If you have ever tried to listen to native speakers of a language you are learning, you probably had trouble understanding them because they seem to be speaking too fast. It turns out that this might not just be because you are new to the language. People who speak different languages actually voice syllables at different rates, so some languages are consistently spoken faster than others. However, this doesn't mean that speakers of these languages convey information faster, according to a new study published in Science Advances.
A study conducted by researchers from the University of Lyon found that languages are constrained by a tradeoff between speed and efficiency. Languages spoken faster will contain less information per syllable, so that universally, languages tend to convey information at the same rate of 39.15 bits per second. Despite the large differences between languages-for instance, English has almost 7,000 distinct syllables, while Japanese only has a few hundred-a combination of biological, cultural, and social factors constrain them to be more similar than you think.
The study investigated 17 Eurasian languages, including Japanese, Mandarin, German, Vietnamese, Spanish, French, and Italian. For each language, the researchers estimated the information density (ID) for each language, or the amount of information that is contained in each syllable, calculated in bits per second. A bit in linguistics is the amount of information contained in a syllable that reduces uncertainty by half. For example, in conversation, if you could narrow a topic of a conversation down by half from a single syllable, that syllable would contain 1 bit of information.
The researchers also asked 10 speakers for each language to read 15 texts and measured the duration and number of syllables spoken. They then calculated the speech rate (SR), the speed at which syllables are produced. You can imagine that speech rate would depend largely on the individual speakers, but the researchers found that it varied more by language than by speaker within a language.
The information rate for each language was then calculated by multiple information density (ID) with average speech rate (SR). The researchers found that languages are more similar to each other in information rate than in speech rate, and that information rate negatively correlated with information density. These findings extend the results from a previous study, which found that English had an information density of 0.91, while Japanese had a density of almost half, at 0.49. However, English was spoken slower, at 6.19 syllables per second, compared to 7.84 syllables per second for Japanese.
Overall, languages occupy a range of information rates, which the researchers suggest are due to the communicative and cognitive limitations of both speakers and listeners. If a high information density language was spoken to fast (termed "high-fast"), this would require the speaker to vocalize more complex sounds and require cognitive planning. As you can imagine, listeners would also have a hard time listening and understanding such speech. On the other hand, "low-slow" languages, low ID languages spoken slowly, would be less efficient and also require speakers and listeners to use more memory.
The researchers hope to broaden their results by studying more languages across the world from regions in Africa and the Americas. They are also interested in extending these findings to conversational speech, not just read speech. Interestingly, this study also relates to previous studies that found that within a single language, faster speakers tend to be less informational. Our brains find a balance between cognitive limitations and communication requirements, so that we can get our points across effectively and efficiently.
References
Coupé, C.; Oh, Y.; Dediu, D.; Pellegrino, F. Different Languages, Similar Encoding Efficiency: Comparable Information Rates across the Human Communicative Niche. Science Advances 2019, 5 (9).
Kluger, J. Slow Down! Why Some Languages Sound So Fast. http://content.time.com/time/health/article/0,8599,2091477,00.html (accessed Oct 13, 2019).