In the early 1960s, a doctoral student at Cornell University wanted to figure out whether there was any truth behind the “cultural stereotype” that certain foreigners speak faster than Americans. He recorded 12 of his fellow students—six Japanese speakers and six American English speakers—monologuing about life on campus, analyzed one minute of each man’s speech, and found that the two groups produced sounds at roughly the same speed. He and a co-author concluded that “the hearer judges the speech rate of a foreign language in terms of his linguistic background,” and that humans the world over were all likely to be more or less equally fast talkers.
In the half century since then, more rigorous studies have shown that, prejudice aside, some languages—such as Japanese, Basque, and Italian—really are spoken more quickly than others. But as mathematical methods and computing power have improved, linguists have spent more time studying not just speech rate, but the effort a speaker has to exert to get a message across to a listener. By calculating how much information every syllable in a language conveys, it’s possible to compare the “efficiency” of different languages. And a study published today in Science Advances found that more efficient languages tend to be spoken more slowly. In other words, no matter how quickly speakers chatter, the rate of information they’re transmitting is roughly the same across languages.
The basic problem of “efficiency,” in linguistics, starts with the trade-off between effort and communication. It takes a certain amount of coordination, and burns a certain number of calories, to make noises come out of your mouth in an intelligible way. And those noises can be more or less informative to a listener, based on how predictable they are. If you and I are discussing dinosaurs, you wouldn’t be surprised to hear me rattle off the names of my favorite species. But if a stranger walks up to you on the street and announces, “Diplodocus!” it’s unexpected. It narrows the scope of possible conversation topics greatly and is therefore highly informative.
Informativity in linguistics is usually calculated per syllable, and it’s measured in bits, just like computer files. The concept can be rather slippery when you’re talking about talking, but essentially, a bit of linguistic information is the amount of information that reduces uncertainty by half. In other words, if I utter a syllable, and that utterance narrows down the set of things I could be talking about from everything in the world to only half the things in the world, that syllable carries one bit of information.
In the new study, the authors calculated the average information density—that is, bits per syllable—of a set of 17 Eurasian languages and compared it with the average speech rate, in syllables per second, of 10 speakers for each language. They found that the rate of information transferred stayed constant—at about 39.15 bits per second, to be exact.
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