. Male gibbons sing to attract females, and mated pairs sing duets as a form of social bonding.

Still, primates are a vocal lot. It’s just that they mainly use their voices to communicate specific meanings. For instance, vervet vocabulary consists of three predator calls—one each for leopard, eagle, and python. Each call is a discrete sound pattern. Vervets may repeat a particular call several times, but they don’t combine various calls into complex sequences. That is, vervets—and primates more generally—have words but no music.

To couch this discussion in more technical terms, we can say that some animal vocalizations feature syntax, while others feature semantics. Syntax is a set of rules for ordering elements, while semantics involves linking arbitrary symbols with things in the world. In animal communication systems, you can have one or the other. But only human language has both syntax and semantics.

Humans engage in all sorts of behaviors that, like birdsong, have syntax but no semantics. Music is the obvious example, which we’ve already alluded to. Dance is another complex behavior that is structured by rules.

Many mundane behaviors also have syntactic structure with no semantic meaning. Brushing your teeth and doing the laundry are just two examples of complex tasks sequenced out of a small sets of simpler—and meaningless—actions.

Humans also employ semantic systems that have no syntax. Street signs like STOP and YIELD serve much the same purpose as alarm calls in the wild. Certain of our gestures are also laden with meaning, which of course varies from culture to culture.

The fact that human languages are composed of words isn’t surprising, given that our closest relatives also use sound symbols to refer to objects or events in the world. What is surprising, though, is the vast difference in the number of symbols we use compared with other primates. The average human knows tens of thousands of words, while the average chimpanzee may not even have a dozen different calls in its repertoire. Even language-trained bonobos acquire at best a vocabulary of a few hundred words.

We can imagine an evolutionary trajectory in which hominids gradually increased their vocabularies from dozens to hundreds to thousands of symbols over the eons. But where syntax comes from is still a mystery, since none of our direct ancestors show any precursors for it.

There are still plenty of scientists who argue that syntax is what marks the great divide between humans and apes. Half a century ago, renowned linguist Noam Chomsky proposed that a genetic mutation rapidly transformed human brains into syntax processors. This explanation for language evolution was the received wisdom of Chomsky’s generation, and as a psycholinguist I took it on faith for many years.

However, the ability to construct complex sound sequences has evolved independently in various lines. Just like songbirds and gibbons, cetaceans such as dolphins and whales also improvise melodies according to patterns. In the human line, syntactic processing abilities most likely evolved gradually over evolutionary time, probably in tandem with our gradually increasing vocabularies.

References

Miyagawa, S., Ojima, S., Berwick, R. C., & Okanoya, K. (2014). The integration hypothesis of human language evolution and the nature of contemporary languages. Frontiers in Psychology, 5, 564.

Nowicki, S. & Searcy, W. A. (2014). The evolution of vocal learning. Current Opinion in Neurobiology, 28, 48-53.

David Ludden is the author of The Psychology of Language: An Integrated Approach (SAGE Publications).