Hierarchical structure

Combinations of the individual elements of human language are not only linear but also hierarchical in nature. This means that human language consists not only of precedence relations (e.g. conjunction) but also of dominance relations (e.g. subordination). This can be demonstrated at every level of linguistic analysis: phonological, morphological, syntactic, semantic, and also at the level of discourse. While cetacean, passerine avian, and primate long call vocalizations may include linear relations at the level of acoustic patterning, there is no documented evidence of any internal hierarchical structure. There may be elements of acoustic hierarchical organization in the vocalizations of humpback whales, however. There have been numerous proposals seeking precursors for hierarchical structure in various aspects of animal cognition and behavior: theory of mind, social cognition related to dominance hierarchies, numerosity, ritual, foraging and food preparation, navigation, etc.