There is enormous variability across the world’s languages. Grammatical rules, phonetic categories, gestures, prosodic cues, and even the speed of languages differ wildly around the globe, making foreign languages particularly challenging to learn for adults. For example, some languages like German and Spanish are spoken very quickly—at a rate of around 7.8 syllables per second. Other languages like Mandarin and Thai are spoken much more slowly, around 5 syllables per second.
Syllables vs. Intonation Units
However, it has been hypothesized that languages create a balance between the speed at which syllables are produced and the informativeness of each syllable (see Coupé et al., 2019). In other words, in languages that are produced more slowly, individual syllables are thought to carry more information (for example, by including more varied phonemes, intonations, or other linguistic information that conveys meaning). Conversely, in languages that are spoken more quickly, there tend to be fewer distinct syllables, and each syllable tends to carry relatively less meaning. In this way, although languages are spoken at very different speeds, the rate at which information is produced and received may be relatively similar.
A new study led by Maya Inbar and colleagues set out to analyze this question systematically by analyzing intonation units (also known as prosodic units) across 48 world languages. Linguistically, intonation units are short segments typically containing a few words that are uttered with a single prosodic contour, often an increase followed by a decrease of speed and volume. The researchers analyzed 668 speech recordings in 48 different languages to estimate the pace at which linguistic information is produced across the languages. Using a computational algorithm validated against human ratings, the researchers computed the average onset time of intonation units in each language and came up with a global average of about 0.6 Hz (0.6 intonation units per second). In other words, each new intonation unit starts about every 1.67 seconds in natural speech. Remarkably, an analysis of the variability of this intonation unit rate across the different languages found that although there was some variability, no single language deviated significantly from this rate. The small differences in intonation unit rate across different languages were not strongly related to the syllable speeds; in other words, whether a language is spoken quickly or slowly doesn’t have much impact on the pace at which intonation units are produced.
This new research supports the idea that some aspects of human communication are indeed universal. Although the world’s languages vary widely in many features, the speed at which information is produced appears to be relatively constant. This finding suggests that there may be a universal rhythm at which human thoughts are produced and understood.
