It has been a basic precept of linguistic theory for 50 years or more that linguistic utterances are essentially fundamentally hierarchical in nature, made up of progressively smaller elements in a manner much like that of a Russian matryoshka doll.
Now, a study by University of Amsterdam (UvA) scientist Rens Bod and fellow researchers at Cornell University and University College London reveals that language structures are actually less complex than long presumed. In their study, they show that language is mainly based on a simple sequential structure in which the individual speech elements are placed one after another, similar to a string of beads. These findings were recently published in the scientific journal Proceedings of the Royal Society B.
The study also has significant implications for a range of other related disciplines. From an evolutionary perspective, the findings by Bod and his colleagues may help bridge the gap between what is known about non-human primate communication systems and human communication. It also has automated language and speech processing applications for the field of computational linguistics, in which the most productive computer models have mainly been those based on sequential rather than hierarchical structures.
Our linguistic system groups words in small clusters that each encapsulates a particular meaning. Sentences are formed from combinations of these word clusters, or constructions, interpreted according to the order in which they are rendered. Hierarchical structure hardly features in this process, only taking over when sequential structure is insufficient for interpretation. For example, the word sequence ‘bread and water’ can be represented as a construction, whereas a construction in the reverse order (‘water and bread’) probably cannot. Bod and his colleagues show that this principle of combination and interpretation holds even for highly complex sentences.
The concept of sequentiality also has simplicity on its side; that language is naturally sequential is borne out in the temporal prompts that help us understand language. Furthermore, the notion of hierarchy fails to account for the fact that language uses a myriad of other signals of meaning, such as context and what was said before.
The digital version of this article was the most downloaded article on the journal’s website last month.
Frank, S.L., Bod, R. and Christiansen, M.H. How hierarchical is language use? Proceedings of the Royal Society B: Biological Sciences, (297(1747), 4522-4531).