Is ‘huh?’ a universal word? A word like ‘Huh?’ —used when one has not caught what someone just said—appears to be universal: it is found to have very similar form and function in spoken languages across the globe. This is one of the findings of a major cross-linguistic study by researchers Mark Dingemanse, Francisco Torreira and Nick Enfield, at the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands. The study was published in the journal PLOS ONE.

Here we summarise the key findings.

Huh? is not trivial. It might seem frivolous or even trivial to carry out scientific research on a word like Huh? But in fact this little word, along with others that function in similar ways (e.g., ‘Sorry?’ ‘What?’) is an indispensible tool in human communication. Without such words we would be unable to signal when we have problems with hearing or understanding what was said. Because conversation moves along so quickly, if we did not have reliable ways of signaling trouble, we would constantly fail to stay ‘on the same page’ in social interaction. While Huh? may seem an unlikely topic of scientific research, in fact human communication, and thus common understanding in social life, relies heavily on the use of such linguistic devices.

Huh? is universal. We sampled 31 spoken languages from diverse language families around the world in this study, and we found that all of them have a word with a near-identical sound and function as English Huh? This is an exception to the normal situation, namely that when words in different languages mean the same thing, they will usually sound completely different: compare, for example, these very different-sounding words for ‘dog’: inu in Japanese, chien in French, dog in English. Why do these differences between the sounds of words across languages occur? Because language does not impose any necessary connection between sound and meaning in words (a principle that linguists call ‘the arbitrariness of the sign’). This study shows that ‘Huh?’ is a rare exception to this otherwise strong rule. Huh? is a word. An objection to our first finding might be that ‘Huh?’ is not a word after all. But our study finds that it is. Although the expression ‘Huh?’ is much more similar across languages than words normally should be, when we zoomed in and looked at the finer details, we discovered that this expression does differ across languages in subtle but systematic ways. These differences give us evidence that ‘Huh?’ is integrated into each linguistic system, thus supporting the view that it is, in fact, a word. Here are some of the subtle differences: In Spanish it’s e. In Dutch it often starts with /h/, as in hè. In Cha’palaa (an indigenous language of Ecuador) it often starts with a glottal stop, as in ʔa, and it has falling intonation, in line with the fact that questions in this language often have falling intonation. Therefore: Huh? is not like those human sounds that happen to be universal because they are innate, such as sneezing or crying. It is a word that has to be learned in subtly different forms in each language. Huh? is not innate. ‘Huh?’ may seem almost primitive in its simplicity, but we don’t find vocalizations with this function in our closest evolutionary cousins. It’s not an involuntary response like a sneeze or a cry of pain. Indeed, to have such a word, specialized for clarifying matters of understanding, only makes sense when a fully functioning cooperative system of communication (i.e., human language) is already in place — babies don’t use it, infants don’t use it perfectly, but children from about 5 have mastered it perfectly, along with the main structures of their grammar. If there is a plausible explanation that doesn’t assume it’s innate, we prefer that, on the standard scientific principle that it is best to keep to the simplest possible assumptions and explanations. In our paper we provide such an explanation: convergent cultural evolution.

Huh? islikely shaped by convergent evolution. In conversation, we are under pressure to respond appropriately and timely to what was just said; when we are somehow unable to do this—for example, when we didn’t quite catch what the other person just said—we need an escape hatch. This particular context places constraints on, and functional motivations for, the form of the word. The signal has to be something maximally simple and quick to produce in situations when we’re literally at a loss to say something; and it has to be a questioning word to signal that the first speaker must now speak again. In language after language, we find a word like ‘Huh?’ that fits the bill perfectly: it is a simple, minimal, quick-to-produce questioning syllable. We propose this is a form of convergent evolution in language. Convergent evolution is a phenomenon well-known from evolutionary biology. When different species live in similar conditions, they can independently evolve similar traits. In a similar way, the similarity of huh? across a set of widely divergent languages may be due to the fact that the constraints from its environment are the same everywhere.