Why are languages spoken at different speeds?

Have you ever switched audio language halfway through a movie? Although foreign languages always sound rapid-fire to untrained ears, as you swap between Thai, Japanese, and English, you’re listening to languages spoken at wildly different speeds. 

In this article, we explore why languages vary in speed and how invisible aspects of how we communicate mean we all get our point across roughly at the same time. 

Which language is the fastest? 

A 2011 study measured the speech rate of seven languages, with Japanese topping the list. Researchers found Japanese speakers fired out at an average of 7.84 syllables per second, while ambling English speakers only hit 6.19 syllables per second.

This makes sense if we think about how these languages are spoken. English has many syllables that contain lots of sounds. Try saying “Smart frogs jumped twelve quick sticks,” as fast as you can. This short sentence contains 29 different phonemes—the basic units of sound in a language—while using just six syllables. Many languages’ syllables, like those in Japanese, only contain a few sounds, so more syllables can be dished out per second.

What’s the fastest language in the world? #language #languages

Every language is spoken at a slightly different speed. Video: What’s the fastest language in the world?, @VLingvo

That means Japanese is roughly 20 percent faster than English. But despite this, Japanese and English speakers can watch the same, dubbed film over an identical length of time. This, in part, owes something to creative audio dubbing, but it’s also because of differences in how the two languages convey meaning.

Different languages still communicate information at the same speed

In the middle of the 20th century, American polymath Claude Shannon made huge contributions to mathematics, electrical engineering, and computer science through his work on information theory. Shannon, who introduced the term “bit” to mean units of information in computing, explored how human speech communicated meaning. Back in 1951, he estimated that the English language had a redundancy rate of 80 percent, so you could chop out four in every five letters and still conserve meaning.

Shannon was a little harsh on English—more recent analyses have revised this figure down to 50 percent—but his basic theory has stood the test of time: languages convey meaning in different densities. And recording a language’s raw speed misses this fundamental factor.

Is there a limit to how much information our brains can process at one time? 

In 2019, researchers at the University of Lyon attempted to determine how the balance between speech rate and information density averaged across 170 speakers reading set texts in 17 languages. They timed how long it took participants to read this text (excluding long pauses). 

The slowest speaker only got through 4.3 syllables every second, while the fastest hit 9.1 syllables a second, demonstrating that speech speed varied significantly. What made things interesting was their calculation of each language’s information density. 

They used Shannon’s original theory to calculate the language’s syllable conditional entropy—essentially, how easy it is to guess what a syllable will be based on the syllable that comes before it. 

Vietnamese, for example, was one of the lowest-ranked languages for speed, but each syllable encoded a lot of information. Vietnamese speakers needed to utter fewer syllables to get their point across than, for example, those speaking Spanish.

Once the researchers combined each language’s speed and information density, they produced a new metric: the information rate. The information rate determines how much information a language can convey per second. 

This information rate varied so little across languages that the researchers were able to settle on a “universal information rate” of 39 bits/second. They suspect that this represents a rough ceiling on how quickly the human brain can understand speech, which prevents language from getting any faster.  

More questions to explore around languages

However, the study wasn’t perfect. Erica Brozovsky, a sociolinguist at Worcester Polytechnic Institute who presents PBS’s language show Otherwords, pointed out that the design couldn’t capture the features of everyday speech because all the participants read from a set text. 

Brozovsky, who wasn’t involved in the study, tells Popular Science, “I don’t read things as naturally as I speak them, so the way that I talk is going to be a lot faster and a lot more natural than it would be when I’m reading.”

Dan Dediu, a linguist at the University of Barcelona and co-author of the 2019 paper, agrees with Brozovsky and tells Popular Science that an ongoing study will look to overcome this limitation by studying a “much more natural use of language.” 

This future work will also incorporate much more data from non-WEIRD (Western Educated, Industrialized, Rich, and Democratic) languages to determine if their information rate holds up at scale. While the results aren’t official, Dediu shares that unfinalized results from this work suggest the information rate may be universal after all.

Even though some languages pack meaning into dense syllables while others spread it out, they are all routed through the same human brain. There’s so much to be discovered in the cultural and linguistic inventions that separate different languages, but how they vary in speed might not matter so much. Science suggests that what we say is more important than the speed at which we speak it.

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

 

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