Languages around the world differ greatly in how many grammatical distinctions they make. This variation is observable even between closely related languages. The speakers of Swedish, Danish, and Norwegian, for example, use the same word hunden, meaning “the dog,” to communicate that the dog is in the house or that someone found the dog or gave food to the dog. In Icelandic, on the other hand, three different word forms would be used in these situations, corresponding to the nominative, accusative, and dative case respectively: hundurinn, hundinn, and hundinum.
This grammatical distinction in the case system, along with many others, sets Icelandic apart from its closely related sister languages. “One prominent hypothesis about why some languages show more complex grammar than others links grammatical complexity to the social environments in which these languages are used,” says first author Olena Shcherbakova from the Max Planck Institute for Evolutionary Anthropology.
For example, Icelandic is primarily learned and used by the local population of over 350,000 people. Such relatively small isolated communities are also called “societies of intimates.” In contrast, the other Scandinavian countries, located in close proximity to their neighbors, have larger populations with substantial proportions of non-native speakers.