"Is 'Huh?' a universal word? Conversational infrastructure and the convergent evolution of linguistic items is a new paper in PLoS One by researchers from the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands. The authors propose that "Huh" is a word, and that convergent evolution has driven multiple, unrelated languages to produce it. The key findings summary shows just how special and interesting this is: "Huh" is not innate (other primates don't say it), but the circumstances of its use (needing to quickly and briefly prompt another speaker to repeat herself) are universal, so languages that share no commonalities still converged on this word.

Huh? is not innate. 'Huh?' may seem almost primitive in its simplicity, but in fact nothing like it is found 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? is likely 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.